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Hydrologic Modeling for the Arid Southwest United States

Lighthouse Publications

Theodore V. Hromadka II

Hydrologic Modeling for the Arid

Southwest United States

Lighthouse PWlicatioos

Hydrologic Modeling for the Arid

Southwest United States

Theodore V. Hromadka II

Professor, School of Natural Science and Mathematics, California State University, Fullerton, and

Senior Managing Engineer, Failure Analysis Associates, Inc.© Newport Beach, California

Lighthouse Publications/MIssion Viejo, CA

This book is printed on recycled papar

Copyright 1996

Library of Congress Catalog Number 93·0805 53

First Lighthouse Publications Edition

Lighthouse Publications P.O. Box 2972

Mission VIejo. CA 92692 (714) 581·9184

Lighthouse Publications wishes to express gratitude and acknowledgement to the County of San Bernardino, Department of Transportation and Flood Control, the funding agency under which this work was orginally initiated, and to the firm Williamson and Schmid, under whose

auspices the work was begun.

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, reuse of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. The use of registered narnes, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relative protective laws and regulations and therefore free for general use.

Notice

No patent liability is assumed with respect to the use of the information contained herein. While every precaution has been taken In the preparation

of this book, the publisher assum9S no responsibility for errors or omissions. Neither is any liability assumed for damages resulting frOm the

use of the information comalned herein.

ISBN: 0·914055·12·7

Table of Contents

Chapter 1 Introduction 1

Chapter 2 Runoff Modeling Techniques 2

2.1. Unit Hydrograph Techniques 2

2.2. Unit Hydrograph Shape 5

2.3. Synthetic Regional Arid S-Graph Development 6

Chapter 3 Design Storm Input 12

3.1. Design Storm PaUerns and Storm Duration 12

3.2. Design Storm Areal Extent 14

3.3. Design Storm Rain/all 15

3.4. Design Storm Pauern Shape 17

3.5. Desert Rainfall Intensity-duration Characteristics 18

3.6. Depth-Area Effects 19

3. 7. Comparison of Depth-Area Reduction Curves 22

Chapter 4 Design Storm Rainfall Mass Versus Critical Duration 26 Relationships

Chapter 5 Effective Rainfall Determination 35

5.1. Loss Rate Estimation Methods 35

5.1. Calibration 0/ Rainfall-Runoff Methods 39

Chapter 6 Confidence Interval Issues and Design Storm 41 Calibration

vii

Chapter 7 Stream Gauge Data Review 45

7.1. Dissimi/(lrity in Flood Frequency Tendencies: California and 45 Arizona Desert Catchments

7.2. Dissimihlrity in Flood Frequency Tendencies: Riverside, San 48 Diego, and San Bernardino Counties

7.3. Comparison of San Bernardino County Hydrology Manual. 48 Peak Flow Estimates to USGS Regression Equation Estimates

7.4. Comparison of San Bernardino County lOO-year Runoff 51 Volume Estimates,for Desert Master Plans of Drainage, to USGS Equations

7.5. Comparison of San Bernardino County lOO-year Runoff 54 Volume Estimates,/or Apple Valley Dry Lake, to Regionalized Dry Lake Runoff Volume Estimates

7.6. Stream Gauge Data Availability 55

Appendix A Rainfall Data 95

Appendix B Rainfall Mass Tabulations 107

Appendix C Excerpt, USGS Water Resources Investigation Report 193 84-4142

AppendixD Stream Gauge Data Tabulation 197

Vlll

Preface

During 1991 and 1992, the California county of San Bernardino (Department of Transportation and Flood Control) funded a comprehensive study of arid hydrology methods and stormflow estimation procedures used in the southwest United States. The San Bernardino County Department of Water Resources also assembled a team of experts in hydrology and stOIDl flow estimation procedures in order to aid in reviewing recommended procedures and algorithms leading to a comprehensive flood control and floodplain stormflow estinlation procedure.

Included in the expert review panel were representatives from the San Bernardino County Water Resources and Planning Divisions, Kern County Floodplain Management Division, Orange County Environmental Management Agency, the U.S. Army Corps of Engineers (Los Angeles District), Riverside County Flood Control District, the University of Arizona at Tucson, the University of California at Davis, the University of Nevada at Las Vegas, the California State University at Fullerton, and several private engineering consultants, including the firm Williamson and Schmid, under whose auspices the work was conducted.

A detailed comparison of several flood control stonnflow estimation procedures used in the southwest United Sates was a significant product produced during the course of this comprehensive study, and provided an in-depth exposition of similarities and dissimilarities in stormflow estinlation methods.

This book provides flood control engineers and planners, floodplain managers, stormflow modelers and researchers a valuable compendium of information as to the stormflow modeling procedures used by several flood control agencies.

iX

!NTItODUCTION

Chapter One

INTRODUCTION

Recently, hydrologic study criteria manuals (or hydrology manuals) were prepared

for the arid southwest regions of Clark County (Las Vegas vicinity, Nevada), and

Maricopa County (phoenix vicinity, Arizona). Both of these hydrology manuals were

prepared in 1990. Other hydrology manuals pertaining to the arid southwest have been

prepared by San Bernardino County, (1986), San Diego County. (1985), and Riverside

County, (1978), Calitornia A hydrology manual is near completion fDr Kern County,

(1991), and closely fDllows the procedures used in the San Bernardino County hydrology

manual (due to the similarity in procedures, reference to the San BernardinD County

procedures will be assumed to also reference the Kern County procedures). These

hydrology manuals are required by the respective Counly agencies, for use in developing

the flood flow quantities that are used in the planning and design of flood control systems,

master plans of drainage. dams, flood plains, among other topics. The five hydrology

manuals contain hydrologic methods, modeling approaches, and data requirements, for use

in the arid southwest region of the United States. in this study, these hydrology manuals

are compared to as modeling approaches, and the individual modeling compDnents are

examined for similarities.

1

· HYDROLOGIC MODELS FoR THE ARID SOUTHWEST UNITED STATES

Chapter Two

RUNOFF MODELING TECHNIQUES


All five hydrology manuals provide different flood flow computation methods

dependent upon catchment size. All five manuals advocate use of a Rational Method

technique, and limit this technique's application to catchment areas according to the limits

shown in Table 1.

2.1. Unit Hydrograph Techniques

For catchment area greater than the Rational Method application limits of Table 1,

other modeling techniques are used, such as the Clark unit hydrograph of an S-graph unit

hydrograph approach (in Maricopa County); an S-graph unit hydrograph approach (San

Bernardino and Riverside Counties); a U.S. Department of Agriculture Soil Conservation

Service of "SCS" unit hydrograph or kinematic wave approach (Clark and San Diego

Counties).

All five hydrology manuals advocate use of a unit hydrograph approach for areas

greater than one square mile. The use of unit hydro graph methods are recommended

according to the area limits of Table 2.

2


Table 1. Rational Method Maximum Area Limitations

County Catchment Area Limits (Acres)

San Bernardino 640

Maricopa 160

Clark 20

Riverside 500

San Diego 3201

(mean) (328)

Notes: 1 Modified Rational Methods may be used up to 15 square miles

From Table 2, all the hydrology manuals include S-graph of SCS unit hydrograph

methods for computing flood flow quantities for areas greater than about 5 square miles.

For catchment areas greater than about 5 square miles, and less than 150 square

miles, (San Bernardino County area limit), unit hydrograph convolution methods are

provided for use in all five hydrology manuals. This section will focus upon the catchment

area range between 5 and 150 square miles. All the manuals use the well-known unit

hydrograph convolution technique, which can be found in numerous texts, (see Hromadka

et ai, 1987). Because all the manuals use unit hydrographs developed from catchment

area, lag, and unit hydrograph shape, a comparison can be re.adily made. Table 3

compares lag estimation formulae.

The U.S. Army Corps of Engineers Los Angeles District office, (hereinafter

termed "COE"), prepared a comprehensive hydrologic documentation study for Clark

County, Nevada, (1988), which is based upon hydrologic methods similar to the subject

hydrology manuals. For further comparison purposed, the COE (\988) results are

included in Table 3.

In Table 3, L is the length of longest watercourse (miles); L. is the length along

longest watercourse upstream to a point opposite the basin centroid, (miles); S is the

longest watercourse slope (feet per mile). The (K;, mi) shown in Table 3 are compared in

Table 4.

3

· HYDROLOGIC MODELS FOR THE ARID SOUtHWEST UNITED STATES

Table 2. Recommended Unit-Hydrograph Method Area Limits

County Area (Square Miles) Method

San Bernardino Greater than 1 5-graph

Notes:

Maricopa

Maricopa

Clark

Riverside

San Diego (mean)

Less than about 5

Greater than about 5

Greater than 20 acres Greater than 500 acres Greater than 320 acres

(Greater than 936 acres)

Clark1

Vnit-Hydrograph

5-graph

SCS 5-graph

SCS

1 The "Clark" VH technique is not associated to "Clark" County, Nevada.

Notes: 1

2

3

Table 3.

Agencv

San Bernardino 1

Maricopa 2

Clark 3

Riverside

San Diego COE (l988)

Catchment Lag Formulae

lag formulae Lag = Kl (LLc/SO.5r1

Lag = K2 (LLc/SO.5)m2

Lag = K3 (LLc/S05)m3

Lag = l<,j (LLc/SO.5}1Tl4

Lag = KS (LLclSO.5)ms

Lag = Kt; (LLc/SO.5)1l1(;

A calibrated lag estimator used is Lag = 0.8 Te, where Tc is the time of concenlraction computed as the sum of normal depth flow travel times For smaller catchments, T c is utilized

Tc is noted to be related to lag for smaller catchments

In Table 4, the exponent variation of 0.33 versus 0.38 produces

negligible variation in lag, in that with respect to use of 0.38, a one hour lag

value has no variation, a 2-hour lag is reduced to 1.83 hours, and a 3-hour lag

is reduced to 2.6 hours. Therefore, the lag estimation procedures between alI

4


three hydrology manuals are essentially identical for the subject catchment

area limits.

2.2. Unit Hydrograph Shape

The remaining consideration, regarding the unit hydrograph methods,

is the unit hydrograph shape. Figure 1 compares the S-graphs used in the

three manuals, normalized with respect to lag as defined in the respective manuals.

Notes: }

2

Table 4. Lag Formula Parameters i Agency Kj2 mj

1 San Bernardino 24n 0.38

2 Maricopa} 20n;or 26n 0.38; or 0.33

3 Clark 20n 0.33

4 Riverside 24n 0.38

5 San Diego 24n 0.38

6 COE (1988) 24n 0.38 (mean) (23.14ii) (0.366)

For Maricopa County, (K2,1l12J pairs are (20n, 0.38) or (26n, 0.33)

n parameters are similar for all manuals (see Hromadka et aI, 1987), and COE (1988)

In Fig. 1a are shown the San Bernardino County "Valley Developed"

and "Valley Undeveloped" S-graphs, Maricopa County's "Phoenix Valley"

and "Phoenix Mountain"; and Clark County's standard SCS unit hydrograph

as converted into S-graph form using the same definition of lag used by San

Bernardino County. Riverside County uses a "Desert" 5-graph which is the

Whitewater River S-graph (Fig. 1a); San Diego County uses the SCS unit

hydrograph. From Fig. 1b, four manuals have S-graph shapes that closely

agree; namely, Clark and San,- Diego County's SCS (converted), San

Bernardino County's "Valley Developed", and MariCopa County's "Phoenix

Valley" (the COE (1988) study, for the Las Vegas area, also recommends use of

5

HYDROLOOIC MODELS FOR THE ARID SOUTHWEST UNITED STATES

the Phoenix Valley 5-graph. The similarity in S-graphs is also noted in COE

(1988; p.4l)). This close similarity in County S-graphs is somewhat surprising

due to the sources of the S-graphs; namely, the "SCS" 5-graph was developed

from the standard SCS unit hydrograph which is regionalized nationwide;

the "Valley Developed" S-graph was synthesized from coastal urbanized

catchments in Los Angeles, California; and the "Phoenix Valley" S-graph was

developed from Phoenix, Arizona severe storms.

Thus, for the same lag value, four of the hydrology manuals will

develop nearly identical unit hydrographs. However, San Bernardino

County does not use the "Valley Developed" S-graph for undeveloped arid

regions, but uses the "Valley Undeveloped" S-graph shown in Fig. la. The Riverside County "Desert" S-graph is the Whitewater River S-graph of Fig.

la. From Fig. la, the "Valley Undeveloped" S-graph closely matches the

Whitewater River arid S-graph. Use of the "Valley Undeveloped" S-graph

would result in a unit hydrograph that, when convoluted with a design rainfall pattern, would generally result in lower peak flow values (about 10-

percent) than when using the "Valley Developed" S-graph, but would not

affect total storm runoff volume.

2.3. Synthetic Regional Arid S-Graph Development

The conventional approach to unit hydrograph development is to

analyze measured rainfall hyetographs and runoff hydrographs using the

following procedure:

1. Separate baseflow from total runoff to get the distribution of direct

runoff.

2. Compute the volume of direct runoff.

3. Eliminate initial abstraction losses.

4. Assume a loss function to separate the remaining distribution of

rainfall into losses and rainfall excess such that the volume of rainfall

excess equals the volume of direct runoff.

6

RUNOFF MODEUNG TECHNIQUES

5. Convert the distribution of direct runoff to a l-inch unit hydrograph (UH).

6. Set the unit-duration of the UH equal to the duration of rainfall excess.

A number of important assumptions are made with this procedure: (1) a

baseflow model must be selected; (2) an initial abstraction model must be selected; and (3) a loss function must be selected. Each of these components

will have a significant effect on the shape and magnitude of the UH.

Vsing this procedure to develop unit hydrographs requires data for

many storms for each watershed and data from many watersheds to

regionalize the VH. Typically, the VB's for storms will be quite different in shape and magnitude. Averaging of the storm-event unit hydrographs usually yields a reasonable UH but it may not produce a UH that will

accurately reproduce the measured runoff for each storm.

Where data are available, the above procedure is the most frequently

used approach. However, sufficient data are rarely available except at

hydrologic research stations. Very little hyetograph/hydrograph data are available in most localities. This is especially true in desert environments. Thus, the procedure described above cannot be used to develop unit

hydrographs for desert regions because of the absence of sufficient

hyetograph/hydrograph data.

Peak discharge data are more readily available, including for desert

regions. An alternative approach that can be used to determine regional unit hydrograph characteristics which makes use of peak discharge data is as

follows:

1. Assume a known dimensionless functional form to represent the

distribution of the unit hydrograph.

2. To scale the dimensionless VH, use the peak discharge records to

compute a peak rate factor (K), which is typically defined by

KAQ qp=-

tp (1)

7

HYDROLOGIC MODELS FOR THE ARID SOUTHWEST UNITED STATES

where qp is the peak discharge (ds); A is the drainage area (square

miles); Q is the runoff depth (inches); and tp is the time-to-peak

(hours).

Since unit hydrographs usually have a shape that closely follows a gamma

probability function, the gamma pdf can be selected as the dimensionless UR.

The time axis can be set by the time-to-peak and the ordinates can be dimensionalized with Eq. 1. For a given drainage area, the time-to-peak can be computed using the time of concentration. For a unit hydrograph, Q

equals one-inch. If a mean value of the peak rate factor K can be computed

for a region, then the regionalized unit hydrograph should provide accurate

designs in the region.

The gamma distribution for the random variable tis:

(2)

in which c and b are the shape and scale parameters, respectively, and g(c) is

the gamma function with argument c, which is given by

g(c)=cCe~(21l)O.5[1.0+..l+~- 139 _ 571 ] c 12c 2882 51840c3 2488320c4 (3)

At the peak of the function, with the magnitude denoted as qp and the time

denoted as tp, the following relationship holds:

f-1 e-tp/b q -..LP __ _ P - bCg(c) (4)

It is known that the mode of the gamma distribution occurs for the value of t

where

tp = b(c -1) (5)

Substituting Eq. 5 into Eq. 4 yields a relationship between the magnitude of the mode, qp, and the shape and scale parameters:

8

RUNOFF MODELING TECIINIQUES

(c - 1)c-1 e1-c

qp ~ bg(c)

Substituting Eq. 5 into Eq. 1, and equating the result of Eq. 6 yields:

(c - l)C e1-c KAQ ~ ---';-,-

g(c)

For qp in cfs, tp in hours, A in square miles, and Q in inches, Eq. 7 becomes

K ~ 645.3 (c - 1)c eJ-c g(c)

(6)

(7)

(8)

Equation 8 indicates that the peak rate factor of a unit hydrograph is directly

and independently related to the shape parameter of the gamma distribution.

Once K is set, and a function is assumed for the unit hydrograph, then the UH can be computed with A, Q, and tp for any watershed. It appears from data

analysis, that the peak rate factor is a regional characteristic, with small values

for high-storage watersheds such as in coastal areas and large values for low

storage watersheds such as those in mountainous areas.

Table 5 gives values for K and c based on Eq. 8. The following third

order polynomial can be used to compute c for a given value of K

c ~ 1.006 + 1.104(10)-3 *K + 1.267(10)-5 *K2 + 1.646(10)-9 *K3 (9)

Figure 2 shows the relationship between c and K.

Since there are little hyetograph/hydrograph data available for the

desert areas of southern California, the peak-rate-factor approach is used.

Twenty-one watersheds have sufficient information available for the South

Lahontan-Colorado desert region (see Fig. 3). The data of Table 5 are from the

U.S.G.S. report (Magnitude and Frequency of Floods in California). The

locations of the 21 gauging stations used are shovJn in Fig. 4. Using the 100-year LP3 peak discharges, peak rate factors were computed. The average peak

rate factor is 444. This is slightly lower than the value of 484 used for the SCS

standard unit hydrograph, with 284 used in coastal areas of Maryland.

9


To test the peak rate factor of 444, 83 watersheds (see Fig. 5) in the desert

area of Pima County, Arizona, were used to compute an average peak rate

factor. Based on data from 83 watersheds, the average was 436, which yields a

UH that is identical to the UH developed from the 21 watersheds from the

Southern California region.

TableS. Peak Rate Factors for Selected Values of the Shape Parameter

Shape Peak Rate Shape Peak Rate Parameter Factor Parameter Factor

c K c K

1.0 0.0 9.0 720.6 1.2 83.4 9.2 729.8 1.4 13.52 9.4 738.8 1.6 175.1 9.6 747.7 1.8 208.4 9.8 756.5 2.0 237.4 10.0 765.2 2.2 263.5 10.2 773.8 2.4 287.3 10.4 782.4 2.6 309.3 10.6 790.8 2.S 392.9 10.S 799.1 3.0 349.3 11.0 S07.4 3.2 367.8 11.2 815.5 3.4 385.3 11.4 823.6 3.6 402.1 11.6 831.6 3.8 418.2 11.8 839.6 4.0 433.7 12.0 847.4 4.2 448.7 12.2 855.2 4.4 463.3 12.4 862.9 4.6 477.3 12.6 870.6 4.8 491.0 12.8 878.1 5.0 504.3 13.0 885.7 5.2 517.3 13.2 893.1 504 529.9 13.4 900.5 5.6 542.3 13.6 907.8 5.8 554.4 13.8 915.9 6.0 566.2 14.0 922.3 6.2 577.8 14.2 929.5 6.4 589.1 14.4 936.6 6.6 600.2 14.6 943.6 6.8 611.2 14.8 950.6 7.0 621.9 15.0 957.6 7.2 632.5 15.2 964.5 7.4 642.9 15.4 971.3 7.6 643.1 15.6 978.1 7.8 663.2 15.8 984.9 8.0 673.1 16.0 991.6 8.2 682.9 16.2 998.2 8.4 692.5 16.4 1004.9 8.6 702.0 16.6 1011.4 8.8 711.4 16.8 1018.0

10


Based on the desert-area computations of peak rate factors, a value of 440 is recommended. The dimensionless unit hydrograph is shown in Fig. 1b

in S-graph form; along with the other 5-graphs previously discussed. To

dimensionalize the UH, the drainage area (sq. mi.), runoff depth (inches), and

time to peak (hours) are required. These values are used with Eq. 1 to

compute the peak discharge, which scales the ordinates. The time axis is

scaled using the time to peak. From Fig. 1b, the synthetic regional arid 5-graph closely matches several other S-graphs derived from rainfall-runoff data.

In summary, the five hydrology manuals and the COE (1988) study

provide unit hydrograph techniques, for catchment areas between about 5 and

150 square miles, which are nearly identical, except that use of the San

Bernardino "Valley Undeveloped" 5-graph or the similar Riverside County

"Desert" S-graph, would generally result in lower runoff peak flow rate

estimates. The San Bernardino County "Valley Developed" S-graph closely matches three other County arid S-graphs shown in Fig. lb. Additionally, a

synthetic S-graph developed from use of a gamma function, closely agrees

with the several other 5-graphs shown in Fig. lb.

11


Chapter Three

DESIGN STORM INPUT

In comparing the hydrology manuals, the focus need not be upon the runoff generator technique (as all five manuals use essentially identical

methods, except than San Bernardino's "Valley Undeveloped", and the

similar Riverside "Desert" S-graph, are milder peak flow rate estimators), but

upon the input into model; that is, the design storm rainfall input, including

pattern shape, depth-area adjustments, and rainfalls.

In the following, the various design storm development techniques are

examined in detail, in order to identify and compare the several components

inherent in each design storm approach.

3.1. Design Storm Patterns and Storm Duration

Maricopa and Clark Counties both utilize sets of 6-hour storm patterns

as representative of local thunderstorm tendencies. Clark County uses a set of

two 6-hour patterns, one for areas less than 10 square miles, the other for

greater areas, as·taken from a set of five storm patterns used in COE (1988).

Maricopa County utilizes a set of five 6-hour patterns, based on catchment areas of about 0.5, 2, 15, 90, and 500 square miles, with interpolation according

to catchment area size. Each of the above storm patterns are rigid

relationships with respect to a single rainfall input; namely, the 6-hour

rainfall. Thus, regardless of location, a specific rainfall pattern defines a fixed

12

DESIGN STORM INPUT

rainfall depth versus duration relationship, with respect to the 6-hour rainfall

depth.

Riverside County uses a set of 1-, 3-, 6-, and 24-hour storm patterns. A

catchment is tested by each storm pattern application in order to develop the

maximum design storm condition. Each storm pattern is a fixed relationship

with respect to total storm rainfall. San Diego County uses a single fixed 6-hour storm pattern for arid conditions.

The San Bernardino hydrology manual uses a single 24-hour storm

pattern that is constructed by nesting T -year return frequency rainfalls to achieve rainfall intensity-duration relationships, fitted to local rainfall data.

Rainfall data used are the 5-, 15-, 30-minutes, 1-,3-,6-, and 24-hour rainfalls of a prescribed return frequency. The construction of the storm pattern closely

follows the procedures given in the U.S. Army Corps of Engineers Hydrologic Engineering Center (or BEe) Training Document #15 (1982).

Thus, all five hydrology manual design rainfall patterns would agree, for a 6-hour storm pattern, as to the 6-hour rainfall depth to be used (to

construct a T-year return frequency design storm)' but would disagree at smaller peak durations of the T-year return frequency pattern, unless the

fixed stOrm pattern happened to match local rain gauge intensity-duration tendencies.

It is noted that the storm pattern construction includes another

influence from so-called "depth-area" relationships, that transform the storm

pattern shape (and rainfall intensity-duration) according to catchment area. This influence will be discussed in a following section. However, for small

catchment areas such as one square mile, all the hydrology manuals provide

for negligible depth-area effects, and hence the above storm pattern construction is essentially used directly. In this case, unless the fixed storm

pattern follows the local rainfall intensity-duration tendencies, the storm

pattern is not providing a T-year return frequency rainfall depth for a

prescribed duration. This topic will also be further addressed in a subsequent

section.

13


It is noted that three Counties use a 6-hour duration storm pattern,

whereas San Bernardino County uses a 24-hour storm pattern (the San

Bernardino procedures include extension of the storm pattern to longer

multi-day durations) and Riverside County uses a set of multi-length storm

patterns, up to 24-hours. For the arid southwest region, most of the 24-hour

design storm rainfall falls within the peak 6-hours, with the remaining

rainfall distributed in the other l8-hours. For example, McCarran Airport

(Las Vegas, Nevada) information shown in the Clark County Hydrology

Manual indicates that, at the lOO-year return frequency, 94-percent of the

rainfall occurs in the peak 6-hours, with the residual 6-percent occurring in

the remaining 18 hours. For a 25-year return frequency event, the peak 6-

hour percentage falls to 85-percent.

Consequently, use of a 24-hour storm pattern would not be an issue in computation of flood flow quantities (especially for flood control systems that

are most sensitive to storm durations less than the peak 6-hours), except that

storms of durations greater than 6-hours are not addressed by a storm pattern

restricted to 6-hours, and hence large-scale detention effects pOSSibly may

escape being tested by a storm pattern of the most critical duration. Reference

to long duration summer "general storms", in which thunderstorms are

embedded, is made in COE (1988, p.ll).

3.2. Design Storm Areal Extent

Several counties address catchment sizes according to the storm size

area limits shown in Table 6. Beyond the area limits of the table, several

county manuals recommend special consideration of other approved

hydrologic estimation techniques.

14

Note: 1

3.3.

DESIGN STORM INPUT

Table 6. Design Storm Areal Limits

County

San Bernardino

Maricopa Clark

Riverside

San Diego

Design Storm Maximum Area (Square Miles)

(mean)

150

100

200

3001

1001 (170)

Limits from county depth-area reduction curves.

Design Storm Rainfall

All five manuals use some form of T-year rainfall data to produce a T

year design storm pattern (e.g., 10-, 25-, 100-year). Each manual utilizes

NOAA rainfall statistics or NOAA Atlas IT (1973), as discussed in Table 7.

From Table 7, Clark County uses a set of adjustment factors that result

in a significant increase in high return frequency storm rainfall values. For a

lOO-year return frequency event, the adjustment is to multiply 100-year return

frequency NOAA Atlas II rainfalls by 1.43. For a 2-year return frequency

rainfall, the adjustment factor is 1.0.

15

Notes:

1

2

HYDROLOGIC MODELS FOR TIlE ARID SOlITHWEST UNITED STATES

Table 7. NOAA Rainfall Data Usage

County

San Bernardino

Maricopa

Clark

Riverside

San Diego

Usage

NOAA Atlas II, modified (as approved by Agency) by local ram gauge analysis l .

NOAA Atlas II.

NOAA Atlas II, modified by adjustment factors2•

NOAA Atlas II.

NOAA Rainfall Statistics.

The State of California Department of Water Resources (or "DWR") provides regional rain gauge analysis, with frequent updates. One such region focuses on the arid southern California.

Adjustment factors provide for an increase in rainfall values of up to a factor of 1.43 for a IOO-year return frequency event. A 2-year return frequency rainfall has an adjustment factor of 1.0.

In order to better examine the Clark County adjustment factor of 1.43

with 100-year return frequency NOAA Atlas II rair;tfall estimates, a

comparison of rainfall return frequency estimates, developed in other studies,

was prepared based upon the McCarran Airport rain gauge (which is a

principal rain gauge used in the original development of the 1.43 factor). In

Fig. 6a are shown the McCarran Airport rain gauge peak 1-hour rainfall data

(shown in median plotting position), along with rainfall estimates developed

by the State of California Department of Water Resources (nDWRn) in 1988;

DWR in 1983; NOAA Atlas II (1973); rainfall estimates developed by French (1983); estimates prepared by Randerson (1984); and estimates from the Clark

County hydrology manual for McCarran Airport. Fig. 6b show similar

comparisons as in Fig. 6a, but for a peak rainfall duration of 3-hours. From

Figs. 6a, 6b, there is a significance difference in estimates of rainfall, and it is

not clear whether the adjustment factors used in the Clark County hydrology

16

DESIGN STORM INPUT

manual are transferable to other arid regions of the southwest United States, for use in estimating T-year return frequency rainfall depths from NOAA Atlas II.

3.4. Design Storm Pattern Shape

In general, all five hydrology manuals use single peaked storm patterns. For comparison purposes, the peak 6 hours of the San Bernardino County design storm pattern may be examined with respect to the Maricopa,

Clark, Riverside, and San Diego, 6-hour design storm patterns. It is recalled that by construction, each County storm pattern (or set) would necessarily agree as to the total 6-hour rainfall depth data to be used (neglecting depth

area effects). The ratio of the design storm time-to-peak versus the total storm duration (i.e., 6 hours) is given in Table 8. Table 9 shows the total mass

of design storm rainfall that is specified to occur prior to the design storm time-la-peak.

From Tables 8 and 9, the five hydrology manuals are in general agreement as to storm pattern shape and time-to-peak (with respect to the peak 6 hours of the design storm pattern).

Notes: 1

2

3

4

Table 8. Ratio of Design Storm Time-Io-Peak versus Total Storm Duration

County San Bernardino1

Maricopa Clark2

Riverside3

San Dieg04 (mean)

Ratio 0.67

0.67

0.62

0.91

0.63 (0.70)

Peak 6 hours of 24-hour storm pattern considered. For the selected storm patterns, Clark County storm characteristics are identical to COE (1988). Riverside County 6-hour storm pattern considered. Storm pattern is of near uniform intensity from hoVrs 3.5 to 4.0.

17

Notes:


Table 9. Total Design Storm Rainfall Mass Prior to Rainfall Time-to-Peak

County

San Bernardino!

Maricopa

Clark3

Riverside 4

San Dieg05 (mean)

Mass (percent)

67

(62.7-83.4)2

782

95.6

60.0 (75)

! Peak 6 hours of 24-hour storm pattern considered.

2 Total rainfall mass decreases as catchment area increases. 3 Characteristics are identical to COE (1988). 4 Riverside County 6-hour storm pattern considered. 5 Storm pattern is of near uniform intensity from hours 3.5 to 4.0.

3.5. Desert Rainfall Intensity-Duration Characteristics

Tables lOa and b provides a comparison of typical rain gauge intensity

duration characteristics for the arid regions of Clark, Maricopa, Riverside, San

Diego, and San Bernardino Counties.

From the Tables, up to BO-percent of the total 24-hour rainfall occurs in

the peak 3-hours; similarly, up to 90-percent of the peak 6-hour rainfall occurs

in the peak 3-hours. For Clark and Maricopa Counties, 67-percent of the 24-

hour rainfall occurs in the peak I-hour duration, which corresponds to near 75-percent of the 6-hour rainfall. Thus, the arid rainfall intensity-duration

characteristics indicate that the dominant runoff producing rainfalls generally

occur between the 1- and 3-hour peak durations, with larger storm durations

being of importance for modeling substantial detention effects. San Bernardino arid rainfall intensity-duration characteristics generally differ

from Clark and Maricopa Counties for shorter storm durations such as the

peak I-hour duration; consequently, Clark and Maricopa County storm

pattern techniques may not be directly transferable between each other, nor to

18

DESIGN STORM INPUT

San Bernardino County arid conditions. Similar differences in rainfall depthduration statistics can be found with Riverside and San Diego County arid

region rain data, and hence transferability of localized design storm events to

other arid regions may be inappropriate due to the differences in rainfall

intensity-duration characteristics. Because the San Bernardino storm pattern

is constructed according to local rainfall intensity-duration data, it is

transferable to other regions (see HEC TD#15, 1982). This property of design

storm transferability exhibited by the San Bernardino County storm pattern,

will be useful in rainfall mass comparisons to be developed in a later section.

Additional arid rain-gauge depth-duration data for San Bernardino,

San Diego, and Riverside Counties are provided in Appendix A.

3.6. Depth-Area Effects

The technique of modifying catchment area-averaged rainfall data, due

to catchment size, is well-known and is generally classified as "depth-area" adjustments (e.g., Hromadka et ai, 1987). The five counties use depth-area

effects, but procedures differ. Table 11 compares depth-area specifications.

Each of the hydrology manuals use area-averaged T -year return frequency

rainfall depths for study purposes. Figure 7 show plots of the various County depth-area curves involved, for several design storm peak rainfall durations,

as well as other depth-area curves, developed by u.S. Army Corps of

Engineers and other Agencies, for comparison purposes.

19

HYDROLOGIC MODELS FOR THE ARID SOtrrHWEST UNITED STATES

Table lOa. Comparison of 100-Year Rainfall Depth-Duration Estimates

San Bernardino Maricopa Clark Riverside San Diego County County County County County

Rainfall Phoenix McCarran Desert Crawford Duration Amboyl Metro2 Airport3 Hot Springs4 RanchS

5-minute .52 (25)6 0.75 (20)6 0.63 (21)6 0.47 (11)6 0.52 (11)6

30-minute 1.14 (54) 2.00 (52) 1.79 (60) 1.25 (28) 1.33 (29)

I-hour 1.32 (62) 2.50 (65) 2.06 (70) 1.59 (36) 1.67 (36)

3-hour 1.62 (76) 3.00 (78) 2.48 (84) 2.36 (53) 2.40 (52)

6-hour 1.83 (86) 3.30 (86) 2.77 (94) 3.13 (70) 3.03 (66)

24-hour 2.12 (100) 3.84 (100) 2.96 (100) 4.45 (100) 4.61 (100)

Table lOb. Comparison of 10-Year Rainfall Depth-Duration Estimates

San Bernardino Maricopa Clark Riverside San Diego County County County County County

Rainfall Phoenix McCarran Desert Crawford Duration Amboy1 Metro2 Airport3 Hot Springs4 Ranch5

5-minute .29 (25)6 0.49 (20)6 0.35 (19)6 0.26 (11)6 0.29 (11)6

30-minute .63 (53) 1.25 (52) 1.01 (56) 0.69 (28) 0.73 (29)

I-hour .73 (62) 1.60 (67) 1.15 (64) 0.88 (36) 0.92 (36)

3-hour .90 (76) 1.89 (79) 1.39 (77) 1.31 (53) 1.33 (52)

6-hour 1.01 (86) 2.10 (88) 1.58 (88) 1.74 (70) 1.68 (66)

24-hour 1.18 (100) 2.40 (100) 1.80 (lOO) 2.47 (100) 2.55 (100)

1 DWR Gauge No. 176. 2 From Maricopa County Hydrology Manual, Figure 3.2. 3 From Clark County Hydrology Manual. Table 505. 4 DWR Gauge No. 2405 5 DWR Gauge No. 2139. 6 Percentage of 24-hour rainfall value.

20

DESIGN STORM lNPlJ[

The Maricopa County storm pattern set, and the corresponding 6-hour

depth-area curve, are based upon a single storm event that occurred on

August 19, 1954 over the Queen Creek area, Arizona. The Clark County 6-

hour set of storm patterns and 6-hour depth-area curve, are a subset of that

used in COE (1988), for the greater Las Vegas area, Nevada. The San

Bernardino County short duration depth-area curves come from a 3-hour

duration 1943 thunderstorm in Sierra-Madre, California and, for 6- and 24-

hour curves, from NOAA Atlas II (the storm pattern construction follows

HEC Training Document #15 (1982), which also uses NOAA Atlas II). The

Riverside County 3- and 6-hour storm patterns are from a 1939 Indio,

California thunderstorm; the depth-area curves follow NOAA Atlas II for all

durations. The San Diego County storm pattern and depth-area curve is for "arid and semi-arid climates", and references the SCS.

Only a 6-hour depth-area adjustment is used by Clark, Maricopa,

Riverside (for the 6-hour slonn), and San Diego Counties which implies that,

from the use of rigid 6-hour storm patterns, all the storm pattern smaller

interior durations are being adjusted by the same 6-hour duration

adjustment. In contrast, the San Bernardino County method uses an

adjustment for each duration. It is noted, however, that the use of a set of

storm patterns (e.g., five patterns used by Maricopa County), with each pattern

being selected based on catchment area, is somewhat analogous to the use of a

set of depth-area reduction curves, in that the smaller interior durations are

being adjusted by virtue of the defined storm pattern shape selection. Using

the set of five storm patterns of Maricopa County, shorter duration depth-area

reduction curves can be synthesized which include the effects of both the

overall 6-hour depth-area reduction, as well as the changing storm pattern shape. Included in the one- and three-hour depth-area curves, of Figs. 7b and

7c, are depth-area curves synthesized from the Maricopa County storm

pattern set of five storms, using the small area storm pattern as the base storm

(Le., no depth-area adjustment).

21

HYDROLOGIC MODELS FOR THE ARID SO!JfHWEST UNITED STATES

3.7. Comparison of Depth-Area Reduction Curves

Figure 7a examines peak 30-minute rainfall depth-area curves, and

indicates that the San Bernardino curve is an approximate average of the

Walnut Gulch (Arizona) and the synthesized Maricopa County depth-area

curves, for areas less than 50 square miles; otherwise, the San Bernardino

curve provides more depth-area reduction. Hence, for catchments where

short duration storms of 3D-minutes have a significant impact on flooding, the runoff estimates will generally vary in magnitude according to the shown depth-area curves.

Notes;

Table 11. Depth-Area Adjustment Procedures

County

San Bernardino

Maricopa! Clark2,3

Riverside4 San Diego

Method

Compute T-year area-averaged rainfall depths for peak 5-, 15-, 30-minute, 1-, 3-, 6-, 24-hour durations. Modify each depth per appropriate depth-area curve.

Compute T -year area-averaged rainfall depth for 6-hour duration. Use single 6-hour depth-area curve, and adjust 6-hour rainfall depth.

1 Maricopa County uses a set of five storm patterns, based on catchment area.

2 Clark County uses a set of two storm patterns, based on catchment area.

3 Six-hour depth-area curve also used in COE (1988).

4 Riverside County's procedure is similar for the 1-, 3-, and 24-hour storm patterns, respectively.

22

DESIGN STORM INPUT

Figure 7b shows several peak one hour depth-area reduction curves.

Generally, the one hour depth-area curve will have a considerable influence

on storm runoff estimates for small catchments that have time-of

concentration values less than about one hour. From Fig. 7b, the San

Bernardino County curve provides the most depth-area reduction for

catchment areas less than 60 square miles, while the synthesized Maricopa

County depth-area curve provides significantly less adjustment for catchment

areas greater than 60 square miles. The synthesized Maricopa County depth

area curve provides less reduction than the San Bernardino County curve for

areas greater than about 15 square miles; otherwise, the two curves are

comparable. Use of the one hour San Bernardino depth-area curve will result

in lower runoff estimates than by use of the synthesized Maricopa County one hour curve. The Riverside County one-hour depth-area curve agrees

with the NOAA Atlas H curve, and provides considerably less reduction than

the other depth-area curves.

Figure 7c considers three-hour depth-area reduction, and shows that

the San Bernardino curve approximates an average between the Tucson,

Arizona depth-area curve and the synthesized Maricopa County curve.

Depth-area curves from the National Weather Service HYDRO-40 publication are also included, which indicate a relative maximum depth-area reduction

for three-hour durations. The three-hour depth-area curves show a

considerable dispersion in reduction values that were not evident in the 30-

and 60-minute depth-area curves. Note that the Tucson depth-area curve

significantly disagrees with the HYDRO-40 curves, which also apply to the

Tucson area. Also note that Maricopa County uses depth-area curves that are

significantly higher in value than the HYDRO-40 curves for that region.

Again, Riverside County uses a 3-hour curve that agrees with NOAA Atlas H,

and provides significantly less reduction than the other curves.

Figure 7d considers 6-hour depth-area adjustment. Again, considerable

dispersion and uncertainty in reduction values is seen. The San Bernardino

curve follows NOAA Atlas II (as does Riverside County) in a philosophy that

"general storms" may influence 6-hour rainfall depths, whereas the other

depth-area curves address thunderstorm effects. The Maricopa County curve

approximates an average of the NOAA Atlas II and HYDRO-40 curves. The

23

HYDROLOGIC MODELS FOR THE ARID SOlITHWEST UNITED STATE.

San Bernardino reduction values are 9-, 10-, and 14-percent higher in values

than the Maricopa County values for 50-, 100-, and ISO-square miles,

respectively. The 6-hour depth-area curve would impact runoff volume

estimates in detention basin design and planning, and peak flow estimates for

catchments with time-of-concentration values typically in the 3- to 6-hour

range (which infrequently occur for areas less than ISO-square miles).

Generally speaking, use of the NOAA Atlas II 6-hour depth-area curve (used

by San Bernardino and Riverside Counties) would result in larger detention

basin requirements than by use of the 6-hour Maricopa County curve. The

Maricopa County depth-area curve is significantly higher in value than the

HYDRO-40 curve for that region. In contrast, the Clark County curve

approximates the HYDRO-40 curve. The Clark County curve provides considerable depth-area reduction; at 150 square miles, the Maricopa County

curve is 47-percent higher in value than the Clark County curve. The San

Diego County depth-area curve provides reduction comparable to Clark

County. Thus, considerable uncertainty is evident as to which 6-hour depth

area curve is appropriate for a region.

Figure 7e examines 24-hour depth-area curves, (only Riverside and San

Bernardino Counties employ a 24-hour design storm). It is noted that the

HYDR0-40 curves suggest that the 24-hour depth-area reduction values may

increase as one approaches the arid regions of San Bernardino and Riverside.

Zones A & C are closest to San Bernardino and Riverside, and there is

approximately a ten-percent variation in depth-area. reduction values

between HYDRO-40, San Bernardino, Riverside Counties, and NOAA Atlas

II.

From Figs. 7, there is significantly closer agreement in depth-area

reduction values for 30-, 60-minute, and 24-hour depth-area relationships

than for 3-, 6-hour depth-area relationships. Perhaps the widest disparity and

uncertainty occurs for the 6-hour set of depth-area curves. For catchments

under 150 square miles, the 6-hour depth-area curves would generally have a

significant impact on runoff volume estimates as considered in detention

basin design. Additionally, 100-year storm desert rainfall data indicates that

90-percent or more of the 24-hour rainfall depth occurs in the peak 6-hours.

Because failure mode for detention basins and dams are usually more

24

DESIGN STORM INPUT

damaging than peak flow channel failures, further research is needed in order

to ascertain which depth-area curve set is most appropriate for a region,

especially longer duration depth-area curves that significantly impact runoff

volume estimates, such as the 6-hour curve.

25

· HYDROLOGIC MODELS FOR TIlE ARID SOUTHWEST UNITED STATES

Chapter Four

DESIGN STORM RAINFALL MASS VERSUS CRITICAL DURATION

RELATIONSHIPS

The design storm critical duration, oe, is the smallest duration of the

design storm that maximizes the hydrologic criterion variable, I, under study

(see Hromadka and Whitley, 1989). For example, for I being the peak flow rate produced from a design storm event, then the critical duration oe, can be

found by increaSing (from zero) the peak storm duration, 0, (where Po(t) is

that portion of the design storm of duration 0, that maximizes ll, until I

becomes maximum; thereafter, for 0> oe, I is still maximized. In general, I,

is a monotonically increasing function of storm duration, 0, where I = l(o),

and

(10)

Thus, given the critical duration, oe, the peak portion of the design storm, Poe(t), of duration oe, maximizes the subject criterion variation, I, and

all that requires consideration in the design storm is Poe( t). The criterion

variable critical duration, oe, is dependent upon the type of criterion variable

being studied; for example, oe would differ between the criterion variables of

26

DESIGN STORM RAINFAll MASS VERSUS CRITICAL DURATION RELATIONSHIPS

peak flow rate, maximum 2-hour runoff volume, maximum 4.5-hour runoff

volume, and maximum possible total storm runoff of any storm duration.

Generally, the most important hydrologic criterion variable for flood

control design and planning, is the peak flow rate. From the above discussion, the peak flow rate is produced from a critical duration, oe, and

larger storm durations need not be considered (except for antecedent storm

considerations; however, all the hydrology manuals do not utilize saturated soil conditions).

For catchment areas less than 150 square miles, the vast majority of

catchments impacted by the subject hydrology manuals have catchment lag

values such that, for the peak flow rate criterion variable, the associated

critical durations are typically less than 3-hours. Consequently, the several

design storm approaches can be compared with respect to criterion variable

estimates such as peak flow rate, by examining critical durations of less than 3-hours.

In the following, criterion variable critical durations of 3D-minutes, 60-. minutes, and l80-minutes, are examined. Because the Maricopa, Clark, and

Riverside Counties design storms are localized events, and these counties

have different rainfall intensity-duration characteristics, the storm patterns

may be nontransferable and cannot be directly compared. The San

Bernardino design storm, however, is constructed from local rain gauge data

and is transferable to the Maricopa, Clark, Riverside, and San Diego County

areas by use of the respective local rainfall data.

For example, the San Bernardino County storm patterns are compared

to the Maricopa County storm patterns by use of the Phoenix Metro area

rainfall intensity-duration data to define the necessary storm pattern rainfall

inputs. Then, design storm patterns for 1-, 5-, 10-, 25-, 50-, and ISO-square mile

catchment areas are developed using the respective county depth-area curve

adjustments and storm patterns. For each storm pattern, the peak 30-, 60-,

and 180-minute durational rainfall masses are computed, and a comparative

ratio computed by

(San Bernardino County-Maricopa County)/ (San Bernardino County) (11)

27


as a function of catchment area size, and design storm rainfall return

frequency of 2-, 10-, 25-, and 100-years. The comparative ratio values of Eq.

(11) include the respective county depth-area curve adjustments (i.e.,

Maricopa storms adjusted per Maricopa depth-area curves, whereas San

Bernardino storms adjusted per San Bernardino depth-area curves);

consequently, the total design storm rainfall mass is being compared, as a

function of catchment area, return frequency, and criterion variable critical

duration.

Figures 8 shows plots of comparative ratio values, Eq. (11), for the

comparison 9f San Bernardino and Maricopa County design storm

approaches, using Maricopa County rainfall characteristics. A criterion

variable, with an associated critical duration of about 60-minutes, would be

estimated using design storm rainfall quantities that differ between San

Bernardino and Maricopa County procedures, according to catchment area

size and storm return frequency, as shown in Figs. 8. Because each County

uses nearly identical unit hydrograph lag and shape factors, and comparable

loss rate values (see next section), the comparative ratio values shown in Figs. 8 are indicative of the corresponding ratio of hydrologic criterion variable

values. From Figs. 8, a linear criterion variable, such as peak flow rate, would

be estimated, using San Bernardino methods, to have higher values than as

estimated by Maricopa methods for critical durations of 30- and 180-minutes,

while have lower values than by the Maricopa methods for critical durations

of 60-minutes, regardless of storm return frequency and catchment area size.

Figures 9 examine the same criterion variable critical durations,

catchment areas, and storm return frequencies, as shown in Figs. 8, except that

the comparative criterion variable is

(San Bernardino County-Clark County) / (San Bernardino County) (12)

From Figs. 9, the San Bernardino County methods produce estimates of

hydrologic criterion variables which produce higher values using San

Bernardino methods than by using Clark County methods, regardless of

critical duration, return frequency, and catchment area.

28

DESIGN STORM RAlNFAliMASS VERSUS CRI11CAL DURATION RELATIONSHIPS

The design storm durational rainfall masses used in Figs. 8 and 9 can be

compared to local rainfall intensity-duration curves, for small catchments

where depth-area reduction does not apply. In this way, the various County

design storm patterns can be directly examined as to what return frequency of

rainfall is being delivered versus peak storm duration, for catchments where

the influence of depth-area reduction is negligible, and hence the influence of

depth-area effects can be removed from the comparison.

Table 12 shows a comparison of the return frequency of rainfalls,

contained in various peak durations of the respective design storm patterns,

using rainfall data for the Phoenix Metro area, for the San Bernardino and the

Maricopa design storms. In Table 12, the 100-, 25-, and IO-year return frequency design storms are examined. Table 13 provides an analogous

comparison as Table 12, but for the design storm patterns of San Bernardino

and Clark Counties, using rainfall data from McCarran Airport, Las Vegas.

Table 12. Comparison of Design Storm Pattern Durational Return Frequency Rainfall (yrs):

San Bernardino County (SBC) vs. Maricopa County (MC) at Phoenix Metro Area

Peak Storm 10-Year Storm 25-Year Storm 100-Year Storm Duration1 SBC MC SBC MC

30-minutes 10 5 25 18

I-hour 10 10+ 25 25+

3-hour 10 10 25 25-

6-hour 10 10 25 25

24-hour2 10 25

Notes: I

2

Depth-area effects neglected for small catchments.

Maricopa design storm is of a 6-hour duration.

29

SBC MC

100 60+

100 100+

100 100-

100 100

100


From Table 12, it is seen that both Maricopa and San Bernardino

County design storms essentially deliver T-year rainfalls, for all storm

durations, throughout the T-year design storm. The Maricopa storm pattern,

however, falls slightly below the T-year rainfall values for the short duration

of 3D-minutes. Consequently, the variation in design storm rainfall masses,

such as demonstrated in Figs. 8, are principally due to the different depth-area reduction effects incorporated in the respective county design storm

approaches, except for the short 3D-minute critical duration wherein the

county design storms deliver different return frequencies of rainfalls.


San Bernardino County (SBC) vs. Clark County (Clark) at McCarran Airport

Peak Storm lO-Year Storm 25-Year Storm lOO-Year Storm Duration} SBC Clark SBC Clark SBC Clark

3D-minutes 10 4 25 7 100 19

I-hour 10 5- 25 10- 100 29

3-hour 10 8 25 18 100 50

6-hour 10 10 25 25 100 100

24-hour2 10 25 100

Notes:

1 Depth-area effects neglected for small catchments.

2 Clark County design storm is of 6-hour duration.

From Table 13, however, there are significant differences between the

return frequency of rainfalls delivered by the Clark County and the San

Bernardino County design storm patterns. For the 100-year design storm

event, the Clark County design storm delivers about a 3D-year return

frequency rainfall for the peak one-hour storm duration, whereas the San

Bernardino storm delivers a 100-year rainfall (it is recalled that the Maricopa

design storm also delivers a 100-year return frequency rainfall for the peak

one-hour duration; see Table 12). Because depth-area effects are not included

in the comparisons of Table 13 (with the assumption of a small catchment),

30

DESIGN STORM RA!NFALLMASS VERSUS CRITICAL DURATION RELATIONSHIPS

the design storm rainfall masses will vary according to Figs. 9, due to a

combination of two effects; namely, differences in design storm interior

duration return frequencies of rainfall, and depth-area reduction effects.

However for small catchments, the design storm rainfall mass variations

shown in Figs. 9 are due to the different rainfall intensity-duration

relationships exhibited by the respective design storm patterns.

Recall from Table 10, about 75-percent of the 6-hour rainfall occurs

within the peak I-hour storm duration at McCarran Airport. However, the

Clark County design storm pattern delivers only 56-percent of the 6-hour

rainfall within the peak I-hour duration. Therefore, the Clark County design

storm pattern peak I-hour rainfall mass requires a multiplicative factor of 1.34 to increase its value to correspond with the rainfall intensity-duration

relationships.

Figures 10 compares design storm rainfall masses, as adjusted for

depth-area effects, between San Bernardino County and Riverside County, for

the DWR Desert Hot Springs rain gauge, using

(San Bernardino County-Riverside County) / (San Bernardino County) (13)

Figures 10 indicates that the San Bernardino design storm delivers

more rainfall mass for short critical durations over small catchments, but the

Riverside design storm delivers more rainfall mass for larger catchment

areas.

Figures 11 show the comparison between San Bernardino and San

Diego Counties, using the DWR Crawford Ranch rain gauge, and an equation

similar to (13). As with Figures 10, the variations between rainfall mass

delivery varies with critical duration and catchment areas. Tables 14 and 15

give the Riverside, San Diego, and San Bernardino County design storm

rainfall return frequency for interior durations, using the local .rain gauge

DWR statistics.

31



San Bernardino County (SBC) vs. Riverside County (RC) at Desert Hot Springs Area

Peak Storm 10-year Storm 25-year Storm loo-year Storm Duration1 SBC RC SDC RC SBC

3D-minutes 10 3+ 25 6 100

I-hour 10 5 25 10 100 3-hour 10 9 25 24 100

6-hour 10 10 25 25 100 24-hour2 10 25 100

Notes: 1

2

Depth-area effects neglected for small catchments.

Riverside County storm is of 6-hour duration.


San Bernardino County (SBC) vs. San Diego County (SDC)

at Crawford Ranch Area

RC

12

30

90

100

Peak Storm Io-year Storm 25-year Storm 100-year Storm Duration! SBC SDC SBC SDC SBC SDC

3D-minutes 10 7 25 15 100 45

I-hour 10 7 25 16 100 50

3-hour 10 9 25 17 100 80

6-hour 10 10 25 25 100 100

24-hour2 10 25 100

Notes:

1 Depth-area effects neglected for small catchments.

2 San Diego County storm is of 6-hour duration.

32

DESIGN STORM RAlNF' ALL MASS VERSUS CRITfCAL DURA TJON REL<t TIONSHIPS

The several counties that use a fixed design storm pattern are not

transferable between regions due to the differing rainfall intensity-duration

relationships; however, the San Bernardino storm pattern (excluding depth

area curves) is transferable due to its construction using local rain gauge data.

From Tables 12-15, the various storm patterns deliver differing return

frequencies of rainfall throughout the storm patterns, which can be compared

for the case of small catchments where depth-area effects can be neglected, and

with respect to the appropriate local rain gauge data. Table 16 provides a

comparison of the several counties 100-year design storm patterns, for

interior duration return frequencies, using respective county local rainfall

data.

Peak Storm Duration

30-minutes

I-hour

3-hour

6-hour

Table 16. Design Storm Interior Duration Return Frequencies 1 for lOO-year Storm Event

San Bernardino Clark Maricopa Riverside

100 19 60+ 12

100 29 100+ 30

100 50 100- 90

100 100 100 100

(mean)2 (100) (36.4) (96) (52.2)

Notes:

San Diego

45

50

80 100

(61.5)

] Based on respective County local rain gauge data, with depth-area effects neglected.

2 Mean computed for durations 3D-minutes to 3-hour, using linear interpolation.

33

HYDROLOGIC MODELS FOR THE ARID SOtJrHWEST UNITED STATES

From Table 16, a major source of difference in design runoff estimates

between county procedures can be seen; namely, the return frequency of

rainfall used in estimating runoff quantities. For example, for a criterion

variable that is most sensitive to a one-hour critical duration of rainfall, the

Clark County approach delivers a 29-year rainfall, whereas the San

Bernardino or Maricopa method delivers a 100-year rainfall. Included in

Table 16 are mean return frequency estimates of the 100-year design storm rainfalls for peak storm durations of 3D-minutes through 3-hours. Because

the majority of runoff impacts, for arid catchment areas less than 150 square

miles, are primarily influenced by storm durations of less than 3-hours (most

of the rainfall is contained in the peak 3-hours, and most catchment time-of

concentration values are less than 3-hours), the mean return frequency

estimates provides a comparison as to the design storm severity; for example,

in Table 16 the San Bernardino and Maricopa design storms are essentially a

lOG-year test whereas Clark County is about a 36-year test. This difference in

mean return frequencies is also exhibited in the other return frequency design storms (see Tables 12-15). Any comparisons between design storm method

runoff estimates will necessarily reflect the noted inherent differences in

design storm rainfall return frequencies; that is in Table 16, a 100-year return

frequency rainfall event will generally produce more runoff than a 36-year

return frequency rainfall event.

Another major source of difference in design runoff ~stimates is due to

the differing depth-area curves being used. From Figs. 7, each County uses

difference depth-area curves. Direct comparisons between curves are difficult

because depth-area relationships differ between regions just as the rainfall

intensity-duration relationships differ. Even the HYDRO-40 depth-area

curves differ significantly across the State of Arizona, and differ from the

depth-area curves used by Maricopa County.

When the effects of different design storm interior duration return

frequencies are coupled to the effects of different depth-area curves, the

resultant varies with respect to both catchment area and design storm critical

duration as shown in Figs. 8-11.

Tabulations of design storm rainfalls used to develop Figs. 8-11 can be found in the Appendix B.

34

F.FFECTIVE RAINFALL DETERMINATION

Chapter Five

EFFECTIVE RAINFALL DETERMINATION

5.1. Loss Rate Estimation Methods

All the Agency design storm methods first modify the design storm

rainfalls according to depth-area relationships, and then subtract (from the

adjusted rainfalls) rainfall losses, in order, to develop effective rainfall quantities. The effective rainfalls are then convoluted with the catchment

unit hydrograph. In this section, the several loss rate estimation techniques

are compared for the unit hydrograph applications. The several loss rate

methods are itemized in Table 17. Each county includes use of the SCS soil group designations in determining loss rate function parameter values. Use

of the SCS antecedent moisture condition, AMC II, or "average" conditions, is

generally used in each manual, although Riverside and San Bernardino

County methods have provisions to use AMC III in "high risk" situations,

such as dam design.

In order to compare los5 estimation techniques, a lOO-year return

frequency event 6-hour design storm rainfall (appropriate for Phoenix Metro area, Arizona) is considered of 3.3-inches for the peak 6-hour5 (3.6-inches for

the 24-hour duration). A SCS soil group B designation with Curve Number

CN=7S, and AMC II is assumed. For western desert urban areas, pervious

3S

\;YDROLOGIC MODELS FOR. THE ARID SOUTHWEST UNITED STATES

area natural desert landscaping have SCS curve numbers (e.g., Clark County

hydrology manual, 1990) of 63, 77, 85, 88, for SCS soil groups A, B, C, D,

respectively, with a mean curve number of about 78. Artificial desert

landscaping have a curve number of CN~96. Because rainfall losses decrease

as CN increases, the use of CN=75 in the example problem demonstrates a

reasonable comparison of loss rate techniques. Runoff comparisons are given

in Table 18, neglecting depth-area effects.

36


Table 17. Loss Rate Methods

Agency Loss rate. f(t)

San Bernardinol f(t) = min (h, y l(t)}

Maricopa2 'VS method #1: min {Ks (1 +T), I(t)}

f(t):

method #2:

t

I(t), for 1=0 I(s) ds $ STRTL

$2, for rt I(s) ds .> STRTL Js=O

Clark, San Diego SCS Curve-Number Technique3

Riverside4 f(t) = min ($3, kI(t»

COE5 (1988)

Notes:

1 $1 = phi index; as a function of SCS Curve Number.

(ii) Y = (1-yield); yield computed from SCS Curve Number based on 24-hour storm rainfall depth (or total storm).

(iii) I(t) = rainfall intensity, at time t > O.

2 (i) Either method may be used.

(iO Green-Ampt model, with Ks = hydraulic conductivity; \if = wetted soil capillary suction; e = soil moisture deficit; F = depth of infiltrated rainfall since storm time t = O.

(iii) STRTL = initial infiltration + surface retention loss.

3 See Hromadka et al (1987), or McCuen (1983).

4 Phi-Index, $3, is used for 3- and 6-hour storm patterns; k is a lowloss constant, usually 0.8 to 0.9.

5 Reconstituted phi index, (jl4i is 0.40 in/hr for dry catchment.

37

HYDROLOGIC MODELS FOR THE ARID SOlITHWEST UNITED STATES

Table 18. Example Problem Loss Rate Comparisons

Agency Constant loss or phi-index (in/hr) Total runoff Cinches)

San Bernardino 0.47 2.28 (2.25)1

Maricopa2 0.25 2.28

Clark3, San Dieg03,5 1.16

Notes:

1

2

3 4

5

6

7

Riverside4

COE (1988)6

0.30

0.40 (mean)7 (0.36)

2.33

1.99 0.87)

24-hour rainfall value used to estimate storm runoff yield. Value in parenthesis is total runoff volume, based on 6-hour rainfall.

Method 2 used. (Surface retention loss assumed to be 0.18 inches (average non-agricultural value); normal initial loss = 0.3 inches.)

Loss rates are per standard SCS methods Low-loss rate assumed as 0.85 (Le., mig-range of 8D- to 90-percent of rainfall). Low-loss rate of 0.05 in/hr neglected.

Reconstituted loss rate shown.

Mean based on six samples.

38


The ranges of constant loss rates, or phi-index values, for AMC II, are shown in Table 19.

Notes: 1

2

3 4

5

Table 19. Constant Loss Rate (Phi-Index) Values

Agency Loss (in/hr), cp

San Bernardino1 o to 1.0

Maricopa2 0.05 to 0.40

Clark3, San Dieg03

Riverside4 o to 0.84

COE (1988)5 0.40

Based on SCS curve number: for CN = 100, ;p = 0.0; CN = 80, ;p = 0.38; CN = 60, C\) = 0.69; CN = 40, 1\1 = 0.92.

Based on SCS soil group: for A, C\) = 0.4; B,4> = 0.25; C, C\) = 0.15; D, I\> = 0.05.

SCS method used. Based pm SCS curve number: for CN = 100, C\) = 0.0; eN = 80, C\) = 0.25; eN = 60, C\) = 0.47; eN = 40, <I> = 0.67.

Reconstituted value, for dry catchments in Las Vegas area.

5.2. Calibration of Rainfall-Runoff Models

The Clark County hydrology manual uses the SCS unit hydrograph

procedure, with a COE lag estimator, coupled to design storm rainfall

patterns, depth-area curves, and rainfall depth adjustments developed from

rainfall data alone. Similarly, the Maricopa hydrology manual is a

hybridization of a unit hydrograph procedure, loss rate estimator, and design

storm techniques. Riverside County and San Diego County also utilize a

mixture of methods.

39

HYDROLOGIC MODELS FOR THE ARlD SOUTHWEST UNITED STATES

The hybridization of rainfall-runoff modeling methods, where

modeling components are mixed together to form other models, oftentimes

do not produce a rainfall-runoff model that is properly integrated. For

example, the synthesis of a unit hydrograph for a catchment reflects the

solution of an inverse integral equation problem where, given several

rainfall-runoff events, transfer functions are evolved which, after averaging

and filtering, result in the basin mean unit hydrograph. The transfer

functions, however, reflect the use of a prescribed loss function.

Consequently, the calibrated unit hydrograph is calibrated with respect to the prescribed loss function used in the original reconstitution studies.

For example, SCS methods and COE methods, develop unit

hydrographs based upon a prescribed loss function. The resulting unit

hydrographs are then used with the same loss function for other study purposes. The San Bernardino County methods are also calibrated methods that reflect use of coupled loss function and unit hydrographs.

Riverside and San Bernardino Counties utilize COE synthesized S

graphs and lag estimation procedures based upon similar phi-index loss rate

procedures. Although the San Bernardino loss function includes a low loss

component, the overall technique is comparable to the phi-index approach

for arid rainfall conditions (due to the majority of runoff being generated by

the phi-index component). Similarly, the Maricopa County loss method #2 is

comparable to the phi-index approach. From Tables 17, 18, and 19, these four

effective rainfall estimators are similar.

Table 18 shows a significant difference in runoff estimates between

Clark and San Diego Counties on the one hand, and the remaining counties'

on the other hand. The differences in total runoff volume are primarily due

to the use of the phi-index versus the SCS cumulative loss rate technique.

Another factor related to Table 18 results is that the San Bernardino County

methods are focused towards achieving a higher level of confidence in runoff

estimates than the other methods considered; this issue of confidence levels

will be discussed in the next section.

40

CONFIDENCE INTERVAL ISSUES AND DESIGN STORM CALIBRATION

Chapter Six

CONFIDENCE INTERVAL ISSUES, AND DESIGN STORM

CALIBRATION

The San Bernardino County hydrology manual is based upon a

calibration of the design storm approach, using Los Angeles rainfall and

stream gauges, where rainfall-runoff data are substantial, and also a

calibration of the rainfall-runoff model using San Bernardino County valley

catchments (valley catchments were studied due to the sparsity of San

Bernardino desert rainfall-runoff data). The calibration of the design storm

was targeted towards achieving runoff estimates that are at the 8S-percent

confidence level (one-sided), based on an Agency policy decision regarding

flood protection goals. Runoff estimates at an 8S-percent confidence level are

higher in value than estimates at a lower confidence level.

For example, the expected value is at a 50-percent confidence level

where, with respect to the Los Angeles calibration rainfall-runoff data and the

criterion variable of peak flow rate, the 8S-percentile is about 1.45 times the

50-percent confidence level value. In comparison, a U.S.G.5. flood frequency

study for Pima County and the City of Tuscon, Arizona (1984) recommend

use of a confidence interval adjustment factor (applied to the 50-percent

confidence interval estimate) when ..... the possible losses due to underdesign

41

HYDROLOGIC MODELS FOR TIlE ARID SOlITHWEST UNITED STATES

of channels or hydraulic structures may be high, and the designer may want

better than a 50-percent chance that an estimated peak discharge is at least as

large as the true discharge for a specific recurrence interval." (p. 19 of U.S.G.S.

WRI 84-4142; see Appendix C). In the cited U.S.G.S. study, upper 8S-percent

confidence interval values had adjustment factors of about 1.4 to 1.8,

depending on the standard error (developed in regression equation synthesis).

San Diego County uses SCS loss rates, design storm, depth-area curves, and unit hydrograph techniques, but includes a COE lag estimator. Riverside

County uses COE unit hydrograph methods, a modification of SCS loss rate

procedures, and NOAA Altas II depth-area curves. Clark County uses SCS

unit hydrographs and loss rates, and COE lag estimator, design storms, and

associated depth-area curves. Maricopa County uses COE unit hydrograph

methods, design storm and depth-area curves, and a modification or direct

use of a Green-Ampt loss function.

An indication as to relative flood frequency confidence levels achieved

between county methods can be developed for those cases where loss rate

estimates are of comparable magnitude. Because the several unit hydrograph

techniques are similar, Figs. 8-11 provide an indication as to runoff estimate

magnitudes with respect to the San Bernardino County methods (which has a

transferable design storm construction), and hence all five hydrology manual

methodologies can be compared with respect to a common baseline method.

Table 20 provides a mean value of the Figs. 8-11 data integrated with

respect to catchment area. Only the 10-year return frequency data are shown

due to the similarity of the Figs. 8-11 data versus design storm return

frequency.

42

CONFIDENCE INTERVAL ISSUES AND DESIGN STORM CALIBRATION

Table 20. Comparison of Mean Design Storm Rainfall Mass versus Critical Duration 1, Integrated with Respect to Drainage Area2

Critical Duration

County 3D-minutes I-hour 3-hour

Maricopa 0.02 -0.20 0.08

Clark 0.41 0.24 0.37

Riverside -0.27 -0.47 -0.10

San Diego -0.16 -0.18 0.11

San Bernardino3 0.00 0.00 0.00

Notes: 1

2

3

Data from Figs. 8-11, for 100-year return frequency design storm.

Tabled values are integration of Figs. 8-11 data, using linear interpolation.

San Bernardino County design storm used as baseline condition in comparison to other county design storms, using respective county local rainfall data.

From Table 20, the relative magnitudes of runoff estimates, and hence

levels of confidence achieved, between the different county methods, can be

compared for the case of comparable loss rate magnitudes (during the

specified critical durations).

• for 3D-minute critical durations:

Riverside> San Diego> San Bernardino = Maricopa> Clark (14a)

• for 60-minute critical durations;

Riverside> San Diego"" Maricopa> San Bernardino> Clark (14b)

• for 3-hour critical durations:

Riverside> San Bernardino> MariCopa> San Diego> Clark (14c)

43

HYDROLOGIC MODELS FOR THE ARID SOlITHWEST UNITED STATES

It is noted that the results of Table 20 and Eqs. 14 reflect design storm

effects as posed for each county's rainfall data. That is, it would be

inappropriate to directly compare the Maricopa design storm to the Clark

County design storm (for example) due to different rainfall intensity-duration

characteristics between counties, among other factors. From Table 16, use of

the Maricopa design storm in Clark County wouLd result in considerably

different design storm interior duration return frequencies, and different

resulting runoff response. That is, the Maricopa County design storm

approach may be appropriate for Maricopa County catchments, and the Clark

County design storm approach may be appropriate for Clark County

catchments, but it may be inappropriate to exchange these two design storm

approaches. It is noted that in Table 16, the Clark County design storm

approach includes the rainfall adjustment to NOAA Atlas II rainfall

estimates.

44

STREAM GAUGE DATA REVlEW

Chapter Seven

STREAM GAUGE DATA REVIEW

7.1. Dissimilarity in Flood Frequency Tendencies: California and Arizona Desert Catchments

In the calibration of design storm rainfall-runoff models, two efforts

are involved:

1. Calibrate the integrated rainfall-runoff model components to represent

local storm events;

2. Calibrate the design storm and model parameters to represent local

flood frequency trends.

Task number 1 involves the collection of detailed rainfall-runoff data for

severe storm events similar in magnitude to the design storm event

anticipated. Task number 2 involves statistical return frequency data for

rainfall and runoff.

Because rainfall is an input into the design storm approach, calibration

efforts need to be focused towards meteorologically similar regions. The State

of Ariwna HYDRO-40 depth-area curves (and storm characteristics) indicate

that as a minimum, two distinct regions exist where depth-area curves differ;

namely, regions A & C versus B & D (see Figs. 12a, b). Because regions A & C

45

HYDROLOGIC MODELS FOR THE ARlD SOUTHWEST UNITED STATES

are closer to San Bernardino County, regions B & D are excluded from further consideration.

Similar to rainfall regions, flood frequency relationships can be used to

subdivide the State of Arizona into five regions where two regions (1 and 2)

may be conjectured to be applicable to San Bernardino (see Figs. 12a, c).

Region 1 is essentially north of the 34-degree latitude, and borders Clark

County, whereas Region 2 includes Maricopa County. U.S.G.S. flood

frequency regression equations for these two Arizona regions differ considerably, and are strict power functions of drainage area. The State of

California is also subdivided into flood frequency regions wherein arid

catchments are found in the Southern Lahontan-Colorado Desert region; this

region's U.S.G.S. flood frequency curves are also strict power functions of

drainage area. Table 21 compares these three sets of U.S.G.5. flood frequency

curves.

Table 21. U.5.G.5. Arid Region Flood Frequency Equations (peak flow rate)1

Return Frequency Arizona2 Arizona2 South Lahontan-Colorado Desert3

Notes: 1

2

3

4

(yrs) Region #1 Region #2

10 25 50

100

127 A0.566 352AO.475 150AO.530

252A°.532 586A°.487 410AO.630

393A°.51O 815AO.494 700AO.680

584Ao.490 1100AO.499 1080Ao.710

Expected Value Estimates Reference: U.S.G.S. ADOT-RS-lS-121 (1978)

Reference: U.5.G.5. Water-Resources Invest. 77-21 (1977)

A = area; square miles

46

STREAM GAUGE DATA REVlEW

From Table 21, there are significant differences in the regression

equation coefficients and exponents, although all three sets of equations are of

similar form. (It is noted that other flood frequency regions in Arizona and

California have U.S.G.S flood frequency equations that include additional

parameters). The considerable differences in flood frequency equations

indicate significant differences in hydrometeorological tendencies throughout

the arid southwest.

From Table 21, a 50-square mile catchment would have a lOO-year

return frequency peak flow rate estimate of 3,971 cis, 7,748 cis, and 17,366 cis,

using regionalized runoff data from northern Arizona, southern Arizona,

and southern California desert catchments, respectively. The ratio of QlOo/QlO estimates, for a 50-square mile catchment, is 3.42, 3.43, and 14.56 for

northern Arizona, southern Arizona, and southern California desert

catchments, respectively. Consequently, flood frequency tendencies differ

considerably in both magnitude and slope between the California and

Arizona U.S.C.S. regionalized flood frequency equations.

Because the northern and southern Arizona flood frequency data are

considered to be sufficiently different to warrant separate regionalization, it is

consistent that the southern California desert region flood frequency data are

sufficiently different from the Arizona regions to require separate

regionalization.

The differences in severe storm events, as noted (among other factors)

by different depth-area curves in Arizona per HYDRO-40 and differences in

various return frequency intensity-duration characteristics, and the

differences in flood frequency equations between Arizona and California as

noted in Table 21, indicate that Arizona and California desert hydrology

conditions may not be sufficiently hydrometeorologically similar to justify

regionalization over the combined regions.

47

HYDROLOGIC MODELS FOR THE ARID SOtTfHWEST UNITED STATES

7.2. Dissimilarity in Flood Frequency Tendencies: Riverside, San Diego, and San Bernardino Counties

From Table 21, the State of Arizona flood frequency relationships differ

significantly between the regions separated near the 34-degree latitude. From

Table lO, rainfall data magnitude and proportions differ significantly between

San Bernardino County desert gauges on the one hand, and San Diego and Riverside desert gauges on the other hand. Figures 12d shows that the arid

regions of San Bernardino, and the arid regions of Riverside and San Diego,

are in identifiably different meteorological regions known as the "northern desert" and "southern desert". These two regions are also approximately separated by the 34-degree latitude (that approximately divides the Arizona

flood frequency regions Nos. 1 and 2) and, consequently, there is significant

evidence to not regionalize San Bernardino with Riverside and San Diego data, based on both flood frequency tendencies (per contiguous State of

Arizona analysis) and rainfall characteristics. However, the U.S.G.S. South

Lahontan-Colorado Desert regression equations regionalize these three

counties together.

7.3. Comparison of San Bernardino County Hydrology Manual Peak Flow Estimates to USGS RegreSSion Equation Estimates

From USGS WRI 77-21 (1977), the South Lahontan-Colorado desert

catchment data set has mean characteristic and parameter values as follows: 2-ycar, 24-hour rainfall = 1.46 inches, area = 5.54 square miles; slope = 387 feet

per mile; watercourse length = 4.01 miles. An examination of San

Bernardino desert rainfall maps indicate that regions with such 2-year 24-

hour rainfalls generally have other associated rainfalls as follows: 2-year 6-

hour = 1.03 inches; 10-year I-hour = 1.03 inches; 100-year I-hour = 1.58 inches;

IOO-year 6-hour = 2.55 inches; 100-year 24-hour = 4.18 inches.

Using the COE lag equation with a basin factor of 0.040 (mean value per

COE, 1988), "Valley-Undeveloped" S-graph, mean slope = 387 ft/mile, and

mean "open-brush" loss rates, runoff peak flow rates can be computed and

compared to the USGS regreSSion estimates. Note that natural conditions are

being compared. Table 22 includes peak flow estimates from various applications of the San Bernardino design storm approach, estimates from the

48


USGS regression equations, and estimates of the 85-percent confidence limit

values using the USGS report WRI 84-4142 mean adjustment factor of 1.6.

Table 22. Comparison of San Bernardino County Hydrology Manual Peak Flow Estimates1

to USGS Regression Equation Estimates2

Catchment Area (square miles) 1 5 25 50 100

lO-year AMC I 656 1,611 2,792 3,178 3,512 lO-year AMC II 770 2,027 4,264 5,696 7,718 100-year AMC II 1,284 3,505 7,988 11,222 16,058 100-year AMC ill 1,420 4,103 10,523 15,804 24,191 USGS Q102 150 352 826 1,193 1,722

1.6Q103 240 563 1,322 1,908 2,756

USGS QtOO2 1,080 3,386 10,616 17,366 28,407

1.6Ql003 1,728 5,418 16,986 27,785 45,451

Notes:

150"

3,788

9,569 20,444 31,720 2,135

3,416

37,883 60,613

1 Mean open brush CN = 78 used; mean rainfall data, for San Bernardino desert regions with 2-year 24-hour rainfall of 1.46 inches used.

2 South Lahontan-Colorado Desert regression equations used; see Table 21.

3 1.6 factor follows from mean adjustment for 8S-percent confidence estimates, per USGS report WRI 84-4142.

4 Data set poorly represents such large catchments.

5 AMC CN adjustments follows SCS procedures.

From Table 22, the San Bernardino County lO-year AMC I design storm

produces peak flow estimates which, when integrated with respect to drainage

area, are approximately 62-percent larger than the USGS 10-year regression

equation estimates that are adjusted to 85-percent confidence. (It is noted that

use of the 1.6 factor for a ten-year return frequency event may be

49

HYDROLOGIC MODELS FOR THE ARID SOtrrnWEST UNITED STATES

conservative, given that 1.6 is also used to develop IOO-year as-percent confidence interval estimates.) However, the IOO-year AMC III design storm

application produces peak flow estimates which, when integrated with respect

to drainage area, are approximately 42-percent less than the USGS IOO-year

regression equation peak flow estimates that are adjusted to 8S-percent

confidence. Similarly, the IOO-year AMC II design storm underestimates the USGS 8S-percent confidence IOO-year estimates by 59-percent. From Table 22,

the IOO-year AMC III design storm produces runoff estimates which slightly underestimate the USGS regression equation 50-percent confidence interval peak flow estimates by about 6-percent. Figure 13 shows the several QlOO peak

flow estimates depicted in Table 22.

It is recalled that in the above "natural" conditions are being examined, as the USGS runoff data would reflect predominantly a history of natural

condition flows. Also, a mean rainfall is used (in the rainfall-runoff model estimates) that corresponds to the mean rainfall data associated to the USGS

stream gauge locations. Finally, it is recalled that mean catchment

topographic characteristics are used that correspond to the mean

characteristics associated to the USGS stream gauge sites.

The cited USGS report WRI 84-4142 (which applies to certain areas of

Arizona) uses an adjustment for uncertainty, based on the concept of

confidence level estimates, using the standard error, by

where

Q* = QOoz(plSL) (I 5)

Q* is the adjusted estimate of peak discharge at confidence level p;

Q is an unadjusted estimate from the regreSSion equation; SL is the standard error, in log units, and

z(p) is the standard normal deviate for cumulative probability p.

The USGS report WRI 84-4142 uses a cumulative normal distribution, and

develops z(p) values shown in Table 23.

50


Table 23. z(p) Values1 for Use in Equation (IS)

p, in percent 50% 60% 70% 80% 90%

z(p) 0.00 0.24 0.52 0.84 1.28

notes:

1 Reference: USGS report WRI 84-4142.

The USGS report WR! 77-21, for the State of California arid regions, has

a standard error, in log units, for a 100-year event, of 0.36, which exceeds the

values shown in the Arizona applications of USGS report WRI 84-4142. For SL = 0.36 and a 85-percent z(p) value from Table 23, Eq. (IS) can be used to

develop a 100-year event 85-percent confidence level adjustment factor of

about 2.35. This adjustment factor for California deserts is significantly higher

than the cited 1.6 mean adjustment factor for the referenced Arizona

catchment region.

7.4. Comparison of San Bernardino County 100-Year Peak Flow Rate Estimates, for Desert Master Plans of Drainage, to USGS Equations

Another comparison can be made by plotting Apple Valley and

Victorville Master Plan of Drainage (MPD) 100-year return frequency peak

flow rates versus the USGS equation estimates (Table 21), as shown in Figs. 14

and 15. In these two figures, the peak flow rates produced from

approximately 250 applications of the San Bernardino County IOO-year design

storm unit hydrograph approach are plotted versus the 100-year USGS

Regression equation and an estimate of the 85-percent confidence limit using

the 1.6 adjustment factor (from USGS report WRI 84-4142).

Figures 14 and 15 indicate that the Apple VaHey and Victorville Master Plans of Drainage Q100 peak flow rate estimates are approximately consistent

with the South Lahontan-Colorado Desert regression equati~n estimates (i.e.,

51

HYDROLOGIC MODELS FOR THE ARID SO\JfHWEST UNITED STATES

the 50-percent confidence level), even though the Master Plan QIOO estimates

correspond to developed desert catchment conditions, and the San

Bernardino County procedures attempt to provide runoff estimates at the 85-

percent confidence leveL

An examination of Figure B-IO of the San Bernardino County

Hydrology Manual, desert rainfall map for the I-hour IOO-year return

frequency duration reveals that the area-averaged rainfall for the entire

County desert region is about 1.34 inches; in comparison, the Apple Valley

and Victorville Master Plans of Drainage catchment mean rainfall (for the

corresponding duration and frequency) is about 1.15 inches. Thus, the Apple

Valley and Victorville local I-hour rainfalls, which would strongly influence

the subject peak flow estimates are about 14-percent less than the mean rainfall for the entire desert area of San Bernardino County.

In the USGS report WRI 77-21, the South Lahontan-Colorado Desert data has a mean 2-year 24-hour rainfall value of 1.45 inches. The associated 1-

hour IOO-year rainfall is about 1.58 inches (from an examination of San

Bernardino County rainfall maps), which implies that the subject Master Plan

rainfall is about 21-percent less than the above I.S8-inch value.

The subject two Master Plans have a mean phi-index loss rate (using AMC III) of 0.30-inch/hour. Assuming that the QlOo peak flow rates are

proportional to peak one-hour effective rainfalls (i.e., rainfall less losses), then the ratio of Q100 peak flow rate estimates due to the cited differences in

the Master Plan local rainfall versus the previously discussed two estimates of

regionally averaged rainfall (Le., in the San Bernardino County desert region,

and in the South Lahontan-Colorado Desert region) is approximately

(1.34 - 0.30) to ( 1.46 - 0.30) l.l5 - 0.30 Ll5 - 0.30

or, 1.22 to 1.36.

The above calculations suggest that when the subject two Master Plans

of Drainage Ql00 peak flow rates are approximately adjusted for the cited

differences in effective rainfall, the Q100 values increase in the range of 22 to

36-percent. This increase indicates that the San Bernardino County design

52


storm unit hydrograph procedures produce QlOO peak flow rates that are

approximately, on the average, at the 70 to 80-percent confidence level, with

respect to the USGS Regression Equations and confidence interval

adjustments shown in the plots of Figs. 14 and 15.

I! is recalled from the previous section that the 8S-percent confidence

level estimates of Figs. 13-15 are based on a mean adjustment factor of 1.6,

obtained from the State of Arizona USGS report WRI 84-4142. However, the State of California USGS report WRI 77-21 data can be used to analogously

develop an adjustment factor of 2.35 for the California arid areas.

53

HYDROLOGIC MODELS FOR TIlE ARlO SOUTHWEST UNITED STATES

7.5. Comparison of San Bernardino County 100-Year Runoff Volume Estimates, for Apple Valley Dry Lake. to R~ionalized Dry Lake Runoff Volume Estimates

Using COE reports from 1979 dry lake runoff volume estimates, the

following comparisons can be made:

Table 24. Total Storm Runoff Volumes

No. Condition Volume (AF) Elevation (ft)

1 50% Confidence1 5,360 2909

2 85% Confidence2 12,740 2912

3 sac Policy of AMC m3 20,370 2915

4 Expected Value4 5,340 2909 from COE reports (Le., 50% Confidence; see No. I above)

Notes:

1 Calibrated using 25-year rainfalls and AMC II.

2 Calibrated using IOO-year rainfall and AMC II.

3 lOO-year rainfall and AMC Ill.

4 June 1979 COE reports for Copper Dry Lake (p.17) and El Mirage Dry Lake (p. 19), averaging 53.4 AF per square mile for 100-year volumes.

5 It should be noted that lOO-year rainfall could be used to compute 50% confidence values, but the loss rates would need to be increased accordingly.

54


7.6. Steam Gauge Data Availability

The following references were used to develop a list of available stream

gauge data for use in developing rainfall-runoff relationships and/or

discharge frequency relationships in San Bernardino County:

• Regional Discharge Frequency Analysis, Hydrologic Documentation Feasibility Study, Las Vegas Wash and Tributaries, Clark County, NV,

U.S. Army Corps of Engineers, Los Angeles, CA, April 1988;

• Desert Unit Hydrograph Development, R.H. McCuen; and

• Transmittal dated August 2, 1991 from Dennis Marfice, U.S. Army

Corps of Engineers, Los Angeles, to Bob Corchero, San Bernardino County.

A list of 204 stream gauges were compiled from these references. This list is provided in Tables 01, 02 and D3, in Appendix D, for gauges located in the Slates of California, Arizona and Nevada, respectively.

A review of the data was done in order to eliminate those data sets

which did not meet current acceptable standards for use in developing flood frequency relationships, i.e., those having a record which contains greater

than 25-percent "zero" or "low" flow years or those containing less than ten

years of record. Of the 204 stream gauges, 55 were excluded for one or both of these reasons. These gauges are indicated in the tables of Appendix 0 by

comments "a" or "h".

Of the 149 remaining stream gauges, additional stream gauges were

excluded due to one of the following reasons:

• one was excluded because it was removed from consideration in the

1988 COE study due to the mountainous nature of the watershed and

significant snowpack (comment "b");

• two were excluded because they were removed from consideration in

the 1988 COE study due to upstream ponding or diversion (comment fie");

55

HYDROLOGIC MODELS FOR THE ARID SOUTHWESTc"NITED STATES

• two were excluded because they were removed from consideration in

the 1988 COE study due to the fact that the gauge data yielded low

standard deviations, not indicative of the study area (comment "d");

• one was excluded because there was no gauge record available in the data base used for this report (comment "e");

• sixty-three were excluded because they are located in NWS HYDRO-40 Region B or D, or in Arizona Flood Frequency Regions 3, 4 or 5, or both

(comments "f" and "g");

leaving a total of 80 stream gauges for consideration.

56


REFERENCES

1. Randerson, D., Meteorologist, National Weather Service, Nevada.

2. French, RH., Precipitation in Southern Nevada, ASCE Journal of

Hydraulic Engineering, Vol. 109, No.7, 1983.

3. U.S. Corps of Engineers, 1988, Feasibility Study, Clark County, Nevada,

Los Angeles District.

4. Miller, J.F., Frederick, RH., Tracey, R.J., 1973, NOAA Atlas II, Vol. IX,

California, NWS.

5. U.S. Army Corps of Engineers HEC Training Document No. 15,

Hydrologic Analysis of Ungauged Watersheds Using HEC-l, 1982.

6. Zehr, RM., Myers, V.A., 9184, Depth-Area Ratios in the Semi-Arid

Southwest United States, NWS HYDRO-40, NOAA.

7. McCuen, RH., Hydrologic Analysis and Design, Prentice Hall, 1989.

8. Hydrology Manuals for Counties of Riverside (1978), San Diego

(Addendum, 1985), San Bernardino (1986), Clark (1990), Maricopa

(1990), Kern (1992).

9. State of California, Department of Water Resources, Rainfall Depth

Duration-Frequency for California, Short Duration Data, revised June

1988.

10. Hromadka II, T.V., McCuen, RH., and Yen, e.e., 1987, Computational

Hydrology in Flood Control Design and Planning, Lighthouse

Publications.

11. Hromadka II, T.V., and Whitley, RI., 1989, Stochastic Integral

Equations in Rainfall-Runoff Modeling, Springer-Verlag.

12. U.S. Geological Survey, Water-Resources Investigations 77-21,

Magnitude and Frequency of Floods in California (1977).

57


13. U.S. Geological Survey, Water-Resources Investigations Report 84-

4142, Estimation of Magnitude and Frequency of Floods in Pima County, Arizona, With Comparisons of Alternative Methods (1984).

14. U.s. Geological Survey, AOOT-RS-1S-121, Methods for Estimating the

Magnitude and Frequency of Floods in Arizona (1978).

58

-*' 0.

~ W (!J a: ~ o ~ o w ~ ~

~ =» u. o IZ W o a: w a.. Z w (!J a: ~ o (j)

o

80

70

60

50

40

30

20 I A4 40 )

I .. I

'. (../

/ 'TI

,/

I' 1

80

I I

~ I

I I

•

100

----

---6-

--

120 140

TIME IN PERCENT OF LAG

LACDA URBAN (VALLEY} SAN BERNAfIDt.lO DEVELOPED) . COLtITY

ses TRIANGULAR

SCS CURylLiNEAR }• CLARK COUNTY AI'Il , SAN DEGO COLmY

PHOENIX \vALLEY }. MARICOPA

PHOENIX, MOUNTAIN , COLtITY

VALLEY l)I'IlEVELOPED }SANBEANARON) , COUNTY AI'I)

WHITEWATER R. (DESfRT) ~~¥~E

CALIBRATED GAMMA

160 180

'" I: Q

'" .• 100 ~ C. e Q

U .:: '" c. '" E Co-' , rI1

..( .... ~ 100

= ell .• ...

~ ~ w C!) a: ~ CJ CJ)

a w ~ ~

~ :J u. o fZ W CJ a: w Cl. z w (!J a::: ~ CJ II)

Ei

80

70

60

50

40 ---- LACDA.UABAN (VALLEY 1 SAN BEANAADNO DEVELOPED) ,COUNTY

. .. _ ...... __ .. -.. --"'-

SCS TRIANGULAR 'leLARK C~TY AM> SCS CURVILINEAR [SAN DEGO COlHrY

30 ------ ...... PHOENI)(,VALLEY } ~.f.rA -- CALIBRATED GAMMA

140 160 180 20 I ;.(?' .

40 ,0'" 80 100 120

TIME IN PERCENT OF LAG

til

= Q til ·c E. s Q U -= 0 ~ '" f ~

I 00

=5 .... t ~ ~

o

G> > ~ ~ (J)

> en J: > "tI m "tI -.j

> :0 > ~ m -l m :0 <0 n

i5 o

N

8

PEAK RATE FACTOR, K

Col o o

~ o o

01 o o

ClI o o

-.j o o

CZI o o

10 o o

Figure 2. Relationship Between the Peak Rate Factor and the Gamma Shape Parameter

61

·~.

NE I

•

o 50 100 150 MILES 1~~~~~ __ ~ti ____ ~i~1

o so 100 ISO lOO KILOMETERS

EXPLANATION

BounQa~ of flood-frequency region

Area

26.400 1li2 11.600 39.000 16.000 IS.000

50.000 1S8.000

Figure 3. Flood Frequency Regions of California

62

• 720

\-I

. ...

\ '~ \ DEATH : WALLEY'" , .. , : ~, . .

, " " ,

----~-\ .. ",7.?3

"""" . " 727 , i MOJAVE DESERT 7~ , ~~t---i-----~=-~--~==~~~~~~~--------~'4-~35' ___ -.:~~ __ J

• 119' • 755

, I ,

118'

nr

SL - CD •

733 •

116'

Figure 4. Location of 21 Stream Gauging Stations Used to Calibrate Peak Rate Factor, K

63

_I.--. 115'

• ;; ~I

, 'UB "'T ... · .... -~• SlIUIIIETUS .....

m.u i " ....

...... :JPl&II&TII!N

:;)all~ WoCi.1fl S:.t11A :IIST ... S"''' 'MTI ..... U~ID GoI&IIG

S'!'AtiOI ~T .. n. __ "'"'"'-'MIl nAn ..

.....- II OMI'aoo

Figure 5. Location of Stream Gauges Used to Verify Peak Rate Factor, K

64

:!!O

.; .... ,;::.1 ,u· .. ,- ,

IISID : C

--.~.--

~-J/' "" .H ..... .:~l"'OS

'0"\,.0'- "' .. ,.... i ... ,

"! ...

\ ,

2.50

2.25

2.00

1.75

en w I () 1.50 Z

Z 0

1.25 I-0« I-0..

() 1.00 w II: 0..

0.75

0.50

0.25

o

RETURN PERIOD (YEARS)

1001 U11 -- -1.1 12 1.3 1.4 1,5 2 -- 3 - 4 5 6 7 8 911 -- - -15 aJ 2; '" - 100 -

.... .~---_.

- .. -

.

......... .... ./ ./

.1 .

1.0 1)

- --_. .. __ .. --,. ." _. -- - .. - ---,.- .- . - - "-- . . --" -- --.. -- ...

--

•. .. - f---I- V t---

1"- '1-- 1- --

--

I#' '--' . ~ .. .'

V J<' l..- t--o. - ..-A f/

;. ~,

1." --4i" t..-' · LEGEND .10 ./ .' , 'o. .:;;. .... V

/' ~ ~ .' L :.o! ./ ·

./ L ~ • .'/ ,. .' ,~"-:;;".2

----<"'.

.-:;-.-9" .'"' 't'" · ;;;- ... I'". .. ./ -JI-;

0-----0 - f---

~ ..,. _---tI t--- . 0-',--:)

·

'" III III g; g; &I

PROBABILITY x 100

Figure 6a. I-Hour Precipitation Data, Las Vegas McCarran Airport 65

9}

;ro 3D 4ll o:D nIl -

- . . - - -.--1- - ._. -

.

.

RANDERSON

RANDERSON PLOTTING POSITIONS

DWR.19BB

DWR MEDIAN PLOTTING POSITIONS

NOAA ATLAS 2. 1973

CLARK COUNTY HYDROLOGY MANUAL. 1990

FRENCH, 1983

oo.s !Il6 009

1001 1.01 2.50

2.25

2.00

1.75 ~

CIJ w :r 0 1.50 Z -Z --0

1.25 i= < !: D-O 1.00 lJJ II: D-

0.75

L.-

O.fA, 1--1-.

0.25 I-

l= 0 .• ," • .0

RETURN PERIOD (YEARS)

1.1 12 13 14 15 2 3 4 5 6 7 8 911 15 '" :0 OIl m

. .

..

-o

17

.

,/ ~

1/ ~

_._. ... . .. . . ~: / i< . ..... V .... " _. -- -

1/

I'

.". 1/

.' 1/ --- . .

I' I-

7' .... :A 1-

'7' .-M: . .' l- LEGEND ..

-'-.. ... .. 4 ~ - ,. -

oo • <>---0 I· _---e

.

0--"--:)

1 -'" 8J -!D - -'" !5 -!II ..

PROBABILITY. 100

Figure 6b. 3·Hour Precipitation Data, Las Vegas McCarran Airport 66

all :Ill 4OO:ill fiX)

..

. - - .

..... ..

- ..

--

OWR, 1988

OWl! MEOIAN PLOTTING POSITION

NOAA ATLAS 2. 1913

CLARK COUNTY HYDROLOGY MANUAL. 1990

FRENCH. 1983

1 1 1 I I .

"'" -_. "'. 999

::I:

~ c z o ~ t::: D..

frl a: D..

!Z o c.

~ IZ W

~ W D..

1.0

0.' i \ I I •

0.8\"~ \ I \

: ~ . 1. ~ I I

07\ \, \ \~ ~~

0.6 \\ ~.\t.? .... ~ .~

\ 'I'! ---\ ~,~

0.5

0.4 ...... .

\ \"t '\~ \ ~ \\ \ "",

~ . 'C~ . ~",.. "'-

............ -''-'~ -----------

• (SYNTHESIZED) 0.3 -I-.....:=~==:.,------.,....-----.,....-

o 50 100 150

AREA (SQUARE MILES)

Figure 7A. Design Storm (30 min.) Depth Area Curves

67

1.0

0.9

O.S

0.7

0.6

0.5

0.4

STORM DATA CAW ANGELUS. CA - JlL 29. 1958 GARRET wtERy. CA - .u. 29. 1958 GLOBE. AZ - .u. 29. 1954 TEM'E. AZ - SEP 14.1969 WALNJT GlLCH. AZ - 100 YEAR

0.3 .l-..J!!!!!!!!!~---~~----.,...--o 50 100 150

AREA (SQUARE MILES)

Figure 7B. Design Storm (60 min.) Depth Area Curves

68

1.0

0.9

0.8

0.7

0.6

0.5

0.4

STORM DATA rucSON. AZ • SEP 24. 1943 BARSTOW. CA • JlL 29. 1958

."",

• (SYNTHESIZED) o. 3 +-.....;:.=.;.;.;.;.;.,;;;;;;;,;;;;;;;;;.:.,. ______ ,.... ____ ~_r_--

o 50 100 150

AREA (SQUARE MILES)

Figure 7C. Design Storm (3 hr.) Depth Area Curves

69

0.4 ....

STORM DATA QLEEN CREEK. AZ - AUG jg. 1Q54

NJIO. CA - SEP 24. 1939 WALMJT <U..CH. AZ - 100 YEAR

0.3+-----------~----------~------------r_~ o 50 100 150

AREA (SQUARE MILES)

Figure 7D. Design Storm (6 hr.) Depth Area Curves

70

0.6

0.5

0.4

O.3+-----------~~----------~------------~--· o 50 100 150

AREA (SQUARE MILES)

Figure 7E. Design Storm (24 hr.) Depth Area Curves

71

" c , 0 ()

III u> "-~ a Q. 0 v

" ~ I

j;-c ~ 0 ()

ai u> "-'

Phoenix Metro Area Adjusted Rainfall Comparison: 2 Year (Rainfalls adjusted using respective County depth-area curves)

San Bernardino vs. Maricopa County 0.3

W, 0.2

1V 0.1

0

-0.1

-0.2

-0.3

=

I ")(

~ I7J')[X ,\

~bX ~~~~~ ~ I'/.PV ~

~ """'" ~ V ~ ~ K t/. ~ ~ l2I... ~ ~ . ./ CL

-0.4 30 min. 60 min. 160 min.

Design Storm Peak Duration (minutes)

e 1 mil. ~ 5 mile ~ 10 mile ~ 25 mile !SS.150 mile rzzI150 mile

Graph Values (8.B. County-Maricopa)l8.B. County)

30 min. 80 min. 180 min. 1 Sq. Mi. 0.14 -O.Ot 0.03 5 Sq. Mi. 0.26 0.03 0.05

10 Sq. Mi. 0.23 -O.Ot 0.08 25 Sq. Mi. 0.18 -0.11 0.11 SO Sq. Mi. 0.09 -0.22 0.09

lSOSq. Mi. -0.04 -0.32 0.04

Figure 8A.

72

'" -c: :J 0 u <D ui "-..... 0 Q. 0 u

.t; 0

:::; I

" -c: :J 0 u IIi vi '-'


San Bernardino vs. Maricopa County

0.3 r--------------------------,

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4 L ______________________ -.J

30 min. 60 min. 180 min.

Design Storm Peck Duretion {minutes}

~ 1 mile ~ 5 mile ~ 10 mile ~ 25 mile tsS]SO mile [ZZI150 mile

Graph Values [(S.B. County-Maricopa)/S.B. County]

30 min. 60 min. 180 min. 1 Sq. MI. 0.07 0.03 0.03 5 Sq. Mi. 0.21 0.05 0.05

10 Sa. Mi. 0.19 0.01 0.Q7 25 Sq. MI. 0.11 -0.07 0.09 50 Sq. MI. 0.03 -0.18 0.09

150 Sq. Mi. -0.13 -0.29 0.05

Figure 8B.

73

>. -c: " 0

<.>

m <h "-~ 0 0-0 v ." 0 ::l! I >. -C

" 0 u

m <.ri '"



0.3

0.2 :0<'

~

0.1

0

-0.1

-0.2

-0.3

~~ ~ rYl0: X ~~IQ~~ x 0 ~

V ~ V/.~[\/

~ t\~ lX~V 'j

OC&~ ~~ ~~ ~ ~

-0.4 30 min. 60 min. 180 min.

Desic]n Slarm Peak Duralion (minul •• )

m 1 mile ~ 5 mile ~ 10 mile lSQ(I25 mile /SSl.50 mile 1Z21150 mile

GraphVaJues [(S.B. County-Maricopa)lS.B. County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.08 -0.02 0.01 SSO. Mi. 0.22 0.02 0.04

10 Sq. MI. 0.18 -0.02 0.07 2SSq. Mi. 0.12 -0.11 0.09 50 Sq. Mi. 0.03 -0.24 0.09

150 Sq. Mi. -0.10 -0.33 I 0.06

Figure 8e.

74

~ c , a

OJ

iii iii '-~ c a. 0 u 'r; 0

::lO I

'" ~ c , 0 ()

iii iii ~



0.3

"'" 0.2

0.1

a

-0.1

-0.2

~[\ I

Q ... t7. \I

~ -~ ~ :.2l\ ~ V, ry f\...

~ ~[~V. ~ t\~ t\v.

~~ ~v. ~~ ~ '/

~ r;; -0.3

30 min. 60 min. 180 min.

Design Storm Peak Duration (minute.)

Pm 1 mile ~ 5 mile ~ 10 mile 50(1 25 mile rss:I 50 mile CZZI' 50 mile

Graph Values [(S.B. County-Maricopa)/S.B. County/

30 min. BOrnin. 180 min. 1 Sq. Mi. 0.08 0.02 0.03 5 Sq. MI. 0.22 0.04 0.06

10 Sq. Mi. 0.18 -0.02 0.05 25 Sq. Mi. 0.13 -0.09 0.10 50 SQ. MI. 0.04 -0.20 0.10

150 Sq. Mi. -0.10 -0.29 0.06

Figure8D.

75

>, ~ C :J 0 u oj (J)

"-~

"" ~ 0

U I

.?:-c :J 0 0

iii 0-

McCarran Airpon Area Adjusted Rainfall Comparison: 2 Year (Rainfalls adjusted using respective County depth-area curves)

San Bernardino VS. Clark County

0.6 r------------------------,

0.5

o.~

0.3

0.2

0.1

o 30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISSJ 50 mile rzzI 150 milo

Graph Values (S.B. County-Clark)lS.B. County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.29 0.24 0.14 5 Sq. MI. 0.25 0.20 0.19

10 Sq. MI. 0.55 0.36 0.30 25 SQ. Mi. 0.46 0.29 0.32 50 Sq. MI. 0.37 0.23 0.39

150 Sq. Mi. 0.26 0.11 0.40

Figure 9A.

76

" ~ " ~ 0 (,)

iii Ul "-~

-" ~

0 (3 I

1> c ~ 0

(,)

iii iii ~

McCarran Airport Area Adjusted Rainfall Comparison: 10 Year (Rainfalls adjusted using respective County depth-area curves)


0.6,------------------------,

0.3

0.2

0.1

o 30 min. 60 min. 180 min.


e I mile ~ 5 mile ~ 10 mile 15Q(125 mile ISS] 50 mile rzzI ISO mile

Graph Values [(S.B. County-CIark)lS.B. County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.34 0.24 0.13 5 sa. Mi. 0.32 0.23 0.20

10 sa. Mi. 0.55 0.36 0.30 25 Sq. Mi. 0.50 0.29 0.33 50 Sq. Mi. 0.43 0.23 0.38

150 Sq. Mi. 0.27 0.14 0.38

Figure 9B.

77

>. ~

" ~ 0 0

ai (/)

"-~ -'" ~

0 (3 I >. ~

" " 0 0

ai iii ~


San Bernardino vs. Clark County

0.6 r--------------------------..,

0.5

0.4

0.3

0.2

0.1

o 30 min. 60 min. 180 min.

Design Storm Peak Duralion (minutes)

m 1 mile ~ 5 mile ~ 10 mile !5Q(] 25 mile rssJ 50 mile 1221150 mile

Graph Values (S.B. County-Clark)lS.B. County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.33 0.25 0.13 580. Mi. 0.29 0.21 0.17

10 Sq. Mi. 0.54 0.36 0.31 25 Sq. Mi. 0.49 0.30 0.35 50 Sq. MI. 0.41 0.23 0.37

150 Sq. Mi. 0.28 0.15 0.38

Figure 9C.

78

~ c , a ()

ai fJ)

"-~

...: ~

0 0 I ~ I: , 0 ()

iii iii ~



0.6,--------------------------,

0.5

0.4

0.3

0.2

0.1

30 min. 60 min. 180 min.


1m! 1 mile . ~ 5 mile. ~ 10 mile rsQ(l 25 mile ISS] 50 mile IZZI 150 mile

Graph Values [(5.B. County-CIark)l5.B. County)

30 min. 80 min. 180 min. 1 Sq. MI. 0.34 0.26 0.15 5 Sq. Mi. 0.30 0.21 0.20

10Sq. Mi. 0.55 0.37 0.32 25 Sq. Mi. 0.49 0.31 0.36 50 Sq. Mi. 0.44 0.24 0.38

150 Sq. Mi. 0.32 0.17 0.39

Figure 9D.

79

]: c ~ 0 u cri vi ...... ~

~

" 'E • > ;;: I ]: c ~ 0 u iii vi ~

Desen Hot Springs Area Adjusted Rainfall Comparison: 2 Year (Rainfalls adjusted using respective County depth-area curves)

San Bernardino vs. Riverside County 0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8 30 min. 60 min. 180 min.

Oesign Storm Peak Duration (minutes)

Pm!!! 1 mile ~ 5 mile ~ 10 mile !SQ(l 25 mile ISSJ 50 mile rz2I 150 mile

Graph Values (S.B.County-Riverside)/S.B.County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.34 0.21 0.00 580. Mi. 0.25 0.09 0.05

10Sq. Mi. 0.16 0.00 0.00 25 Sq. Mi. -0.06 -0.21 -0.06 5OSq. MI. -0.29 -0.47 -0.06

150 Sq. Mi. -0.62 -0.69 -0.21

Figure lOA.

80

>. -c :> 0 0 ai Ul "'-~ " :;! ~

" I> > a: I ,., -c: :> 0

0 ai ui ~

Desert Hot Springs Area Adjusted Rainfall Comparison: 10 Year (Rainfalls adjusted using respective County depth-area curves)

San Bernardino vs. Riverside County

0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8 .30 min. 60 min. 180 min .


elmile ~5mile ~ 10 mile ~ 25 mile iSS] SO mile rzzi150 mile

Graph Values [(S.B.County-Aiverside)lS.B.County]

30 min. 60 min. 180 min. 1 Sq. Mi. 0.36 0.20 0.00 5 Sa. Mi. 0.27 0.09 0.00

10sa. MI. 0.19 -0.02 0.00 25 Sa. Mi. -0.02 -0.25 -0.02 so-sa. Mi. -0.26 -0.49 -0.08

150 Sq. Mi. -0.59 -0.74 -0.15

Figure lOB.

81

,.. ~ c: ~ 0

0 a! (J)

"-~ " ." .;; .. " ti I

? " 0 q m <Ii ~



0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8 30 min. 60 min. 180 min.


m'mile ~ Smile ~ 10 mile ~ 25 mile ISS] 50 mile rz2I, 50 mile

Graph Values (S.B.County-Riverside)/S.B.County)

SO min. 60 min. 180 min. 1!1q. Mi. 0.S6 0.20 0.02 5 Sq. Mi. 0.27 0.10 0.02

10 Sq. Mi. 0.18 -0.01 0.00 25 Sq. Mi. -0.02 -0.23 -0.04 SO Sq. Mi. -0.27 -0.49 -0.08

1SOSq. Mi. -0.57 -0.72 -0.16

Figure We.

82

'" ~ c ~ 0 ()

al I/)

"-~

" " .;;; ~

" > ;;: I >. ;: ~ 0 0 ai ch ~

Desen Hot Springs Area Adjusted Rainfall Comparison: 100 Year (Rainfalls adjusted using respectiVe County depth-area curves)


0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.6 30 min. 60 min. 180 min.


e 1 mile ~ 5 mile ~ 10 mile ISQ(] 25 mile !SS:I 50 mile rzzl 150 mile

Graph Values [(S.B.County-RiversideVS.B.County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.36 0.20 0.03 5 Sq. Mi. 0.28 0.10 0.01

10 Sq. Mi. 0.18 -0.02 0.00 25 Sq. MI. -0.01 -0.23 -0.03 50 Sq. Mi. -0.25 -0.47 -0.09

150 Sq. Mi. -0.57 -0.72 -0.17

Figure lOD.

83

.i!> c ~ 0 0 c:i V> "-~ >. C ~ 0

0 ci vi I >. -c ~ 0 0 IIi ui ~

Crawford Ranch Area Adjusted Rainfall Comparison: 2 Year (Rainfalls adjusted using respective County depth-area curves)

San Bernardino vs. San Diego County 0.2,-----------------------.,

0.1

0

-0.1

-0.2

-0.3 L ____________________ ----I

30 min. 60 min. 180 min.


~ 1 mile ~ 5 mil. ~ 10 mile ~ 25 mil. ISS] 50 mil. iZZl150 mile

Graph Values

[(S.B.County-S.D.County)/S.B.County] 30 min. SO min. 180 min.

1 Sq. Mi. 0.13 0.10 0.00 5 Sq. Mi. 0.02 -0.03 0.00

10 Sq. Mi. -0.13 -0.17 -0.05 25 Sq. Mi. -0.21 -0.21 0.17 50 Sq. Mi. -0.27 -0.20 0.19

150 Sq. Mi. N/A N/A N/A

Figure llA.

84

>. ~

C , 0

Q

ai [J)

"-~

>-'E , 0

Q

q [J)

I >. -c , 0

Q

ai vi ~


San Bernardino VS. San Diego County 0.2r-----------------------------------------------,

0.1

0

-0.1

-0.2

-0.3

-0.4 L-______________________________________ -'

30 min. 60 min. 180 min.


e 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISS] 50 mile r22l150 mile

Graph Values [(S.B.County-5.D.County)/S.B.County]

30 min. 60 min. 180 min. 1 Sq. Mi. 0.13 0.10 0.05 5 Sq. Mi. 0.01 -0.01 0.02

10 SQ. Mi. -0.13 -0.16 0.00 25 Sq. Mi. -0.22 -0.21 0.10 50 Sq. Mi. -0.29 -0.27 0.19

150 SQ. Mi. N/A N/A N/A

Figure lIB.

85

,., ~

0 ~ 0 q <D en " ~ ,., ~

0 ~ 0 ()

ci vi I

'" -0

" 0 ()

ai en ~


San Bernardino vs. San Diego County

0.3

0.2

0.1

0

-0.1

-0.2

~ ~ - l\:

~ ~ L ~ ~ ~

r,;,x ~~ ~ ~ ~ ) ~ :\ ;X

~ ~ ~ tr&l)l

~ ~ :x

~ ~ ~ R$ ~

IU.!

~ ~ ~ ~ ~

-0.3 30 min. 60 min. 180 min.


e 1 mile ~ 5 mile ~ 10 mile ~ 25 mil. ISS] 56 mil. !ZZI150 mile

Graph Values ((S.B.County-S.D.County)/S.B.County)


10 SQ. MI. -0.12 -0.16 0.00 25 Sq. Mi. -0.20 -0.20 0.' , 51) Sq. MI. -0.25 -0.23 0.20

150 Sq. Mi. NtA NtA NlA

Figure lIe.

86

>. -c , 0 {)

iii If)

...... >: -c , 0 ~ 0 <Ii I ~ c , 0 ()

aj If) ~


San Bernardino VS. San Diego County

0.3 ,--------------------------,

0.2

0.1

0

-0.1

-0.2

-0.3 L-______________________ --'

30 min. 60 min. 180 min.


~ 1 mile ~ 5 mile r?@ 10 mile ISO?l 25 mile ~ 50 mile rz2] 150 mile

Graph Values [(S.B.County-S.D.CountyVS.B.CountyJ


10 Sq. Mi. -0.12 -0.16 0.00 25 Sq. MI. -0.19 -0.21 0.12 50 SQ. Mi. -0.26 -0.24 0.21


Figure lID.

87

gg

122' 0' , 110' 3B' - 12 118' 116' 114' 112 38'

I I "I I I

"'i ~.

~ .... ~ >-'"t .' Q.

~

as. Q

= 00 g >iii ~

'" .-. 00 =~ Co ~ Co --

122' ~V'l ./ I "- SAN r= I 36'

S.k ..... field • APACHE

KERN

34' / '!tG~II1="1 ~£=j II 134' %yP~r,I; ?;/; r . _

120'

Santa AnaORANGE

118' PACIFIC OCEAN

32'-

fMPERIAL

. I I · ... ~/~~ ctCIiSE I 32' ~

116' 114'

MEXICO 110'

00 .."

122' 0' , 110' 38'- 12 lIS' 116' 114' 112 3S'

I '\:1 I I

36'--/ 'V "~1i'; ~ ~~ l.. "_ 122'

"'"l cia-= ~ .... N

~

'r" 1- 36' APACHE

B

~ 34' ~ ~ I ~ it It!' 1- 34' ~~dD~ 0'. kV

A GILA 1:1 I Santa An. ~ I ORANGE o J.. o ~

~ ~ ., <0 = '"

120'

PACIFIC OCEAN

A - 0 : HYDRO-40 REGIONS

lIS'

32' -~[t--+ ___ -+I~-"':::~~'~Z~%:~ ~I~, '/: . /') ctCIiSE , 32' ~,., . "i

116' 114'

MEXICO 110'

" 0

122· 120· . 110. 38·- 118· 116· 1,4· 112 38'

I 1 ""I I I

">j -. IJQ = ~ .... N (1 ~ -Q Q ~

">j "'l ~

.,Q

= ~ = n '<

~ IJQ _. Q = D) -_. E'l ... -. Q = :::t' ~

IJQ _. Q

= en

122·

!

~,//,'//m'h;l~~~ 0· I \.... I 4 I 1- 36 APACHE

34· I ?'Grn~~'S, ~ ,/ , , . .... A-"d II I 34

120·

PACIFIC OCEAN

32' \: I - I ~""~;~Im ~: C,CIISE I 3, t . /~I

ARIZONA FLOOD FREQUENCY REGIONS 1 - NORTHWEST PLATEAU

116' 114·

MEXICO SANTA 112· CRUZ

CALIFORNIA FLOOD FREQUENCY REGIONS 2 - SOUTHWEST DESERT AREA 3 - CENTRAL MOUNTAIN AREA 4 - NORTHEAST PLATEAU AREA 5 - SOUTHEAST MOUNTAIN AREA

C - SIERRA CC - CENTRAL COAST SC - SOUTH COAST

SL-CD - SOUTH LAHONTAN ~ COLORADO DESERT

110·

"" -

122' 120' , 110' 3S' 118' 116' 114' 112 38'

I I l'\J I I

, '/ / I \ \ I tj~JA)E~''l»/!.2il~ (" I- 36' 36'

I

122' AMelE

""l -. IIQ

= ~ ..... N

~

34' I 'C~1'U~ J 134 '1., "/ .%}.,..'?( ,

(j --, 9 ~

~

~ :I ~ 120'

PACIFIC OCEAN

CLIMATE ZONES * 7 - NORTHERN DESERTS 8 - SOUTHERN DESERTS

liB'

32' :,/////,;:-'/~ .,/ '.W~"«'/! '/.-"~"//;;' -/ .~/. %/. .• 32

\l6' 114 '

MEXICO SANTA 112' CRUZ 110'

* REFERENCE: WeatherData, Inc.

o .... _- ... -... -..... -. __ ........... -... _--....... -..... , ........... , 0

<'I

. ., .. " ................................... ~ ...... "........ ,

o , ....... <1 ....... ···0, ......... ,................ I'"

\ -:\ 11\

................... ~\

~~ en ~ ....\\<1..0 ......................... . ~~\

.- -.. ,--.... : ... _- .. ,.-.. -.............. -;. .... --.......... -....... -.-.~ ... .

c;\ ~\ ~\ .

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-

-

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o II)

..... , ...................... ,....... . .......... ; ...................... ;......................,. , ..... .. :k .......... ~ \

0 0 0 0 0 0 0 0 <> 0 <> <> <> <> <> CI 0 CI 0 0 0 CI 0 0 0 ci II) on .... <'> (II -

C/100 (cis)

Figure 13. Comparison of Mean Natural Condition Peak Flow Rate Estimates Between San Bernardino County Methods and USGS

Regression Equations

92

o z w

~

= = ,Q 0 ::= ;: -0 .="'0 o c:: u 0 u (ij-~ ctI :::l .... _ :::l ctI= ctI = c:: = ctI ctI Q) CD E E --00 :E:E « CICI c:: c:: 'en 'en :::l ::J 00 00 ,.... T"-

OO

<]0

o o ......... -· .. ·T.·.··· ...... ··· .... ;.·.··· .... ··.··· .. \····T .. ·········· .. ··-·····T··· .. · .. ···-········ .. ···:····· ................. y- ... -........-................ --.... -........................ ~

\!. N

. {j. 0

......................... : .................... _ ............ _. . ......... ~----.----...... : ............. --........................................................................ "......... .. --....". ;

... _ ....... -.--~ ........ -.-........ -~ .... -........ -....... -.. ~ .. -=~.--... :~ ..... --.----.-...... ~ .. -... --.......... -.... : ....... -...... --................................. ~-........... -.... _ ... -g . : ~~. i .. ~

, ~, ; , ;

... _ ....... _._~ ...... _ .... _ ........ l ............ _ ......... %.\ ................ , ............................ 7 .......... -................ -............................................ -............ ! , ~~;. -: Co .ce.:i.··

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~ g~ C!,~ o -l:i

Il:

0'" o o CD

<:> o o CD

o o o

• f·· .. ·--···--.. ------·--·····"·····················-········--·· .. ·-·······_·····r··············-······ .. T··· .. ······· ....... _ .... t ... _-...............: • :.~.\ .

i : .: ~. :; 0 : .. 0

. ··············_······_-'!"····················_-····t··-...... --.... - ..... +-...... - ....... -....... ~ ...... --.... ·· .. · __ ···t···_·····_··············t-············· __ ···.•.. . .......•. ;: • ..;; .......... ;............. Q

1 i j ••• ~ .. ~. N 1 !:. , : :!.. • j ~ i··,," ,

;

i ______ ~------~------~----~ __ ----~------~------~ __ --~------~O 00000 0 000 00000 000 000 a C Q C a ~ • N 0 CD CD • N ~ 'W""" 't""" ....

0100 (e's)

Figure 14. Apple Valley Master Plan of Drainage (Recommended Alternative 1)

Q100 (Using AMC III) vs. USGS Regression Equations (1977)

93

.. .. .

0 CI CI C' ...

0 0 0 .. ...

0 0 0 CI CI CI 0 CI CI 0:> 0 0 0 0 0

N 0 rti rti .; ... .. Q 100 (#$)

Figure 15. Victorville Master Plan of Drainage (Recommended Alternative 2)

QI00 (Using AMC III) vs. USGS Regression Equations (1977)

94

0 0 0 0 N

0 0 0 CC -0 0 0 CC .-

S 0 .. -0 0 q N

-~ ~

g~ ~~ 0

-~ It: "I:

0 0 0 CD

0 0 0

C

0 0 0 .. 0 0 0

CII

0 CI 0 0 0

N

APPENDIX A

RAINFALL DATA

95

APPENDIX A

DESERT UNIT HYDROGRAPH DEVELOPMENT

The conventional approach to unit hydrograph development is to

analyze measured rainfall hyetographs and runoff hydrographs using the following procedure:

1. Separate baseflow from total runoff to get the distribution of direct runoff.

2. Compute the volume of direct runoff.

3. Eliminate initial abstraction losses.

4. Assume a loss function to separate the remaining distribution of

rainfall. into losses and rainfall excess such that the volume of rainfall

excess equals the volume of direct runoff.

5. Convert the distribution of direct runoff to a i-inch unit hydrograph (UH).

6. Set the unit-duration of the UH equal to the duration of rainfall excess.

A number of important assumptions are made with this procedure: 0) a

basetlow model must be selected; (2) an initial abstraction model must be

selected; and (3) a loss function must be selected. Each of these components

will have a significant effect on the shape and magnitude of the UH.

Using the procedure to develop unit hydrographs requires data for

many storms for each watershed and data from many watersheds to

regionalize the UH. Typically, the UH's for storms will be quite different in

shape and magnitude. Averaging of the storm-event unit hydrographs

usually yields a reasonable UH but it may not produce a UH that will

accurately reproduce the measured runoff for each storm.

96

Where data are available, the above procedure is the most frequently

used approach. However, sufficient data are rarely available except at

hydrologic research stations. Very little hyetograph/hydrograph data are

available in most localities. This is especially true in desert environments.

Thus, the procedure described above cannot be used to develop unit

hydrographs for desert regions because of the absence of hyetograph/

hydrograph data.

Peak discharge data are more readily available, including for desert

regions. An alternative approach that can be used to fit a unit hydrograph

and that makes use of peak discharge data is as follows:

1. Assume a known dimensionless functional form to represent the

distribution of the unit hydrograph.

2. To scale the dimensionless UH, use the peak discharge records to

compute a peak rate factor (K), which is typically defined by

KAQ qp=

tp (1)

where qp is the peak discharge (cfs); A is the drainage area (square miles); Q is the runoff depth (inches); and tp is the time-to-peak

(hours).

Since unit hydrographs usually have a shape that closely follows a gamma

probability function, the gamma pdf can be selected as the dimensionless UH.

The time axis can be set by the time-to-peak and the ordinates can be

dimensionalized with Eq. 1. For a given drainage area, the time-to-peak can

be computed using the time of concentration. For a unit hydrograph, Q

equals one-inch. If a mean value of the peak rate factor K can be computed

for a region, then the regionalized unit hydrograph should provide accurate

designs in the region.

The gamma distribution for the random variable tis:

(2)

97

in which c and b are the shape and scale parameters, respectively, and g(c) is

the gamma function with argument c, which is given by

g(c) : ce c< (21t )0.5 [1.0 + _1_ + _1 _ _ 139 _ 571 1 c 12c 2882 518402 2488320c4 J (3)

At the peak of the function, with the magnitude denoted as qp and the time

denoted as tp, the following relationship holds:

t<-l e-1p/b q -....[p_-

P - bC g(c) (4)

It is know that the mode of the gamma distribution occurs for the value of t

where

(5)

Substituting Eq. 5 into Eq. 4 yields a relationship between the magnitude of the mode, qp, and the shape and scale parameters:

(c - l)c-l e1-c

qp: bg(c)

Substituting Eq. 5 into Eq. 1, and equating the result of Eq. 6 yields:

(c _l)C e1-c KAQ: g(c)

For qp [ : 1 cfs, tp [ : 1 hours, A [ : 1 sq. mi., and Q [ : 1 inches, Eq. 7 becomes

K = 645.3 (c - l)C e1-c g(c)

(6)

(7)

(8)

Equation 8 indicates that the peak rate factor of a unit hydrograph is directly

and independently related to the shape parameter of the gamma distribution.

Once K is set, and a function is assumed for the unit hydrograph, then the UH can be computed with A, Q, and tp for any watershed. It appears from data

analysis, that the peak rate factor is a regional characteristic, with small values

for high-storage watersheds such as in coastal areas and large values for low

storage watersheds such as those in mountainous areas.

98

Table 1 gives values for K and c based on Eq. 8. The following thirdorder polynomial can be used to compute c for a given value of K

c = 1.006 + 1.104(10)-3 *K + 1.267(10)-5 *K2 + 1.646(10)-9 *K3 (9)

Figure 1 shows the relationship between c and K.

Since there is no hyetograph/hydrograph data available for the desert

areas of southern California, the peak-rate-factor approach is used. Twenty

one watersheds have sufficient information available for the South Lahontan-Colorado desert region (see Figure 2). The data of Table 2 are from

the USGS report (Magnitude and Frequency of Floods in California). The

location of the 21 gauging stations is shown in Figure 3. Using the 100-year

LP3 peak discharges, peak rate factors were computed. The average peak rate factor is 444. This is slightly lower than the value of 484 used for the SCS

standard unit hydrograph, with 284 used in coastal areas of Maryland.

To test the peak rate factor of 444, 83 watersheds (see Figure 4 and Table 3) in the desert area of Pima County, Arizona, were used to compute an

average peak rate factor. Based on data from e 83 watersheds, the average was

436, which yields a UH that is identical to the UH developed from the 21

watersheds from the Southern California region.

Based on the desert-area computations of peak rate factors, a value of

440 is recommended. The dimensionless unit hydrograph is shown in Figure

5. The ordinates are given in Table 4. To dimensionalize the UH, the drainage area (sq. mL), runoff depth (inches), and time to peak (hours) are

required. These values are used with Eq. 1 to compute the peak discharge, which scales the ordinates. The time axis is scaled using the time to peak.

99

Table AI. DWR Precipation Gauges / San Bernardino County

lQO.7Year

Victor- Iron Parker Amboy! Baker2 Barstow3 Daggett4 NeedlesS ville6 Mountain7 Res8 Average9

5-minute .52 .21 .18 .31 .53 .19 .50 .58 AD

3O-minute 1.14 .63 .50 .75 1.28 .55 1.29 1.31 .97

I-hour 1.32 .95 .59 .89 1.51 .72 1.44 1.60 1.18

3-hour 1.62 1.27 .72 1.30 2.10 1.25 1.93 2.19 1.65

6-hour 1.83 1.42 .85 1.57 2.47 1.72 2.18 2.55 1.95

24-OOur 2.12 1.64 .99 2.00 3.10 2.73 2.81 3.48 2.56

lO~Ye.ar

Victor- Iron Parker Amboy! Baker2 Barstow3 Daggett4 NeedlesS ville6 Mountain7 Res8 Average9

5-minute .29 .14 .12 .20 .29 .13 .27 .32 .23

3D-minute .63 Al .33 .49 .71 .36 .71 .73 .57

I-hour .73 .62 .38 .58 .84 .47 .80 .88 .69

3-hour .90 .83 .47 .85 1.17 .81 1.07 1.21 .97

6-hour 1.01 .92 .56 1.02 1.37 1.12 1.21 1.41 1.15

24-hour 1.18 1.07 .65 1.30 1.72 1.78 1.55 1.93 1.51

1 DWR Gauge No. 176, E1ev. = 635 ft, n = 25-27 yrs.

2 DWR Gauge No. 436, Elev. = 940 ft, n = 19-31 yrs.


4 DWR Gauge No. 2255, Elev. = 1975 ft n = 23-44 yrs.

5 DWR Gauge No. 6115, Elev. = 480 ft, n = 23-42 yr •.




9 Weighted average based on length of record for each duration.

100

Table A2. DWR Precipation Gauges / Riverside County

lQO.:Ye.ar.

Desert Hot Springs 1 Cabazon2 Blythe3 Therma14

5-minute .47 .43 .44 .36

30-minute 1.25 1.10 1.10 .74

I-hour 1.59 1.73 1.53 1.12

3-hour 2.36 3.51 2.20 1.82

6-hour 3.13 4.97 2.54 2.38

24-hour 4.45 7.71 3.43 3.21

lQ::Y.ear.

Desert Hot Springs1 Cabazon2 Blythe3 Therma14

5-minute .26 .25 .24 .20

30-minute .69 .65 .61 .41

I-hour .88 1.02 .85 .62

3-hour 1.31 2.06 1.22 1.01

6-hour 1.74 2.92 1.41 1.32

24-hour 2.47 4.53 1.90 1.78


2 DWR Gauge No. 1250, Elev. = 1820 ft, n = 11 yrs.


4 DWR Gauge No. 8892, Elev. = -120 ft, n = 21-44 yrs.

AverageS

.43 1.()6

1.42

2.22

2.82

3.98

AverageS

.24

.59

.79

1.24

1.58

2.23


101

Table A3. DWR Precipation Gauges / San Diego and Imperial Counties

lQO.:Y~.a.r.

Crawfordl El CentroZ Yuma3 Ranch (SOC) (Imperial Co.) (AZ)

5-minute .50 .34 .55 30-minute 1.29 1.05 1.52 I-hour 1.62 1.48 1.75 3-hour 2.39 2.09 2.36 6-hour 3.02 2.49 2.42 24-hour 4.61 3.10 3.28

lQ~Y.f.ar

Crawford l EI Centr02 Yuma3 Ranch (SDC) (Imperial Co.) (AZ)

5-minute 0.28 .19 .30

30-minute 0.71 .58 .84

I-hour 0.89 .82 .97

3-hour 1.32 1.16 1.31

6-hour 1.68 1.38 1.34

24-hour 2.55 1.72 1.82





102

Average4

.47

1.32 1.61

2.27

2.63

3.62

Average4

.26

.72

.89

1.26

1.46

2.01

1 i • t • II)

~ I II) •

~

., I

103

I II 1\ I

I

• 1

lP • I

J

Table AI. DWR Precipation Gauges / San Bernardino County

lOQ-Year

Victor- Iron Parker Amboyl Bakerl Barstow3 Daggett4 NeedlesS ville6 Mountain' R£s8 Average'"

S-minute .52 .21 .18 .31 .53 .19 .50 .58 .40

3D-minute 1.14 .63 .50 .75 1.28 .55 1.29 1.31 .97

I-hour 1.32 .95 .59 .89 1.51 .72 1.44 1.60 1.18

3-hour 1.62 1.27 .72 1.30 2.10 1.25 1.93 2.19 1.65

6-hour 1.83 1.42 .85 1.57 2.47 1.72 2.18 2.55 1.95

24-hour 2.12 1.64 .99 2.00 3.10 2.73 2.81 3.48 2.56

lQ-Y~iir

Viclor- Iron Parker Amboyl Baker2 Barstowl Daggelt4 NeedlesS ville6 Mountain' Res8 Averar,<!

5-minule .29 .14 .12 .20 .29 .13 .27 .32 .23

3O-minute .63 .41 .33 .49 .71 .36 .71 .73 .57

I-hour .73 .62 .38 .58 .84 .47 .80 .88 .69

3-hour .90 .83 .47 .85 1.17 .81 1.07 1.21 .97

6-hour 1.01 .92 .56 1.02 1.37 1.12 1.21 1.41 1.15

24-hour 1.18 1.07 .65 1.30 1.72 1.78 1.55 1.93 1.51



3 DWRGauge No. 519, Elev. = 2142 ft,n = 6-10 yrs.

4 DWR Gauge No. 2255, Elev. = 1975 ft, n = 23-44 yn.

5 DWRGauge No. 6115, Elev. = 480 ft,n = 23-42 yn.

6 DWR Gauge No. 9325, £lev. = 2859 ft, n = 24-44 yn.


8 DWR Gauge No. 6699, Elev. = 738 fl, n = 23-44 yrs.

9 Weighted average based on 1ength of record for each duration.

104

Table A2. DWR Precipation Gauges / Riverside County

lQQ-Ygar

Desert Hot Springsl Cabazon2 Blythe3 Therma14

5-minute .47 .43 .44 .36

30-minute 1.25 1.10 1.10 .74 I-hour 1.59 1.73 1.53 1.12 3-hour 2.36 3.51 2.20 1.82

6-hour 3.13 4.97 2.54 2.38

24-hour 4.45 7.71 3.43 3.21

lQ-Xlililr

Desert Hot Springsl Cabazon2 Blythe3 Thermal4

5-minute .26 .25 .24 .20

30-minute .69 .65 .61 .41

I-hour .88 1.02 .85 .62

3-hour 1.31 2.06 1.22 1.01

6-hour 1.74 2.92 1.41 1.32

24-hour 2.47 4.53 1.90 1.78

1 DWR Gauge No. 2405, Elev. = 1080 ft, n = 29-37 yrs. 2 DWR Gauge No. 1250, Elev. = 1820 ft, n = 11 yrs. 3 DWR Gauge No. 925, Elev. = 390 ft, n = 27-46 yrs. 4 DWR Gauge No. 8892, Elev. = -120 ft, n = 21-44 yrs.

AverageS

.43 1.06 1.42 2.22 2.82 3.98

AverageS

.24

.59

.79

1.24

1.58 2.23


105

Table A3. DWR Predpation Gauges / San Diego and Imperial Counties

lOO-Year

Crawford1 EICentr02 Yuma3 Ranch (SOC) (Imperial Co.) (AZ)

5-minute .50 .34 .55 30-minute 1.29 1.05 1.52 I-hour 1.62 1.48 1.75 3-hour 239 2.09 2.36 6-hour 3.02 2.49 2.42 24-hour 4.61 3.10 3.28

lO-Year

Crawford1 ElCentr02 Yuma3 Ranch (SOC) (Imperial Co.) (AZ)

5-minute 0.28 .19 .30

30-minute 0.71 .58 .84

I-hour 0.89 .82 .97

3-hour 1.32 1.16 1.31

6-hour 1.68 1.38 1.34

24-hour 2.55 1.71. 1.82

1 DWR Gauge No. 2139, Elev. = 1500 ft, n = 24-36 yrs. 2 DWR Gauge No. 2713, Elev. = 3 it, n = 22-44 yrs. 3 DWR Gauge No. 9890, Elev. = 194 it, n '" 35-40 yrs. 4 Weighted average based on length of record for each duration.

106

Average4

.47 1.32 1.61 2.27 2.63 3.62

Average4

.26

.71.

.89

1.26

1.46 2.01

APPENDIXB

RAINFALL MASS TABULATIONS

107

" -c , 0 u

m vi "-0-0. 0 u ." 0

:::;; I >-c: , 0 u

ai !!!.



0.3 ~----------------------~

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4 L-______________________ --'

30 min. 60 min. 180 min.


m I mile ~ 5 mile ~ 10 mile ~ 25 mile lSS]5D mil. LZ2l15D mil.

Graph Values [(S.B. County-Maricopa)fS.B. Countyl

30 min. 60 min. 180 min. 1 Sq. Mi. 0.14 -0-01 0.03 5 Sq. Mi. 0.26 0.03 0.05

10 Sq. Mi. 0.23 -0.01 0.08 25 Sq. MI. 0.18 -0.11 0.11 50 Sq. Mi. 0.09 -0.22 0.09

150 Sq. Mi. -0.04 -0.32 0.04

!Os

" ~ c ~ 0 u <Ii III "-~ c Q. 0 u '0 c ::; I

" ~ c ~ 0

U

ID vi ~



o.~ ~-----------------------~

0.2

D.l

0

-0.1

-02

-0.3

-0.4 L _______________________ _

30 min. 60 min. 1 BO min.

Design 5torm Peak Durotion (minutes)

~ 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISSJ 50 mile rzzJ 150 mile

Graph Values [(S.B. County-Maricopa)/S.B. County)

30 min. 60 min. 180 min. 1 Sq. Mi. 0.07 0.03 0.03 5Sq. Mi. 0.21 0.05 0.05

10 Sq. Mi. 0.19 0.01 0.07 25 Sq. Mi. 0.11 -0.07 0.09 50 Sq. Mi. 0.03 -0.18 0.09

150 Sq. Mi. -0.13 -0.29 0.05

109

:>,

c ~ 0 ()

cD IJ}

"'-~ 0

" 0 v ·c 0 ::; I .0 c " 0 ()

ID vi ~



0.3,--------------------------,

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4 L ______________________ --"

30 min. 60 min. 180 min.

Design Storm Peok Duretion (minutes)

~ 1 mile ~ 5 mile ~ 10 mile I2Q(] 25 mile IS.SJ 50 mile 1ZZ1150 mile

Graph Values (S.B. County-Maricopa)/S.B. County]

30 min. 60 min. 180 min. 1 Sq. Mi. 0.08 -0.02 0.Q1 5-Sq. Mi. 0.22 0.02 0.04

10 Sq. Mi. 0.18 -0.02 0.07 25 Sq. Mi. 0.12 -0.11 0.09 50 Sq. Mi. 0.03 -0.24 0.09

150 Sq. Mi. -0.10 -0.33 0.06

llO

" " , 0

r.J

III vi ....... ~

0 a. 0 v ." 0 :! I ~ c " 0

(.)

ai vi ~

Phoenix Metro Area Adjusted Rainfall Comparison: 100 Year (Rainfalls adjusted using respective County depth-area cUlVes)


0.3 r-----------------------,

0.2

0.1

0

-0.1

-0.2

-0.3L-----------------------------------------------~ 30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile !221] 25 mile ISSl 50 mile CZZI 150 mile

Graph Values [(S.B. County-Maricopa)lS.B. County)

30 min. SO min. 180 min. , Sq. Mi. 0.08 . 0.02 0.03 5 Sq. Mi. 0.22 0.04 0.06

10 Sq. Mi. 0.18 -0.02 0.05 25 Sq. Mi. 0.13 -0.09 0.10 50 Sq. Mi. 0.04 -0.20 0.10

150 Sq. Mi. -0.10 -0.29 0.06

III

1 sq. mile TIme DiSl.

0:00 0.0 0:15 0.8 0:30 1.6 0:45 2.5 1:00 3.5 1:15 4.1 1:30 5.0 1:45 5.8 2:00 6.6 2:15 7.5 2:30 8.7 2:45 9.9 3:00 11.9 3:15 14.8 3:30 23.0 3:45 40.7 4:00 77.8 4:15 88.1 4:30 91.9 4:45 94.5 5:00 95.7 5:15 96.8 5:30 98.0 5:45 99.0 6:00 100.0

15 min. 30 min 1 hour 2 hour 3 hour 6 hour

15 min. 30 min. 1 hour 2 hour 3 hour Shour I·

2 1.24

Mass 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.11 0.12 0.15 0.18 0.29 0.50 0.96 1.09 1.14 1.17 1.19 1.20 1.22 1.23 1.24

Phoenix Metro Area Precipitation Maricopa County Design Storm

Storm Frequency year 5 year 10 -year 25 year inches 1.72 inches 2.07 Inches 2.55 inches Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.02 0;02 0.02 0.02 0.01 0.03 0.02 0.03 0.01 0.04 0.02 0.01 0.04 0.01 0.05 0.02 0.06 0.02 0.01 0.06 0.02 0.07 0.02 0.09 0.03 0.01 0.07 0.01 0.08 0.01 0.10 0.01 0.01 0.09 0.02 0.10 0.02 0.13 0.03 0.01 0.10 0.01 0.12 0.02 0.15 0.02 0.01 0.11 0.01 0.14 0.02 0.17 0.02 0.01 0.13 0.02 0.16 0.02 0.19 0.02 0.02 0.15 0.02 0.18 0.02 0.22 0.03 0.01 0.17 0.02 0.20 0.02 0.25 0.03 0.03 0.20 0.03 0.25 0.05 0.30 0.05 0.03 0.25 0.05 0.31 0.06 0.38 0.08 0.11 0.40 0.15 0.48 0.17 0.59 0.21 0.21 0.70 0.30 0.84 0.36 1.04 0.45 0.46 1.34 0.64 1.61 o.n 1.98 0.94 0.13 1.52 0.18 1.82 0.21 2.25 0.27 0.05 1.58 0.06 1.90 0.08 2.34 0.09 0.03 1.63 0.05 1.96 0.06 2.41 0.07 0.02 1.65 0.02 1.98 0.02 2.44 0.03 0.01 1.66 0.01 2.00 0.02 2.47 0.03 0.02 1.69 0.03 2.03 0.03 2.50 0.03 0.01 1.70 0.01 2.05 0.02 2.52 0.02 0,01 1.72 0.02 2.07 0.02 2.55 0.03

Maximum Values (depth in inches) 0.46 0.64 o.n 0.94 0.67 0.94 1.13 1.39 0.91 1.27 1.51 1.67 1.05 1.46 1.76 2.16 1.11 1.53 1.64 2.28 1.24 1.72 2:07 2.55

SO 2.96

Mass 0.00 0.02 0.05 0.07 0.10 0.12 0.15 0.17 0.20 0.22 0.26 0.29 0.35 0.44 0.68 1.20 2.30 2.61 2.72 2.80 2.83 2.87 2.90 2.93 2.96

Maximum Values (intensity in incheslhour) 1.84 2.56 3.08 3.76 1.34 1.88 2.26 2.78 0.91 1.27 1.51 1.87 0.53 0.73 0;88 1.08 0.37 0.51 0.61 0.76 0.21 0.29 0.35 0.43.

112

year 100 year inches 3.26 inches Delta Mass Delta 0.00 0.00 0.00 0.02 0.03 0.03 0.03 0.05 0.02 0.02 0.08 0.03 0.03 0.11 0.03 0.02 0.13 0.02 0.03 0.16 0.03 0.02 0.19 0.03 0.03 0.22 0.03 0.02 0.24 0.02 0.04 0.28 0.04 0.03 0.32 0.04 0.06 0.39 0.07 0.09 0.48 , 0.09 0.24 0.75 0.27 0.52 ·1.33 1 0•58 1.10 2.54 1.21 0.31 "2.87 1 0•33 0.11 3.00 0.13 0.08 3.08 0.08 0.03 3.12 0.04 0.04 3.18 . 0.04 0.03 3.19 0.03 0.03 3.23 0.04 0.03 3.26 0.03

1.10 1.21 1.62 1.79 2.17 2.39 2.51 I .·2.76 2.65 2.92

. 2.96 3.26

4.40 4.64 3.24 3.58 2.17 2.39 1.26 ··········1:38

0.88 I

0.97 . 0.49 0.54

5 SQ.

Time 0:00 0:15 0:30 0:45 1:00 1:15 1:30 1:45 2:00 2:15 2:30 2:45 3:00 3:15 3:30 3:45 4:00 4:15 4:30 4:45 5:00

. 5:15 5:30 5:45 6:00

mile Dist.

0.0 1.1 1.7 2.7 3.8 4.8 5.9 6.8 7.B 8.9

10.1 11.6 13.7 tlU 26.8 45.7 68.7 82.6 89.0 93.0 94.9 96.2 97.4 98.8

100.0

15 min. 30min. 1 hour


Storm Frequency 2 year 5 year 10 year 25 vear

1.21 inches 1.67 inches 2.02 inches 2.48 inches Mass Delta Mass Della Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0:01 0.02 0.02 0.02 0;02 0.03 0.03 0.02 0.01 0.03 0.01 0.03 0.01 0.04 0.01 0.03 0.01 0.05 0.02 0.05 0.02 0.07 0.03 0.05 0.02 0.06 0.01 0.08 0.03 0.09 0.02 0.06 0.01 0.08 0.02 0.10 0.02 0.12 0.03 0.07 0.01 0.10 0.02 0.12 0.02 0.15 0.03 0.08 0.01 0.11 0.01 0.14 0.02 0.17 0.02 0.09 0.01 0.13 0.02 0.16 0.02 0.19 0.02 0.11 0.02 0.15 0.02 0.18 0.02 0.22 0.03 0.12 0.01 0.17 0.02 0.20 0.02 0.25 0.03 0.14 0.02 0.19 0.02 0.23 0.03 0.29 0.04 0.17 0.03 0.23 0.04 0.28 0.05 0.34 0.05 0.22 0.05 0.30 0.07 0.37 0.09 0.45 0.11 0.32 0.10 0.45 0.15 0.54 0.17 0.66 0.21 0.55 0:23 0.76 0.31 0.92 0.38 1.13 0.47

0.83 0.28 US 1. 0.39 1.39 0.47 1.70 0.57

.1.00 0;17 ·1.38 0.23 1.67 0.28 2.05 0.35 1.08 0.08 1.49 0.11 1.80 0.13 2.21 0.16 1.13 0.05 . 1.55 0.06 1.88 0.08 2.31 0.10 1.15 0.02 1.58 0.03 1.92 0.04 2.35 0.04

.U6 ·0:01 !1.61 0:03 1.94·· 1 .. 0:02 2.39 0.04

1.18 0.02 1.63 0.02 1.97 0.03 2.42 0.03 .1.20 ().02 . 1.65 , .... 0;02 .2.00 0.03 2.45 0.03 1.21 0.Q1 1.67 0.02 2.02 0.02 2.48 0.03

Maximum Values (depth in inches) 0.28 0.39 0.47 0.57 0.51 0.70 0.85 1.04 0.78 1.08 1.30 1.60

50 2.88

Mass 0.00 0.03 0.05 0.08 0.11 0.14 0.17 0.20 0.22 0.26 0.29 0.33 0.39 0.52 o.n 1.32 1.98 2.38 2.56 2.68 2.73 2.n 2.81 2.85 2.88

2hour . (t99· I 1.36 I 1.65 2.02

3 hour 1.05 1.46 1.76 2.17 6 hour 1.21 1;67 2:02 2.48

Maximum Values (intensity in inches/hour) 15 min. 1.12 1.56 1.88 2.28

I·· 30 min. I· ·1:02 1.40. 1:70 2.08 ! 1 hour 0.78

.... 1.08 1.30 1.60

2 hour I OA9 0.68 0.83 LOI

3 hour 0.35 0.49 0.59 0.72 6 hour I> ·0:20 0.28 ·0:34 0.41

113

year 100 year inches 3.17 inches Delta Mass Della 0.00 0.00 0.00 0.03 0.03 0.03 0.02 0.05 0.02 0.03 0.09 0.04 0.03 0.12 0.03 0.03 0.15 0.03 0.03 0.19 0.04 0.03 0.22 0.03 0.02 0.25 0.03 0.04 0.28 0.03 0.03 0.32 0.04 0.04 0.37 0.05 0.06 0.43 0.06 0.13 0.57 0.14 0.25 0.85 0.28 0.55 1.45 ,.0,60 0.66 2.18 0.73 0.40 2.62 0.44 O.lB 2.B2 0.20 0.12 2.95 0.13 0.05 3.01 0.06 0.04 3.05 ·0.04 0.04 3.09 0.04 0.04 3.13 0.04 0.03 3.17 0.04

0.S6 0.73 1.21 1.33 1.86 2.05 2.35 2:58 2.51 2.77 2.88 3.17

2.S4 2.92 2.42 .2:66 1.8S 2.05 1.18 ·1.29 0.84 0.92 0.48 ·0:53

10 SQ. mile TIme DiSl.

0:00 0.0 0:15 1.3 0:30 1.9 0:45 2.9 1:00 4.4 1 :15 5.7 1:30 6.9 1:45 8.1 2:00 9.4 2:15 10.6 2:30 12.1 2:45 13.6 3:00 15.9 3:15 20.4 3:30 28.8 3:45 46.6 4:00 67.7 4:15 80.8 4:30 87.8 4:45 92.0 5:00 94.7 5:15 96.1 5:30 97.4 5:45 98.7 6:00 100.0

15 min. 30 min. 1 hour 2 hour 3 hour 6 hour


2 1.18

Mass 0.00 0.02 0.02 0.03 0.05 0.07 0.08 0.10 0.11 0.13 0.14 0.16 0.19 0.24 0.34 0.55 0.80 0.95 1.04 1.09 1.12 U3 1.15 1.16 1.18


Storm Frequency year 5 year 10 year 25 year inches 1.64 inches 1.97 inches 2.43 inches Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.02 0.02 0.03 0.03 0.03 0.03 0.00 0.03 0.01 0.04 0.01 0.05 0.02 0.01 0.05 0.02 0.06 0.02 0.07 0.02 0,02 0.07 0.02 0.09 0.03 0.11 0.04 0,02 0.09 0.02 0.11 0.02 0.14 0.03 0.Q1 0.11 0.02 0.14 0.03 0.17 0.03 0.02 0.13 0.02 0.16 0.02 0.20 0.03 0.01 0.15 0.02 0.19 0.03 0.23 0.03 0.02 0.17 0.02 0.21 0.02 0.26 0.03 0.01 0.20 0.03 0.24 0.03 0.29 0.03 0.02 0.22 0.02 0.27 0.03 0.33 0.04 0,03 0.26 0.04 0.31 0.04 0.39 0.06 0.05 0.33 0.07 0.40 0.09 0.50 0.11 0.10 0.47 0.14 0.57 0.17 0.70 0.20 0.21 0.76 0.29 0.92 0.35 1.13 0.43 0.25 1.11 0.35 1.33 I 0.41 1.S5 0.52 0.15 1.33 0.22 1.59 0.26 1.96 0.31 0.09 1.44 0.11 1.73 0.14 2.13 0.17 0.05 1.51 0.07 1.81 0.08 . 2.24 0.11 0,03 1.55 0.04 1.87 0.06 2.30 0.06 0,01 1.SS 0.03 1~89 0.02 2.34 0.04 0,02 1.60 0.02 1.92 0.03 2.37 0.03 0.01 1.62 .0.02 1.94 0.02 2.40 0.03 0.02 1.64 0.02 1.97 0.03 2.43 0.03

Maximum Values (depth in inches) 0.25 0.35 0.41 0.52 0.46 0.64 0.76 0.95 0.71 1.00 1.19 1.46 0.93 1.29 1.54· '.91 1,00 1.41 1.68 2.08 1.18 '.64 1.97 2.43

50 2.82

Mass 0.00 0.04 O.OS 0.08 0.12 0.16 0.19 0.23 0.27 0.30 0.34 0.38 0.45 0.58 O.Bl 1.31 1.91 2.28 2.48 2.59 2.67 2.71 2.75 2.78 2.82

-

Maximum Values (intensity in inches/hour) 1.00 1.40 1.64 2.08 0.92 1.28 1.52 1.90 0.71 1.00 1.19 1.46 0.47 0.65 0.77

,

0.96 0.33 0.47 0.56 0.69 0.20 0.27 0.33 0.41

114

year 100 year inches 3.18 inches Delta Mass Delta 0.00 0.00 0.00 0.04 0.04 0.04 0.01 O.OS 0.02 0.03 0.09 0.03 0.04 0.14 0.05 0.04 0.18 0.04 0.03 0.22 0.04 0.04 0.26 0.04 0.04 0.30 0.04 0.03 0.34 0.04 0.04 0.38 0.04 0.04 0.43 0.05 0.07 0.51 0.06 0.13 0.65 0.14 0.23 0.92 t· 0.27 0.50 1.48 0.56 0.60 2.15 0.S7 0.37 2.57 0.42 0.20 2,79 0,22 0.11 2.93 0.14 O.OS 3.01 0.08 0.04 I· 3.06 0.05 0.04 3.10 0.04 0.03 3.14 ·0.04 0.04 3.18 0.04

0.60 0.67 1.10 1.23 1.70 1,92 2:21 2.50 2.41 2,72 2.82 3.18

2,40 2.68 2.20 2.46 1.70 1,92 1.11 1.25 O.BO 0,91 0.47· 0.53

i , i 25 sq. mile

Time Dist. 0:00 0.0 0:15 1.7 0:30 2.4 0;45 3.5 1:00 5.4 1:15 6.9 1:30 8.3

I 1;45 9.9 2:00 11.5

I 2;15 12.9 , 2:30 14.6 I 2;45 16.4

3:00 18.9 3;15 23.7 3:30 31.9 3:45 47.9 4:00 66.7 4:15

... 79.0

4:30 86.1 4:45 90.6 5:00 94.1 5:15 95.6 5:30 97.1 5:45 98.6 6:00 100.0

15 min. 30min. 1 hour 2 hour 3 hour 6 hour


2 1.13

Mass 0.00 0.02 0.03

1 0.04 0.06 0.08 0.09 0.11 0.13 0.15 0.16 0.19 0.21

I 0.27 0.36 0.54 0.75 0.89 0.97 1.02 1.06

1'1.08 1.10

11.11 1.13


Storm Frequency year 5 year 10 year 25 year inches 1.57 inches 1.89 inches 2.32 inches Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.03 0.03 0.03 0.03 0.04 0.04 0.01 0.04 0.01 0.05 0.02 0.06 0.02 0.01 0.05 0.01 0.07 0.02 0.08 0.02 0.02 0.08 0.03 0.10 0.03 0.13 0.05 0.02 0.11 0.03 0.13 0.03 0.16 0.03 0.01 0.13 0.02 0.16 0.03 0.19 0.03 0.02 0.16 0.03 0.19 0.03 0.23 0.04 0.02 0.18 0.02 0.22 0.03 0.27 0.04 0.02 0.20 0.02 0.24 0.02 0.30 0.03 0.01 0.23 0.03 0.28 0.04 0.34 0.04 0.03 0.26 0.03 0.31 0.03 0.38 0.04 0.02 0.30 0.04 0.36 0.05 0.44 0.06 0.06 0.37 0.07 0.45 0.09 0.55 0.11 0.09 0.50 0.13 0.60 0.15 0.74 0.19 0.18 0.75 0.25 0.91 0.31 1.11 0.37 0.21 1.05 0.30 1.26 0.35 1.55 0.44 0.14 1.24 0.19 1.49 0.23 1.83 0.28 0.08 1.35 0.11 1.63 0.14 2.00 0.17 0.05 I 1.42 0.07 1.71 0.08 2.10 0.10 0.04 1.48 0.06 1.78 0.07 2.18 0.08 0.02 11.50 0.02 1.81 0.03 2.22 0.04 0.02 1.52 0.02 1.84 0.03 2.25 0.03 0.01 1.55 0.03 : 1.86 0.02 2.29 0.04 0.02 1.57 0.02 1.89 0.03 2.32 0.03

Maximum Values (depth in inches) 0.21 0.30 0.35 0.44 0.39 0.55 0.66 0.81 0.62 0.87 1.04 1.28 0.83 1.16 1.40 1.72 0.93 1.30 1.57 1.92 1.13 1.57 1.89 2.32

50 2.70

Mass 0.00 0.05 0.06 0.09 0.15 0.19 0.22 0.27 0.31 0.35 0.39 0.44 0.51 0.64 0.86 1.29 1.80 2.13 2.32 2.45 2.54 2.58 2.62 2.66 2.70

Maximum Values (intensity in inches/hour) 0.84 1.20 1.40 1.76 0.78 1.10 1.32 1.62 0.62 0.87 1.04 1.28 0.42 0.58 0;70 0.86 0.31 0.43 0.52 0.64 0.19 0.26 0.32 0.39

115

year 100 year inches 2.97 inches Delta Mass Delta 0.00 0.00 0.00 0.05 0.05 0.05 0.Q1 0.07 0.02 0.03 0.10 0.03 0.06 0.16 0.06 0.04 0.20 0.04 0.03 0.25 0.05 0.05 0.29 0.04 0.04 0.34 0.05 0.04 0.38 0.04 0.04 0.43 0.05 0.05 0.49 0.06 0.07 0.56 0.07 0.13 0.70 0.14 0.22 0.95 0.25 0.43 1.42 0.47 0.51 1.98 0.56 0.33 2.35 0.37.. 0.19 2.56 0.21 0.13 2.69 0.13 0.09 2.79 0.10 0.04 2.84 0.05 0.04 2.88 0.04 0.04 2.93 0.05 0.04 2.97 0.04

0.51 0.56 0.94 1.03 1.49 1.65 2.01 2.20 2.23 2.46

'2.70 2.97

2.04 2.24 1.88 2.06 1.49 1.65 1.01 1.10 0.74 0.82 0.45 0.50'

50 sq. mile Time Dist.

0:00 0.0 0:15 1.9 0:30 3.1 0:46 4.6 1:00 6.4 1:16 8.0 1:30 9.6 1:45 11.5 2:00 13.2 2:15 14.8 2:30 16.6 2:45 18.6 3:00 21.5 3:15 26.3 3:30 34.S 3:45 49.2 4:00 66.2 4:15 78.0 4:30 84.9 4:45 89.5 5:00 93.3 5:15 95.0 5:30 96.7 5:45 98.4 6:00 100.0



2 1.08

Mass 0.00 0.02 0.03 0.06 0.07 0.09 0.10 0.12 0.14 0.16 0.18 0.20 0.23 0.28 0.37 0.53 0.71 0.84 0.92 0.97 1.01

. "1.03

1.04 1.06 1.08


Storm Frequency year 5 year 10 year 25 year inches 1.50 inches 1.Bl inches 2.22 inches Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.03 0.03 0.03 0.03 0.04 0.04 0.01 0.05 0.02 0.06 0.03 0.07 0.03 0.02 0.07 0.02 0.08 0.02 0;10 0.03 0.02 0.10 0.03 0.12 0.04 0.14 0.04 0.02 0.12 0.02 0.14 0.02 0.18 0.04 O.Ot 0.14 0.02 0.17 0.03 0.21 0.03 0.02 0.17 0.03 0.21 0.04 0.26 0.05 0.02 0.20 0.03 0.24 0.03 0.29 0.03 0.02 0.22 0.02 0.27 0.03 0.33 0.04 0.02 0.25 0.03 0.30 0.03 0.37 0.04 0.02 0.28 0.03 0.34 0.04 0.41 0.04 0.03 0.32 0.04 0.39 0.05 0.48 0.07 0.05 0.39 0.07 0.48 0.09 0.58 0.10 0.09 0.52 0.13 0.63 0.15 o.n 0.19 0.16 0.74 0.22 0.89 0.26 1.09 0.32 0.18 0.99 0.25 1.20 0.31 1.47 0.38 0.13 1.17 0.18 1.41 0.21 I' 1.73 0.26 0.08 1.27 0.10 1.54 0.13 1.88 0.15 0.05 1.34 0.07 1.62 0.08 1.99 0.11 0.04 1.40 0.06 1.69 0.07 2.07 0.08 0.02 1.43 0.03 1.72 0.03 2.11 0.04 0.01 1.45 0.02 1.75 0.03 2.15 0.04 0.02 1.48 0.03 1.78 0.03 2.18 0.03 0.02 1.50 0.02 1.81 0.03 2.22 0.04

Maximum Values (depth in inches) 0.18 0.25 0.31 0.38 0.34 0.47 0.57 0.70 0.56 0.78 0.93 1.15 0.77 1.06 t.28 1.58 0.87 1.21 1.45 1.78 LOB 1.50 1.81 2.22

50 2.58

Mass 0.00 0.05 0.08 0.12 0.17 0.21 0.25 0.30 0.34 0.38 0.43 0.48 0.55 0.68 0.89 1.27 1.71 2.01 2.19 2.31 2.41 2.45 2.49 2.54 2.58

Maximum Values (intensity in inches/hour) 0.72 1.00 1.24 1.52 0.68 0.94 t.14 1.40 0.56 0.78 0.93 1.15 0.39 0.53 0.64 0.79 0.29 0.40 0.48 0.59 0.18 0.25 0.30 0'.37

116

year 100 year inChes 2.84 inches Delta Mass Delta 0.00 0.00 0.00 0.05 0.05 0.05 0.03 0.09 0.04 0.04 0.13 ·0.04 0.05 0.18 0.05 0.04 I 0.23 0.05 0.04 0.27 0.04 0.05 0.33 0.06 0.04 0.37 0.04 0.04 0.42 0.06 0.05 0.47 0.05 0.05 0.53 0.06 0.07 0.61 0.08 0.13 0.75 0.14 0.21 0.98 0.23 0.38 1.40, 0.42 0.44 1.88 0.48 0.30 2.22 0.34 0.18 2.41 0.19 0.12 2.54 0.13 0.10 2.65 0.11 0.04 2:70" I" 0.05

0.04 2.75 0.05 0.05 2.79 0.04 0.04 2.84 0.05

0.44 0.48 0.82 0.90 1.33 1.47 1.83 2.01 2.07 2.28 2.58 2.84

1.76 1.92 1.64 1.80 1.33 1.47 0.92 1.01 0.69 0.76 0.43 0.47


0:00 0.0 0:15 2.1 0:30 3.6 0:45 S.2 1 :00 7.2 1:15 B.8 1 :30 10.6 1:45 12.7 2:00 14.5 2:15 16.3 2:30 18.2 2:45 20.5 3:00 23.6 3:15 28.5 3:30 36.8 3:45· 50.2 4:00 65.5 4:15 76.9 4:30 83.8 4:45 88.6 5:00 92.5 5:15 94.4 5:30 96.3 5:45 98.2 6:00 100.0


15 min. 30min. 1 hour 2 hour 3 hour 6 hour

2 1.01

Mass 0.00 0.02 0.04 0.05 0.07 0.09 0.11 O.lS O.lS 0.16 0.18 0.21 0.24 0.29 0.37 0.51 0.66 0.78 0.85 0.89 0.93


Storm Frequency year 5 year 10 year 25 year inches 1.39 inches 1.6B inches 2.06 inches Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.03 0.03 0.04 0.04 0.04 0.04 0.02 0.05 0.02 0.06 0.02 0.07 0.03 0.01 0.07 0.02 0.09 0.03 0.11 0.04 0.02 0.10 0.03 0.12 0.03 0.15 0.04 0;02 ·0.12 0.02 0.15 O.OS 0.18 O.OS 0.02 0.15 0.03 0.18 0.03 0.22 0.04 0.02 0.18 0.03 0.21 0.03 0.26 0.04 0.02 0.20 0.02 0.24 0.03 O.SO 0.04 0.01 0.23 0.03 0.27 0.03 0.34 0.04 0.02 0.25 0.02 0.31 0.04 0.37 0.03 0.03 0.28 0.03 0.34 0.03 0.42 0.05 0.03 0.33 O.OS 0.40 0.06 0.49 0.07 O.OS 0.40 0.07 0.48 0.08 0.S9 0.10 0.08 O.Sl 0.11 0.62 0.14 0.76 0.17

, . 0.14 0.70 0.19 0.84 0.22 1.03 0.27

,0.15 0.91 0.21 1.10 0.26 1.35 0.32 0.12 1.07 0.16 11.29 0.19 1.58 0.23 0.07 1.16 0.09 1.41 0.12 1.73 0.15

..• 0.04 1.23 1··.0.07 1.49 0.08 1.83 0.10 0.04 1.29 0.06 1.55 0.06 1.91 0.08

0:95· 0.02 ······1.31 0.02 .·1.59 ·0.04· 1.94 0;03 0.97 0.02 1.34 0.03 1.62 0.03 1.98 0.04

,.·.0:99 .0.02 . 1.36 0.02 .1.65 I 0.03 2.02 . 0.04 1.01 0.02 1.39 0.03 1.68 0.03 2.06 0.04

Maximum Values (depth in inches) 0.15 0.21 0.26 0.32

0.29 0.40 0.48 0.59

0.49 0.67 I

0.81 0.99 0.68· 0.95 i. 1.15 1.41

0.79 1.08 1.32 1.60 . 1.01 1:39 ·1.68 2.06

50 2.40

Mass 0.00 0.05 0.09 0:12 0.17 0.21 0.25 0.30 0.35 0.39 0.44 0.49 0.57 0.68 0.88 1.20 1.57 1.85 2.01 2.13 2.22 2.27 2.31 2.36 2.40

Maximum Values (intensity in inches/hour) 0.60 0.84 1.04 1.28

i 0:58 0.80 ' ... ···0.96· 1.18

0.49 0.67 0.81 0.99 ...

0:34 O.4B . ....

0:58 0.71

0.26 0.36 0.44 0.53

0:17 0;23 0:28 0.34

117

year 100 year inches 2.64 inches Delta Mass Delta 0.00 0.00 0.00 0.05 0.06 0:06 0.04 0.10 0.04 O.OS 0.14 0.04 0.05 0.19 0.05 0.04 0.23 0.04 0.04 0.28 0.05 0.05 0.34 0.06 O.OS 0.38 0.04 0.04 0.43 0.05 0.05 0.48 0.05 0.05 0.54 0.06 0.08 0.62 0.08 0.11 0.7S 0.13 0.20

10.97 0.22

0.32 . 1.33 1 0•36

0.37 11.73 0.40 0.28 2.03 0.3D 0.16 2.21 0.18 0.12 I 2.34 .0.13. 0.09 2.44 0.10 0.05 2.49 0.05· 0.04 2.54 0.05 0.05 ·2.59 '0.05 0.04 2.64 0.05

0.37 0.40 0.69 0.76 1.17 1.28 1.64 1:80 1.88 2.06

-2.40 2.64

1.48 1.60 1.38 1.52 1.17 1.28 0.82 . • 0:90 0.63 0.69

I 0.40 0.44

150 sq. mile TIme DiSl.

0:00 0.0 0:15 2.2 0:30 3.7 0:45 5.4 1:00 7.3 1:15 9.0 1:30 10.9 1:45 13.0 2:00 14.9 2:15 16.8 2:30 18.9 2:45 21.2 3:00 24.4 3:15 29.3 3:30 37.7 3:45 50.5 4:00 64.9 4:15 76.2 4:30 83.3 4:45 88.1 5:00 92.1 5:15 94.1 5:30 96.1 5:45 98.1 6:00 100.0


15min. 30min. 1 hour 2 hour 3 hour 6 hour

2 0.96

Mass 0.00 0.02 0.04 0.05 0.07 0.09 0.10 0.12 0.14 0.16 0.18 0.20 0.23 0.28 0.36 0.48 0.62

I 0.73 0.80 0.85. 0.88 0.90 0.92 0.94 0.96


Storm Frequency year 5 year 10 year 25 year inches 1.32 inches 1.60 inches 1.96 inches Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 I. 0.03 0.03 0.04 0.04 0.04 0.04

1. 0.02 0.05 ,. 0.02 0.06 0.02 0.07 0.03 0.01 0.07 0.02 0.09 0.03 0.11 0.04 0.02 0.10 0.03 0.12 0.03 0.14 0.03 0.02 0.12 0.02 0.14 0.02 0.18 0.04 am 0.14 0.02 0.17 0.03 0.21 0.03 0.02 0.17 0.Q3 0.21 0.04 0.25 0.04 0.02 0.20 0.03 0.24 0.03 0.29 0.04 0.02 0.22 0.02 0.27 0.03 0.33 0.04 0.02 0.25 0.03 0.30 0.03 0.37 0.04 0.02 0.28 0.03 0.34 0.04 0.42 0.05 0.03 0.32 0.04 0.39 0.05 O.4B 0.06 0.05 0.39 0.07 0.47 0.08 0.57 0.09

I 0.08 O.SO 0.11 0.60 0.13 0.74 0.17 0.12 0.67 0.17 0.81 0.21 0.99 0.25 0.14 0.86 0.19 1.04 0.23 1.27 0.28 0.11 1.01 0.15 1.22 0.18 1.49 0.22 0.07 1.10 0.09 1.33 0.11 1.63 0.14 0.05 1.16 0.06 1.41 0.08 1.73 0.10 0.03 1.22 0.08 1.47 0.06 1.81 0.08 0;02 1.24 I· 0.02 I. 1.51 0.04 1.84 . 0.03 0.02 1.27 0.03 1.54 0.03 1.88 0.04 0.02 1.29 0.02 1.1.57 . 0;03 1.92 0.04 0.02 1.32 0.03 1.60 0.03 1.98 0.04

Maximum Values (depth in inches) 0.14 0.19 0.23 0.28 0.26 0.38 0.44 0.53 0.45 0.62 0.75 0.92 0.65 0.88 1.07 1.31 . 0.74 1.02 1.24 1.51 0.98 1.32 1.S0 1.96

50 2.28

Mass 0.00 0.05 0.08 0.12 0.17 0.21 0.25 0.30 0.34 0.38 0.43 0.48 0.56 0.67 0.86 1.15 1.48 1.74 1.90 2.01 2.10 2.15 2.19 2.24 2.28

- .

Maximum Values (intensity in inches/hour) 0.56 0.76 0.92 1.12 0.52 0.72 0.B8 1.06 0.45 0.62 0.75 0.92 0.33 0.44 0.53

1 0.66

0.25 0.34 0.41 0.50 0.16 0.22 0;27 0.33

118

year 100 year inches 2.51 inches Delta Mass Delta 0.00 0.00 0.00 0.05 0.06 I· 0.06 0.03 0.09 0.03 0.04 0.14 O.OS 0.05 0.18 0.04 0.04 0.23 0.05 0.04 0.27 0.04 0.05 0.33 0.06 0.04 0.37 0.04 0.04 0.42 0.05 0.05 0.47 0.05 0.05 0.53 0.06 O.OB 0.61 0.08 0.11 0.74 . 0.13 0.19 0.95 0.21 0.29 1.27 10.32 0.33 1.63 0.36 0.26 1.91 0.28 0.16 2.09 0.18 0.11 2.21 1 0.12 0.09 2.31 0.10 0.05 2.36 , •• 0.05 0.04 2.41 0.05 0.05 2.46 O.OS 0.04 2.51 0.05

0.33 0.36 0.62 0;68 1.07 1.17 1.53 1;68 1.n 1.94 2.28 2.51

1.32 1.44 1.24 1.36 1.07 1.17 0.76 0.84 0.59 0.65 0.38 0.42

PHOENIX METRO AREA PRECIPITATION SAN BERNARDINO COUNTY DESIGN STORM

1 SQ. MI.

POINT RAINFALL DEPTHS (IN. )

DURATION 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

30-MIN. 0.80 1.10 1.25 1.55 1. 75 2.00

l-HR. 0.93 1. 35 1.60 1.90 2.25 2.50

3-HR. 1.14 1.62 1.89 2.31 2.70 3.00

6-HR. 1.20 1.80 2.10 2.58 2.94 3.30

24-HR. 1.44 2.04 2.40 3.12 3.36 3.84

MAXIMUM ADJUSTED PRECIPITATION DEPTHS (IN. )

DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.971 0.31 0.41 0.48 0.56 0.65 0.73

30-MIN. 0.971 0.78 1.07 1.21 1. 51 1.70 1.94

l-HR. 0.971 0.90 1.31 1.55 1.84 2.18 2.43

3-HR. 0.996 1.14 1.61 1.88 2.30 2.69 2.99

6-HR. 0.998 1.20 1.80 2.10 2.57 2.93 3.29

24-HR. 0.999 1.44 2.04 2.40 3.12 3.36 3.84

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN./HR.)


5-MIN. 0.971 3.73 4.89 5.71 6.76 7.81 8.74

30-MIN. 0.971 1.55 2.14 2.43 3.01 3.40 3.88

l-HR. 0.971 0.90 1. 31 1.55 1.84 2.18 2.43

3-HR. 0.996 0.38 0.54 0.63 0.77 0.90 1.00

6-HR. 0.998 0.20 0.30 0.35 0.43 0.49 0.55

24-HR. 0.999 0.12 0.17 0.20 0.26 0.28 0.32

119


5 SQ. MI.



5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

30-MIN. 0.80 1.10 1.25 1.55 1. 75 2.00

l-HR. 0.93 1.35 1.60 1.90 2.25 2.50

3-HR. 1.14 1.62 1.89 2.31 2.70 3.00

6-HR. 1.20 1. 80 2.10 2.58 2.94 3.30

24-HR. 1. 44 2.04 2.40 3.12 3.36 3.84


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 2S-YR. 50-YR. 100-YR.

5-MIN. 0.857 0.27 0.36 0.42 0.50 0.57 0.64

30-MIN. 0.857 0.69 0.94 1.07 1. 33 1.50 1.71

l-HR. 0.857 0.80 1.16 1.37 1.63 1.93 2.14

3-HR. 0.979 1.12 1. 59 1.85 2.26 2.64 2.94

6-HR. 0.989 1.19 1.78 2.08 2.55 2.91 3.26

24-HR. 0.994 1.43 2.03 2.39 3.10 3.34 3.82

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN .jHR.)


5-MIN. 0.857 3.29 4.32 5.04 5.96 6.89 7.71

3D-MIN. 0.857 1.37 1.89 2.14 2.66 3.00 3.43

l-HR. 0.857 0.80 1.16 1.37 1.63 1.93 2.14

3-HR. 0.979 0.37 0.53 0.62 0.75 0.88 0.98

6-HR. 0.989 0.20 0.30 0.35 0.43 0.48 0.54

24-HR. 0.994 0.12 0.17 0.20 0.26 0.28 0.32

120


10 SQ. MI.



5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

3D-MIN. 0.80 1.10 1.25 1.55 1. 75 2.00

1-HR. 0.93 1.35 1.60 1.90 2.25 2.50

3-HR. 1.14 1. 62 1.89 2.31 2.70 3.00

6-HR. 1.20 1. 80 2.10 2.58 2.94 3.30

24-HR. 1.44 2.04 2.40 3.12 3.36 3.84



5-MIN. 0.750 0.24 0.32 0.37 0.44 0.50 0.56

30-MIN. 0.750 0.60 0.83 0.94 1.16 1. 31 1.50

l-HR. 0.750 0.70 1.01 1.20 1.43 1. 69 1.88

3-HR. 0.955 1.09 1.55 1.80 2.21 2.58 2.86

6-HR. 0.979 1.17 1. 76 2.06 2.53 2.88 3.23

24-HR. 0.987 1.42 2.01 2.37 3.08 3.32 3.79

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN./HR. )


5-MIN. 0.750 2.88 3.78 4.41 5.22 6.03 6.75

30-MIN. 0.750 1.20 1.65 1.88 2.33 2.63 3.00

1-HR. 0.750 0.70 1.01 1.20 1.43 1.69 1.88

3-HR. 0.955 0.36 0.52 0.60 0.74 0.86 0.96

6-HR. 0.979 0.20 0.29 0.34 0.42 0.48 0.54

24-HR. 0.987 0.12 0.17 0.20 0.26 0.28 0.32

121


25 SQ. MI.


DURATION 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. lOa-YR.

5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

30-MIN. 0.80 1.10 1.25 1.55 1.75 2.00

I-HR. 0.93 1. 35 1.60 1.90 2.25 2.50

3-HR. 1.14 1. 62 1.89 2.31 2.70 3.00

6-HR. 1.20 1.80 2.10 2.58 2.94 3.30

24-HR. 1.44 2.04 2.40 3.12 3.36 3.84


DURATION DEPTH-AREA 2-YR. 5-YR. la-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.570 0.18 0.24 0.28 0.33 0.38 0.43

30-MIN. 0.595 0.48 0.65 0.74 0.92 1.04 1.19

1-HR. 0.605 0.56 0.82 0.97 1.15 1. 36 1.51

3-HR. 0.910 1.04 1.47 1.72 2.10 2.46 2.73

6-HR. 0.958 1.15 1. 72 2.01 2.47 2.82 3.16

24-HR. 0.974 1.40 1.99 2.34 3.04 3.27 3.74


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 2S-YR. 50-YR. lOa-YR.

5-MIN. 0.570 2.19 2.87 3.35 3.97 4.58 5.13

30-MIN. 0.595 0.95 1.31 1.49 1.84 2.08 2.38

1-HR. 0.605 0.56 0.82 0.97 1.15 1. 36 1.51

3-HR. 0.910 0.35 0.49 0.57 0.70 0.82 0.91

6-HR. 0.958 0.19 0.29 0.34 0.41 0.47 0.53

24-HR. 0.974 0.12 0.17 0.19 0.25 0.27 0.31

122


50 SQ. MI.



5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

30-MIN. 0.80 1.10 1.25 1.55 1.75 2.00

l-HR. 0.93 1. 35 1.60 1.90 2.25 2.50

3-HR. 1.14 1.62 1.89 2.31 2.70 3.00

6-HR. 1.20 1.80 2.10 2.58 2.94 3.30

24-HR. 1. 44 2.04 2.40 3.12 3.36 3.84



5-MIN. 0.430 0.14 0.18 0.21 0.25 0.29 0.32

30-MIN. 0.468 0.37 0.51 0.59 0.73 0.82 0.94

l-HR. 0.492 0.46 0.66 0.79 0.93 loll 1.23

3-HR. 0.840 0.96 1.36 1.59 1.94 2.27 2.52

6-HR. 0.929 loll 1.67 1.95 2.40 2.73 3.07

24-HR. 0.957 1.38 1.95 2.30 2.99 3.22 3.67



5-MIN. 0.430 1.65 2.17 2.53 2.99 3.46 3.87

30-MIN. 0.468 0.75 1.03 1.17 1.45 1.64 1.87

l-HR. 0.492 0.46 0.66 0.79 0.93 1.11 1.23

3-HR. 0.840 0.32 0.45 0.53 0.65 0.76 0.84

6-HR. 0.929 0.19 0.28 0.33 0.40 0.46 0.51

24-HR. 0.957 0.11 0.16 0.19 0.25 0.27 0.31

123


100 SQ. MI.



5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

3D-MIN. O.BO 1.10 1.25 1.55 1. 75 2.00

1-HR. 0.9:3 1. :35 1.60 1.90 2.25 2.50

3-HR. 1.14 1. 62 1.89 2.:31 2.70 3.00

6-HR. 1. 20 LBO 2.10 2.58 2.94 3.30

24-HR. 1.44 2.04 2.40 3.12 3.36 3.84



5-MIN. 0.300 0.10 0.13 0.15 0.17 0.20 0.23

30-MIN. 0.355 0.2B 0.39 0.44 0.55 0.62 0.71

1-HR. 0.402 0.37 0.54 0.64 0.76 0.90 1.01

3-HR. 0.747 0.B5 1.21 1.41 1. 73 2.02 2.24

6-HR. 0.889 1.07 1.60 1.87 2.29 2.61 2.93

24-HR. 0.935 1.35 1.91 2.24 2.92 3.14 3.59



5-MIN. 0.300 1.15 1.51 1. 76 2.09 2.41 2.70

30-MIN. 0.355 0.57 0.78 0.89 1.10 1.24 1.42

1-HR. 0.402 0.37 0.54 0.64 0.76 0.90 1.01

3-HR. 0.747 0.28 0.40 0.47 0.58 0.67 0.75

6-HR. 0.889 0.18 0.27 0.31 0.3B 0.44 0.49

24-HR. 0.935 0.11 0.16 0.19 0.24 0.26 0.30

124


150 SQ. MI.



5-MIN. 0.32 0.42 0.49 0.58 0.67 0.75

30-MIN. 0.80 1.10 1.25 1.55 1. 75 2.00

l-HR. 0.93 1.35 1.60 1.90 2.25 2.50

3-HR. 1.14 1.62 1.89 2.31 2.70 3.00

6-HR. 1.20 1.80 2.10 2.58 2.94 3.30

24-HR. 1. 44 2.04 2.40 3.12 3.36 3.84



5-MIN. 0.243 0.08 0.10 0.12 0.14 0.16 0.18

30-MIN. 0.310 0.25 0.34 0.39 0.48 0.54 0.62

l-HR. 0.362 0.34 0.49 0.58 0.69 0.81 0.91

3-HR. 0.688 0.78 loll. 1.30 1.59 1.86 2.06

6-HR. 0.870 1.04 1.57 1.83 2.24 2.56 2.87

24-HR. 0.923 1.33 1.88 2.22 2.88 3.10 3.54



5-MIN. 0.243 0.93 1.22 1. 43 1.69 1.95 2.19

30-MIN. 0.310 0.50 0.68 0.78 0.96 1.09 1.24

l-HR. 0.362 0.34 0.49 0.58 0.69 0.81 0.91

3-HR. 0.688 0.26 0.37 0.43 0.53 0.62 0.69

6-HR. 0.870 0.17 0.26 0.30 0.37 0.43 0.48

24-HR. 0.923 0.11 0.16 0.18 0.24 0.26 0.30

125

>. C ~ 0 ()

(D

(I) '-.. ~

..: ~

0 ()

I ~ c ~ 0 ()

ID vi ~



0.6r-----------------------------------------------,

0.5

0.4

0.3

0.2

0.1

30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile 50{] 25 mile rss:l50 mile I2Zl 150 mile

Graph Values [(S.B. County-Clark)lS.B. County]


10Sq. Mi. 0.55 0.36 0.30 25 Sq. Mi. 0.46 0.29 0.32 50 Sq. MI. 0.37 0.23 0.39

150 Sq. Mi. 0.26 0.11 0.40

126

'" c ~ 0

0

ai V> ....... ~

"'" ~ 0 U I >. -c ~ 0

0

ai <Ii ~


San Bernardino vs. Clark County 0.6r-----------------------------------------------~

0.5

0.4

0.3

0.2

0.1

30 min. 60 min. 180 min.


~ 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISS) 50 mile rz:zJ 150 mile

Graph Values I(S.B. County-Clark)lS.B. County)


10 Sq. Mi. 0.55 0.36 0.30 25 Sq. MI. 0.50 0.29 0.33 50 Sq. Mi. 0.43 0.23 0.38

150 Sq. Mi. 0.27 0.14 0.38

127

>-~ c , D ()

ai Ul '.. 2 -E ()

I Z. c , D ()

ai vi ~


San Bernardino VS. Clark County 0.6,..------------------------,

0.5

o.~

0.3

0.2

0.1

30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISS:'! 50 mile rzzI150 mile

Graph Values ((5.8. County-Clark)l5.B. Countyl

30min. 60min. lS0 min. 1 Sq. Mi. 0.33 0.25 0.13 5 Sq. Mi. 0.29 0.21 0.17

10 Sq. Mi. 0.54 0.36 0.31 25 Sq. MI. 0.49 0.30 0.35 50 Sq. Mi. 0.41 0.23 0.37

150 Sq. Mi. 0.28 0.15 0.3&

128

" c ~ 0

(.)

<Ii III "-~ 0 U I

J:;-c ~ 0

(.)

CD

VI ~



0.6,..-----------------------....,

0.5

0.4

0.3

0.2

0.1

30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile ~ 25 mile iSS] SO mile [ZZJ 150 mile

Graph Values [(S.B. County-Clark)lS.B. County]

30 min. SO min. 180 min. 1 Sq. Mi. 0.34 0.26 0.15 5 Sq. Mi. 0.30 0.21 0.20

10 Sq. MI. 0.55 0.37 0.32 25 Sq. Mi. 0.49 0.31 0.36 5050. Mi. 0.44 0.24 0.38

150 Sq. Mi. 0.32 0.17 0.39

129

SON 3 1 sq. mile

Time Cist. 0:00 0.0 0:05 2.0 0:10 5.7 0:15 7.0. 0:20 8.7 0:25 10.8 0:30 12.4 0:35 13.0 0:40 13.0 0:45 13.0 0:50 13.0 0:55 13.0 1:00 13.0 1:05 13.3 1 :10 14.0 1:15 14.2 1 :20 14.8 1:25 15.8 1:30 17.2 1:35 18.1 1:40 19.0 1:45 19.7 1 :50 19.9 1:55 20.0 2:00 20.1 2:05 20.4 2:10 21.4 2:15 22.9 2:20 24.1 2:25 24.9 2:30 25.1 2:35 25.6 2:40 27.0 2:45 27.8 2:50 28.1 2:55 28.3 3:00 29.5 3:05 32.2 3:10 35.2 3:15 40.9 3:20 49.9 3:25 59.0 3:30 71.0 3:35 74.4 3:40 78.1

McCarran Airport Area Precipitation Clark: County Design Storm

Storm Frequency 2j'ear 5 year 10 year 25 year 50

0.70 inches 1.18 inches 1.53 inches 1.99 inches 2.34 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0~02 0.02 0.03 0.03 ·0.04· 0.04 0.05 0.04 0.03 0.07 0.05 0.09 0.06 0.11 0.07 0.13 0.05 0.01 0.08 0.01 0.11 0.02 0.14 0.03 '. 0.16 0.05 0.01 0.10 0.02 0.13 0.02 0.17 0.03 0.20 0.08 0;02 0.13 0.03 0.17 0;04 ' 0.21 0.04 10;25 0.09 0.01 0.15 0.02 0.19 0.02 0.25 0.04 0.29

I· 0.09 0.00 0.15 0.00 0.20 0.01 0.26 0.01 0.30 0.09 0.00 0.15 0.00 0.20 0.00 0.26 0.00 0.30 0.09 0.00 0.15 0.00 0.20 0.00 0.26 0.00 0.30 0.09 0.00 0.15 0.00 0.20 0.00 0.26 0.00 0.30 0.09 0.00 0.15 0.00 0.20 0.00 0.26 0.00 0.30 0.09 0.00 0.15 0.00 0.20 0.00 0.26 0.00 0.30 0.09 0.00 0.16 0.01 0.20 0.00 0.26 0.00 0.31 0.10 0.01 0.17 0.01 0.21 0.01 0.28 0.02 0.33 0.10 0.00 0.17 0.00 0.22 0.01 0.28 0.00 0.33 0.10 0.00 0.17 0.00 0.23 0,01 0.29 0.01 0.35 0;11 0.01 0.19 0.02 0.24 0.01 0.31 0.02 0:37 0.12 0.01 0.20 0.01 0.26 0.02 0.34 0.03 0.40 0.13 0.01 0.21 0.01 0.28 0.02 0.36 0.02 0.42 0.13 0.00 0.22 0.01 0.29 0.01 0.38 0.02 0.44 0.14 0.01 0.23 0.01 0.30 0.01 0.39 0.01 0.46 0.14 0.00 0.23 0.00 0.30 0.00 1 .. 0.40 0.01 0.47 0.14 0.00 0.24 0.01 0.31 0.01 0.40 0.00 0.47 0.14 0.00 0.24 0.00 0.31 0.00 0.40 0.00 0.47 0.14 0.00 0.24 0.00 0.31 0.00 ... 0.41 0.01 DA8 0.15 0.01 0.25 0.01 0.33 0.02 0.43 0.02 0.50 0:18 0.01 0:27 0.02 1 0.35 0.02 0.46 I 0.03' 0;54 0.17 om 0.28 0.01 0.37 0.02 0.48 0.02 0.56 0.17 0.00 0.29 0.01 0.38 0.01 0.50 0.02 0.58 0.18 0.01 0.30 0.01 0.38 0.00 0.50 0.00 0.59 0.18 0.00 0.30 0.00 0.39 0.01 I 0.51 0.01 0.60 0.19 0.01 0.32 0.02 0.41 0.02 0.54 0.03 0.63 0.19 0.00 0;33 0.01 0.43 0.02 0.55 0.01 0.65 0.20 0.01 0.33 0.00 0.43 0.00 0.56 0.Q1 0.66 0.20 0.00 0.33 0.00 0.43 0.00 0.56 0.00 0.66 0.21 0.01 0.35 0.02 0.45 0.02 0.59 0.03 0.69 0.23 0.02 0.38 0.03 0.49 0.04 0.64 0.05 0.75 0.25 0.02 0.42 0.04 .0.54 0.05 0.70 0.06 0.82 0.29 0.04 0.48 0.06 0.63 0.09 0,81 0.11 0.96 0.35 0.06 0.59 0.11 0.76 0.13 0.99 0.18 1.17 0.41 0.06 0.70 0.11 0.90 0.14 1.17 0.18 1.38 0.50 0.09 0.84 0.14 1.09 0.19 1.41 0.24 1.66 0.52 0.02 0.88 0.04 1.14 0.05 1.48 0.07 1.74 0.55 0.03 0.92 0.04 1.19 0.05 1.55 0.07 1.83

130

Page 1 ot 2

year 100 year inches 2.69 Inches Delta Mass Delta 0.00 0.00 0.00 0.05 0.05 0.05 0.08 0.15 0.10 0.03 0.19 0.04 0.04 0.23 0.04

.··0.05 • ···.0.29 0.06 0.04 0.33 0.04 0.01 0.35 0.02 0.00 0.35 0.00 0.00 0.35 0.00 0.00 0.35 0.00 0.00 0.35 0.00 0.00 0.35 0.00 0.01 0.36 0.01 0.02 0.38 0.02

... 0.00 .. 0-38 I 0.00 0.02 0.40 0.02 0:02 ... 0)43 10.03 0.03 0.46 0.03 0.02 0.49 10.03 0.02 0.51 0.02 0.02 0.53 0.02 0.01 0.54 0.01

··0;00 0.54 0.00 0.00 0.54 0.00 0.01 0;55. , 0.01 0.02 0.58 0.03 0;04 ·0.62 0.04 0.02 0.65 0.03 0:02 0.67 0.02 0.01 0.68 0.01 0;01 0:69 1 •• 0.01 0.03 0.73 0.04 0.02 0:75 1 0.02 0.Q1 0.76 0.01 0.00 0.76 1 ..... 0•00 0.03 0.79 0.03 0.06 0.87 0.08 0.07 0.95 0.08 0.14 1.10 I·· 0.15

0.21 1.34 1 0.24 0.21 1.59 10.25 0.28 1.91 0.32 0.08 2.00 0.09 0.09 2.10 0.10

SDN3 5 sq. mile

TIme Dist. 3:45 81.2 3:50 81.9 3:55 83.5 4:00 85.1 4:05 85.6 4:10 86.0 4:15 86.8 4:20 87.6 4:25 88.8 4:30 91.0 4:35' 92.6 4:40 93.7 4:45 95.0 4:50 97.0 4:55 97.6 5:00 98.2 5:05 9B.5

.

5:10 98.7 .5:15 98.9 5:20 99.0 5:25 99.3 5:30 99.3 5:35

1 99.4

5:40 99.5 5:45 99.8 5:50 99.8 5:55

, 99.9

6:00 100.0

5 min. 15 min. 30 min. t hour 3 hour 6 hour

5 min. 15 min. 30min. 1 hour 3 hour 6 hour.

McCarran Airport Area Precipitation Clark County Design Storm

Storm Frequency 2 year 5 year 10 year 25 year

0.65 inches 1.07 inches 1.38 inches 1.86 inches 50

2.18 ' Mass Delta Mass Delta Mass Delta Mass Delta Mass

0:53 0:02 0.87 0.03 1:12 0.04 1.51 0.06 1.77 0.53 0.00 0.88 0.01 1.13 0.01 1.52 0.01 1.79

I 0.54 ,0.01 0.89 0.01 1.15 0.02. 1.55 0.03 1.82 0.55 0.01 0.91 0.02 1.17 0.02 1.58 0.03 1.86

1 0:56 0.01 0.92 0.01 1.18 0.01 1:59 ·0.01 1:87 0.56 0.00 0.92 0.00 1.19 0.01 1.60 0.Q1 1.87

.. 0.56 0.00 0.93 0.01 1.20 0.01 1.61 .. 0.01 L89 0.57 0.01 0.94 0.01 1.21 0.01 1.63 0.02 1.91 0.58 0:01 . 0.95 0.01 1.23 0.02 1.65 0.02 1.94 0.59 0.01 0.97 0.02 1.26 0.03 1.69 0.04 1.98 0.60 "0.01 0.99 0.02 1.28 0.02 1.72 0.03 2.02 0.61 0.01 1.00 0.01 1.29 0.01 1.74 0.02 2.04 0.62 0.01 1.02 0.02 1.31 0.02 1.77 0.03 2.07 0.63 0.01 1.04 0.02 1.34 0.03 1.80 0.03 2.11 0.63 0.00 1.04 0.00 1.35 0.01 1.82 0.02 2.13 0.64 0.01 1.05 0.01 1.36 0.01 1.83 0.Q1 2.14 0.64 0;00 1.05 0.00 1.36 0.00 1.B3 0.00 2.15 0.64 0.00 1.06 0.01 1.36 0.00 1.B4 0.01 2.15 0.64 I. 0.00 1.06 0.00 1.36 0.00 1.84 0.00 2.16 0.64 0.00 1.06 0.00 1.37 0.01 1.84 0.00 2.16 0:65 1 0;01 1.06 0.00 1.37 0.00 1.85 0.01 2.16 0.65 0.00 1.06 0.00 1.37 0.00 1.85 0.00 2.16

1 0.65 1 0.00 1.06 0.00 1 1.37 0.00 1.85 0.00 2.17 0.65 0.00 1.06 0.00 1.37 0.00 1.85 0.00 2.17 0:65 0.00 1.07 0.01 1.38 0.01 1;86 0;01 2.18 0.65 0.00 1.07 0.00 1.38 0.00 1.86 0.00 2.18 0;65 "0;00 1.07 0.00 ,.38' 0.00 '1.86 1 0:06 2.18 0.65 0.00 1.07 0.00 1.38 0.00 1.86 0.00 2.18

Maximum Values (depth in inches) 0.08 0.13 0.17 0.22 0.19 0.32 0.42 0.56 0.28 0.46 0.59 0.80 0:36 0.59 0.76 1;02 0.51 0.83 1.08 1.46

, ..... . 0.65 1.07 ' .. 1:38 1.86

Maximum Values (intensity in inches/hour) 0.96 1.56 2.04 2.64 0.76 1.28 1.68 2.24 0.56 0.92 1.18 1.60

i 0.36 0.59 0.76 1:02 0.17 0.2B 0.36 0.49 0.11 0.18 0.23 0:31

131

Page 2 of 2

year 100 year inches 2.51 inches Delta Mass Delta 0.07 2.04 0.08 0.02 2.06 0.02 0.03 2.10 0.04 . 0.04 2.14 0.04 0.01 2.15 0.01 0.00 2.16 0.01 0.02 2;18 . 0.02

0.02 2.20 0.02 0.03 2.23 0.03 0.04 2.28 0.05 0.04 2.32 0:04 0.02 2.35 0.03 0.03 2.38 0.03 0.04 2.43 0.05 0.02 2.45 .' 0.02 0.01 2.46 ..... 0.01 0.01 12:.47 0.01 0.00 2.48 0.01 0.01 1·2.48 0;00 0.00 1 2.48 0.00 0.00 2.49 .. 0.01

0.00 2.49 0.00 0.01 2.49 O~OO 0.00 2.50 0.01 0.01 2.50 0.00' 0.00 2.50 0.00 0.00 2;51 10:01 0.00 2.51 0.00

0.26 0.30 0.66 ;0.75 0.93 1.08 1.20 1.39 1.70 1.96 2.18

.. ,2:51.

3.12 3.60 2.64 '.' . ~.OO 1.86 2.16 1.20 ........ 1.39 0.57 0.65 0.36 0.42

SON 3 5 SQ. mile

Time Dist. 0:00 0.0 0:05 2.0 0:10 5.7 0:15 7.0 0:20 8.7 0:25 10.8 0:30 12.4 0:35 13.0 0:40 13.0 0:45 13.0 0:50 13.0 0:55 13.0 1:00 13.0 1:05 13.3 1 :10 14.0 1:15 14.2 1:20 14.8 1:25 15.8 1:30 17.2 1:35 18.1 1:40 19.0 1:45 19.7 1:50 19.9 1:55 20.0 2:00 20.1 2:05 20.4 2:10 21.4 2:15 22.9 2:20 24.1 2:25 24.9 2:30 25.1 2:35 25.6 2:40 27.0 2:45 27.8 2:50 28.1 2:55 28.3 3:00 29.5 3:05 32.2 3:10 35.2 3:15 40.9 3:20 49.9 3:25 59.0 3:30 71.0 3:35 74;4 3:40 78.1



0.65 Inches 1.07 inches 1.38 inches 1.86 inches 50 year

2.18 inches Mass Delta Mass Delta Mass Della Mass Della Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

. 0.01 0.01 0.02 0.02 0.03 0.03 0.04 0.04 0.04 0.04 0.04 0.03 0.06 0.04 0.08 0.05 0.11 0.07 0.12 0.08 0.05 O.Of 0.07 O.Of 0.10 0.02 0.13 0.02 0;15 I· 0.03 0.06 0.01 0.09 0.02 0.12 0.02 0.16 0.03 0.19 0.04 0;07. O.Of 0.12 0.03 0.15 0.03 0.20 0.04 0.24 I. 0.05 0.08 0.01 0.13 0.01 0.17 0.02 0.23 0.03 0.27 0.03 0.08 0.00 0.14 0.01 0.18 0.01 0.24 0.01 0.28 I· 0.01 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.00 0.28 0.00 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.00 0.28 0.00 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.00 0.28 0.00 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.00 0.28 0.00 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.00 0.28 0.00 0.09 0.01 0.14 0.00 0.18 0.00 0.25 0.01 0.29 0.01 0.09 0.00 0.15 0.01 0.19 0.01 0.26 0.01 0.31 0.02 0.09 0.00 0.15 0.00 0.20 0.01 0.26 0.00 0.31 0.00 0.10 0.01 0.16 0.01 0.20 0.00 0.28 0.02 0.32 0.01 0;10 0.00 0.17 0.01 0.22 0.02 0.29 0.01 0.34 0.02 0.11 0.01 0.18 0.01 0.24 0.02 0.32 0.03 0.37 0.03 0.12 0.01 0.19 0.01 0.25 0.01 0.34 0.02 0.39 0.02 0.12 0.00 0.20 0.01 0.26 0.01 0.35 0.01 0.41 0.02 0:13 0.01 0.21 0.01 0.27 0.01 0.37 0.02 0.43 0.02 0.13 0.00 0.21 0.00 0.27 0.00 0.37 0.00 0.43 0.00 0;13 0.00 0.21 0.00 0.28 0.01 0.37 0;00 0.44 I·. 0.01 0.13 0.00 0.22 0.01 0.28 0.00 0.37 0.00 0.44 0.00

·0;13 0.00 0.22 0.00 0.28 0.00 0.38 0.01 0.44 10 .00 0.14 0.01 0.23 0.01 0.30 0.02 0.40 0.02 0.47 0.03

IC);15 . 0.01 0.25 0.02 0.32 0.02 0.43 0:03 0;50 1 0.03 0.16 0.01 0.26 0.01 0.33 0.01 0.45 0.02 0.53 0.03 0:16 0.00 0.27 0.01 0.34 . 0.01 0.46 0.01 0.54 0.01 0.16 0.00 0.27 0.00 0.35 0.01 0.47 0.01 0.55 0.Q1

1 0:17 0.01 0.27 0.00 0.35 0:00 0:48 0.01 0.56 0.01 0.18 0.01 0.29 0.02 0.37 0.02 0.50 0.02 0.59 0.03

1 0•18 0.00 0.30 0.01 0.38 0.01 0.52 0.02 0.61 0.02 0.18 0.00 0.30 0.00 0.39 0.01 0.52 0.00 0.61 0.00 0.18 0.00 0.30 0.00 0.39 0.00 0.53 0.01 0.62 0.01 0.19 0.01 0.32 0.02 0.41 0.02 0.55 0.02 0.64 0.02 0.21 0.02 0.34 0.02 0.44 0.03 0.60 0.05 0.70 0.06 0.23 0.02 0.38 0.04 0.49 0.05 0.65 0.05 0.77 0.07

1 .. 0

.27 0.04 0.44 0.06 0.56 0.07 0.76 0.11 0.89 0.12

0.32 0.05 0.53 0.09 0.69 0.13 0.93 0.17 1.09 0.20 0.38 0.06 0.63 0.10 0.81 0.12 1.10 0.17 1.29 0.20 0.46 0.08 0.76 0.13 0.98 0.17 1.32 0.22 1.55 0.26 0;48 0.02 0.80 0.04 1.03 0.05 1.38 0.06 1.6Z 0.07 0.51 0.03 0.84 0.04 1.08 0.05 1.45 0.07 1.70 0.08

132

Page 1 of 2

100 year 2.51 inches

Mass Della 0.00 0.00 0.05 0.05

1. 0.14 0.09 0.18 1 0.04 0.22 0.04 0.27 0.05 0.31 0.04 0;33 0.02 0.33 0.00 0.33 0.00 0.33 0.00 0.33 0.00 0.33 0.00 0.33 0.00 0.35 0.02 0.36. I 0.01 0.37 0.01 0.40 0.03 0.43 0.03 0.45 1 ... 0.02 . 0.48 i o.03 0:49 0.01 0.50 0.01 0.50 . 0,00 0.50 0.00

1. 0•51 0.01 0.54 0.03 0:57 0.03 0.60 0.03 0.62 0.02 0.63 0.01

10:64 .··0.01 0.68 0.04 0.70 ·0.02 0.71 0.01

1.0.71 0.00 0.7~ 0.03 0.81 I· 0.07 0.88 0.07 1.03 0.15 1.25 0.22 1;48 0.23 1.78 0.30 1.87 0.09 1.96 0.09

SON 3 1 sq. mile

Time Dist. 3:45 81.2 3:50 81.9 3:55 83.5 4:00 85.1 4:05 85.6 4:10 86.0 4:15 86.8 4:20 87.6 4:25 88.8 4:30 91.0 4:35 92.6 4:40 93.7 4:45 95.0 4:50 97.0 4:55 97.6 5:00 98.2 5:05 98.5 5:10 98.7 5:15 98.9· 5:20 99.0 5:25 99.3 5:30 99.3 5:35 99.4. 5:40 99.5 5:45 I 99.8 5:50 99.8 .......

99:9 5:55 ..... 6:00 100.0

5 min. 16min; 30min. 1 hour .. 3 hour 6 hour

5 min. 15min ...• 30min.




2.34 Mass Delta Mass Delta Mass Delta Mass Delta Mass .0.57 0.02 0.96 0.04 1.24 0.05 1.62 0.07 1.90

0.57 0.00 0.97 0.01 1.25 0.01 1.63 0.01 1.92 1. 0•58 0.01 10.99 0.02 1.28 0.03 1.66 0.03 1.95

0.60 0.02 1.00 0.01 1.30 0.02 1.69 0.03 1.99

1 0.60 0.00 1.01 0.01 1.31 0.01 1.70 0.01 2.00 0.60 0.00 1.01 0.00 1.32 0.01 1.71 0.01 2.01

1 0.61 0.01 1.02 0.01 1.33 0.01 1.73 0.02 2.03 0.61 0.00 1.03 0.01 1.34 0.01 1.74 0.01 2.05

1 0.62 0.01 1.05 0.02 1.36 0.02 1.77 0.03 2.08 0.64 0.02 1.07 0.02 1.39 0.03 1.81 0.04 2.13 0.65 0.01 1.09 0.02 1.42 0.03 1.84 0.03 2.17 0.66 0.01 1.11 0.02 1.43 0.01 1.86 0.02 2.19 0.67 0.01 1.12 0.01 1.45 0.02 1.89 0.03 2.22 0.68 0.01 1.14 0.02 1.48 0.03 1.93 0.04 2.27

... 0.68 0.00 1.15 0.01 1.49 0.01 1.94 0.01 2.28

.. 0.69 0.01 1.16 0.01 1.50 0.01 1.95 0.01 2.30

. 0.S9 0.00 1.16 0.00 1.51 0.01 1.96 0.01 2.30 0.S9 0.00 1.16 0.00 1.51 0.00 1.96 0.00 2.31

0.69 ·0.00 1.17. 0.01 1.51 0.00 1.97 0.01 2.31

0.69 0.00 1.17 0.00 1.51 0.00 1.97 0.00 2.32 0.70 0.01 1:17 0.00 1.52 0.01 1.98 0.01 2.32

0.70 0.00 ".'7 0.00 1.52 0.00 1.98 0.00 2.32

,0.70 0.00 1.17 0.00 1.52 0.00 1.98 0.00 2.33 0.70 0.00 1.17 0.00 1.52 0.00 1.98 0.00 2.33

10.70 . 0.00 I·· 1;18 0.01 1 , :53 0.01 1.99 0.01 2.34 0.70 0.00 1.18 0.00 1.53 0.00 1.99 0.00 2.34

k ····0.00.· 1'1;53 '0.00 ..

I 0.70 U8. 0.00 1.99 0.00 2.34 0.70 0.00 1.18 0.00 1.53 0.00 1.99 0.00 2.34

Maximum Values (depth in inches) 0.09 0.14 0.19 0.24

I 0.21 I 0.36 I 0.46 0.60

0.30 0.50 0.65 0.85 0;38 0.66 0.85 1.10 0.55 0.92 1.19 1.55 0.70 1.18 . 1.53 1.99

Maximum Values (intensity in inches/hour) 1.08 1.68 2.28 2.88 0.84 ..... 1.44 1.84 2.40 •

0.60 1.00 1.30 1.70

.1hour .•. ' 0.38 0:66 0.B5 1.10

3 hour 0.18 0.31 0.40 0.52 Shour 0.12 0.20 0.26 0.33

133

Page 2 of 2

year 100 year inches 2.69 inches Delta Mass Delta 0.07 2.18 0.08 0.02 2.20 0.02 0.03 2.25 0.05 0.04 2.29 0.04 0.01 2.30 0.01' 0.01 2.31 0.01 0.02 2.~ I· 0.02 0.02 2.36 0.03 0.03 2.39 0.03 0.05 2.45 0.06 0.04 2.49 0.04 0.02 2.52 0.03 0.03 2.56 0.04 0.05 2.61 0.05 0.01 2.63 . 0.02 0.02 2.64 0.01 0.00 2.65 0.01 0.01 2.66 0.01 0.00 2.66 0.00 0.01 2.66 0.00 0.00 2.67 0.01 0.00 2.67 O.O~ 0.01 2.67 1. 0.00 0.00 2.68 0.01 .0.01 2.68 1. 0.00 0.00 2.68 1. 0•00 •.

1 0.00 ' 2.69 0:01 0.00 2.69 0.00

0.28 0.32 0.70 0.81 1.01 1.15 1;29 lA9 1.83 2.10 2:34 2.69

3.36 3.84 2.80 3.24 2.02 2.30 1.29 1.49 O.Sl 0.70 0.39 0.45

SONS 10 sq. mile

TIme Dist. 0:00 0.0 0:05 2.0 0:10 5.9 0:15 8.0 0:20 11.0 0:25 14.4 0:30 15.0 0:35 16.0 0:40 16.8 0:45 17.1 0:50 18.0 0:55 18.2 1:00 18.7 1:05 19.0 1:10 19.7 1:15 20.2 1:20 21.0 1:25 22.0 1:30 23.0 1:35 24.1 1:40 25.0 1:45 25.9 1:50 26.5 1:55 28.0 2:00 29.0 2:05 30.0 2:10 30.5 2:15 30.9 2:20 31.0 2:25 31.7 2:30 32.1 2:35 32.7 2:40 33.3 2:45 34.6 2:50 36.1 2:55 38.1 3:00 40.S 3:05 43.0 3:10 47.7 3:15 51.4 3:20 56.1 3:25 63.0 3:30 71.0 3:35 72.0 3:40 73.1


Storm Frequency 2 year 5 year 10 year 25 year 50M

0.62 inches 1.05 inches 1.36 inches 1.76 inChes 2.07 inChes Mass Delta Mass Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.02 0.02 0.03 0.03 0.04 0.04 0.04 0.04 0.04 0.03 0.06 0.04 0.08 0.05 0.10 0.06 0.12 0.08 0;05 I 0.01 0.08 0.02 0.11 0.03 0.14 0.04 0:17 0.05 0.07 0.02 0.12 0.04 0.15 0.04 0.19 0.05 0.23 0.06 0.09 0:02 0.15 0.03 0.20 0:05 0.25 0.06 0.30 0.07 0.09 0.00 0.16 0.01 0.20 0.00 0.26 0.01 0.31 0.01 0.10 0.01 0;17 0.01 0.22 0.02 0.28 0.02 0.33 0.02 0.10 0.00 0.18 0.01 0.23 0.01 0.30 0.02 0.35 0.02 0.11 0.01 0.18 0.00 0.23 0.00 0.30 0.00 0.35 0.00 0.11 0.00 0.19 0.01 0.24 0.01 0.32 0.02 0.37 0.02 0.11 0.00 0.19 0.00 0.25 0.01 0.32 0.00 0.38 0.01 0.12 0.01 0.20 0.01 0.25 0.00 0.33 0.01 0.39 0.01 0.12 0.00 0.20 0.00 0.26 0.01 0.33 0.00 0.39 0.00 0.12 0.00 0.21 0.01 0.27 0.01 0.35 0.02 0.41 0.02 0.13 0.01 0.21 0.00 0.27 0.00 0.36 0.01 0.42 0.01 0.13 0.00 0.22 0.01 0.29 0.02 0.37 0.01 0.43 0.01 0:14 0.01 0.23 ; . 0.01 0.30 0.01 0.39 0.02 0.46 0.03 0.14 1 .. 0.00 0.24 0.01 0.31 0.01 0.40 0.01 0.48 0.02 0:15 0.01 0.25 .. 0.01 0.33 0.02 0.42 0.02 0.50 0.02 0.16 0.01 0.26 0.01 0.34 0.D1 0.44 0.02 0.52 0.02 0.16 0.00 0.27 0.01 0.35 0.01 0.46 0.02 0.54 0.02 0.16 0.00 0.28 0.01 0.36 0.D1 0.47 0.01 0.55 0.01

... 0.17 0.01 0.29 0;01 0:38 0.02 0.49 0.02 0.58 0.03 0.18 0.01 0.30 0.01 0.39 0.01 0.51 0.02 0.60 0.02

r 0.19 10.01 0.32 1 .. 0•02 0.41 0.02 0.53 0.02 0.62 0.02 0.19 0.00 0.32 0.00 0.41 0.00 0.54 0.01 0.63 0.01

, 0.19 0.00 0.32 0.00 0.42 .. 0;01 0.54 10.00 0.64 0.01

0.19 0.00 0.33 0.01 0.42 0.00 0.55 0.01 0.64 0.00 0.20 0.01 0.33 0.00 0.43 0.01 0.56 0.01 0.66 0.02 0.20 0.00 0.34 1. 0.01 0.44 0.01 0.56 0.00 0.66 0.00 0:20 0.00 0.34 0.00 0.44 0.00 0.58 0.02 I. 0.68 0.02 0.21 0.01 , 0.35 0.01 0.45 0.01 0.59 0.01 0.69 0.01 0:21 0.00 0.36 0.01 0.47 0.02 0.61 0.02 0.72 0.03 0.22 0.01 0.38 0.02 0.49 0.02 0.64 0.03 0.75 0.03 0.24 0.02 0.40 0.02 0.52 0.03 0.67 0.03 0.79 0.04 0.25 0.01 0.43 0.03 0.55 0.03 0.72 0.05 0.84 0.05 0.27 0;02 0.45 0.02 0.58 0.03 0.76 0.04 , 0.89 0.05 0.30 0.03 0.50 0.05 0.65 0.07 0.84 0.08 0.99 0.10 0.32 0.02 0.54 0.04 0.70 0.05 0.90 0.06 1.06 0.07 0.35 0.03 0.59 0.05 0.76 0.06 0.99 0.09 1.16 0.10 0.39 0.04 0.66 0.07 0.86 0.10 1.11 0.12 1.30 0.14 ..

0.44 0.05 0.75 0.09 0.97 0.11 1.25 0.14 1.47 0.17 0.45 0.01 0.76 0.01 0.98 0.01 1.27 0.02 1.49 0.02 0.45 0.00 0.77 0.01 0.99 0.01 1.29 0.02 1.51 0.02

134

Page 1 of 2

100 year 2.38 inChes

Mass Delta 0.00 0.00 0.05 0.05 0.14 0.09 0.19 0.05 0.26 0.07 0.34 1 0.08 0.36 0.02 0.38 0.02 0.40 0.02 0.41 0.01 0.43 0.02 0.43 0.00 0.45 0.02 0.45 0.00 0.47 0.02 0.48 0.01 0.50 0.02 0.52 ··0.02 0.55 LO.03 0.57 0.02 0.60 I 0.03 0.62 0.02 0.63 0.01 0.67 0.04 0.69 0.02 0;71 10.02 0.73 0.02 0.74 0.01 0.74 0.00 0.75 0.01 0.76 0.01 0.78 0.02 0.79 0.01 0.82 ,0.03 0.86 0.04 0.91 0.05 0.97 0.06 1.02 '·0.05 1.14 0.12 1.22 I· 0.08 1.34 0.12 1.50 0.16 1.69 0.19 1.71 0.02 1.74 0.03

SON 5 10 sq. mile

Time Dist. 3:45 75.2' 3:50 77.! 3:55 79.0 4:00 79.5 4:05

, 80.4

4:10 81.0 4:15 82.0 4:20 82.6 4:25 84.0 4:30 85.9 4:35 88.9 4:40 91.0 4:45 93.8 4:50 96.6 4:55 97.0 5:00 97.4 5:05 97.9 5:10 98.1 5:15 ........ .98.3 5:20 .. 98.5 5:25. I 98.9 5:30 99.0 5:35 99.2 5:40 99.3 5:45 .... 99:6' 5:50 99.7 5:55

•..... 99.9

6:00 100.0

5 min. ···15inin. 30min. 1 hour 3 hour 6 hour

5 min. 15 min. 30mln. .1 hour 3 hour 6 hour




2.07 Mass Dena Mass Della Mass Della Mass Delta Mass 0:47 1 0.02 0.79 0.02 1.02 0.03 1.32 0.03 1.56 0.48 0.01 0.82 0.03 1.06 0.04 1.37 0.05 1.61

.0:49 10.01 0.8S 0.01 1.07 0.01 1.39 0.02 1.64 0.49 0.00 0.83 0.00 1.08 0.Q1 1.40 0.01 1.65

i'0.50 0.01 0.84 0.01 1.09 0.01 1.42 0.02 1.66 0.50 ..... 0.00 0.85 0.01 1.10 0.01 1.43 0.01 1.68

'0.51 0.01 0.86· 0.01 1.12 0.02 1.44 0.01 1.70 0.51 .0.00 0.87 0.01 1.12 0.00 1.45 0.01 1.71 0.52 .0.01 0.88 0.01 1.14 0.02 1.48 0.03 1.74 0.53 0.01 0.90 0.02 1.17 0.03 1.51 0.03 1.78 0.55 0.02 0.93 0.03 1.21 0.04 1.1;6 0.05 1.84 0.56 0.01 0.96 0.03 1.24 0.03 1.60 0.04 1.88 0.58 0.02 0.98 0.02 1.28 0.04 1.65 0.05 1.94 0.60 0.02 1.01 0.03 1.31 0.03 1.70 0.05 2.00

iO.60 0.00 1.02 0.01 1.32 0.01 1.71 0.01 2.01 0.60 0.00 1.02 0.00 1.32 0.00 1.71 0.00 2.02 0.61' 0.01 1.03 0.01 1.33 0,01 1.72 0.01 2.03 0.61 0.00 1.03 0.00 1.33 0.00 1.73 0.01 2.03 0.61' .0.00 ".03 0.00 1.34 0.01 1.73 0.00 2.0S 0.61 1 0.00 1.03 0.00 1.34 0.00 1.73 0.00 2.04 0.61 I 0.00 IT04' 0.01 1.35 0.01 1.74 0.01 2.05 0.61 1 0.00 1.04 0.00 1.S5 0.00 1.74 0.00 2.05

(0.62 . 0.01 1.04 0.00 .... 1.35 0.00 1.75 0.01 2.05 0.62 0.00 1.04 0.00 ~.S5 0.00 1.75 0.00 2.06 0.62 "0:00 I '1;05 1. 0;01 1.35 0.00 1.75 0.00 2.06 0.62 0.00 1.05 0.00 1.S6 0.01 1.75 0.00 2.06

{O.62 0:00 11:05 . 0.00 "1:36 0.00 I 1;76 O.Or 2.07 0.62 0.00 1.05 0.00 1.36 0.00 1.76 0.00 2.07

Maximum Values (depth in inches) 0.05 0.09 0.11 0.14 .0.12 0~2f 0.27 0:35 0.15 0.27 0.34 0.45 0.25 0.43 0.55 0.72 0.42 0.72 0.93 1.20 0:62 1;05 1.36 1.76


.0.48 0.84 1.08 1.40

0.30 0.54 0.68 0.90 0.25 0.43 0.55 0.72 0.14 0.24 0.31 0.40 0.10 0;18 0.23 0.29

135

Page 2012

year 100 year inches 2.38 inches Delta Mass Della 0.05 1.79 0.05 0.05 1.85 0.06 O.OS 1.88 0.03 0.01 1.89 0.01 0.01 1.91 0.02 0.02 1.93 0.02 0.02 1.95. 0.02 0.01 1.97 0.02 0.03 2.00 0.03 0.04 2.04 0.04 0.06 2.12 0.08 0.04 2.17 0.05 0.06 2.23. 0.06 0.06 2.30 0.07 0.01' 2.31 0.01 0.01 2.32 0.01 0:01 2.33 I 0.01 0.00 2.33 0.00

•.. 0.00 2:34 0.01. 0.01 2.34 0.00

. 0.01 2:35 ,0.01 0.00 2.36 0.01 0.00 2.36 I>O.Q().

0.01 2.36 0.00 10.00 '2.37 ! .•. 0.01

0.00 2.37 0.00 0:01 ,2.38 "··0;01 . 0.00 2.38 0.00

0.17 0.19 0.41 0.47 0.52 0.60 0.85 0:97 1.42 1.63 2:07 2:38'

2.04 2.28 .1.64 .j;84 1.04 1.20 0:85 Oi97 0.47 0.54 0;35 0.40

SDN 5 25 sa. mile

TIme Dis!. 0:00 0.0 0:05 2.0 0:10 5.9 0:15 8.0 0:20 11.0 0:25 14.4 0:30 15.0 0:35 16,0 0:40 16.8 0:45 17.1 0:50 18.0 0:55 18.2 1:00 18.7 1:05 19.0 1 :10 19.7 1:15 20.2 1:20 21.0 1:25 22.0 1 :30 23.0 1:35 24.1 1:40 25.0 1:45 25.9 1:50 26.5 1:55 28.0 2:00 29.0 2:05 30.0 2:10 30.5 2:15 30.9 2:20 31.0 2:25 31.7 2:30 32.1 2:35 32.7 2:40 33.3 2:45 34.6 2:50 36.1 2:55 38.1 3:00 40.8 3:05 43.0 3:10 47.7 3:15 51.4 3:20 56.1 3:25 63.0 3:30 71.0 3:35 72.0 3:40 73.1


Storm Frequency 2 year 5 year 10 year 25 year 50 year

0.55 inches 0.93 inches 1.21 inches 1.57 Inches 1.84 inches Mass Delta Mass Delta Mass Della Mass Dena Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.04 0.04 0.03 0.02 0.05 0.03 0.07 0.05 0.09 0.06 0.11 0.07 0.04 0.01 0.07 0.02 0.10 0.03 0.13 0.04 0.15 0.04 0.06 0.02 0.10 0.03 0.13 0.03 0.17 0.04 0.20 0.05 0.08 0.02 0.13 0.03 0.17 0.04 0.23 0.06 0.26 0.06 0.08 0.00 0.14 0.01 0.18 0.01 0.24 0.01 0.28 0.02 0.09 0.01 0.15 0.01 0.19 0.01 0.25 0.01 0.29 0.01 0.09 0.00 0.16 0.01 0.20 0.01 0.26 0.01 0.31 0.02 0.09 0.00 0.16 0.00 0.21 0.01 0.27 0.Q1 0.31 0.00 0.10 0.01 0.17 0.01 0.22 0.01 0.28 0.01 0.33 0.02 0.10 0.00 0.17 0.00 0.22 0.00 0.29 0.01 0.33 0.00 0.10 0.00 0.17 0.00 0.23 0.01 0.29 0.00 0.34 0.01 O.lO 0.00 0.18 0.01 0.23 0.00 0.30 0.01 0.35 0.01 0.11 0.01 0.18 0.00 0.24 0.01 0.31 0.01 0.36 0.01 0,11 0.00 0.19 0.01 0.24 0.00 0.32 0.01 0.37 0.01 0.12 0.01 0.20 0.01 0.25 0.01 0.33 0.01 0.39 0.02 0.12 0.00 0.20 0.00 0.27 0.02 0.35 0.02 0.40 0.01 0.13 0.01 0.21 0.01 0.28 0.01 0.36 0.01 0.42 0.02 0:13 0.00 0.22 0.01 0.29 0.01 0.38 0.02 0.44 0.02 0.14 0.01 0.23 I .. 0.01 0.30 0.01 0.39 0.01 0.46 0.02 0:14 0.00 0.24 0.01 0.31 0.01 0.41 0.02 0.48 0.02 0.15 0.01 0.25 0.01 0.32 0.01 0.42 0.01 0.49 0.Q1 0.15 0.00 0.26 0.01 0.34 0.02 0.44 0.02 0.52 0.03

I 0.16 0.01 0.27 0.01 0.35 0.01 0.46 0.02 0.53 0.01 0.17 0.01 0.28· 0.01 0.36 0.01 0.47 0;01 0.55 0.02 0.17 0.00 0.28 0.00 0.37 0.01 0.48 0.01 0.56 0.Q1 0.17 0.00 0.29 0.01 0.37 0.00 0.49 0.01 1 0:57 I 0.01 0.17 0.00 0.29 0.00 0.38 0.01 0.49 0.00 0.57 0.00 0.17 0.00 0.29 0.00 0.38 0.00 0.50 0.01 0.58 0.01 0:18 0.01 0.30 0.01 0.39 0.01 0.50 0.00 0.59 0.01 0;18 0.00 0.30 0.00 0.40 0.01 0.51 I·· 0.01 0.60 0.01 0.18 0.00 I 0.31 0.01 0.40 0.00 0.52 0.01 0.61 0.01 I .. ,

0.32 0.01 0.42 0.02 1 .. 0.54 0.02 0.64 0.03 1. 0.19 0.01 . 0.20 0.01 0.34 0.02 0.44 0.02 0.57 0.03 0.66 0.02 0.21 0.01 0.35 0:01 0.46 0.02 0.60 0.03 0.70 1. 0•04 0.22 0.01 0.38 0.03 0.49 0.03 0.64 0.04 0.75 0.05 0;24 0.02 0.40 0.02 0.52 0.03 0.68 0.04 0.79 0.04 0.26 0.02 0.44 0.04 0.58 0.06 0.75 0.07 0.88 0.09 0:28 0.02 0.48 0.04 0.62 0.04 0.81 0.06 0.95 0.07 0.31 0.03 0.52 0.04 0.68 0.06 0.88 0.07 1.03 0.08 0.35 0.04 0.59 0.07 0.76 0.08 0.99 0.11 1.16 0.13 0.39 0.04 0.66 1·· 0.D7 0.86 0.10 1.11 0.12 1.31 0.15 0.40 0.01 0.67 0.01 0.87 0.01 1.13 0.02 1.32 0.01 0.40 0.00 0.68 0.01 0.88 0.01 1.15 0.02 1.35 0.03

136

Page I of 2


Mass Delta 0.00 0.00 0.04 0.04 0.13 0.09 0.17 0.04 0.23 0.06 0.31 0.08 0.32 0.01 0.34 . 0.02 0.36 0.02 0;36 0.00 0.38 0.02 0.39 0.01 0.40 0.01 0.40 0.00 0.42 0.02 0.43 0.01 0.45 0.02

. 0.47 1. 0.02 0.49 0.02 0.51 0.02 0.53 0.02 0.55 0.02 0.56 0.01

1.0,59 I 0.03 0.61 0.02 .0~64. 10.03 0.65 0.01 0.66 10.01 0.66 0.00 0.67 I·· 0.01 0.68 1~·01

'0;69 0.01 0.71 0.02 0.73 .. 0.02 0.77 0.04 0.81:: I 0.04 0.86 1 0.05 0.91 0.05 1.01 0.10 1.09 1 0.08 1.19 0.10 1.34: 0.15 1.51 0.17 1.53 1. 0.02 1.55 0.02

SDN5 25 sq. mile

TIme DiSl. 3:45 75.2 3:50 n.9 3:55 79.0 4:00 79.5 4:05 80.4 4:10 81.0 4:15 82.0 4:20 82.6 4:25 84.0 4:30 85.9 4:35 88.9 4:40 91.0 4:45 93.8 4:50 96.6 4:55 97.0 5:00 97.4 5:05 97.9 5:10 98.1 5:15 98.3 5:20 98.5 5:25, 98.9 5:30 99.0 5:35

, 99.2

5:40 99.3 5:45 99.6 5:50 99.7

I 5:55·' 99.9 6:00 100.0

5 min. .15min. 30 min. 1 hour 3 hour S:houf

5 min. 15min. 30 min. lhour 3 hOur 6 hour




1.84 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.41' •... 0.01 0.70 0.02 0.91 0.03 1.18 0.03 1.38 0.43 0.02 0.72 0.02 0.94 0.03 1.22 0.04 1.43 OA3 0.00 0.73 0.01 0.96 0.02 1.24 0;02 1.45 0.44 0.01 0.74 0.01 0.96 0.00 1.25 0.01 1.46 0.44 0.00 0.75 0.01 0.97 0.01 1.26 0.01 lA8 0.45 0.01 0.75 0.00 0.98 0.01 1.27 0.01 1.49

,.0.45 0.00 0.76 0.01 0.99 0.01 1.29 0.02 1.51 0.45 0.00 o.n 0.01 1.00 0.01 1.30 0.01 1.52 0.46 0.01 0.78 0.01 1.02 0.02 1.32 0.02 1.55 0.47 0.01 0.80 0.02 1.04 0.02 1.35 0.03 1.58 0.49 0.02 0.83 0.03 1.08 0.04 1.40 0.05 1.64 0.50 0.D1 0.85 0.02 1.10 0.02 1.43 0.03 1.67 0.52 0.02 0.87 0.02 1.13 0.03 1.47 0.04 1.73 0.53 0.01 0.90 0.03 1.17 0.04 1.52 0.05 1.78 0.53 0.00 0.90 0.00 1.17 0.00 1.52 0.00 1.78 0.54 0.01 0.91 0.01 1.18 0.01 1.53 0.01 1.79 0.54 0.00 0.91 0.00 1.18 0.00 1.54 0.01 1.80

0.54 0.00 0.91 0.00 1.19 0.01 1.54 0.00 1.81

0.54 0.00 0.91 0.00 1.19 0.00 1.54 0.00 1.81

0.54 , .. 0.00 0.92 0.01 1.19 0.00 1.55 0.01 1.81 ' . ();54 .' 0.00 , 0.92 0.00 1.20 ' . 0.01 1.55 0.00 1.82

0.54 0.00 0.92 , ... 0.00 1.20 0.00 1.55 0.00 1.82 (;:55 0.01 0.92 1.20 0.00 1.56 0.01 1.83

1 0.00 0.55 0.00 0.92 0.00 1.20 0.00 1.56 0.00 1.83

,0;55 1'0;00 0.93 " 0.01 1.21 0.01 1;56 0;00 1.83

0.55 0.00 0.93 0.00 1.21 0.00 1.57 0.01 1.83

Q;55 ,0:00 0.93 0.00 1.21 "'0;00 .1.57 , 0:00 1;84

0.55 0.00 0.93 0.00 1.21 0.00 1.57 0.00 1.84

Maximum Values (depth in inches) 0.04 0.07 0.10

I 0.12

0.11 D.', 8 0:24 0.30 0.14 0.24 0.30 0.40 , 0.22 .0.38 O.SO 0.64

,

0.38 0.64 0.83 1.07

. 0.55 0;93 1.21 1.57


0.44 .0.72 0:96 1.20

0.28 0.48 0.60 0.80

'i······ .. 0;22 . 0.38 0;50 0.64 0.13 0.21 0.28 0.36

." .....• 0:09 0.16 0:20 0.26

137

Page 2 Of 2

year 100 year inches 2.12 indies Delta Mass Delta 0.03 1.59 0.04 0.05 1.65 0.06 0.02 1.67 . 0.02 0.01 1.69 0.02 0.02 1.70 0.01 0.01 1.72 0.02 0.02 1.74 0.02 0.01 1.75 0.01 0.03 1.78 0.03' 0.03 1.82 0.04 0.06 1.88 0.06 0.03 1.93 0.05 0.06 1.99 0.06 0.05 2.05 0.06 0.00 2.06 0.01 0.01 2.06 0.00 0.01 2.08

.; 0.02.

0.01 2.08 0.00 0.00 . 2.08 \O.OQ 0.00 2.09 0.01 0.01 '2.10 0:01 0.00 2.10 0.00 0.01 .' 2.10 0.00 0.00 2.11 0.Q1 0.00 2.11 10.00 0.00 2.11 0.00 0;01 2.12 0;01 0.00 2.12 0.00

0.15 0.17 0.36 0.,,2 0.47 0.54 0.75 '.0.86 1.26 1.45 1.84 '2.1.2

1.80 2.04 1.44

" cc . .. JAII!

0.94 1.08 0.75 . . ..... o-.8.f 0.42 0.48 0.31 .' 0:35

SON 5 50 SQ. mile

Time Disl. 0:00 0.0 0:05 2.0 0:10 5.9 0:15 8.0 0:20 11.0 0:25 14.4 0:30 15,0 0:35 16.0 0:40 16.8 0:45 17.1 0:50 18.0 0:55 18.2 1:00 18.7 1:05 19.0 1 :10 19.7 1:15 20.2 1:20 21.0 1:25 22.0 1 :30 23.0 t:35 24.1 1:40 25.0 1:45 25.9 1 :50 26.5 1:55 28.0 2:00 29.0 2:05 30.0 2:10 30.5 2:15 30.9 2:20 31.0 2:25 31.7 2:30 32.1 2:35 32.7 2:40 33.3 2:45 34.6 2:50 36.1 2:55 38.1 3:00 40.8 3:05 43.0 3:10 47.7 3:15 51.4 3:20 56.1 3:25 63.0 3:30 71.0 3:35 12.0 3:40 13.1

McCarran Airport Area Precipitation Clark County DeSign Storm

Storm Frequency 2vear

5 ___ 10 year 25 Year 50 year

0.49 inches 0.83 inches 1.07 inches 1.39 inches 1.64 inches Mass Delta Mass Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.03 0.03 O.OS 0.02 0.05 0.03 0.06 0.04 0.08 0.05 0.10 0.07 0.04 0.01 0.07 0.02 0.09 0.03 0.11 O.OS' 0.13 0.03 0.05 0.01 0.09 0.02 0.12 0.03 0.15 O.~ 0.18 0.05 0.07 0.02 0.12 0.03 0.15 0.03 0.20 0.05 0.24 0.06 0.07 0.00 0.12 0.00 0.16 0.01 0.21 0.01 0.25 0.01 0.08 0.01 0.13 0.01 0.17 0.01 0.22 0.01 0.26 0.01 0.08 0.00 0.14 om 0.18 0.01 0.23 0.01 0.28 0.02 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.01 0.28 0.00 0.09 0.01 0.15 om 0.19 0.01 0.25 0.01 0.30 0.02 0.09 0.00 0.15 0.00 0.19 0.00 0.25 0.00 0.30 0.00 0.09 0.00 0.16 0.Q1 0.20 0.01 0.26 0.01 0.31 0.01 0.09 0.00 0.16 0.00 0.20 0.00 0.26 0.00 0.31 0.00 0.10 0.Q1 0.16 0.00 0.21 0.01 0.27 0.01 0.32 0.01 0.10 0.00 0.17 0.01 0.22 0.01 0.28 0.01 0.33 0.01 0.10 0.00 0.17 0.00 0.22 0.00 0.29 0.01 0.34 0.01 0.11 0.01 0.18 0.Q1 0.24 0.02 0.31 0.02 0.36 0.02 0.11 0.00 0.19 om 0.25 0.01 0.32 0,01 /.0.38 0.02 0.12 0.01 0.20 0.01 0.26 0.01 0.33 0.01 I 0.40 0.02 0.12 0.00 0.21 0.01 0.21 0.01 0.35 0.02 0.41 0.01 0.13 0.01 0.21 0.00 0.28 0.01 0.36 0.01 0.42 0.01 0.13 0.00 0.22 0.01 0.28 0.00 0.37 0.01 0.43 0.01 0.14 0.01 0.23 ! .. 0.01·· 1 0.30 0.02 0.39' I 0.02 0.46 0.03 0.14 0.00 0.24 0.01 0.31 0.01 0.40 0.01 0.48 0.02 0.15 0.01 0.25 .0.01 0.32 ! 0.01 0.42 , 0.02 1.0•49 0.01 0.15 0.00 1 0.25 ·0.00 0.33 0.01 0.42 0.00 0.50 0.01 0 .. 15 1 0.00 0.26 rO.Ol 10.33 I 0.00 0.43 0.01 1°·51 0.01 0.15 0.00 0.26 0.00 0.33 0.00 0.43 0.00 0.51 0.00 0.16 10.01 0.26 .0.00 ·0.34 0.01 0.44 I 0.01 ' 0.52 ·0.01 0.16 0.00 0.27 0.01 0.34 0.00 0.45 0.01 0.53 0.01 0.16 I 0.00 0.27· 0.00 0.35 ·0.01 0.41$.

I . .().s4 0.01 I 0.00 0.16 0.00 0.28 0.01 0.36 0.01 0.46 0.01 0.55 0.01 0.17 0.01 0.29 0.01 0.37 0.01 0.48, 0.02 0.57 0.02 0.18 0.01 0.30 0.01 0.39 0.02 0.50 0.02 0.59 0.02 0.19 0.01 0.32 0.02 0.41 0.02 0.53 0.03 0.62 0.03 0.20 0,01 0.34 0.02 0.44 0.03 0.51 0.04 1 .. 0 .61 0.05 0.21 0.01 0.36 0.02 0.46 0.02 0.60 0.03 0.11 0.04 0.23 0.02 0.40 0.04 I, 0.51 0.05 0.66 0.06 0.78 0.07 0.25 0.02 0.43 1 .. 0.03 0.55 0.04 0.71 0.05 0.84 0.06 0.27 0.02 0.47 0.04 0.60 0.05 0.78 0.07 0.92 0.08 0.31 0.04 0.52 0.05 0.67 0.07 O.BB 0.10 1 1.03 0.11 0.35 0.04 0.59 0.01 0.76 0.09 0.99 0.11 1.16 0.13 0.35 0.00 0.60 0.01 0.77 0.01 1.00 0.01 1.18 0.02 0.36 0.01 0.61 0.01 0.78 0.01 1.02 0.02 1.20 0.02

138

Page 1012


Mass Delta 0.00 0.00 0.04 0.04 0.11 0.07 0.15 0.04 0.21 0.06 0.27 0.06 0.28 0.01 0.30 0.02 0.32 0.02 0.32 0.00 0.34 0.02 0.34 0.00 0.35 0.01 0.36 0.01 0.37 0.01 0.38 0.01 0.39 0.01 0.41 O.o~· 0.43 0.02 0.45 [0.02 0.41 0.02 0.49 0.02 0.50 0.01 0.53 0.03 0.55 0.02

I 0.56 1 0•01 0.57 0.01

10.58 .,.0.01 0.58 0.00 0.60 lO.02 0.60 0.00 0.61 0.01 0.63 0.02

1,0.65 0.02 0.68 0.03 0.72 ,0.04 0.77 0.05 0.81 '0.04 0.90 0.09 , 0.97 1°·07 1.05 0.08

.. 1.18 0,13 1.33 0.15 1.35 0.02 1.31 0.02

50 TIme 3:45 3:50 3:55 4:00

I 4:05 4:10 4:15 4:20 4:25 4:30 4:35 4:40 4:45 4:50 4:55 5:00 5:05 5:10 5:15 5:20 5:25 5:30 5:35 5:40 5:45 5:50 5:55 6:00

SONS sq. mile

Dist. 75.2 77.9 79.0 79.5 80.4 81.0 82.0i 82.6 84.0 85.9 88.9 91.0 93.8 96.6 97.0 97.4 97.9 98.1

I 98.3 98.5

[98;9 99.0 99.2 99.3 99.6 99.7 99.9

100.0

5 min.


Storm Frequency 2 year 5 year 10 year 25 year 50

0.49 inches 0.83 inches 1.07 inches 1.39 inches 1.64 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.37 0.01 ,0.62. 0.01 0.80 0.02 1.05 0.03 1.23 0.38 0.01 0.65 0.03 0.83 0.03 1.08 0.03 1.28 0.39 0.01 0.66. 0.01 0.85 0.02 1.10 0.02 1.30 0.39 0.00 0.66 0.00 0.85 0.00 1.11 0.01 1.30

'.'0.39 0.00 0:67 0.01 0.86 0.01 1.12 0.01' 1.32 0.40 0.01 0.67 0.00 0.87 0.01 1.13 0.01 1.33 0.40 0.00 . 0.68 0.01 1 0.88 0.01 1.14 0.01 11.34 0.40 0.00 0.69 0.01 0.88 0.00 1.15 0.01 1.35 0.41 0.01 0.70 0.01' 0.90 0.02 1.17 0.02 1.38 0.42 0.01 0.71 0.01 0.92 0.02 1.19 0.02 1.41

. 0.44 0.02 0.74 0.03 0.95 0.03 1.24 0.05 1.46 0.45 0.01 0.76 0.02 0.97 0.02 1.26 0.02 1.49 0.46 0.01 0.78 0.02 1.00 0.03 1.30 0.04 1.54 0.47 0.01 0.80 0.02 1.03 0.03 1.34 0.04 1.58 0.48 0.01 1°·81 0.01 1.04 0.01 1.35 0.01 1.59 0.48 0.00 O.Bl 0.00 1.04 0.00 1.35 0.00 1.60 0.48 0.00 0.81 0.00 1.05 0.01 1.36 0.01 . 1.61 0.48 0.00 0.81 0.00 1.05 0.00 1.36 0.00 1.61

i. 0.48 0.00 I 0.82 0.01 1.05 0.00 1.37 0.01 1.61 0.48 0.00 0.82 0.00 1.05 0.00 1.37 0.00 1.62 0.48 ' 0.00 0.82 0·00 '1.06 0.01 1.37 0.00 1'1.62 0.49 0.01 0.82 0.00 1.06 0.00 1.38 0.01 1.62 0.49 0.00 0.82 0.00 · ..• 1.06 0.00 1.38 0.00 1.63 0.49 0.00 0.62 0.00 1.06 0.00 1.38 0.00 1.63

year inches Delta 0.03 0.05 0.02 0.00 0.02 0.01

I. 0.01 0.01

I 0.03 0.03 0.05 0.03 0.05 0.04

, .. 0.01

I 0.01 0.01 0.00 0.00 0.01 0.00 0.00 0.01 0.00

'.0.49 0.00 1°·83 0.01 1.07 0.01 1;38 0.00 1.63 . 0.00 .

0.49 0.00 0.83 0.00 1.07 0.00 1.39 0.01 1.64 0.01

(0.49 0.00 10.83 0.00 1:07 . to.oo 1.39 0.00' I·.· 0.00 I 1.64 0.49 0.00 0.83 0.00 1.07 0.00 1.39 0.00 1.64 0.00

Maximum Values (depth in inches) 0.04 0.07 0.09 0.11 0.13

15 min; ••••••••••••••• I 0:16

,-.',".

0.21 0.28 0.32 0.10 , I 30min. 0.13 0.21 0.27 0.36 0.42 1 hour . ..... 0.20 ' . 0.34 . . 0.44 0.57. ! 0.S8 3 hour 0.34 0.57 0.73 0.95 1.12

6 hour 0.49 0.83 ' .. 1;07 1.39 ... 1:64

Maximum Values (intensity in inches/hour) 5 min. 0.48 0.84 1.08 1.32 .. 1.56 ....

15 min. 0.40 .... 0;64 0.84 1.12. .. 1.28

30 min. 0.26 0.42 0.54 0.72 0.84

1.hour ..•... .•....... 0.20 .. •••••• • 0.34< I. 0.44 0.57. ."

. 0.68 3 hour 0.11 0.19 0.24 0.32 0.37 Shour 0.08 0.14 0.18 0.23 0.27

139

Page 2 012


Mass Delta 1.41 0.04 1.46 0.05 1.49 0.03 1.49 0.00 1.51 0.02 1.52 0.01 1.54 0.02 1.55 0.01 1,58 0.03 1.61 0.03 1.67 0.06 1.71 0.04 1.76 0.05 I.B2 0.06 1.B2 0.00 1.B3 0.01 1.84 0.01 1.84 0.00 1.85 0.01 1.85 0.00 1,88 0.01 1.86 0.00 1.86 0.00 1.B7 0.01 1.87 0.00 1.B7 0.00 1:88 '. 0;01 1.88 0.00

0.15 0:36 0.47 0.77 1.28 1.88

1.80 b •. ( 0.94 0.77" 0.43 0:31

SONS 100 sq. mile

Time Cisi. 0:00 0.0 0:05 2.0 0:10 5.9 0:15 8.0 0:20 11.0 0:25 14.4 0:30 15.0 0:35 16.0 0:40 16.8 0:45 17.1 0:50 18.0 0:55 18.2 1:00 18.7 1:05 19.0 1: 10 19.7 1:15 20.2 1:20 21.0 1:25 22.0 1:30 23.0 1:35 24.1 1:40 25.0 1:45 25.9 1:50 26.S 1:55 28.0 2:00 29.0 2:05 30.0 2:10 30.5 2:15 30.9 2:20 31.0 2:25 31.7 2:30 32.1 2:35 32.7 2:40 33.3 2:45 34.6 2:50 36.1 2:55 38.1 3:00 40.8 3:05 43.0 3:10 41.1 3:15 51.4 3:20 56.1 3:25 63.0 3:30 71.0 3:35 72.0 3:40 73.1

McCarTan Airport Area PreCipitation Clark County Design Storm

Storm Frequency 2 year S year 10 year 25 year

0.43 inChes 0.73 inches 0.95 inches 1.23 inches 50 vear

1.45 inches Mass Celta Mass Delta Mass Delta Mass Celta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0:02 0.03 0.03

,,0.03 0.02 0.04 0.03 0.06 0.04 0.07 0.05 0.09 0.06 ",0.03 0.00 0.06 0.02 0.08 0.02 0.10 0.03 0.12 0.03

0.05 0.02 O.OB 0.02 0.10 0.02 0.14 0.04 0.16 0.04 O.OS, 0.01 0.11 0.03 0.14 0.04 I 0.18 0.04 0.21 0.05 0.08 0.00 0.11 0.00 0.14 0.00 0.18 0.00 0.22 0.01 0.07 0.01 0.12 0.01 0.15 0.01 0.20 0:02 0.23 0.01 0.07 0.00 0.12 0.00 0.16 0.01 0.21 0.01 0.24 0.01 0.07 0.00 0.12 0.00 0.16 0.00 0.21 0.00 0.25 0.01 0.08 0.01 0.13 0.01 0.17 0.01 0.22 0,01 0.26 0.01 0.08 0.00 0.13 0.00 0.17 0.00 0.22 0.00 0.26 0.00 0.08 0.00 0.14 0.01 0.18 0.01 0.23 0.01 0.27 0.01 0.08 0.00 0.14 0.00 0.18 0.00 0.23 0.00 0.28 0.01 0.08 0.00 0.14 0.00 0.19 0.01 0.24 0.01 0.29 0.01 0;09 0.01 0.15 0.01 0.19 0.00 0.25 0.01 0.29 0.00 0.09 0.00 0.15 0.00 0.20 0.01 0.26 0.01 0.30 0.01 0.09 0.00 0.16 0.01 0.21 0.01 0.27 0.01 0.32 0.02 0.10 0.01 0.17 0.01 0.22 0.01 0.28 0.01 0.33 0.01 0.10 0.1l0 0.18 0.01 0.23 0.01 0.30 0.02 D.35 0.02 0.11 0.01 0.18 0.00 0.24 0.01 0.31 0.01 0.36 0.01

. 0.11 0.00 0.19 0.01 0.25 0.01 0.32 0.01 0.38 0.02 0.11 0.00 0.19 0.00 0.25 0.00 0.33 0.01 0.38 0.00 0.12 0.01 0;20 0.01 0.27 0.02 0.34 0:01 0.41 0.03 0.12 0.00 0.21 0.01 0.28 0.01 0.36 0.02 0.42 0.01 0.13 0.01 0.22 0.01 0.29 0.01 0.37 0.01 0.44 0.02 0.13 0.00 0.22 0.00 0.29 0.00 0.38 0.01 0.44 C.OO 0;13 0.00 0.23 0.01' 0.29 0;00 0.38 0:00 . 0.45 0.01 0.13 0.00 0.23 0.00 0.29 0.00 0.38 0.00 0.45 0.00 0;14 ,0.01 0.23 0.00 0;30 0.01 0;39 0.01 0.46 0.01 0.14 0.00 0.23 0.00 0.30 0.00 0.39 0.00 0.47 0.01 0:14 0.00 0.24 0.01 0.31 0.01 0.40 0.01 0;47 0.00 0.14 0.00 0.24 0.00 0.32 0.01 0.41 om 0.48 ",0.01 0.15 0.01 0.25 0.01 0.33 0.01 0.43 0.02 0.50 0.02 0.16 0.01 0.26 0,01 0.34 0.01 0.44 om 0.52 0.02 0;16 0.00 0.28 0.02 0.36 0.02 0.47 0.03 0.55 0.03 0.18 0.02 0.30 0.02 0.39 0.03 O.SO 0.03 0.59 0.04 0.18 0.00 0.31 0.01 0.41 0.02 0.53 0.03 0.62 0.03 0.21 0.03 0.35 0.04 0.45 0.04 0.59 0.06 0.69 0.07 0.22 0.01 0.38 0.03 0.49 0.04 0.63 0.04 0.75 0.06 0.24 0.02 0.41 0.Q3 0.53 0.04 0.69 0.06 0.81 0.06

1,°·27 0.03 0.46 0.05 0.60 . 0.07 o.n 0.08 0.91 0.10 0.31 0.04 0.52 0.06 0.67 0.07 0.87 0,10 1.03 0.12 0.31 0.00 0.53 0.01 0.68 0.01 0.89 o.oa 1.04 0.01 0.31 0.00 0.53 0.00 0.89 0.01 0.90 0.01 1.06 0.02

140

Page 1012


Mass Delta 0.00 0.00 0.03 0.03 0.10 0.07 0.13 0:03 0.18 0.05 0.24 0.06 0.25 0.01 0.27. 0.02 0.28 0.01 0.28 0.00 0.30 0.02 0.30 0.00 0.31 0.01 0.32 0.01 0.33 0.01 0.34 0.01 0.35 0.01 0.37 0.02 0.38 0.01 0.40 0.02 0.42 0.02 0.43 0.01 0.44 L 0.01

I 0.46 0.02 0.48 0.02

k O•SO 0.02

1 0.51 ' 0.01 .. 0.51 0.00

0.51 0.00 0;53 L 0.02 0.53 0,00

,,0:54 0;01 0.55 0.01 0.57 0.02 0.60 0.03

"'0.63 0.03 0.68 0.05 0;71 0.03 0.79 0.08

,0.85 0,06 0.93 O.OS

.. 1.,.05 0.12 1.18 0,13 1.20 0.02 1.21 0.01

SONS 100 sq. mile

Time Dist. 3:45 75.2 3:50 n,9 3:55 79.0 4:00 79.5 4:05 80.4 4:10 81.0 4:15 82.0 4:20 82.6 4:25 84.0 4:30 85.9 4:35 88.9 4:40 91.0 4:45 93.8 4:50 96.6 4:55 97.0 5:00 97.4 5:05 97.9 5:10 98.1

1 5:15 98.3 5:20 98.5

.5:25 98.9 5:30 99.0

.5:35 99.2 5:40 99.3 5:45 99.6 5:50 99.7

1 . 1 5.55 99.9 6:00 100.0

5 min. 15 min. 30min. 1 hour 3 hour S hour

5 min. 15 min. 30 min. 1 hour 3 hour Shour



0.43 inches 0.73 inches 0.95 inches 1.23 inches 1.45 inches Mass Delta Mass Delta Mass Delta Mass Delta Mass Delta 0.32 0.01 0.55 0.02 0.71 0.02 0.92 0.02 1.09 0.03 0.33 0.01 .0.57 0.02 0.74 0.03 0.96 0.04 1.13 0.04

·0:34 '0.01 0.58 !·0.01 0.75 0.01 0.91 0.01 1.15 0.02 0.34 0.00 0.58 0.00 0.76 0.01 0.98 0.01 1.15 0.00 0.35 0.01 0.59 0.01 0.76 0.00 0.99 0.01 1.17 0.02 0.35 0.00 0.59 0.00 0.77 0.01 1.00 0.01 1.17 0.00 0.35 0.00 0.60 0.01 0.78 0.01 1.01 0:01 1:19 0.02 0.36 0.01 0.60 0.00 0.78 0.00 1.02 0.01 1.20 0.01 0:36 0.00 0.61 0.01 0.80 0.02 1.03 0.01 1;22 0.02 0.37 0.01 0.63 0.02 0.82 0.02 1.06 0.03 1.25 0.03

.. 0.38 0.01 0.65 0.02 0.84 0.02 1.09 0.03 1.29 0.04 0.39 0.01 0.66 0.01 0.86 0.02 1.12 0.03 1.32 0.03 0.40 0.01 0.68 0.02 0.89 0.03 1.15 0.03 1.36 0.04 0.42 0.02 0.71 0.03 0.92 0.03 1.19 0.04 1.40 0.04

0.42 0.00 0.71 0.00 0.92 0.00 1.19 0.00 1.41 0.01 0.42 0.00 0.71 0.00 0.93 0.01 1.20 0.01 1.41 0.00 0.42 0,00 0.71 0.00 0.93 0.00 1.20 0.00 1.42 0.01 0.42 0.00 0.72 0.01 0.93 0.00 1.21 0.01 1.42 0.00 0.42 0.00 0.72 0.00 0.93 0.00 1.21 0.00 1.43 0.01

0.42 0.00 0.72 I?'OO 0.94 0.01 1.21 0.00 1.43 0.00

0.43 to.Ol 0.72 0.00 0:94 0.00 1.22. 0.01 1.43 0.00

0.43 0.00 0.72 0.00 0.94 0.00 1.22 0.00 1.44 0.01 1·0.43 0:00 0.72 0.00 0.94 0.00 1.22 0.00 1.44 0.00

0.43 0.00 0.72 0.00 0.94 0.00 1.22 0.00 1.44 0.00

!0.43 (tOO 0.73 0.01 1 0.95 0;01 1:23 0;01 1.44 0.00

0.43 0.00 0.73 0.00 0.95 0.00 .. 1.23 0.00 1.45 0.01

0;43 10:00 ..

0.73 0.00· 0.95 0;00 10.00 1. 1,45 0.00 ·1:23 1 0.00 0.43 0.00 0.73 0.00 0.95 0.00 1.23 1.45 0.00

Maximum Values (depth in inches) 0.04 0.06 0.07 0.10 0.12

I·· , 0;09 1 0.14 a,18 0.24 0.28

0.10 0.18 0.24 0.31 0.37 I 0.18 0.30 0.39 ·0.50 0.60

0.30 0.50 0.65 0.84 0.99 .. 0;43 0.73 0.95· 1.23 1.45

Maximum Values (intensity in inches/hour) 0.48 0.72 0.84 1.20 1.44

0;36 0.56 0.72 0~96 1.12

0.20 0.36 0.48 0.62 0.74

0;18 .0.30 ·.0.39 .0.50 O.SO

0.10 0.17 0.22 0.28 0.33

0.07 0.12 0.16 0:21 0.24

141

Page 2012


Mass Delta 1.25 0.04 1.29 0.04 1.31 0.02 1.32 0.Q1 1.33 0.01· 1.34 0.01

.1.36 0.02· 1.37 0.01 1.39 0.02 1.43 0.04 1.48 0.05 1.51 0.03 1.56 0.05 1.60 0.04 1.61 0.01 1.62 0.01

... 1.63 ·0;01 1.63 0.00

".63 0.00 1.64 0.01 1.64 0.00 1.64 0.00 1.65

10.01

1.65 0.00 1.65 0.00 1.66 0.01 .1.66 O.rio 1.66 0.00

0.13 ··0.33 0.42 0.68 1.14 1.66.

1.56 .'t3Z 0.84 0.61l 0.38

.0.28

SONS 150 sq. mile

Time Dist. 0:00 0.0 0:05 2.0 0:10 5.9 0:15 8.0 0:20 11.0 0:25 14.4 0:30 15.0 0:35 16.0 0:40 16.8 0:45 17.1 0:50 18.0 0:55 18.2 1:00 18.7 1:05 19.0 1 :10 19.7 1:15 20.2 1:20 21.0 1:25 22.0 1:30 23.0 1:35 24.1 1:40 25.0 1:45 25.9 1:50 26.5 1:55 28.0 2:00 29.0 2:05 30.0 2:10 30.5 2:15 30.9 2:20 31.0 2:25 31.7 2:30 32.1 2:35 32.7 2:40 33.3 2:45 34.6 2:50 36.1 2:55 38.1 3:00 40.8 3:05 43.0 3:10 47.7 3:15 51.4 3:20 56.1 3:25 I 63.0 3:30 71.0 3:35 72.0 3:40 73.1


St F arm requenc' 2 __ 5 year 10 year 25 year 50 year

0.40 inChes 0.67 inChes 0.87 inChes 1.13 inChes 1.33 inches Mass Delta Mass Delta Mass Delta Mass Delta Mass Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0:01 .0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.02 0.01 0.04 0.03 0.05 0.03 0.07 0.05 0.08 0.05 0.03 0:01 0.05 0.01 0.07 0.02 0.09 0.02 0.11 0.03 0.04 0.01 0.07 0.02 0.10 0.03 0.12 0.03 0.15 0.04 0~O6' 0.02 0;10 0.03 0.13 0:03 0.16 0.04 1·0.19 0.04 0.06 0.00 0.10 0.00 0.13 0.00 0.17 0.01 0.20 0.01 0.06 0.00 0.11 0.01 0.14 0.01 0.18 0.01 0.21 0.01 0.07 0.01 0.11 0.00 0.15 0.01 0.19 0.D1 0.22 0.01 0:07 0.00 0.11 0.00 0.15 0.00 0.19 0.00 0.23 0.01 0.07 0.00 0.12 0.01 0.16 0.01 0.20 0.01 0.24 0.01 0.07 0.00 0.12 0.00 0.16 0.00 0.21 0.01 0.24 0.00 0.07 0.00 0.13 0.01 0.16 0.00 0.21 0.00 0.25 0.01 0.08 0.01 0.13 0.00 0.17 0.01 0.21 0.00 0.25 0.00 0.08 0.00 0.13 0.00 0.17 0.00 0.22 0.01 0.26 0.01 0.08 0.00 0.14 0.01 0.18 0.01 0.23 0.01 0.27 0.01 0.08 0.00 0.14 0.00 0.18 0.00 0.24 0.01 0.28 0.01 0~09 0.01 0.15 0.01 0.19 0.01 0.25 0.01 0.29 0.01 0.09 0.00 0.15 0.00 0.20 0.01 0.26 0.01 0.31 0.02 0.10 0.01 0.16 0.01 0.21 0.01 0.27 0.01 0.32. 0.01 0.10 0.00 0.17 0.01 0.22 0.01 0.28 0.01 0.33 0.01 0.10 0.00 0.17 0.00 0.23 0.01 0.29 0.01 0.34 0.01 0.11 0.01 0.18 0.01 0.23 0.00 0.30 0.01 0.35 0.01

·0.11 .0;00 0.19 0.01 0:24 0.01 0.32 0.02 0.37 0.02 I 0.12 0.01 0.19 0.00 0.25 0.01 0.33 0.01 0.39 0.02 \ 0.12 1 .. 0 .00 0.20 0.01 1·0.26 0.01 0.34 0.01 DAD 0.01

0.12 0.00 0.20 0.00 0.27 0.01 0.34 0.00 0.41 0.01 0~'2 0:00 0.21 1 0.01 1>0:27 0.00 0.35 0.01 OAI 0.00 0.12 0.00 0.21 0.00 0.27 0.00 0.35 0.00 0.41 0.00 0:13 0.01 0.21 0.00 1···0.28 0.01 0.36 0.01··· ·0.42 0.01 0.13 0.00 0.22 0.01 0.28 0.00 0.36 0.00 0.43 0.01 0:13 0.00 0.22 0.00 1 ... 0.28 0.00 0.37 0.01 1"0;43 0.00 0.13 0.00 0.22 0.00 0.29 0.01 0.36 0.01 0.44 0.01

·(1:14 1 ... 0

.01 0.23 0.01 0.30 0.01 0.39 0.01 0.46 0.02

0.14 0.00 0.24 0.01 0.31 0.01 0.41 0.02 0.48 0.02 0.15 0.01 0.26 0.02 0.33 0.02 0.43 0.02 I 0.51· 0.03 0.16 0.01 0.27 0.01 0.35 0.02 0.46 0.03 0.54 0.03 0.17 0.01 0.29 0.02 0.37 0.02 0.49 0.03 I· 0.57 0.03 0.19 0.02 0.32 0.03 0.41 0.04 0.54 0.05 0.63 0.06 0.21 0.02 0.34 0.02 1 0.45 0.04 0.58 0.04 0.68 0.05 0.22 0.01 0.38 0.04 0.49 0.04 0.63 0.05 0.75 0.07 0.25 0.03 0.42 0.04 0.55 I 0.06 0.71 0.08 0.84 0.09 0.28 0.03 0.48 0.06 0.62 0.07 0.80 0.09 0.94 0.10 0.29 0.01 0:48 0.00 0.63 0.01 0.81 0.01 0.96 0.02 0.29 0.00 0.49 0.01 0.64 0.01 0.83 0.02 0.97 0.01

142

Page 1012


Mass Della 0.00 0.00 0.03 0.03 0.09 0.06 0.12 0.03 ..

0.17 0.05 0.22 0.05 0.23 om 0.24 0.01 0.26 0.02 0.26 0.00 0.27 0.01 0.28 0.01 0.28 0.00 0.29 0.01 0.30 0.01 0.31 0.01 0.32 0.01 0.33 0.01 0.35 0.02 0.37 10.02 0.38 0.01 0.39 .0.01 0.40 0.D1 0.43 0.03 0.44 0.01 0.46 \····0.02. 0.46 0.00 0.47 r. 0.01 0.47 0.00 0.48 0.01 0.49 I 0.01 0.50 . 0.01 0.51 L 0.01 0.53 0.02 0.55 0.02 0.58 0.03 0.62 0.04 0.65 0.03 0.73 0.08 0.78 0.05 0.85 0.07 0.96 0.11 1.08 0.12 1.09 1 .. 0.01 1. II 0.02

SON 5 150 SQ. mile

TIme Oisl. 3:45 75.2 3:60 77.9 3:55 79;0 4:00 79.5 4:05 I 80.4 4:10 81.0 4:15 82.0 4:20 82.6 4:25 84.0 4:30 85.9 4:35 88.9 4:40 91.0 4:45 93.8 4:50 96.6 4:55 91.0 5:00 97.4 5:05 91.9 5:10 98.1 5:15 98.3 5:20 98.5 5:25 98.9

.

5:30 99.0



0.4 inches 0.67 indies 0.87 inches 1.13 inches 50

1.33 Mass Delta Mass Delta Mass Delta Mass Della Mass

1 0;30 0.01 0.50 0.01 ·.0.65 0.01 O.SS 0.02 1.00 0.31 0.01 0.52 0.02 0.68 0.03 0.88 0.03 1.04 0.32 . 0.01 0.53 0.01· 0.69 0.01 0.89 0.01 1.05 0.32 0.00 0.53 0.00 0.69 0.00 0.90 0,01 1.06

FC;32· ,0.00 0.54 0.01 0.70 0.01 0.91 0.01 1.07 0.32 0.00 0.54 0.00 0.70 0.00 0.92 0.01 1.08

..• 0.33 0.01 0.55 0.01 0.71 0.01 0.93 0.01 1.09 0.33 0.00 0.55 0.00 0.72 0.01 0.93 0.00 1.10

.·0.34 . 0.01 0.56 0.01· 0.73 0.01 0.95 0.02 1.12 0.34 0.00 0.58 0.02 0.75 0.02 0.97 0.02 1.14

··0.36 0.02 0.60 0.02 0.77 0.02 1 .00 0.03 1.18 0.36 0.00 0.61 0.01 0.79 0.02 1.03 0.03 1.21 0.38 0.02 0.63 0.02 0.82 0.03 1.06 0.03 1.25 0.39 0,01 0.65 0.02 0.84 0.02 1.09 0.03 1.28

<0.39 0.00 0.65 0.00 0.84 0.00 1.10 0.01 1.29 0.39 0.00 0.65 0.00 0.85 0.01 1.10 0.00 1.30 0.39 0.00 0.66 0.01 0.85 0.00 1.11 0.01 1.30 0.39 0.00 0.66 0.00 0.B5 0.00 1.i1 0.00 1.30

·0.39. 0.00. 0.66 0.00 0.86 0.01 1.11 0.00 1.31 0.39 0.00 0.66 0.00 0.86 0.00 1.11 I. 0.00 1.31 0.40 0.01 0;66 0;00 0.86 0.00 1.12 0.01 1.32 0.40 0.00 0.66 0.86 0.00 1.12 0.00 1.32

.. 5:35. ......... 99.2 '. 0.40 ·0.00 ·0.66 o.~ 0.00 0:86 0.00 1.12 0.00 1.32.

5:40 5:45 5:50 5:55 6:00

99.3 99.6 99.7 99:9

100.0

5 min. 15 min .... 30 min.

. 1 hour . 3 hour 6 hour

5 min. 15 min. 30 min.

. 1 hour 3 hour 6 hour

0.40 0.00 0.61 0.01 0.86 0.00 1.12 0.00 1.32 )0.40 0.00 ···0:67 0.00 (0:87 0.01 1.13 0.01 1.32

0.40 0.00 0.61 0.00 0.87 0.00 1.13 0.00 1.33 0.40· 0.00 ···0:67 0.00· 0.81 0.00 1.13 0.00 1.33 0.40 0.00 0.61 0.00 0.81 0.00 1.13 0.00 1.33

Maximum Values (depth in inches) 0.03 0.06 0.07 0.09 0.07 0.14 0.17 0.22 0.10 0.17 0.23 0.29 0.17 0.27 0.36 0.46 0.21 0.46 0.60 0.77 0:40 0.61 0.87 1.13

Maximum Values (intensity in inches/hour) 0.36 0.72 0;84 1.08 0.28 0.56 0.68 0.88 0.20 0.34 0.46 0.58

·0.17 0.27 0.360.46 . 0.09 0.15 0.20 0.26 0.01 0.11 0.15 0.19

143

Page2of2

year 100 year inches 1.52 inches Della Mass Delta 0.03 1.14 0.03 0.04 1.18 0.04 0.01 1.20 0.02 0.01 1.21 0.01 0.01 1.22 1·0.01 0.D1 1.23 0.01 0.01 1.25 0.02 0.D1 1.26 0.01 0.02 1.28. 0.02 0.02 1.31 0.03 0.04 1.35 0.04 0.03 1.38 0.03 0.04 1.43 0.05 0.03 1.47 0.04 0.01 1.47 ·0.00 0.01 1.48 0.Q1 0.00 1.49 0;01 0.00 1.49 0.00 0.01 1;49 .. 0.00 0.00 1.50 0.01 0.01 1:50· 0.00· 0.00 0.00 1.50

,0.00 I 1;51 0.01 ...... ' ...

0.00 0.00 0.01 O.{)O 0.00

0.10 <0:26

0.34 0:54 0.91 1;33 .

1.20 .. 1 .. 04

0.68 .0;54

0.30 0.22

1.51 0.00 1.51 0.00 1.52 0.01 U2 :0;00 1.52 0.00

0.12 p:ao 0.38

·0.62· 1.04

.1.52

1.44

. .. t.20 0.16

..·.·.>/ .. 0;62 0.35

.0:26

McCARRAN AIRPORT AREA PRECIPITATION SAN BERNARDINO COUNTY DESIGN STORM

1 SQ. MI.


DURATION 2-YR. S-YR. 10-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1.01 1.31 1.55 1. 79

l-HR. 0.52 0.89 1.15 1.50 1. 78 2.06

3-HR. 0.64 1.08 1.39 1.82 2.15 2.48

6-HR. 0.72 1.22 1.58 2.05 2.41 2.77

24-HR. 1.20 1. 60 1.80 2.40 2.70 2.96



5-MIN. 0.971 0.15 0.26 0.34 0.45 0.52 0.61

30-MIN. 0.971 0.43 0.76 0.98 1.27 1.51 1. 74

1-HR. 0.971 0.50 0.86 1.12 1.46 1. 73 2.00

3-HR. 0.996 0.64 1. 08 1.38 1.81 2.1.4 2.47

6-HR. 0.998 0.72 1.22 1.58 2.05 2.41 2.76

24-HR. 0.999 1.20 1.60 1.80 2.40 2.70 2.96



5-MIN. 0.971 1. 75 3.15 4.08 5.36 6.29 7.34

30-MIN. 0.971 0.85 1.51 1.96 2.54 3.01 3.48

l-HR. 0.971 0.50 0.86 1.12 1.46 ~1. 73 2.00

3-HR. 0.996 0.21 0.36 0.46 0.60 0.71 0.82

6-HR. 0.998 0.12 0.20 0.26 0.34 0.40 0.46

24-HR. 0.999 O.lO 0.13 0.15 0.20 0.22 0.25

144


5 SQ. MI.


DURATION 2-YR. 5-YR. la-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1.01 1.31 1.55 1. 79

I-HR. 0.52 0.89 1.15 1.50 1. 78 2.06

3-HR. 0.64 1. 08 1.39 1.82 2.15 2.48

6-HR. 0.72 1.22 1.58 2.05 2.41 2.77

24-HR. 1.20 1. 60 1.80 2.40 2.70 2.96


DURATION DEPTH-AREA 2-YR. S-YR. la-YR. 2S-YR. 50-YR. 100-YR.

S-MIN. 0.B57 0.13 0.23 0.30 0.39 0.46 0.54

30-MIN. 0.B57 0.38 0.67 0.87 1.12 1.33 1.53

l-HR. 0.857 0.45 0.76 0.99 1.29 1.53 1.77

3-HR. 0.979 0.63 1.06 1.36 1.78 2.10 2.43

6-HR. 0.989 0.71 1.21 1.56 2. 03 2.38 2.74

24-HR. 0.994 1.19 1.59 1.79 2.39 2.68 2.94


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 2S-l/'R. 50-YR. lOa-YR.

5-MIN. 0.857 1.54 2.78 3.60 4.73 5.55 6.48

30-MIN. 0.B57 0.75 1.34 1. 73 2.25 2.66 :3.07

1-HR. 0.857 0.45 0.76 0.99 1.29 1. 53 1.77

3-HR. 0.979 0.21 0.35 0.45 0.59 0.70 O.Sl

6-HR. 0.989 0.12 0.20 0.26 0.34 0.40 0.46

24-HR. 0.994 0.10 0.13 0.15 0.20 0.22 0.25

145


10 SQ. MI.



5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1.01 1.31 1.55 1. 79

I-HR. 0.52 0.89 1.15 1.50 1.78 2.06

3-HR. 0.64 1.08 1.39 1.82 2.15 2.48

6-HR. 0.72 1.22 1.58 2.05 2.41 2.77

24-HR. 1. 20 1.60 1.80 2.40 2.70 2.96



5-MIN. 0.750 0.11 0.20 0.26 0.35 0.41 0.47

3D-MIN. 0.750 0.33 0.59 0.76 0.98 1.16 1.34

I-HR. 0.750 0.39 0.67 0.86 1.13 1. 34 1.55

3"'"HR. 0.955 0.61 1.03 1. 33 1. 74 2.05 2.37

6-HR. 0.979 0.70 1.19 1.55 2.01 2.36 2.71

24-HR. 0.987 1.18 1.58 1. 78 2.37 2.66 2.92


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. lOa-YR.

5-MIN. 0.750 1.35 2.43 3.15 4.14 4.86 5.67

30-MIN. 0.750 0.66 1.17 1. 52 1.97 2.33 2.69

1-HR. 0.750 0.39 0.67 0.86 1.13 1. 34 1.55

3-HR. 0.955 0.20 0.34 0.44 0.58 0.68 0.79

6-HR. 0.979 0.12 0.20 0.26 0.33 0.39 0.45

24-HR. 0.987 0.10 0.13 0.15 0.20 0.22 0.24

146


25 SQ. MI.



5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1.01 1. 31 1.55 1.79

l-HR. 0.52 0.89 1.15 1.50 1. 78 2.06

3-HR. 0.64 1.08 1. 39 1. 82 2.15 2.48

6-HR. 0.72 1.22 1.58 2.05 2.41 2.77

24-HR. 1. 20 1.60 1.80 2.40 2.70 2.96



5-MIN. 0.570 0.09 0.15 0.20 0.26 0.31 0.36

30-MIN. 0.595 0.26 0.46 0.60 0.78 0.92 1.07

1-HR. 0.605 0.31 0.54 0.70 0.91 1.08 1.25

3-HR. 0.910 0.58 0.98 1.26 1.66 1.96 2.26

6-HR. 0.958 0.69 1.17 1.51 1.96 2.31 2.65

24-HR. 0.974 1.17 1.56 1. 75 2.34 2.63 2.88



5-MIN. 0.570 1.03 1.85 2.39 3.15 3.69 4.31

30-MIN. 0.595 0.52 0.93 1.20 1.56 1.84 2.13

l-HR. 0.605 0.31 0.54 0.70 0.91 1.08 1.25

3-HR. 0.910 0.19 0.33 0.42 0.55 0.65 0.75

6-HR. 0.958 0.11 0.19 0.25 0.33 0.38 0.44

24-HR. 0.974 0.10 0.13 0.15 0.19 0.22 0.24

147


50 SQ. MI.

POINT RAINFALL DEPTHS (IN.)


5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1. 01 1.31 1.55 1.79

1-HR. 0.52 0.89 1.15 1.50 1. 7B 2.06

3-HR. 0.64 LOB 1. 39 1.82 2.15 2.48

6-HR. 0.72 1.22 1. 58 2.05 2.41 2.77

24-HR. 1.20 1.60 1.80 2.40 2.70 2.96

MAXIMUM ADJUSTED PRECIPITATION DEPTHS (IN .)


5-MIN. 0.430 0.06 0.12 0.15 0.20 0.23 0.27

30-MIN. 0.468 0.21 0.37 0.47 0.61 0.73 0.84

1-RR. 0.492 0.26 0.44 0.57 0.74 0.88 1. 01

3-RR. 0.840 0.54 0.91 1.17 1.53 1.81 2.08

6-HR. 0.929 0.67 1.13 1.47 1.90 2.24 2.57

24-HR. 0.957 1.15 1.53 1.72 2.30 2.58 2.83

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN ./RR.)


5-MIN. 0.430 0.77 1.39 1.81 2.37 2.79 3.25

30-MIN. 0.468 0.41 0.73 0.95 1. 23 1.45 1. 68

1-HR. 0.492 0.26 0.44 0.57 0.74 0.88 1.01

3-HR. 0.840 0.18 0.30 0.39 0.51 0.60 0.69

6-HR. 0.929 0.11 0.19 0.24 0.32 0.37 0.43

24-HR. 0.957 0.10 0.13 0.14 0.19 0.22 0.24

148


100 SQ. M!.



5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1.01 1.31 1.55 1.79

1-HR. 0.52 0.89 1.15 1.50 1. 78 2.06

3-HR. 0.64 1.08 1.39 1.82 2.15 2.48

6-HR. 0.72 1.22 1. 58 2.05 2.41 2.77

24-HR. 1. 20 1. 60 1. 80 2.40 2.70 2.96


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. laO-YR.

5-MIN. 0.300 0.05 0.08 0.11 0.14 0.16 0.19

30-MIN. 0.355 0.16 0.28 0.36 0.47 0.55 0.64

I-HR. 0.402 0.21 0.36 0.46 0.60 0.72 0.83

3-HR. 0.747 0.48 0.81 1. 04 1.36 1. 61 1.85

6-HR. 0.889 0.64 1.08 1.40 1.82 2.14 2.46

24-HR. 0.935 1.12 1.50 1.6B 2.24 2.52 2.77

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN ./HR.)

DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. 100-YR,

5-MIN. 0.300 0.54 0.97 1.26 1.66 1.94 2.27

3D-MIN. 0.355 0.31 0.55 0.72 0.93 1.10 1.27

i-HR. 0.402 0.21 0.36 0.46 0.60 0.72 0.83

3-HR. 0.747 0.16 0.27 0.35 0.45 0.54 0.62

6-HR. 0.889 0.11 0.18 0.23 0.30 0.36 0.41

24-HR. 0.935 0.09 0.12 0.14 0.19 0.21 0.23

149


150 SQ. MI.



5-MIN. 0.15 0.27 0.35 0.46 0.54 0.63

30-MIN. 0.44 0.78 1.01 1.31 1.55 1.79

I-HR. 0.52 0.89 1.15 1.50 1.78 2.06

3-HR. 0.64 1. 08 1.39 1.82 2.15 2.48

6-HR. 0.72 1. 22 1. 58 2.05 2.41 2.77

24-HR. 1.20 1. 60 1. 80 2.40 2.70 2.96



5-MIN. 0.243 0.04 0.07 0.09 0.11 0.13 0.15

3D-MIN. 0.310 0.14 0.24 0.31 0.41 0.48 0.55

I-HR. 0.362 0.19 0.32 0.42 0.54 0.64 0.75

3-HR. 0.688 0.44 0.74 0.96 1.25 1. 48 1.71

6-HR. 0.870 0.63 1.06 1.37 1.78 2.10 2.41

24-HR. 0.923 1.11 1.48 1.66 2.22 2.49 2.73


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. lOO-YR.

5-MIN. 0.243 0.44 0.79 1. 02 1.34 1.57 1.84

3D-MIN. 0.310 0.27 0.48 0.63 0.81 0.96 1.11

I-HR. 0.362 0.19 0.32 0.42 0.54 0.64 0.75

3-HR. 0.688 0.15 0.25 0.32 0.42 0.49 0.57

6-HR. 0.870 0.10 0.18 0.23 0.30 0.35 0.40

24-HR. 0.923 0.09 0.12 0.14 0.18 0.21 0.23

150

>--c :! 0 U tIl III "-~ ~

"0 .~

" • > ;;: I

'" -c ~ 0 u IIi vi ~

Desert Hot Springs Area Adjusted RainfaJl Comparison: 2 Year (Rainfalls adjusted using respective County depth-area curves)


0.4

0.3 f--

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

\\ ~ ~

-L ~ ~ ~ E;2l'\ ~ ~~ ~ ~ '/ ~ !/ r; tQ~ r; ~ ~ ~ [;, ~ ~ ..L

r/ ~ ~ r; ~ ~ [;, ~ ~ 1/

~ ~ '/ lL

~ -O.B

30 min. 60 min. 180 min.

Design Sterm Peak Duretion (minutes)

~ 1 mile ~ 5 mile ~ 10 mile ~ 25 mile JS:SJ 50 'mile rz2j 150 mile

Graph Values ((S.B.County-Riverside)lS.B.County]

30 min. 60 min. 180 min. 1 Sq. Mi. 0.34 0.21 0.00 5SQ. Mi. 0.25 0.09 0.05

10 Sq. Mi. 0.16 0.00 0.00 25 Sq. Mi. -0.06 -0.21 -0.06 50 Sq. Mi. -0.29 -0.47 -0.06

150 SQ. Mi. -0.62 -0.69 -0.21

151

1:-c 3 0

0 ai

'" "-~ ~ '0 ... -• > ~ I

1:-c 3 0 ()

III

~



0.4

0.3

0.2

0.1

a

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-O.B 30 min. 60 min. 180 min.

Oesi9" Storm Peak Duration (minutes)

~ 1 mile ~5mile ~ 10 mile ['iQZ] 25 mile ISSJ 50 mile rzzJ 150 mile

Graph Values I(S.B.County-Riverside)lS.B.County)


10 Sq. Mi. 0.19 -0.02 0.00 25 Sq. Mi. -0.02 -0.25 -0.02 so Sq. Mi.·' -0.26 -0.49 -0.08

150 Sq. Mi. -0.59 -0.74 -0.15

152



0.4,-------------------------,

0.3

0.2

0.1

-0.1 1-------1

-0.21------J>,.

-0.3 I------'-V /1-------1'>

-0.4 1------1

-0.5 1--------lI JI-------==r /1-----------1

-0.6 I---------------l,,'l------------j

-0.7 1--------------+'/1----------1 -0.8 L ______________________ --'

30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile ~ 25 mile iSS] 50 mile 1Z2i150 mile

Graph Values [(S.B.County-Riverside)lS.B.County)

30 min. GO min. 180 min. 1 Sq. Mi. 0.36 0.20 0.02 5 Sq. Mi. 0.27 0.10 0.02

1090. Mi. 0.18 -0.01 0.00 25 Sq. Mi. -0.02 -0.23 -0.04 50 Sq. Mi. -0.27 -0.49 -0.08

150 Sq. MI. -0.57 -0.72 -O.lG

153

'" C ~ 0 0 ai If)

:::: 0

" .~ ~

~ > ii I

'" ~ c ~ 0

l! 'I! If) ~



0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8 30 min. 60 min. 180 min.


m, mile ~5mile rz:zlIO mile ~ 25 mile rssJ 50 mile iZ2l150 mile

Graph Values [(S.B.County-Riverside)lS.B.County]


10Sq. Mi. 0.18 -0.02 0.00 25 Sq. Mi. -0.01 -0.23 -0.03 50 Sq. Mi. -0.25 -0.47 -0.09

150 Sq. Mi. -0.57 -0.72 -0.17

154

1 sq. mile Time Dis!. 0:00 0.0 0:05 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0:50 6.4 0:55 7.1 1 :00 7.9 1:05 8.7 1:10 9.5 1:15 10.3 1:20 11.1 1:25 11.9 1:30 12.7 1:35 13.5 1:40 14.3 1:45 15.1 1:50 15.9 1:55 16.7 2:00 17.6 2:05 18.4 2:10 19.3 2:15 20.2 2:20 21.1 2:25 22.0 2:30 22.9 2:35 23.8 2:40 24.7 2:45 25.7 2:50 26.7 2:55 27.7 3:00 28.7 3:05 29.7 3:10 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3:35 36.9 3:40 38.3

Desert Hot Springs Area Precipitation Riverside County 6-Hr Design Storm


0.76 inches 1.31 inches 1.73 inches 2.28 inches 2.70 Mass Delta Mass Delta Mass Delta Mass Delta Mass

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.02 0.01 0.03 0.02 0.03 0.01 0.00 0.02 0.01 0.03 0.01 0.04 0.01 0.05 0.02 0.01 0.03 0.01 0.04 0.01 0.05 om 0.06 0.02 0.00 0.04 0.01 0.05 0.01 0.07 0.02 0.08 0.03 0.01 0.05 0.01 0.06 0.01 0.08 0.01 0.10 0.03 0.00 0.06 0.01 0.07 0.01 0.10 0.02 0.12 0.04 0.01 0.07 0.01 0.09 0.02 0.11 0.01 0.14 0.04 0.00 0.07 0.00 0.10 0.01 0.13 0.02 0.15 0.05 0.01 0.08 0.01 0.11 0.01 0.15 0.02 0.17 0.05 0.00 0.09 0.01 . 0.12 0.01 0.16 0.01 0.19 0.06 0.01 0.10 0.01 0.14 0.02 0.18 0.02 0.21 0.07 0.01 0.11 0.01 0.15 0.01 0.20 0.02 0.23 0.07 0.00 0.12 0.01 0.16 0.01 0.22 0.02 0.26 0.08 0.01 0.13 0.01 0.18 0.02 0.23 0.01 0.28 0.08 0.00 0.15 0.02 0.19 0.01 0.25 0.02 0.30 0.09 0.01 I 0.16 0.01 0.21 0.02 0.27 0.02 0.32 0.10 0.01 0.17 0.01 0.22 0.01 0.29 0.02 0.34 0.10 0.00 0.18 0.01 0.23 0.01 0.31 0.02 0.36 0.11 0.01 0.19 0.01 0.25 0.02 0.33 0.02 0.39 0.11 0.00 . 0.20 I 0.01 0.26 0.01 0.34 0.01 0.41 0.12 0.01 0.21 0.01 0.28 0.02 0.36 0.02 0.43 0.13. 0.01 . ··• .. ·0:22 0.01 •. 0.29 0.01 0.38 0.02 0.45

0.13 0.00 .... 0.23 0.01 0.30 0.01 0.40 0.02 0.48 0.14 0.01 0.24 0.01 0.32 0.02 0.42 0.02 0.50 0.15 0.01 0.25 0.01 0.33- 0.01 0.44 0.02 0.52

0.15 0.00 0.26 1 .. 0.01 0.35 0.02 0:46 0.02 0.55 0.16 0.01 0.28 0.02 0.37 0.02 0.48 0.02 0.57 0.17 0.01 '0.29 0.01 0.38 0.01 0.50 0.02 0.59 0.17 0.00 0.30 0.01 0.40 0.02 0.52 0.02 0.62 0.18 0.01 0:31 0.01 0.41 . 0.01 0.54 0.02 0.64 0.19 0.01 0.32 0.01 0.43 0.02 0.56 0.02 0.67

0.20 0.01 0.34 0.02 I· 0.44 0.01 0.59 0.03 0.69 0.20 0.00 0.35 0.01 0.46 0.02 0.61 0.02 0.72

0.21 0.01 1 0.36 0.Q1 0.48 0.02 0.63 0.02 0.75 0.22 0.01 0.38 0.02 0.50 0.02 0.65 0.02 0.77

0.23 0.Q1 '0.39 0.01 0.51 0.01 0.68 0.03 0.80 0.23 0.00 0.40 0.01 0.53 0.02 0.70 0.02 0.83

0.24 0.01 0.42 0.02 0.55 0.02 0.73 0.03 0.86 0.25 0.01 0.43 0.01 0.57 0.02 0.75 0.02 0.89

0.26 0.01 ... ·0.45 0.02 0.59. 0.02 0.78 0.03 0.92

0.27 0.01 0.47 0.02 0.61 0.02 0.81 0.03 0.96 0.28 0.01 0.48 0.01 0.64 0.03 0.84 0.03 1.00 0.29 0.01 0.50 0.02 0.66 0.02 0.87 0.03 1.03

155

Page 1 of 2

year 100 year inches 3.11 inches Delta Mass Delta 0.00 0.00 0.00 0.01 0.02 0.02 0.02 0.03 0.01 0.02 0.05 0.02 0.01 0.07 0.02 0.02 0.09 0.02 0.02 0.11 0.02 0.02 0.13 0.02 0.02 0.16 0.03 0.01 0.18 0.02 0.02 0.20 0.02 0.02 0.22 0.02 0.02 0.25 0.03 0.02 0.27 0.02 0.03 0.30 0.03 0.02 0.32 0.02 0.02 0.35 0.03 0.02 0.37 0.02 0.02 0.39 0.02 0.02 0.42 . 0.03

0.03 0.44 0.02 0.02 0.47 0.03 0.02 0.49 0.02 0.02 0.52 0.03 0.03 0.55 0.03 0.02 0.57 0.02 0.02 0.60 0.03 0.03 0.63 0.03 0.02 0.66 0.03 0.02 0.68 0.02 0.03 0.71 0.03 0.02 0;74 0.03 0.03 o.n 0.03 0.02 0.80 0.03 0.03 0.83 0.03 0.03 0.86 0:03 0.02 0.89 0.03 0.03 0.92 0.03 0.03 0.96 0.04 0.03 0.99 0.03 0.03 1.03 0.04 0.03 1.06 0.03 0.04 1.10 0.04 0.04 1.15 0.05 0.03 1.19 0.04

1 sq. mile Time OiSl. 3:45 39.8 3:50 41.3 3:55 42.9 4:00 44.5 4:05 46.2 4:10 48.0 4:15 49.9 4:20 51.9 4:25 54.0 4:30 56.1 4:35 58.3 4:40 60.6 4:45 63.0 4:50 65.4 4:55 67.9 5:00 70.5 5:05 73.6 5:10 77.2 5:15 81.1 5:20 85.3 5:25 90.0 5:30 95.6 5:35 97.5 5:40 98.4 5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

5 min. 15 min. aDmin. 1 hour 3 hour 6 hour

5 min. 15 min.

I SOmin. 1 hour :3 hour 6 hour

Desert Hot Springs Area Precipitation Riverside County 6-Hr DeSign Storm

Storm Frequency 2 year 5 year 10 vear 25 year 50

0.76 inclles 1.31 inches 1.73 inches 2.28 inches 2.7 Mass Della Mass Della Mass Della Mass Della Mass 0.30 0.01 0.52 0.02 0.69 0.03 0.91 0.04 1.07 0.31 0.01 0.54 0.02 0.71 0.02 0.94 0.03 1.12 0.33 0.02 0.56 0.02 0.74 0.03 0.98 0.04 1.16 0.34 0.01 0.58 0.02 0.77 .0.03 1.01 0.03 1.20 0.35 0.01 0.61 0.03 0.80 0.03 1.05 0.04 1.25 0.36 0.01 0.63 0.02 0.83 0.03 1.09 •. 0.04 1.30 0.38 0.02 0.65 0.02 0.86 0.03 1.14 0.05 1.35 0.39 0.01 0.68 0.03 0.90 0.04 1.18 0.04 1.40 0.41 0.02 0.71 0.03 0.93 0.03 1.23 0.05 1.46 0.43 0.02 0.73 0.02 0.97 0.04 1.28 0.05 1.51 0.44 0.01 0.76 0.03 1.01 0.04 1.33 0.05 1.57 0.46 0.02 0.79 0.03 1.05 0.04 1.38 0.05 1.64 0.48 0.02 0.83 0.04 1.09 0.04 1.44 0.06 1.70 0.50 0.02 0.86 0.03 1.13 0.04 1.49 0.05 1.77 0.52 0.02 0.89 0.03 1.17 0.04 1.55 0.06 1.83 0.54 0.02 0.92 0.03 1.22 0.05 1.S1 O.OS 1.90 0.56 0.02 0.96 0.04 1.27 0.05 1.68 0.07 1.99 0.59 0.03 1.01 0.05 1.34 0.07 1.76 0.08 2.08 0.62 0.03 1.06 0.05 1.40 0.06 1.85 0.09 2.19 0.65 0.03 1.12 0.06 1.48 0.08 1.94 0.09 2.30 0.68 0.03 1.18 0.06 1.56 0.08 2.05 0.11 2.43 0.73 0.05 1.25 0.07 1.65 0.09 2.18 0.13 2.58 0.74 0.01 1.28 0.03 1.69 ·0.04 2.22 0.04 2.63 0.75 0.01 1.29 0.01 1.70 0.01 2.24 0.02 2.66 0.75 0.00 1.30 0.01 1.71 0.01 2.26 0.02 2.67 0.76 0.01 1.30 0.00 1.72 0.01 2.27 0.01 2.69 0.76 0.00 1.31 0.01 1.73 ! 0:01 2.28 0:01 2.69 0.76 0.00 1.31 0.00 1.73 0.00 2.28 0.00 2.70

Maximum Values (depth in inches) 0.05 0.07 0.09 0.13 0.11 0.19· 0.25 0.33 0.19 0.33 0.43 0.57 0.30 0.52 0.68 0.90 0.56 0.97 1.28 1.68 0.76 \.31 1.73 2.28

Maximum Values (intensity in inches/hour) 0.60 0.84 1.08 1.56 0.44 0.76 1.00 1.32 0.38 0.66 0.86 1.14 0.30 0.52 0.68 0.90 0.19 0.32 0.43 0.5~ 0.13 0.22 0.29 0.38

156

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year 100 year inches 3.11 inches Delta Mass Delta 0.04 1.24 0.05 0.05 1.28 0.04 0.04 1.33 0;05 0.04 1.38 0.05 0.05 1.44 0.06 0.05 1.49 0.05 0.05 1.55 0.08 0.05 1.61 0.06 0.06 1.68 0.07 0.05 1.74 0.06 0.06 1.81 0.07 0.07 1.88 0.07 0.06 1.96 0.08 0.07 2.03 0.07 0.06 2.11 0.08 0.07 2.19 0.08 0.09 2.29 0.10 0.09 2.40 0.11 0.11 2.52 0.12 0.11 2.65 0.13 0.13 2.80 0.15 0.15 2.97 0.17 0.05 3.03 o.oe 0.03 3.06 0.03 0.01 3.0B 0.02 0.02 3.09 0.01 0.00 3.10 0,01 0.Q1 3.11 0.01

0.15 0.17 0.39 0.45 0.68 0.78 1.07 1.23 1.99 2.29 2.70 3;11

1.80 2.04 1.56 1.80 1.36 1.56 1.07 1.23 0.66 0.76 0.45 0.52

5 so . 'Tlile Time I (JiSt.

0:00 0.0 0:05 . 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0:50 6.4 0:55 7.1 1:00 7.9 1:05 8.7 1 :10 9.5 1:15 10.3 1:20 11.1 1:25 11:9. 1:30 12.7 1:35 13.5 1:40 14.3 1:45 15.1 1:50 15.9 1:55 16.7 2:00 17.6 2:05 18.4 2:10 19.3 2:15 20.2 2:20 21.1 2:25 22.0 2:30 22.9 2:35 23.8· 2:40 24.7 2:45 25.7 2:50 26.7 2:55 27.7 3:00 28.7 3:05 29.7 3:10 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3:35 36.9 3:40 38.3




0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.02 0.01 0.02 0.01 0.03 0.01 0.00 0.02 0.01 0.03 0.01 0.04 0.02 0.05 0.02 0.01 0.03 0.01 0.04 0.01 0.05 0.01 0.06 0.02 0.00 0.04 0.01 0.05 0.01 0.07 0.02 0.08 0.03 0.01 0.05 0.01 0.06 0.01 0.08 0.01 0.10 0.03 0.00 0.06 0.01 0.07 0.01 0.10 0.02 0.12 0.04 0.01 0.07 0.01 0.09 0.02 0.11 0.01 0.13 0.04 0.00 0.07 0.00 0.10 0.01 0.13 0.02 0.15 0.05 0.01 0.08 0.01 0.11 0.01 0.14 0.01 0.17 0.05 0.00 0.09 0.01 0.12 0.01 0.16 0.02 0.19 0.06 0.01 0.10 0.01 0.14 0.02 0.18 0.02 0.21 0.07 0.01 0.11 0.Q1 0.15 0.01 0.20 0.02 0.23 0.07 0.00 0.12 0.01 0.16 0.01 0.21 0.01 0.25 0.08 0.01 0.13 0.01 0.18 0.02 0.23 0.02 0.28 0.08 0.00 0.15 0.02 0.19 0.01 0.25 0.02 0.30 0.09 0.01 0.16 0.01 0.20 0.01 0.27 0.02 0.32 0.10 0.01 0.17 0.Q1 0.22 0.02 0.29 0.02 0.34

0.10 0.00 0.18 0.01 0:23 0.01 0:31 0.02 0.36 0.11 0.01 0.19 0.01 0.25 0.02 0.32 0.01 0.38 0.11 0.00. 0.20 0.01 0.26 0.01 0.34 0.02 0.40 0.12 0.01 0.21 0.01 0.27 0.01 0.36 0.02 0.43 0.13 10.01 0.22 0.01· ·.····0:29 0.02 0.38 0.02 0.45

0.13 0.00 0.23 0.01 0.30 0.01 0.40 0.02 0.47

1°·14 I· 0.01 0.24 0.01 ·0.32 0;02 0.42 0.02 0.49 0.14 0.00 0.25 0.01 0.33 I 0 .. 01 0.44 0.02 0.52

0.15 0.01 0.26 0.01 C);35 0.02 0.46 0.02 0:54 0.16 0.01 0.28 0.02 0.36 0.01 0.48 0.02 0.57 0.17 0.01 I 0.29 0.01 '0.38 ·'·0:02 0.50 0.02 0.59

0.17 0.00 0.30 0.01 0.39 0.01 0.52 0.02 0.61

0.18 0.01 0.31 0.01 iOAr ····.·0.02 0.54 0.02 0.64 0.19 0.01 0.32 0.01 0.42 0.01 0.56 0.02 0.66

0.19 0.00 0.34 0.02 .0.44 .. 0.02 0.58 0.02 0.69

0.20 0.01 0.35 0.01 0.46 0.02 0.60 0.02 0.72

1 .. 0:21 0.01 0.36 0.01 0.48 0.02 0.63 0.03 0.74

0.22 0.01 0.38 0.02 0.49 0.01 0.65 0.02 0.77

0.22 0.00 0.39 0.01 1 0.51 0.02 0.67 0.02 0.80

0.23 0.01 0.40 0.01 0.53 0.02 0.70 0.03 0.83

0.24 0.Q1 0.42 0:02 0.55 0.02 0.72 0.02 0.85

0.25 0.01 0.43 0.01 0.57 0.02 0.75 0.03 0.88

0.26 0.01 0.45 0.02 1 0.59 0.02 0.77 0.02 0.92 ..

.. 0.27 0.01 0.47 0.02 0.61 ... 0.02 0.80 0.03 0.95 · .. 0.28 0.01 O.4B 0.01 0:63 ·0.02 0.B3 0.03 0.99

0.29 0.01 0.50 0.02 0.66 0.03 0.B7 0.04 1.03

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year 100 year inches 3.10 inches Delta Mass Delta 0.00 0.00 0.00 0.01 0.02 0.02 0.02 0.03 0.01 0.02 0.05 0.02 0.01 0.07 0.02 0.02 I .. 0.09 0.02 0.02 0.11 0.02 0:02 0.13 0.02 0.01 0.16 0.03 0.02 0.18 0.02 0.02 0.20 0.02 0.02 0.22 0.02 0.02 0.24 0.02 0.02 0.27 0.03 0.02 0.29 0.02 0.03 0.32 0.03 0.02 0.34 0.02 0.02 0.37 0.03 0.02 0.39 0.02 0.02 0.42 0.03 0.02 0.44 0.02 0.02 0.47 0.03 0.03 0.49 0.02 0.02 1 0;52 0.03 0.02 0.55 0.03 0.02 1 0•57 0.02 0.03 0.60 0.03 0.02· 0.63 0.03 0.03 0.65 0.02 0.02 0.68 0.03 0.02 0.71 0.03 0.03 0.74 0.03. 0.02 0.77 0.03 0.03 .0.80 0.03 0.03 0.83 O.O~ 0.02 0.86 0.03 0.03 0.89 0.03 0.03 0.92 0.03 0.03 0.95 0.03 0.02 0.99 0.04 0.03 1.02 0.03 0.04 1 1.06 0.04 0.03 I. 1.10 0.04 0.04 '1.14 1'()'04 0.04 1.19 0.05

5 sq. mile i TIme Dist.

3:45 39.8 3:50 41.3 3:55 42.9 4:00 44.5 4:05 46.2 4:10 48.0 4:15 49.9 4:20 51.9

I 4:25 54.0 4:30 56.1

I 4:35 58.3 • I 4:40 60.6

I 4:45 63.0 4:50 65.4 4:55 67.9 5:00 70.5 5:05 73.6 5:10 77.2 5:15 81.1 5:20 85.3 5:25 90.0 5:30 95.6 5:35 97.5 5:40 98.4 5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

5 min. 15 min. so min. 1 hour 3 hour 6 hour

5min. 15 min. 30 min. 1 hour 3 hour 6 hour



0.75 inches 1.31 inches 1.72 inches 2.26 inches 2.68 inches Mass Della Mass Delta Mass Delta Mass Delta Mass Delta 0.30 0.01 0.52 0.02 0.68 0.02 0.90 0.03 1.07 0.04 0.31 0.01 0.54 0.02 0.71 0.03 0.93 0.03 1.11 0.04 0.32 0.01 0.56 0.02 0.74 0.03 0.97 0.04 US 0.04 0.33 0.01 0.58 0.02 0.77 0.03 1.01 0.04 1.19 0.04 0.35 0.02 0.61 0.03 0.79 0.02 1.04 0.03 1.24 0.05 0.36 0.01 0.63 0.02 0.83 0.04 1.0e 0.04 1.29 0.05 0.37 0.01 0.65 0.02 0.86 0.03 1.13 0.05 1.34 0.05 0.39 0.02 0.S8 0.03 0.89 0.03 1.17 0.04 1.39 0.05 0.41 0.02 0.71 0.03 0.93 0.04 1.22 0.05 1.45 0.06 0.42 0.01 0.73 0.02 0.96 0.03 1.27 0.05 1.50 0.05 0.44 0.02 0.76 0.03 1.00 0.04 1.32 0.05 1.56 0.06 0.45 0.01 0.79 0.03 1.04 0.04 1.37 0.05 1.62 0.06 0.47 0.02 0.83 0.04 1.08 0.04 1.42 0.05 1.69 0.07 0.49 0.02 0.8S 0.03 1.12 0.04 1.48 0.06 1.75 0.06 0.51 0.02 0.89 0.03 1.17 0.05 1.53 0.05 1.82 0.07 0.53 0.02 0.92 0.03 1.21 0.04 1.59 0.06 1.89 0.07 0.55 0.02 0.96 0.04 1.27 0.06 1.66 0.07 1.97 0.08 0.58 0.03 1.01 0.05 1.33 0.06 1.74 0.08 2.07 0.10 O.Sl 0.03 LOS 0.05 1.39 0.06 1.83 0.09 2.17 0.10 0.64 0.03 1.12 0.06 1.47 0.08 1.93 0.10 2.29 0.12 0.68 0;04 1.18 0.06 1.55 0.06 2.03 0.10 2.41 0.12 0.72 0.04 1.25 0.07 1.64 0.09 2.16 0.13 2.56 0.15 0.73 0.01 1.28 0.03 1.68 0.04 2.20 0.04 2.61 0.05 0.74 0.01 1.29 0.01 1.69 0.01 2.22 0.02 2.64 0.03

·0:74 0.00 1.30 0.01 1.70 0.01 1 ... 2.24 0.02 2.65 0.01 0.75 0.01 1.30 0.00 1.71 0.01 2.25 0.Q1 2.S7 0.02 0.75 0.00 1.31 0.01 ';72 0.01 2.26 0.01 2.S7 0.00 0.75 0.00 1.31 0.00 1.72 0.00 2.26 0.00 2.68 0.01

Maximum Values (depth in inches) 0.04 0.07 0.09 0.13 0.15 0.11 0.19 0.25 0.33 0.39 0.19 0.33 0.43 0.57 0.67 0.30 0.52 0.68 0.89 t.06 0.55 0.97 1.27 1.66 1.97 0.75 1.31 1.72 2.25 2.68

Maximum Values (intensity in inches/hour) 0.48 0.B4 1.08 1.56 1.80 0.44 0.76 1.00 1.32 1.56 0.38 0.66 0.86 1.14 1.34 0.30 0.52 0.68 0.89 1.06 0.18 0.32 0.42 0.55 0.66

. 0.13 0.22 0.29 0.38 0.45

158

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100 year 3.1 inches

Mass Delta 1.23 0.04 1.28 0.05 1.33 0.05 1.38 0.05 1.43 . 0.05 1.49 0.06 1.55 0;06 1.61 0.06 1.67 0.06 1.74 0.07 1.81 0.07 1.88 0.07 1.95 0.07 2.03 o.oa 2.10 0.07 2.19 0.09 2.28 0.09 2.39· 0.11 2.51 0.12 2.64 0.13 2.79 0.15 2.96 0.17 3.02

10.06

3.05 0.03 3.07 ··0.02 3.08 0.01 3.09 10:01 3.10 0.01

0.17 0.45 0.77 1.22 2.28 3:10

2.04 1.80 1.54 1.22 0.76 0.52

10 sq. mile Time I Dis!. 0:00 0.0 0:05 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0:50 6.4 0:55 7.1 1:00 7.9 1:05 8.7 1 :10 9.5 1:15 10.3 1:20 11.1 1:25 11.9 1 :30 12.7 1:35 13.5 1 :40 14.3 1:45 15.1 1 :50 15.9 1:55 16.7 2:00 17.6 2:05 lB.4 2:10 19.3 2:15 20.2 2:20 21.1 2:25 22.0 2:30 22.9 2:35 23.8 2:40 24.7 2;45 25.7 2;50 26.7 2;55 27.7 3:00 2B.7 3;05 29.7 3:10 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3;35 36.9 3:40 38.3



0.74 inches 1.29 inches 1.71 inches 2.24 inches 2.66 inches Mass Delta Mass Delta Mass Delta Mass Delta Mass I Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0;01 0.01 0.Q1 0.01 0.01 0.01 0.01 0.00 0.02 0.01 0.02 0.01 0.03 0.02 0.01 0.00 0.02 0.01 0.03 0.01 0.04 0.02 0.05 0.02 0.02 0.01 0.03 0.01 0.04 0.01 0.05 0.01 0.06 0.01 0.02 0.00 0.04 0.01 0.05 0.01 0.06 · 0.01 0.08 0.02 0.03 0.01 0.05 0.01 0.06 0.01 0.08 0.02 0.10 0.02 0.03 0.00 0.06 0.01 0.07 0.01 0.10 0.02 0.11 0.01 0.04 0.01 0.06 0.00 0.09 0.02 0.11 0.01 0.13 0.02 0.04 0.00 0.07 0.01 0.10 0.01 0.13 0.02 0.15 0.02 0.05 0.Q1 0.08 0.01 0.11 0.01 0.14 0.01 0.17 0.02 0.05 0.00 0.09 0.01 0.12 0.01 0.16 0.02 . 0.19 0.02 0.06 0.01 0.10 0.01 0.14 0.02 0.18 0.02 0.21 0.02 0.06 0.00 0.11 0.01 0.15 0.01 0.19 0.01 0.23 0.02 0.07 0.01 0.12 0.01 0.16 0.01 0.21 0.02 0.25 0.02 0.08 0.01 0.13 0.01 0;18 0.02 0.23 0.02 0.27 0.02 0.08 0.00 0.14 0.01 0.19 0.01 0.25 0.02 0.30 0.03 0.09 0.01 0.15 0.01 0.20 0.01 0.27 0.02 0.32 0.02 0.09 0.00 0.16 0.01 0.22 0.02 0.28 0.01 0.34 0.02 0.10 0.01 0.17 0.01 0.23 0.01 0.30 0.02 0.36 0.02 0.11 0.01 0.18 0.01 0.24 0.01 0.32 0.02 0.38 0.02

1 0.11 0.00 0.19 0.01 0.26 0.02 0.34 0.02 0.40 0.02 0.12 0.01 0.21 0.02 0.27 0.01 0.36 0.02 0.42 0.02 0.12 0.00 0.22 0.01 0.29 0.02 1 0.37 0.01 0.44 0.02 0.13 0.01 0.23 0.01 0.30 0.01 0.39 0.02 0.47 0.03 0.14 0.01 0.24 0.01 0.31 0.01 0.41 · 0.02 0.49 0.02 0.14 0.00 0.25 0.01 0.33 0.02 0.43 0.02 0.51 0.02

.0.15 0.01 0.26 0.01 0.35 0.02 .0.45 0.02' 0.54 0.03 0.16 0.01 0.27 0.01 0.36 0.01 0.47 0.02 0.56 0.02 0.16 0.00 0.2B 0.01 0:38 0.02 ····0.49 0.02 0.59 0.03

0.17 0.01 0.30 0.02 0.39 0.01 0.51 0.02 0.61 0.02

0.18 0.01 0.31 0.01 0.41 0.02 0.53 0.02 . 0.63 0.02 0.18 0.00 0.32 0.01 0.42 0.01 0.55 0.02 0.66 0.03

0.19 0.01 0.33 0.01 0.44 0.02 0.58 0.03 0.68 0.02 0.20 0.01 0.34 0.01 0.46 0.02 0.60 0.02 0.71 0.03

1 0.20 0.00 0.36 0.02 0.47 0.01 0.62 '·0.02 0.74 0.03 0.21 0.01 0.37 0.01 0.49 0.02 0.64 0.02 0.76 0.02 0.22 0.01 0.38 0.01 0.51 0.02 I· 0.67 0.03 0.79 0.03 0.23 0.01 0.40 0.02 0.53 0.02 0.69 0.02 0.82 0.03

0.24 0.01 0.41 0.01 0.55 0.02 0.71 · 0.02 0.85 0.03 0.24 0.00 0.43 0.02 0.56 0.01 0.74 0.03 0.88 0.03

0.25 0.01 0.44 0.01 0.58 0.02 0.77 0.03 0.91 0.03 0.26 0.01 0.46 0.02 0.61 0.03 0.80 0.03 0.94 0.03

0.27 0.01 0.48 0.02 0.63 0.02 0.83 0.03 0.98 0.04 0.28 0.01 0.49 0.01 0.65 0.02 0.86 0.03 1.02 0.04

159

Page 1 of 2


Mass Delta 0.00 0.00 0.02 0.02 0.03 0.01 0.05 0.02 0.07 0.02 0.09 0.02 0.11 0.02 0.13 0.02 0.15 0.02 0.17 0.02 0.20 0.03 0.22 0.02 0.24 0.02 0.27 0.03 0.29 0.02 0:32 0.03 0.34 0.02 0.37 0.03 0.39 0.02 0.41 0.02 0.44 0.03 CA6 0.02 0.49 0.03 0.51 0;02 0.54 0.03 0;56 0.02 0.59 0.03 0;62 0.03 0.65 0.03 0:68 0;03' 0.70 0.02 0:73' 1 0.03 0.76 0.03

.0.79 0.03' 0.82 0.03 0:85 0.03 0.88 0.03 0;9~ 0.03 0.95 0.04 0:98 0.03 1.01 0.03 1.05 0.04. 1.09 0.04 1:13 0.04 1.18 0.05

10 sq. mile Time Dist. 3:45 39.8 3:50 41.3 3:55 42.9 4:00 44.5 4:05 46.2 4:10 48.0 4:15 49.9 4:20 51.9 4:25 54.0 4:30 56.1 4:35 58.3 4:40 60.6 4:45 63.0 4:50 65.4 4:55 67.9 5:00 70.5 5:05 73.6 5:10 77.2 5:15 81.1 5:20 85.3 5:25 90.0 5:30 95.6 5:35 97.5 5:40 98.4 5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

5min. 15 min. 30 min. , hour 3 hour 6 hour

5 min. lSmin. 30 min. 1 hour 3 hour 6 hour


Storm Frequency 2vear 5 year 10 year 25 year 50 year

0.74 inches 1.29 inches 1.71 inches 2.24 inches 2.66 inches Mass Delta Mass Delta Mass Delta Mass Della Mass Delta 0.29 0.01 0.51 0.02 0.68 0.03 0.89 0.03 1.06 0.04 0.31 0.02 0.53 0.02 0.71 0.03 0.93 0.04 1.10 0.04 0.32 0.01 0.55 0.02 0.73 0.02 0.96 I 0.03 1.14 0.04 0.33 0.01 0.57 0.02 0.76 0.03 1.00 0.04 1.18 0.04 0~34 0.01 0.60 0.03 0.79 0.03 1.03 0.03 1.23 0.05 0.36 0.02 0.62 0.02 0.82 0.03 LOS 0.05 1.28 0.05 0.37 0.01 0.64 0.02 0.85 0.03 1.12 0.04 1.33 0.05 0.38 0.01 0.67 0.03 0.89 0.04 1.16 0.04 1.38 0.05 0.40 0.02 0.70 0.03 0.92 0.03 1.21 0.05 1.44 0.06 0.42 0.02 0.72 0.02 0.96 0.04 1.26 0.05 1.49 0.05 0.43 0.01 0.75 0.03 1.00 0.04 1.31 0.05 1.55 O.OS 0.45 0.02 0.78 0.03 1.04 0.04 1.36 0.05 1.61 0.06 0.47 0.02 O.Sl 0.03 1.08 0.04 1.41 0.05 1.68 0.07 0.49 0.01 0.84 0.03 1.12 0.04 1.46 0.05 1.74 0.06 0.50 0.02 0.88 0.04 1.16 0.04 1.52 0.06 1.81 0.07 0.52 0.02 0.91 0.03 1.21 0.05 1.58 0.06 1.88 0.07 0.54 0.02 0.95 0.04 1.26 0.05 1.65 0.07 1.96 0.08 0.57 0.03 1.00 0.05 1.32 0.06 1.73 0.08 2.05 0.09 0.60 0.03 1.05 0.05 1.39 0.07 1.82 0.09 2.16 0.11 0.63 0.03 1.10 0.05 1.46 0.07 1.91 0.09 2.27 0.11 0.67 0.04 1.16 0.06 1.54 0.08 2.02 0.11 2.39 0.12 0.71 0.04 1.23 0.07 1.63 0.09 2.14 0.12 2.54 0.15 0.72 0.Q1 1.26 0.03 1.67 0.04 2.18 0.04 2.59 0.05 0.73 0.01 1.27 0.01 1.68 0.01 2.20 0.02 2.62 0.03 0.73 0.00 1.2B 0.01 1.69 0.01 2.22 0.02 2.63 0.01 0.74 0.01 1.28 0.00 1.70 0.01 2.23 0.01 2.65 0.02 0.74 0.00 1.29 0.01 1.71 0.01 2.24 0.01 2.65 0.00 0.74 0.00 1.29 0.00 1.71 0.00 2.24 0.00 2.66 0.01

Maximum Values (depth in inches) 0.04 0.07 0.09 0.12 0.15 0.11 0.18 0.24 0.32 0.38 0.19 0.32 0.42 0.56 0.66 0.29 0.51 0.67 0.88 1.05 0.54 0.95 1.26 1.65 1.96 0.74 1.29 1.71 2.24 2.66

Maximum Values (intensity in inches/hour) 0.48 0.84 1.08 1.44 1.80 0.44 0.72 0.96 1.28 1.52 0.38 0.64 0.84 1.12 1.32 0.29 0.51 0.67 0.S8 1.05 0.18 0.32 0.42 0.55 0.65 0.12 0.22 0.29 0.37 0.44

160

Page 2 of 2

100 year 3.07 Inches

Mass Della 1.22 0.04 1.27 0.05 1.32 0.05 1.37 0.05 1.42 0.05 1.47 0.05 1.53 0.06 1.59 0.06 1.66 0.07 1.72 0.06 1.79 0.07 1.86 0.07 1.93 0.07 2.01 O.OS 2.08 0.07 2.16 0.08 2.26 0.10 2.37 0.11 2.49 0.12 2.62 0.13 2.76 0.14 2.93 0.17 2.99 0.06 3.02 0.03 3.04 0.02 3.05 0.01 3.06 0.01 3.07 0.01

0.17 0.44 0.77 1.21 2.26 3.07

2.04 1.76 1.54 1.21 0.75 0.51

25 sq. mile Time Dis\. 0:00 0.0 0:05 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0:50 6.4 0:55 7.1 1:00 7.9 1:05 8.7 1:10 9.5 1:15 10.3 1:20 11.1 1:25 11.9 1:30 12.7 1:35 13.5 1:40 14.3 1:45 15.1 1:50 15.9 1:55 16.7 2:00 17.6 2:05 18.4 2:10 19.3 2:15 20.2. 2:20 21.1 2:25 22.0 2:30 22.9 2:35 I· 23.8 2:40 24.7 2:45 25.7 2:50 26.7 2:55 27.7 3:00 28.7 3:05 29.7 3:10 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3:35 36.9 3:40 38.3




0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.Q1 0.01 0.01 0.00 0.02 0.01 0.02 0.01 0.03

•. 0.01 0.00 ·0.02 0.01 0.03 0.01 0.04 0.02 0.04

.. 0.02 0.01 0.03 0.01 0.04 0.01 0.05 0.01 0.06 0.02 0.00 0.04 0.01 0.05 0.01 0.06 0.01 0.08 0.03 0.Q1 0.05 0.01 0.06 0.01 0.08 0.02 0.09 0;03 0.00 0.05 0.00 0.07 0.01 0.09 0.01 0.11 0.04 0.Q1 0.06 0.01 0.08 0.01 0.11 0.02 0.13 0.04 0.00 0.07 0.01 0.09 0.01 0.12 0.01 0.15 0.05 0.01 0.08 0.01 0.11 0.02 0.14 0.02 0.17 0.05 0.00 0.09 0.01 0.12 0.01 0.16 0.02 0.18 0.06 0.01 0.10 0.01 0.13 0.01 0.17 0.01 0.20 0.06 0.00 0.11 0.01 0.14 0.01 0.19 0.02 0.23 0.07 0.01 0.12 0.01 0.16 0.02 0.21 0.02 0.25 0.08 0.01 0.13 0.01 0.17 0.01 0.23 0.02 0.27 0.08 0.00 0.14 0.01 0.18 0,01 0,24 0.01 0.29 0.09 0.01 0.15 0.01 0.20 0.02 0.26 0.02 0.31 0.09 0.00 0.16 0.01 0.21 0.01 0.28 0.02 0.33 0.10 0.01 0.17 0.01 0.22 0.01 0.30 0.02 0.35 0.10 0.00 0.18 0.01 0.24 0.02 0.31 O.Of 0.37 0.11 0.01 0.19 0.01 0.25 0.01 0.33 0.02 0.39 0.12 0.01 0.20 0.01 1°·26 0.01 0.35 0.02 0.41

0:12 0.00 0.21 .0;01 .0.28 0.02 0.37 0.02 0.43 0.13 0.01 0.22 0.01 0.29 •..• 0.01 0.39 0.02 0.46 0.13 0.00 0.23' '.· ••. ·.0.01 ,. 0.31 • 0.02 0.40 0;01 0.48 0.14 0.01 0.24 0.01 0.32 0.01 0.42 0.02 0.50 0.15 0.01 0.25 0.01 ,.0.34 0.02 0.44 0.02 0.52 0.15 0.00 0.27 0.02 0.35 0.01 0.46 0.02 0.55

0.16 0.01 0.28· 1>0.01 '·0;37 0.02 0.48 0.02 0.57

0.17 0.01 0.29 0.01 0.38 0.01 0.50 0.02 0.59

0.17 0.00 0.30 1·,,0.01 0.40 0.02 0.52 0.02 0.62 0.18 0.01 0.31 0.01 0.41 0.01 0.54 0.02 0.64

I 0.19 0.Q1 0.32 0.01 0.43 ' 0.02 0.56 0.02 1 0.67 0.19 0.00 0.34 0.02 0.44 0.01 0.58 0.02 0.69

I·· 0.20 0.01 0.35 1 0 .01 0.46 0.02 0.61 0.03, 0.72

0.21 0.01 0.36 1 0.01 0.48 0.02 0.63 0.02 0.74 10.22 0.01 0.37 0.01 0.49 0.01 0:65 0.02 0.77

0.22 0.00 0.39 0.02 0.51 0.02 0.67 0.02 0.80

i >0;23 0.01 0.40 0.01 0.53 0.02 0.70 0.03 0:83

0.24 0.01 0.42 0.02 0.55 0.02 0.72 0.02 0.85 0.25 0.01 0.43 0.01 0.57 0.02 0.75 0.03 0.89

0.26 0.01 0.45 0.02 0.59 0.02 0.78 0.03 0.92

... 0.27 0.01 0.46 0.01 0.61 0.02 0.81 0.03 0:96 0.28 0.01 0.48 0.02 0.64 0.03 0.84 0.03 0.99

161

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year 100 year inches 2.99 inches Delta Mass Delta 0.00 0.00 0.00 0.01 0.01 0.01 0.02 0.03 0.02 0.01 0.05 0.02 0.02 0.07 0.02 0.02 0.09 0.02 0.01 0.11 0.02 0.02 0.13 0.02 0.02 0.15 0.02 0.02 0.17 0.02 0.02 0.19 0,02 0.01 0.21 0,02 0.02 0.24 0,03 0.03 0.26 0.02 0.02 0.28 0,02 0.02 0.31 0.03 0.02 0.33 0.02 0.02 0.36. 0.03 0.02 0.38 0.02 0.02 0.40 0.02 0.02 0.43 0.03 0.02 0.45 0.02 0.02 0.48 0.03 0.02 .0.50 0.02 0.03 0.53 0,03 0.02 0.55 0.02 0.02 0.58 0.03 0.02 0;60 0.02 0.03 0.63 0.03 0.02 I·' 0;66 0.03 0.02 0.68 0.02 0.03 ,0.71 0.03 0.02 0.74 0,03 0,03 0.77 0,03 0.02 0.80 0,03 0.03 0.83 , .. 0,03 0.02 0.86 0.03 0.03 ' 0:89 '··0.03 0.03 0.92 0.03 0.03 0.95 0.03 0.02 0.99 0.04 0.04 1.02 0.03

,.0.03 1.06 0.04 0:04 1.10 0.04 0.03 1.15 0.05

I 25 SQ. mile . Time DIs!.

I 3:45 39.8 I 3:50 41.3

3:55 42.9 4:00 44.5 4:05 46.2

I 4:10 48.0 4:15 49.9

I 4:20 51.9 I

! 4:25 54.0

I 4:30 56.1

I 4:35 58.3 4:40 60.6 4:45 63.0

i 4:50 65.4 I 4:55 67.9 I

70.5 I 5:00 5:05 73.6 5:10 77.2 5:15 au 5:20 85.3 5:25 90.0

I 5:30 95.6 5:35 97.5 5:40 98.4 5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

I 5 min. I 15 min. f

! 30min.

I 1 hour I 3 hour ! 6 hOur

i 5 min.

I 15·min. f 30min.

I 1 hOur 3 hOur

i a hour



0.73 inches 1.26 inches 1.66 inelles 2.19 inches 2.59 inches Mass Delta Mass Delta Mass Oelta Mass Delta Ma6/! Delta 0.29 0.01 0.50 0.02 0.66 0.02 0.87 0.03 1.03 0.04 0.30 0.01 0.52 0.02 0.69 0.03 0.90 0.03 1.07 0.04 0.31 0.01 0.64 0.02 0.71 0.02 0.94 0.04 1.11 0.04 0.32 0.01 0.56 0.02 0.74 0.03 0.97 0.03 1.15 0.04 0.34 0.02 0.58 0.02 0.77 0.03 1.01 0.04 1.20 0.05 0.35 0.01 0.60 0.02 0.80 0.03 1.05 0.04 1.24 0.04 0.36 0.01 0.63 0.03 0.83 0.03 1.09 0.04 1.29 0.05 0.38 0.02 0.65 0.02 0.8a 0.03 1.14 0.05 1.34 0.05 0.39 0.01 0.68 0.03 0.90 0.04 1.18 0.04 1.40 0.06 0.41 0.02 0.71 0.03 0.93 0.03 1.23 0.05 1.45 0.05 0.43 0.02 0.73 0.02 0.97 0.04 1.28 0.05 1.51 0.06 0.44 0.01 0.76 0.D3 1.01 0.04 1.33 0,05 1.57 0,06 0.46 0.02 0.79 0.03 1.05 0.04 1.38 0.05 1.63 0.06 0.48 O.OZ 0.82 0.03 1.09 0.04 1.43 0.05 1.69 0.06 0.50 0.02 0.86 0.04 1.13 0.04 1.49 0.06 1.76 0.07 0.51 0.01 0.89 0.03 1.17 0.04 1.54 0,05 1.83 0.07 0.64 0.03 0.93 0.04 1.22 0.05 1.61 0.07 1.91 0.08 0.66 0.02 0.97 0.04 1.28 0.06 1.69 0.08 2.00 0.09 0.59 0.03 1.02 0.05 1.35 0.07 1.7a 0.09 2.10 0.10 0.62 0.03 1.07 0.05 1.42 0.07 1.87 0.09 2.21 0.11 0.66 0.04 1.13 O.OS 1.49 0.07 1.97 0.10 2.33 0.12 0.70 0.04 1.20 0.07 1.59 0.10 1 .. 2.09 0,12 2.48 0.15 0.71 0.01 1.23 0.03 1.62 0.03 2.14 0.05 2.53 0;05 0.72 0.01 1.24 0.01 1.63 0.01 1 2.15 0.01 2.55 0.02 0.72 0.00 1.25 0.01 t.64 0.01 2.17 0.02 2.56 0.01 0.73 0.01 1.25 0.00 1.65 0.01 2.18 0.01 2.58 0.02 0.73 0.00 1.26 0.01 1.66 0.01 2.19 0.01 2.58 0.00 0.73 0.00 1.26 0.00 1.66 0.00 2.19 0.00 2.59 0.01

Maximum Values (depth in inches) 0.04 0.07 0.10 0.12 0.15 0.11 0.18 0.24 0.31 0.38 0.19 0.31 0.42 0.55 0.65 0.29 0.49 0.66 0.8S 1.03 0.64 0,93 1.22 1.62 1.91 0.73 1.26 1.66 2.19 2.59

Maximum Values (intensity in inches/hour) 0.48 0.84 1.20 1.44 1.BO 0.44 0.72 0.96 1.24 1.52 0.3a 0.62 0.84 1.10 1.30 0.29 0.49 0.66 0.B6 1.03 0.18 0.31 0.41 0.54 0.64 0.12 0.21 , 0.28 0.37 0.43

162

Page2of2


Mass Dalta 1.19 0.04 1.23 0.04 1.:;!8 0.05 1.33 0.05 1~38 0.05 1.44 0.06 1.49 0.05 1.55 0.06 1.61 0.06 1.68 0.07 1.74 0.06 1.81 0.Q7 1.88 0.07 1.96 0.08 2.Q3 0.07 2.11 0.08 2.20 0.09 2.31 0.11 2.42 . 0.11 2.55 0.13 2.69 0.14 2.86 0.17 2.92 0.06 2.94 0.02 2.96 1. 0.02 2.98 0.02 2.98 0.00 2.99 0.01

0.17 0.44 0.75 US 2.21 2.99

2.04 1.76 1.50 1.18 0.74 0.50

50 sq. mile TIme Dist. 0:00 0.0 0:05 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0;50 6.4 0:55 7.1 1:00 7.9 1:05 8.7 1 :10 9.5 1 :15 10.3 1:20 11.1 1:25 11.9 1:30 12.7 1:35 13.5 1:40 14.3 1:45 15.1 1:50 15.9 1:55 16.7 2;00 17.6 2:05 18.4 2:10 19.3 2:15 20.2 2:20 21.1 2:25 22.0 2:30 22.9 2:35 23.8 2:40 24.7 2:45 25.7 2:50 26.7 2:55 27.7 3:00 28.7 3:05 29.7 3:10 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3:35 36.9 3:40 38.3



0.71 inches 1.23 inches 1.62 inches 2.13 inches 2.52 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.02 0.01 0.02 0.01 0.03 0.01 0.00 0.02 0.01 0.03 . 0.01 0.04 0.02 0.04 0.02 0.01 0.03 0.01 0.04 0.01 0.05 0.01 0.06 0.02 0.00 0.04 0.01 0.05 0.01 0.06 , 0.01 0.07 0.03 0.01 0.04 0.00 0.06 0.01 0.08 0.02 0.09 0.03 0.00 0.05 0.01 0.07 0.01 0.09 0.01 0.11 0.04 0.01 0.06 0.01 0.08 0.01 0.11 0.02 0.13 0.04 0.00 0.07 0.01 0.09 0.01 0.12 0.01 0.14 0.05 0.01 0.08 0.01 0.10 0.01 0.14 0.02 0.16 0.05 0.00 0.09 0.01 0.12 0.02 0.15 0.01 0.18 0.06 0.01 0.10 0.01 0.13 0.01 0.17 0.02 0.20 0.06 0.00 0.11 0.01 0.14 0.01 0.19 0.02 0.22 0.07 0.01 0.12 0.01 0.15 0.01 0.20 0.01 0.24 0.07 0.00 0.13 0.01 0.17 0.02 0.22 0.02 0.26 0.08 0.01 0.14 0.01 0.18 0.01 0.24 0.02 0.28 0.08 0.00 0.15 0.01 0.19 0.01 0.25 0.01 0.30 0.09 0.01 0.16 0.01 0.21 0.02 0.27 0.02 0.32 0.10 0.01 .0.17 0.01 0.22 0.01 0.29 0.02 0.34 0.10 0.00 0.18 0.01 0.23 0.01 0.30 0.01 0.36 0.11 0.01 0.19 0.01 0.24 0.01 0.32 0.02 0.38 0.11 0.00 0.20 0.01 0.26 0.02 0.34 0.02 0.40 0.12 0.01

.... 0.21 0.01 0.27. 0.01 .. 0.36 I'· 0.02 ·'·0.42

0.12 0.00 0.22 0.01 0.29 0.02 0.37 0.01 0.44 0.13 0.01 ..•. 0:23 0.01 0.30 I 0;01 0.39· 0.02 ··.0.46 0.14 0.01 0.24 0.01 0.31 0.01 0.41 0.02 0.49 0:14 0.00 .0.25 0.01 0.33 0.02 0.43 0.02 0.51 0.15 0.01 0.26 0.01 0.34 0.01 0.45 0.02 0.53

0.16 0.01 0.27 0.01 0.36 0.02 0;47 0.02 0:55 0.16 0.00 0.28 0.01 0.37 0.01 0.49 0.02 0.58 0.17 0.01 0.29 0.01 0.39 0.02 ,0.51 0.02 0.60 0.18 0.01 0.30 0.01 0.40 0.01 0.53 0.02 0.62 0:18 0.00 0.32 0.02 0.42 0.02 0.55 1 0.02 0.65 ..

0.19 0.01 0.33 0.01 0.43 0.01 0.57 0.02 0.67 0.20 0.01· 0.34 0.01 0.45 0.02 0.59 0.02 0.70 0.20 0.00 0.35 0.01 0.46 0.01 0.61 0.02 0.72 0.21 0.01 0.37 0.02 0.48 0,02 .0.63 0.02 0.75 0.22 0.01 0.38 0.01 0.50 0.02 0.66 0.03 0.78 0.23 0.01 .0.39 0.01 0:52 10.02 0:68 0.02 0.80 0.23 0.00 0.41 0.02 0.53 0.01 0.70 0.02 0.83

0.24 0.01 0.42 1 .. 0.01 0.55 0.02 .. 0.73 0.03 0.86 0.25 0.01 0.44 0.02 0.58 0.03 0.76 0.03 0.89 0.26 0.01 0.45 0.01 0.60 0.02 0.79 .. 0.03. 0.93 0.27 0.01 0.47 0.02 0.62 0.02 0.82 0.03 0.97

163

Page 1 of 2

year 100 year inches 2.91 inches Delta Mass Delta 0.00 0.00 0.00 0.01 0;01 0.01 0.02 0.03 0.02 0.01 0.05 0.02 0.02 0.07 0.02 0.01 0;08 0.01 0.02 0.10 0.02 0.02 0.13 0.03 0.02 0.15 0.02 0.01 0.17 0.02 0.02 0.19 0.02 0.02 0.21 0.02 0.02 0.23 0.02 0.02 0.25 0.02 0.02 0.28 0.03 0.02. I 0:30 0.02 0.02 0.32 0.02 0.02 ,0;35 0.03 0.02 0.37 0.02 0.02 0:39 0.02 0.02 0.42 0.03 0.02 0.44 I 0.02 0.02 0.46 0.02 0.02 0:49 • 0.03 0.02 0.51 0.02 0.02 ·0.54 . 0.03 0.03 0.56 0.02 0.02 0;59 0.03 0.02 0.61 0.02 0.02 ... 0.64 10.03 0.03 0.67 0.03 0.02 IJ);69 , 0.02 0.02 0.72 0.03 0.03 I· 0;75 0.03 0.02 0.78 0.03 0.03 !0;81 i o.03 0.02 0.84 0.03 0.03 0;86 0:02 0.03 0.90 0.04 0.02 .······0.93: 10.03 0.03 0.96

1 ... 0

.03

0.03 1.00 . 0.04 0.03 1.03 0.03 ..

0.04 . . 1;0'1 0,04· ........

0.04 1.11 0.04

50 SQ. mile Time Dislo 3:45 39.8 3:50 41.3 3:55 42.9 4:00 44.5 4:05 46.2 4:10 48.0 4:15 49.9 4:20 51.9 4:25 54.0 4:30 56.1 4:35 58.3 4:40 60.6 4:45 63.0 4:50 65.4 4:55 67.9 5:00 70.5 5:05 73.6 5:10 77.2 5:15 81.1 5:20 85.3 5:25 90.0 5:30 95.6 5:35 97.5 5:40 98.4 5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

5 min. 15 min. 30min. 1 hour 3 hour 6 hour

5 min. 15 min. 30min. 1 hour 3 hour 6 hour


Storm Frequency 2 vear 5 year 10 year 25 year 50 year

0.71 inches 1.23 inches 1.62 inches 2.13 inches 2.52 inches Mass Delta Mass Delta Mass Delta Mass Delta Mass Delta 0.28 0.01 0.49 0.02 0.64 0.02 0.85 0.03 1.00 0.03 0.29 0.01 0.51 0.02 0.67 0.03 0.88 0.03 1.04 0.04 0.30 0.01 0.53 0.02 0.69 0.02 0.91 0.03 1.08 0.04 0.32 0.02 0.55 0.02 0.72 0.03 0.95 0.04 1.12 0.04 0.33 0.01 0.57 0.02 0.75 0.03 0.98 0.03 1.16 0.04 0.34 0.01 0.59 0.02 0.78 0.03 1.02 0.04 1.21 0.05 0.35 0.01 0.61 0.02 0.81 0.03 1.06 0.04 1.26 0.05 0.37 0.02 0.64 0.03 0.84 0.03 1.11 0.05 1.31 0.05 0.38 0.01 0.66 0.02 0.87 0.03 1.15 0.04 1.36 0.05 0.40 0.02 0.69 0.03 0.91 0.04 1.19 0.04 1.41 0.05 0.41 0.01 0.72 0.03 0.94 0.03 1.24 0.05 1.47 0.06 0.43 0.02 0.75 0.03 0.98 0.04 1.29 0.05 1.53 0.06 0.45 0.02 0.77 0.02 1.02 0.04 1.34 0.05 1.59 0.06 0.46 0.01 0.80 0.03 1.06 0.04 1.39 0.05 1.65 0.06 0.48· 0.02 0.84 0.04 1.10 0.04 1.45 0.06 1.71 0.06 0.50 0.02 0.87 0.03 1.14 0.04 1.50 0.05 1.78 0.07 0.52 0.02 0.91 0.04 1.19 0.05 1.57 0.07 1.85 0.07 0.55 0.03' 0.95 0.04 1.25 0.06 1.64 0.07 1.95 0.10 0.58 0.03 1.00 0.05 1.31 0.06 1.73 0.09 2.04 0.09 0.61 0.03 1.05 0.05 1.38 0.07 1.82 0.09 2.15 0.11 0.64 0.03 1.11 0.06 1.46 0.08 1.92 0.10 2.27 0.12 0.68 0.04 1.18 0.07 1.55 0.09 2.04 0.12 2.41 0.14 0.69 0.01 1.20 I 0.02 1.58 0.03 2.08 0.04 2.46 0.05 0.70 0.01 1.21 0.01 1.59 0.01 2.10 0.02 2.48 0.02 0.70 0.00 1.22 L 0.01 1.60 0.01 2.11 0.01 ,. 2.49 0.01 0.71 ,0.01 1.22 0.00 1.61 0.01 2.12 0.01 2.51 0.02 0.71 0.00 1.23 I 0.01 1.62 0.01 ' 2.13 0;01 2.51 0.00 0.71 0.00 1.23 0.00 1.62 0.00 2.13 0.00 2.52 0.01

Maximum Values (depth in inches) 0.04 0.07 0.09 0.12 0.14 0.10 ·0.18 0.24 0.31 0.37 0.18 0.31 0.41 0.54 0.63 0:28 0.49 0.64 0.85 1.00 0.52 0.91 1.19 1.57 1.86

. 0.71 1:23 1.62 2.13 2.52

Maximum Values (intensity in inches/hour) 0.48 0.84 1.08 1.44 1.68 0.40 0.72 0.96 1.24 1.48 0.36 0.62 0.82 1.08 1.26 0.28 0.49 0.64 0.85 1.00 0.17 0.30 0.40 0.52; 0.62 0.12 0.21 0.27 : 0;36 0.42

164

Page 2 of 2


Mass Delta 1.16 0.05 1.20 0.04 1.25 0.05 1.29 0.04 1.34 0.05 1.40 0.06 1.45 0.05 1.51 0.06 1.57 0.06 1.63 0.06 1.70 0.07 1.76 0.06 1.83 0.07 1.90 0.07 1.98 0.08 2.05 0.07 2.14 0.09 2.25 0.11 2.36 0;11 2.48 0.12 2.62 0.14 2.78 0.16 2.84 0.06 2.86 0.02 2.88 0.02 2.90 0.02 2.90 0.00 2.91 0.01

0.16 0.42 0.73 1.15 2.15 2.91

1.92 1.68 1.46 1.15 0.72 0.49

100 SQ. mile Time Disl. 0:00 0.0 0:05 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0:50 6.4 0:55 7.1 1:00 7.9 1:05 B.7 1 :10 9.5 1:15 I 10.3 1:20 11.1 1:25 11.9 1:30 12.7 1:35 13.5 1:40 14.3 1:45 15.1 1:50 15.9 1:55 16.7 2:00 17.6 2:05 18.4 2:10 19.3 2:15 20.2 2:20 21.1 2:25 22.0 2:30 22.9 2:35 23.8 2:40 24.7 2:45 25.7 2:50 26.7 2:55 27.7 3:00 28.7

1 3:05 29.7

3:10 I. 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3:35 36.9 3:40 38.3



0.68 inches 1.17 inches 1.55 inches 2.04 inches 2.41 ' Mass Della Mass Delta Mass Delta Mass I Delta Mass

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.Q1 0.Q1 0.00 0.02 0.01 0.02 0.01 0.03 0.01 0.00 0.02 0.01 0.03 0.01 0.03 0.01 0.04 0.02 0.Q1 0.03 0.01 0.04 0.01 0.05 0.02 0.06 0.02 0.00 0.03 0.00 0.04 0.00 0.06 0.01 0.07 0.02 0.00 0.04 0.01 0.06 0.02 0.07 0.01 0.09 0.03 0.01 0.05 0.01 0.07 0.01 0.09 0.02 0.10 0.03 0.00 0.06 0.01 0.08 0.01 0.10 0.01 0.12 0.04 0.01 0.07 0.01 I· 0.09 0.01 0.12 0.02 0.14 0.04 0.00 0.Q7 0.00 0.10 0.01 0.13 0.01 0.15 0.05 0.Q1 0.08 0.01 0.11 0.01 0.14 0.01 0.17 0.05 0.00 0.09 0.01 0.12 0.01 0.16 0.02 0.19 0.06 0.01 0.10 0.01 0.13 0.01 0.1S 0.02 0.21 0.06 0.00 0.11 0.01 0.15 0.02 0.19 0.01 0.23 0.07 0.01 0.12 0.01 0.16 0.01 0.21 0.02 0.25 0.08 0.01 0.13 0.01 0.17 0.01 0.23 0.02 0.27

0.08 0.00 0.14 0.01 0.18 0.01 0.24 0.01 0.29

0.09 0.01 0.15 0.01 0.20 0.02 0.26 0.02 0.31

0.09 0.00 0.16 0.01 0.21 0.01 0.28 0.02 0.33 0.10 0.Q1 0.17 0.01 0.22 0.01 0.29 0.01 0.34

0.10 0.00 0.18 0.01 0.23 0.01 0.31 0.02. 0.36 0.11 0.Q1 0.19 0.Q1 0.25 0.02 0.32 0.01 0.38

0.11 0.00 0.20 :'0.01 10.26 0.01 0.34 0.02. 0:40

0.12 0.01 0.21 0.01 0.27 0.01 0.36 0.02 0.42 0.13 am 0.22 .0.01· 0.29 0.02 0.38 0.02 0.44 0.13 0.00 0.23 0.01 1 .. 0 .30 0.Q1 0.39 0.Q1 0.47

0.14 am .0.24 0.01 0;31 0;01 0.41 0.02 0.49

0.14 0.00 0.25 0.01 0.33 0.02 0.43 0.02 0.51

0.15 0.01 0.26 0.01 0.34 0.01 0.45 0.02 0.53

0.16 0.01 0.27 0.01 0.35 0.01 0.47 0.02 0.55

0.16 0.00 0.28 0.01 0.37 '0.02 0.49 0.02 0.57 0.17 0.01 0.29 0.01 0.38 0.01 0.50 0.01 0.60

0.17 0.00 0.30 I' .. 0.01 0.40 10.02 0.52 0.02 0.62

O.lS 0.01 0.31 0.01 0.41 0.01 0.54 0.02 0.64

0.19 0,01 0.32 0.01 0.43 0.02 0.57 0.03 0;67

0.20 0.01 0.34 0.02 0.44 0.01 0.59 0.02 0.69

0.20 0.00 0.35 0;01 0.46 . 0;02 0.B1 0.02. 0.72

0.21 0.01 0.36 0.01 0.48 0.02 0.63 0.02 0.74

0.22 0.01 0;37 10.01 0.49 1\0.01 0.65 0.02 0.77

0.22 0.00 0.39 0.02 0.51 0.02 0.67 0.02 0.80

0.23 0.Q1 0.40 0.01 0.53 0.02 0.70 0.03. 0.82

0.24 0.Q1 0.42 0.02 O.~ .... 0.02 0.72 0.02 0.86

0.25 0.01 0.43 0.01 0.57 0.02 0.75 0.03 0.89

0.26 0.01 0.45 0.02 0.59 0.02 0.78 0.03 0.92

165

Page 1 of 2

year lOa year inches 2.79 inches Delta Mass I Delta 0.00 0.00 0.00 0.01 0.01 0.01 0.02 0.03 0.02 0.01 0.05 0.02 0.02 0.06 0.01 0.01 0.08 0.02 0.02 0.10 0.02 0.01 0.12 0.02 0.02 0.14 0.02 0.02 0.16 0.02 0.01 O.lB 0.02 0.02 0.20 0.02 0.02 0.22 0.02 0.02 0.24 0.02 0.02 0.27 0.03 0.02 0.29 0.02

. 0.02 0.31 0.02 0.02 0.33 0.02 0.02 0.35 0.02 0.02 1 0.38 0.03 0.01 0.40 0.02 0.02 0.42 0.02 0.02 0.44 0.02 0.02 I····· .. 0.47 0.03 0.02 0.49 0.02 0.02 0.51 0.02 0.03 0.54 0.03 0.02 .0:56 0.02 0.02 0.59 0.03 0.02 I· 0.61 0.02 0.02 0.64 0.03 0.02 .0.66 0.02 0.03 0.69 0.03 0.02 0,72 0.03 0.02 0.74 0.02 0.03 0.17 0 .. 03 0.02 0.80 0.03 0;03 0.83 0.03 0.02 0.B6 0.03 0.D3 0.89 '0.03 0.03 0.92 0.03

10.02 1 0.95 0.03 0.04 0.99 0.04 0.03 1.03 0.04 0.03 1.07 0.04

100 sq. mile TIme Dist. 3:45 39.S· 3:50 41.3 3:55 42.9 4:00 44.5 4:05 46.2 4:10 48.0 4:15 49.9 4:20 51.9 4:25 54.0 4:30 56.1 4:35 58.3 4:40 60.6 4:45 63.0 4:50 65.4 4:55 67.9 5:00 70.5 5:05 73.6 5:10 77.2 5:15 81.1 5:20 85.3 5:25 90.0 5:30 95.6 5:35 97.5 5:40 9804

5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

Smin. 15 min. 30 min. 1 hour 3 hour 6 hour

Smin. 15 min. 30 min. 1 hour 3 hour 6 hour


Storm Frequency 2vear 5 year 10 year 25 year 50

0.6S inches 1.11 Inches 1.55 inches 2.04 inches 2.41 Mass Delta Mass Delta Mass Delta Mass Delta Mass ·0.27 0.01 0.41 0.02 1. 0.62 0.03 0.81 0.03 0.96 0.28 0.01 0.48 0.01 0.64 0.02 0.84 0.03 1.00

1 0•29 0.01 0.50 0.02 10.66 0.02 ., 0.88 0.04 1.03

1 0.30 0.01 0.52 0.02 0.69 0.03 0.91 0.03 1.01 0.31 0.01 0.54 0.02 0.72 0.03 0.94 0.03 1;11 0.33 0.02 0.56 0.02 0.74 0.02 0.98 0.04 1.16

IQ·34 0.01 0.58 0.02 0.71 0.03 1.02 0.04 1.20 0.35 0.01 0.61 0.03 0.80 0.03 1.06 0.04 1.25 0.37 0.02 0.63 0.02 0.84 0.04 1.10 0.04 1.30 0.38 0.01 0.66 0.03 0.87 0.03 1.14 0.04 1.35 0040 0.02 0.68 0.02 0.90 0.03 1.19 0.05 1.41 0.41 0.01 0.71 0.03 0.94 0.04 1.24 0.05 1.46 0.43 0.02 0.74 0.03 0.98 0.04 1.29 0.05 1.52 0.44 0.01 o.n 0.03 1.01 0.03 1.33 0.04 1.58 0046 0.02 0.79 0.02 1.05 0.04 1.39 0.06 1.64 0.48 0.02 0.82 0.03 1.09 0.04 1.44 0.05 1.70

I I .. 0.50 0.02 0.86 0.04 1.14 0.05 1.50 0.06 1.77 0.52 0.02 0.90 0.04 1.20 0.06 1.57 0.07 1.B6

I 0.55 0.03 0.95 0.05 1.26 0.06 1.65 0.08 1.95 0.58 0.03 1.00 0.05 1 1.32 0.06 1.74 0.09 2.06 0.61 0.03 1.05 0.05 1.40 0.08 1.84 0.10 2.17 0.65 0.04 1.12 0.07 1.48 0.08 1.95 0.11 2.30 0.66 0.01 1.14 0.02 1.51 0.03 1.99 0.04 2.35 0.67 0.01 1.15 0.01 1.53 0.02 2.01 0.02 2.37 0:67 0.00 1.16 0.01 1'1.53 0.00 1,2.02 0.01 2:39 0.68 0.01 1.16 0.00 1.54 0.01 2.03 0.01 2.40

.. 0.68 1 0.00 1.17 0.01 .1;55 0.01 2.04 0.01 2.41 0.68 0.00 1.17 0.00 1.55 0.00 2.04 0.00 2.41

Maximum Values (depth in inches) 0.04 0.07 0.08 0.11 0.10 0.17 0.22. 0.30 0.17 0.30 0.39 0.51 0.27 0.46 0.61 0.81 0.50 0.86 1.14 1.50

I 2.04 0.68 1.17 1.55

Maximum Values (intensity in inches/hour) 0.48 0.B4 0.96 1.32 0040 0.68 0.88 1.20 0.34 0.60 0.78 1.02 0.27 0.46 0.61 0.81 0.17 0.29 0.38 0.50 0.11 0.19 0.26 0.34

166

Page 2 of 2

year 100 year inches 2.79 inches Delta Mass Delta 0.04 1.11 0.04 0.04 1.15 0.04 0.03 1.20 0.05 0.04. 1.24 0.04 0.04 1.29 0.05 0.05 1.34 0.05 0.04 1.39 0.05 0.05 1.45 0.06 0.05 1.51 0.06 0.05 1.57 0.06 0.06 1.63 0.06 0.05 1.69 0.06 0.06 1.76 0.07 0.06 1.82 0.06 0.06 1.89 0.07 0.06 1.97 0.08 0.07 2.05 0.08 0.09 2.15 0.10 0.09 2.26 0.11 0.11 2.38 0.12 0.11 2.51 0.13 0.13 2.67 0.16 0.05 1. 2.72 0.05 0.02 I 2.75 0.03 0.02 2.76 0.01 0.01 2.78 0.02 0.01 2.78 1 0:00 0.00 2.79 0.01

0.13 0.16 0.35 0.41 0.60 0.70 0.95 1.10 1.78 2.06 2.41 2.79

1.56 1.92 1.40 1;64 1.20 1.40 0.95 1.10 0.59 0.69 0.40 0047

150 sq. mile TIme I Dist. 0:00 0.0 0:05 0.5 0:10 1.1 0:15 1.7 0:20 2.3 0:25 2.9 0:30 3.6 0:35 4.3 0:40 5.0 0:45 5.7 0:50 6.4 0:55 7.1 1:00 7.9 1:05 8.7 1 :10 9.5 1 :15 10.3 1:20 11.1 1:25 11.9 1 :30 12.7 1:35 13.5 1:40 14.3 1 :45 15.1 1 :50 15.9 1:55 16.7 2:00 17.6 2:05 18.4 2:10 19.3 2:15 20.2 2:20 21.1 2:25 22.0 2:30 22.9 2:35 23.8 2:40 24.7 2:45 25.7 2:50 26.7 2:55 27.7 3:00 28.7 3:05 29.7 3:10 30.8 3:15 31.9 3:20 33.0 3:25 34.2 3:30 35.5 3:35 36.9 3:40 38.3



0.66 inches 1.14 inches 1.51 inches 1.98 inches 2.35 year inches

Mass Delta Mass Delta Mass Delta Mass Delta Mass I Delta 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.02 0.01 0.02 0.01 0.03 0.02 0.01 0.00 0.02 0.01 0.03 0.01 0.03 0.01 0.04 0.01 0.02 0.01 0.03 0.01 0.03 0.00 0.05 0.02 0.05 0.01 0.02 0.00 0.03 0.00 0.04 0.01 0.06 0.01 0.07 0.02 0.02 0.00 0.04 0.01 0.05 0.01 0.07 0.01 O.OB 0.01 0.03 0.01 0.05 0.01 0.06 0.01 0.09 0.02 0.10 0.02 0.03 0.00 0.06 0.01 0.08 0.02 0.10 0.01 0.12 0.02 0.04 0.01 0.06 0.00 0.09 0.01 0.11 0.01 0.13 0.01 0.04 0.00 0.07 0.01 0.10 0.01 0.13 0.02 0.15 0.02 0.05 0.01 0.08 0.01 0.11 0.01 0.14 0.01 0.17 0.02 0.05 0.00 0.09 0.01 0.12 0.01 0.16 0.02 0.19 0.02 0.06 0.01 0.10 0.01 0.13 0.01 0.17 0.01 0.20 0.01

0.06 0.00 0.11 0.01 0.14 0.01 0.19 0.02 0.22 0.02 0.07 0.01 0.12 0.01 0.16 0.02 0.20 0.01 0.24 0.02 0.07 0.00 0,13 0.01 0.17 0.01 0.22 0.02 0.26 0.02 0.08 0.01 0.14 0.01 0.18 0.01 0.24 0.02 0.28 0.02 0.08 0.00 0.14 0.00 0.19 0.01 0.25 0.Q1 0.30 0.02 0.09 0.01 0.15 0.01 0.20 0.01 0.27 0.02 0.32 0.02 0.09 0.00 0.16 0.D1 0.22 0.02 0.28 0.01 0.34 0.02 0;10 0.Q1 0.17 0.01 0.23 0.01 0.30 0.02 0.35 0.01 0.10 0.00 0.18 0.01 0.24 0.01 0.31 0.01 0.37 0.02 0.11 0.01 0.19 0.01 0.25 1·0.01 0.33 0.02 0.39 0.02 0.12 0.01 0.20 0.01 0.27 0.02 0.35 0.02 0.41 0.02 0;12 . 0.00 0.21 0.01 0.28 1.·.0.01 0.36 . 0;01 0.43 0.02

0.01 ..

0.13 0.22 0.01 0.29 0.01 0.38 0.02 0.45 0.02 0.13 ,.0.00 0:23 0.01 0.31 0.02 0.40 I 0.02 0.47 0.02 0.14 0.01 0.24 0.01 0.32 0.01 0.42 0.02 0.50 0.03

0.15 0.01 0.25 0.01 0.33 0.01 0;44 10.02 I·· 0.52 0.02 0.15 0.00 0.26 0.01 0.35 0.02 0.45 0.01 0.54 0.02

0.16 0.01 0.27 0.01 0.36 .0.01 0.47 . 0.02 0.56 0.02 0.16 0.00 0.28 0.01 0.37 0.01 ,0.49 0.02 0.58 0.02

0.17 0.01 0.29 0.01 0.39 0.02 .0.51 0.02 0.60 0.02 0.18 0.01 0.30 0.01 0.40 0.01 0.53 0.02 0.63 0.03

0.18 0.00 0.32 0.02 0.42 0.02 1 0.55 0.02 0.65 0.02 0.19 0.01 0.33 0.01 0.43 0.01 0.57 0.02 0.67 0.02

1 .. 0.20 0.01 0.34 0.01 0.45 I·· 0.02 0.59. 0.02 0.70 0.03 0.20 0.00 0.35 0.01 0.47 0.02 0.61 .. 0.02 0.72 0.02

·0.63 0:21 0.01 0.36 0.01 0048 0.01· ...• 0.02 0.75 0.03

0.22 0.01 0.38 0.02 0.50 0.02 0.65 0.02 0.78 0.03 0.23 0.01 0.39 0.01 0.52 0.02 .0.68 0.03 0.80 0.02

0.23 0.00 0.40 0.01 0.54 0.02 0.70 0.02 0.83 0.03 0.24 0.01 0.42 0.02 0.56 .. 0.02 0.73 0.03 0.87 0.04

0.25 0.01 0.44 0.02 0.58 0.02 0.76 0.03 0.90 0.03

167

Page 1 of 2


Mass Delta 0.00 0.00 0.01 0.01 0.03 0.02 0.05 0.02 0.06 0.01 0.08 0.02 0.10 0.02 0.12 0.02 0.14 0.02 0.15 0.01 0.17 0.02 0.19 0.02 0.21 0.02 0.24 0.03 0.26 0.02 0;28 0.02 0.30 0.02 0.32. • 0.02 0.34 0.02 0.37 0.03 0.39 0.02 0.41 0.02 0.43 0.02 0;45 0.02 0.48 0.03 0.50 · .••. ·0.02 0.52 0.02

··.0.55 0.03 0.57 1 0.02 0:60 ·0.03 0.62 0.02

... 0.64 0.02 0.67 0.03 0.70 1 0.03 0.72 0.02 0.75 .. ·0.03 0.78 0.03 0,80 0.02. 0.83 0.03 0;86 ....

0.03 0.89 0.03 0.93 0.04 0.96 0.03 1.od 0.04 .... ;

1.04 0.04

150 sq. mile TIme Dist. 3:45 39.8 3:50 41.3 3:55 42.9 4:00 44.5 4:05 46.2 4:10 48.0 4:15 49.9 4:20 51.9 4:25 54.0 4:30 56.1 4:35 58.3

I 4:40 60.6 4:45 63.0 4:50 65.4 4:55 67.9 5:00 70.5 5:05 73.6 5:10 n.2 5:15 81.1 5:20 85.3 5:25 90.0 5:30 95.6 5:35 97.5 5:40 98.4 5:45 99.0 5:50 99.5 5:55 99.8 6:00 100.0

5 min. 15 min. 30 min. 1 hour 3 hour 6 hour

5 min. 15min. 30 min. 1 hour 3 hour 6 hour



0.66 inches 1.14 inches 1.51 inches 1.98 Inches 2.35 inches

Page 2 of 2


Mass Delta Mass Delta Mass Delta Mass Delta Mass Delta I Mass Delta 0.26 0.01 0.45 0.01 0.60 0.02 0.79 0.03 0.94 0.04 1.08 0.04 0.27 0.01 0.47 0.02 0.62 0.02 0.82 0.03 0.97 0.03 1.12 0.04 0.28 0.01 0.49 0.02 0.65 0.03 0.85 0.03 1.01 0.04 1.16 0.04 0.29 0.01 0.51 0.02 0.67 0.02 0.88 0.03 1.05 0.04 1.21 0.05 0.30 0.01 0.53 0.02 0.70 0.03 0.91 0.03 1.09 0.04 1.25 0.04 0.32 0.02 0.55 0.02 0.72 0.02 0.95 0.04 1.13 0.04 1.30 0.05 0.33 0.01 0.57 0.02 0.75 0.03 0.99 0.04 1.17 0.04 1.35 0.05 0.34 0.01 0.59 0.02 0.78 0.03 1.03 0.04 1.22 0.05 1.41 0.06 0.36 0.02 0.62 0.03 0.82 0.04 1.07 0.04 1.27 0.05 1.46 0.05 0.37 0.01 0.64 0.02 0.85 0.03 1.11 0.04 1.32 0.05 1.52 0.06 0.38 0.01 0.66 0.02 0.88 0.03 1.15 0.04 1.37 0.05 1.58 0.06 0.40 0.02 0.69 0.03 0.92 0.04 1.20 0.05 1.42 0.05 1.64 0.06 0.42 0.02 0.72 0.03 0.95 0.03 1.25 0.05 1.48 0.06 1.71 0.07 0.43 0.01 0.75 0.03 0.99 0.04 1.29 0.04 1.54 0.06 1.n 0.06 0.45 0.02 0.77 0.02 1.03 0.04 1.34 0.05 1.60 0.06 1.84 0.07 0.47 0.02 0.80 0.03 1.06 0.03 1.40 0.06 1.66 0.06 1.91 0.07 0.49 0.02 0.84 0.04 1.11 0.05 1.46 0.06 1.73 0.07 1.99 0.08 0.51 0.02 0.88 0.04 1.17. 0.06 1.53 0.07 1.81 0.08 2.09 0.10 0.54 0.03 0.92 0;04 1.22 0.05 1.61 0.08 1.91 0.10 2.20 0.11 0.56 0.02 0.97 0.05 1.29 0.07 1.69 0.08 2.00 0.09 2.31 0.11 0.59 0.03 1.03 0.06 1;36 0.07 1.78 0.09 2.12 0.12 2.44 0.13 0.63 0.04 1.09 0.06 1.44 0.08 1.89 0.11 2.25 0.13 2.59 0.15 0.64 0.01 1.11 0.02 1.47 0.03 1.93 0.04 2.29 0.04 2.64 0.05 0.65 0.01 1.12 0.01 1.49 0.02 1.95 0.02 2.31 0.02 2.67 0.03 0.65 0.00 1.13 0.01 1.49 0.00 1.96 0.01 2.33 0.02 2.68 ··0.01

0.66 0.01 1.13 0.00 1.50 0.01 1.97 0.01 2.34 0.01 2.70 0.02 0;66 ·0.00 1.14 0;01 1 1.51 0.01 1.98 0.01 2,35 0.01 2.70 ···0.00 0.66 0.00 1.14 0.00 1.51 0.00 1.98 0.00 2.35 0.00 2.71 0.01

Maximum Values (depth in inches) 0.04 0.06 0.08 0.11 0.13 0.15 0.09 0.17 0.22 0.28 0.34 0.39 0.16 0.29 0.38 0.49 0.59 0.68 0.26 0.45 0.59 0.78 0.93 1.07 0.48 0.84 1.11 1.46 1.73 2.00 0.66 1.14 1.51 1.98 2.35 2.71

Maximum Values (intensity in inches/hour) 0.48 0.72 0.96 1.32 1.56 1.80 0.36 0;68 0.S8 1.12 1.36 1.56 0.32 0.58 0.76 0.98 1.18 1.36 0.26 0.45 0.59 0.78 0.93 1.07 0.16 0.28 0.37 0.49 0.58 0.67 0.11 0.19 0.25 0.33' 0.39 0.45

168

DESERT HOT SPRINGS AREA PRECIPITATION SAN BERNARDINO COUNTY DESIGN STORM

1 SQ. MI.


DURATION 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. 100-YR

5-MIN. 0.11 0.20 0.26 0.34 0.41 0.47

3D-MIN. 0.30 0.52 0.69 0.91 1.06 1.25

I-HR. 0.39 0.67 0.88 1.16 1.38 1.59

3-HR. 0.57 0.99 1.31 1.72 2.04 2.36

6-HR. 0.76 1.32 1. 74 2.29 2.71 3.13

24-HR. 1.08 1. 85 2.47 3.26 3.85 4.45


DURATION DEPTH-AREA 2-YR. S-YR. 10-YR. 25-YR. 50-YR. 100-YR

5-MIN. 0.971 0.11 0.19 0.25 0.33 0.40 0.46

30-MIN. 0.971 0.29 0.50 0.67 0.88 1.05 1.21

l-HR. 0.971 0.38 0.65 0.85 1.13 1.34 1.54

3-HR. 0.996 0.57 0.99 1.30 1. 71 2.03 2.35

6-HR. 0.998 0.76 1.32 1.74 2.29 2.70 3.12

24-HR. 0.999 1.06 1.65 2.47 3.26 3.65 4.45


DURATION DEPTH-AREA 2-YR. 5-YR. la-YR. 25-YR. 50-YR. 100-YR

5-MIN. 0.971 1.28 2.33 3.03 3.96 4.78 5.48

3D-MIN. 0.971 0.58 1.01 1.34 1.77 2.10 2.43

1-HR. 0.971 0.38 0.65 0.85 1.13 1.34 1.54

3-HR. 0.996 0.19 0.33 0.43 0.57 0.68 0.76

6-HR. 0.998 0.13 0.22 0.29 0.36 0.45 0.52

24-HR. 0.999 0.09 0.15 0.21 0.27 0.32 0.37

169


5 SQ. MI.



5-MIN. 0.11 0.20 0.26 0.34 0.41 0.47

30-MIN. 0.30 0.52 0.69 0.91 1.08 1.25

I-HR. 0.39 0.67 0.88 1.16 1.38 1.59

3-HR. 0.57 0.99 1. 31 1.72 2.04 2.36

6-HR. 0.76 1. 32 1. 74 2.29 2.71 3.13

24-HR. 1. 08 1.85 2.47 3.26 3.85 4.45



5-MIN. 0.857 0.09 0.17 0.22 0.29 0.35 0.40

30-MIN. 0.857 0.26 0.45 0.59 0.78 0.93 1.07

I-HR. 0.857 0.33 0.57 0.75 0.99 1.18 1.36

3-HR. 0.979 0.56 0.97 1.28 1.68 2.0f) 2.31

6-HR. 0.989 0.75 1.31 1.72 2.26 2.68 3.10

24-HR. 0.994 1.07 1.84 2.46 3.24 3.83 4.42

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN ./HR. )

DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 2s-YR. 50-YR. 100-YR.

5-MIN. 0.857 1.13 2.06 2.67 3.50 4.22 4.83

30-MIN. 0.857 0.51 0.89 1.18 1.56 1.85 2.14

I-HR. 0.857 0.33 0.57 0.75 0.99 1.18 1. 36

3-HR. 0.979 0.19 0.32 0.43 0.56 0.67 0.77

6-HR. 0.989 0.13 0.22 0.29 0.38 0.45 0.52

24-HR. 0.994 0.09 0.15 0.20 0.27 0.32 0.37

170


10 SQ. MI.


DURATION 2-YR. 5-YR. 10-YR. 25-'(R. 50-YR. 100-YR.

5-MIN. 0.11 0.20 0.26 0.34 0.41 0.47

30-MIN. 0.30 0.52 0.69 0.91 1.08 1.25

1-HR. 0.:39 0.67 0.88 1.16 1. 38 1.59

3-HR. 0.57 0.99 1.31 1. 72 2.04 2.36

6-HR. 0.76 1.32 1. 74 2.29 2.71 3.1:l

24-HR. 1. 08 1. 85 2.47 J • .2 6 3.85 4.45



5-MIN. 0.750 0.08 0.15 0.20 0.26 0.31 0.35

30-MIN. 0.750 0.23 0.39 0.52 0.6B O.Bl 0.94

I-HR. 0.750 0.29 0.50 0.66 0.87 1.04 1.19

3-HR. 0.955 0.54 0.95 1.25 1.64 1.95 2.25

6-HR. 0.979 0.74 1.29 1. 70 2.24 2.65 3.06

24-HR. 0.987 1.07 1.83 2.44 3.22 3.80 4.39

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN·/HR. )


5-MIN. 0.750 0.99 1.80 2.34 3.06 3.69 4.23

30-MIN. 0.750 0.45 0.78 1.04 1.37 1.62 1.88

I-HR. 0.750 0.29 0.50 0.66 0.87 1.04 1.19

3-HR. 0.955 0.18 0.32 0.42 0.55 0.65 0.75

6-HR. 0.979 0.12 0.22 0.28 0.37 0.44 0.51

24-HR. 0.987 0.09 0.15 0.20 o. ;!7 0.32 0.37

17l


25 SQ. MI.



5-MIN. O. l.l. 0.20 0.26 0.34 0.41 0.47

30-MIN. 0.30 0.52 0.69 0.91 1. 08 1.25

l-HR. 0.39 0.67 0.88 1.16 1. 38 1.59

3-HR. 0.57 0.99 1.31 1. 72 2.04 2.36

6-HR. 0.76 1. 32 1. 74 2.29 2.71 3.13

24-HR. 1. 08 1. 85 2.47 3.26 3.85 4.45


DURATION DEPl'H-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.570 0.06 0.11 0.15 0.19 0.23 0.27

30-MIN. 0.595 0.18 0.31 0.41 0.54 0.64 0.74

l-HR. 0.605 0.24 0.41 0.53 0.70 0.83 0.96

3-HR. 0.910 0.52 0.90 1.19 1.57 1.86 2.15

6-HR. 0.958 0.73 1.26 1.67 2.19 2.60 3.00

24-HR. 0.974 1.05 1.80 2.41 3.18 3.75 4.33



5-MIN. 0.570 0.75 1. 37 1. 78 2.33 2.80 3.21

30-MIN. 0.595 0.36 0.62 0.82 1.08 1.29 1.49

l-HR. 0.605 0.24 0.41 0.53 0.70 0.83 0.96

3-HR. 0.910 0.17 0.30 0.40 0.52 0.62 0.72

6-HR. 0.958 0.12 0.21 0.28 0.37 0.43 0.50

24-HR. 0.974 0.09 0.15 0.20 0.26 0.31 0.36

172


50 SQ. Mt.



5-MIN. 0.11 0.20 0.26 0.34 0.41 0.47

3D-MIN. 0.30 0.52 0.69 0.91 1. 08 1.25

1-HR. 0.39 0.67 0.88 1.16 1. 38 1.59

3-HR. 0.57 0.99 1.31 1.72 2.04 2.36

6-HR. 0.76 1. 32 1. 74 2.29 2.71 3.13

24-HR. '1.08 1. 85 2.47 3.26 3.85 4.45


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. 100-YR

5-MIN. 0.430 0.05 0.09 0.11 0.15 0.18 0.20

30-MIN. 0.468 0.14 0.24 0.32 0.43 0.51 0.59

1-HR. 0.492 0.19 0.33 0.43 0.57 0.68 0.78

3-HR. 0.840 0.48 0.83 1.10 1.44 1. 71 1.98

6-HR. 0.929 0.71 1.23 1.62 2.13 2.52 2.91

24-HR. 0.957 1.03 1.77 2.36 3.12 3.68 4.26

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN .jHR. )

DURATION DEPTH-AREA 2-YR. 5-YR. la-YR. 25-YR. 50-YR. 100-YR

5-MIN. 0.430 0.57 1.03 1.34 1.75 2.12 2.43

3D-MIN. 0.468 0.28 0.49 0.65 0.85 1. 01 1.17

l-HR. 0.492 0.19 0.33 0.43 0.57 0.68 0.78

3-HR. 0.840 0.16 0.28 0.37 0.48 0.57 0.66

6-HR. 0.929 0.12 0.20 0.27 0.35 0.42 0.48

24-HR. 0.957 0.09 0.15 0.20 0.26 0.31 0.35

173


100 SQ. MI.



5-MIN. 0.11 0.20 0.26 0.34 0.41 0.47

30-MIN. 0.30 0.52 0.69 0.91 1.08 1.25

1-HR. 0.39 0.67 0.88 1.16 1. 38 1.59

3-HR. 0.57 0.99 1.31 1.72 2.04 2.36

6-HR. 0.76 1. 32 1. 74 2.29 2.71 3.13

24-HR. 1.08 1. 85 2.47 3.26 3.85 4.45



5-MIN. 0.300 0.03 0.06 0.08 0.10 0.12 0.14

30-MIN. 0.355 0.11 0.18 0.24 0.32 0.38 0.44

1-HR. 0.402 0.16 0.27 0.35 0.47 0.55 0.64

3-HR. 0.747 0.43 0.74 0.98 1. 28 1.52 1. 76

6-HR. 0.889 0.68 1.17 1.55 2.04 2.41 2.78

24-HR. 0.935 1.01 1. 73 2.31 3.05 3.60 4.16



5-MIN. 0.300 0.40 0.72 0.94 1.22 1.48 1.69

30-MIN. 0.355 0.21 0.37 0.49 0.65 0.77 0.89

l-HR. 0.402 0.16 0.27 0.35 0.47 _0.55 0.64

3-HR. 0.747 0.14 0.25 0.33 0.43 0.51 0.59

6-HR. 0.889 0.11 0.20 0.26 0.34 0.40 0.46

24-HR. 0.935 0.08 0.14 0.19 0.25 0.30 0.35

174


150 SQ. MI.



5-MIN. O.ll 0.20 0.26 0.34 0.41 0.47

30-MIN. 0.30 0.52 0.69 0.91 1.08 1.25

I-HR. 0.39 0.67 0.88 1.16 1.38 1.59

3-HR. 0.57 0.99 1. 31. 1.72 2.04 2.36

6-HR. 0.76 1.32 1. 74 2.29 2.71 3.13

24-HR. 1. 08 1.85 2.47 3.26 3.85 4.45



5-MIN. 0.243 0.03 0.05 0.06 0.08 0.10 0.11

30-MIN. 0.310 0.09 0.16 0.21 0.28 0.33 0.39

I-HR. 0.362 0.14 0.24 0.32 0.42 0.50 0.58

3-HR. 0.688 0.39 0.68 0.90 1.18 1.40 1.62

6-HR. 0.870 0.66 1.15 1.51 1.99 2.36 2.72

24-HR. 0.923 1.00 1.71 2.28 3.01 3.55 4.ll


DURATION DEPTH-AREA 2-YR. 5-YR. la-YR. 25-YR. 50-YR. 100-YR.

5-MIN. 0.243 0.32 0.58 0.76 0.99 1.20 1.37

30-MIN. 0.310 0.19 0.32 0.43 0.56 0.67 0.78

l-HR. 0.362 0.14 0.24 0.32 0.42 0.50 0.58

3-HR. 0.688 0.13 0.23 0.30 0.39 0.47 0.54

6-HR. 0.870 O.ll 0.19 0.25 0.33 0.39 0.45

24-HR. 0.923 0.08 0.14 0.19 0.25 0.30 0.34

175

:;. c

" 0 <.> <Ii (I)

"-~ '" c " 0

<.> 0 vi I :;. c " 0 l! CD (I) ~


San Bernardino VS. San Diego County

0.2.-----~----------------------------------------_.

0.1

0

-0.1

-0.2

-0.3 L-______________________ -'

30 min. 60 min. 180 min.

Design Storm Peok Durotion (minutes)

~ 1 mil. ~ 5 mile ~ 10 mile 12C2l25 mile iSS] 50 mile [Z2] 150 miie

Graph Values [(S.B.County-S.D.County)lS.B.CountyJ


10 Sq. Mi. -0.13 -0.17 -0.06 25 Sq. Mi. -0.21 -0.21 0.17 50 Sq. Mi. -0.27 -0.20 0.19

150 Sq. Mi. NfA N/A N/A

176


San Bernardino VS. San Diego County 0.2,--------------------------,

0.1 I-~)Ij.-------..,...,...._--------_..._,do,. \1-----4

-0.1 ~---{;

-0.2 '------I;\.I\.~-----_K)4.,,1_-----------j

-0.3 ~---~===.-------------------l

-0.4 L--______________________ --.l

30 min. 60 min. 180 min.


m 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISSJ 50 mile rzzi150 mile

Graph Values [(S.B.County-S.D.County)lS.B.County]


10 Sq. Mi. -0.13 -0.16 0.00 25 Sq. Mi. -0.22 -0.21 0.10 50 Sq. Mi. -0.29 -0.27 0.19


177

'" c ~ 0

'< III UJ ...... ~

::-c ~ 0 ()

Q

UJ I

::-c

" 0 0 <Ii til ~

CraWford Ranch Area Adjusted Rainfall Comparison: 25 Year (Rainfalls adiusted using respective County depth-area curves)


0.3r-----------------------------------------------~

0.2

0.1

a

-0.1

-0.2

-0.3L-----------------------------------------------~ 30 min. 60 min. 180 min.

Oesign Storm PeaK Duration (minutes)

~ 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISS] 50 mile LZ2I150 mile

Graph Values [(S.B.County-S.D.CountyYS.B.CountyJ

30 min. eo min. 180 min. 1 Sq. Mi. 0.13 0.09 0.03 5 Sq. Mi. 0.01 -0.02 0.02

10 Sq. Mi. -0.12 -0.16 0.00 25 Sq. Mi. -0.20 -0.20 0.11 50 Sq. Mi. -0.25 -0.23 0.20


178

:p c , 0 ()

ai ui '. ~

:p c , 0 ()

0 Ul I

:p c , 0 '< CD

0-



0.3 ,-------------------------,

0.2

0.1

0

-0.1

-0.2

-0.3 '---------------------------' 30 min. 60 min. 180 min.

Design Storm Peok Durotion (minutes)

~ 1 mile ~ 5 mile ~ 10 mile ~ 25 mile ISSJ SO'mile iZ2l150 mile

Graph Values [(S.B.County-S.D.County)lS.B.CountyJ

30 min. 60 min. 180 min. 1 Sq. Mi. 0.13 0.10 0.05 5 SQ. Ml. 0.02 -0.01 0.03

10SQ. Mi. -0.12 -0.16 0.00 25 SQ. Mi. -0.19 -0.21 0.12 50 SQ. Mi. -0.26 -0.24 0.21


179


0:00 0.0

I 0:15 2.0 0:30 3.5 0;45 5.5 1:00 7.0

I 1:15 9.0 1:30 11.5 1:45 14.0 2:00 16.5 2:15 19.5 2:30 22.0 2:45 25.0 3:00 29.0 3:15 34.5 3:30 40.0 3:45 59.0 4:00 77.0 4:15 82.0 4:30 87.0 4:45 89.0 5:00 92.0 5:15 94.0 5:30 96.0 5:45 98.0 6:00 100.0


15min. 30min. 1 hour 2 hour 3 hour 6 hour

Crawford Ranch Area Precipitation San Diego County Desert Design Storm


0.73 inches 1.27 inches 1.68 inches 2.22 inches 2.62 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.03 0.03 0.03 0.03 0.04 0.04 0.05 0.03 0.02 0.04 0.Q1 0.06 0.03 0.08 0.04 0.09 0.04 0.01 0.07 0.03 0.09 0.03 0.12 0.04 0.14 0.05 0.01 0.09 0.02 0.12 0.03 0.16 0.04 0.18 0.07 0.02 0.11 0.02 0.15 0.03 0.20 0.04 0.24 0.08 0.01 0.15 0.04 0.19 0.04 0.26 0.06 0.30 0.10 0.02 0.18 0.03 0.24 0.05 0.31 0.05 0.37 0.12 0.02 0.21 0.03 0.28 0.04 0.37 0.06 0.43 0.14 0.02 0.25 0.04 0.33 0.05 0.43 0.06 0.51 0.16 0.02 0.28 0.03 0.37 0.04 0.49 0.06 0.58 0.18 0.02 0.32 0.04 0.42 0.05 0.56 0.07 0.66 0.21 0.03 0.37 0.05 0.49 0.07 0.64 0.08 0.76 0.25 0.04 0.44 0.07 0.58 0.09 0.77 0.13 0.90 0.29 0.04 0.51 0.07 0.67 0.09 0.89 0.12 1.05 0.43 0.14 0.75 0.24 0.99 0.32 1.31 0.42 1.55 0.56 0.13 0.98 0.23 1.29 0.30 1.71 0.40 2.02 0.60 0.04 1.04 0.06 1.38 0.09 1.82 0.11 2.15 0.64 0.04 1.10 0.06 1.46 0.08 1.93 0.11 2.28 0.65 0.01 1.13 I 0.03 1.50 0.04 1.98 0.05 2.33 0.67 0.02 1.17 0.04 1.55 0.05 2.04 0.06 2.41 0.69 0.02 1.19 0.02. 1.58 0.03 2.09 0.05 2.46 0.70 0.01 1.22

10.03 1.61 0.03 2.13 0.04 2.52

0.72 0.02 1.24 0.02 1.65 0.04 2.18 10.05 2.57 0.73 0.01 1.27 0.03 1.68 0.03 2.22 0.04 2.62

Maximum Values (depth in inches) 0.14 0.24 0.32 0.42 0.27 0.47 0.62 0.82 0.35 0.61 0.80 1.07 0.48 0.82 1.09 1044 0.56 0.95 1.27 1.67 0.73 1.27 . 1.68 2.22

Maximum Values (intensity in inches/hour) 0.56 0.96 1.28 1.68 0.54 0.94 1:24 1.64 0.35 0.61 0.80 1.07 0.24 0.41 0.55 0.72 0.19 0.32 0.42 0.56 0.12 0.21 0;28 0.37

180

year 100 year inChes 3.03 inChes Delta Mass Delta 0.00 0.00 0.00 0.05 0.06 0.06 0.04 0.11 0.05 0.05 0.17 0.06 0.04 0.21 0.04 0.06 0.27 0.06 0.06 0.35 0.08 0.07 0.42 0.07 0.06 0.50 0.08 0.08 0.59 0.09 0.07 0.67 0.08 0.08 0.76 0.09 0.10 0.88 0.12 0.14 1.05 0.17 0.15 1.21 0.16 0.50 1.79 0.58 0.47 2.33 0.54 0.13 2.48 0.15 0.13 2.64 0.16 0.05 2.70 0.06 0.08 2.79 0.09 0.05 2.85 0.06 0.06 2.91 0.06 0.05 2.97 0.06 0.05 3.03 0.06

0.50 0.58 0.97 1.12 1.26 1.45 1.70 1.97 1.98 2.29 2.62 3.03

2.00 2.32 1.94 2.24 1.26 1.45 0.85 0.99 0.66 0.76 0.44 0;51


0:00 0.0 0:15 2.0 0:30 3.5 0:45 5.5 1:00 7.0 1:15 9.0 1:30 11.5 1:45 14.0 2:00 16.5 2:15 19.5 2:30 22.0 2:45 25.0 3:00 29.0 3:15 34.5 3:30 40.0 3:45 59.0 4:00 77.0 4:15 82.0 4:30 87.0 4:45. 89.0 5:00 92.0 5:15 94.0 5:30 96.0 5:45 98.0 6:00 100.0





0.73 inches 1.27 inches 1.68 inches 2.22 inches 2.62 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.03 0.03 0.03 0;03 0.04 0.04 0~05

0.03 0.02 0.04 0.01 0.06 0.03 0.08 0.04 0.09 0.04 0.01 0.07 .. 0.03 0.09 0.03 0.12 0.04 0.14 0.05 0.01 0.09 0.02 0.12 0.03 0.16 0.04 0.18 0.07 0.02 0.11 0.02 0.15 0.03 0.20 0.04 0.24 0.08 0.01 0.15 0.04 0.19 0.04 0.26 0.06 0.30 0.10 0.02 0.18 0.03 0.24 0.05 0.31 0.05 0.37 0.12 0.02 0.21 0.03 0.28 0.04 0.37 0.06 0.43 0.14 0.02 0.25 0.04 0.33 0.05 0.43 0.06 0.51 0.16 0.02 0.28 0.03 0.37 0.04 0.49 0.06 0.58 0.18 0.02 0.32 0.04 0.42 0.05 0.56 0.07 0.66

0.21 0.03 0.37 0.05 0.49 0.07 0.64 0.08 0.76 0.25 0.04 0.44 0.07 0.58 0.09 0.77 0.13 0.90 0.29 0.04 0.51 0.07 0.67 0.09 0.89 0.12 1.05 0.43 0.14 I 0.75 .0.24 0.99 0.32 1.31 0.42 1.55

1. 0.56 0.13 0.98 0.23 1.29 0.30 1.71 0.40 2.02 I· 0.60 0.04 1.04 0.06 1.38 .0.09 1.82 0.11 2.15

0.64 0.04 1.10 0.06 1.46 0.08 1.93 0.11 2.28 0.65 0.01 1.13 1.0.03 1.50 0.04 1.98 0.05 2.33 0.67 0.02 1.17 0.04 1.55 0.05 2.04 0.06 2.41

!0.69 0.02 1.19 0:02 1.58 ··0.03 2.09 0.05 2A6

0.70 0.01 1.22 1 0.03 1.61 0.03 2.13 0.04 2.52

0.72 0.02 ·1.24··· 10;02 1;65 0.04 2.18 0.05 2.57 0.73 0.01 1.27 0.03 1.68 0.03 2.22 0.04 2.62

Maximum Values (depth in incheS) 0.14 0.24 0.32 0.42 0.27 0.47 0.62 0.82

0.35 0.61 0.80 1.07

0.48 I ·0.82 1:09 1.44

0.56 0.95 1.27 1.67

0.73 1.27 ...•.. 1.68 2.22 I .


0.54 ......

0.94 .1:24 1:64

0.35 0.61 0.80 1.07 0.24· 0.41 0.55 0:72 0.19 0.32 0.42 0.56 0.12 0:21 . 0.28 0.37

181

year 100 year inches 3.03 inches Delta Mass Delta 0.00 0.00 0.00 0;05 ·0.06 0.06 0.04 0.11 0.05 0.05 . 0.17 0.06 0.04 0.21 0.04 0.06 0.27 0.06 0.06 0.35 0.08 0.07 0.42 0.07 0.06 0.50 0.08 0.08 0.59 0.09 0.07 0.67 0.08 0.08 0.76 0.09 0.10 0.88 0.12 0.14 .1.05 0.17 0.15 1.21 0.16 O.SO L 1.79 .. 0.58 0.47 2.33 0.54 0.13 2.48 0.15 0.13 2.64 0.16 0.05 2,70 ·0.06 0.08 2.79 0.09

.0.05 12.85 ··0.06 0.06 2.91 0.06 0.05 ·2.97 0.06 0.05 3.03 0.06

0.50 I

0.58 0.97 . 1.12. 1.26 1.45 1.70 '.i 1.97 1.98 2.29 2.62

..... 3.03

2.00 2.32 1.94· ·2.24

I 1.26 1.45 O.SS I 0:99 0.66 0.76 0.44 .! O:Sf


0:00 0.0 0:15 2.0 0:30 3.5 0:45 5:5· 1:00 7.0 1:15 .. 9.0 1:30 . 11.5 1:45 14.0 2:00 16.5 2:15 19.5 2:30 22.0 2:45 25.0 3:00 29.0 3:15 34.5 3:30 40.0 3:45 59.0 4:00 77.0 4:15 82.0 4:30 87.0 4:45 89.0 5:00 1. 92.0

I 5:15 94.0. 5:30 96.0 5:45 98.0 6:00 100.0

16 min. 30 min. 1 hour 2 hour 3holW 6 hour

15 min. 30 min 1 hour 2 hour 3 haUl' 6 hour



0.73 inches 1.27 inches 1.68 inches 2.22 inches 2.62 Mass Delta Mass Delta Mass Delta Mass Delta Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0;01. 0.01 0.03 0.03 0.03 0.03. 0.04 0.04 0;05 0.03 0.02 0.04 0.01 0.06 0.03 0.08 0.04 0.09

/0:04 0.01 f·O.07 0.03 .0.09 .. 0.03 0.12 ·0.04 0;14 0.05 0.01 0.09 0.02 0.12 0.03 0.16 0.04 0.18 0.07 0.02 0.11 0.02 0.15 0.03 0.20 0.04 0.24 0.08 0.01 0.15 0.04 0.19 0.04 0.26 0.06 0.30 0.10 0.02 0.18 0.03 0.24 0.05 0.31 , 0.05 0.37 0.12 0.02 0.21 0.03 0.28 0.04 0.37 i 0.06 0.43 0.14 0.02 0.25 0.04 0.33 0.05 0.43 0.06 0.51 0.16 0.02 0.2B 0.03 0.37 0.04 0.49 0.06 0.58 0.18 0.02 0.32 0.04 0.42 0.05 0.56 0.07 0.66 0.21 0.03 0.37 0.05 0.49 0.07 0.64 0.08 0.76 0.25 0.04 0.44 0.07 0.58 0.09 0.77 0.13 0.90 0.29 0.04 0.51 0.07 0.67 0.09 0.89 0.12 1.05

.0:43 1. 0.14 0.75 0.24 0.99 0.32 1.31 0.42 1.55 0.56 0.13 0.98 0.23 1.29 0.30 1.71 0.40 2.02 0.60 0.04 1.04 0.06 1.38 0.09 1.82 0.11 2.15

1°·64 0.04 1.10 0.06 1.46 0.08 1.93 0.11 2.28 I 0.65 0.01 1.13 0.03 1.50 0.04 1.98 0.05 2.33

0.67 0.02 1.11 0.04 1.55 0.05 2.04 0.06 2.41 10.69 0.02 1.19 0.02 1:58 0.03 2.09 0.05 2:46

1. 0.70 0.01 1.22 0.03 1.61 0.03 2.13 0.04 2.52 0.72 0.02 1.24 0.02 ·1.65 0.04 2.18 0.05 2.57 0.13 0.01 1.21 0.03 1.68 0.03 2.22 0.04 2.62

Maximum Values (depth in inches) 0.14 0.24 0.32 0.42 0.27 0.41 0.62 0.82 0.35 0.61 0.80 1.07 0.48 0.82 1.09 1.44 0.56 0.95 1.27 1.67 0.13 1:27 1.68 2.22


I 0.54 0.94

I 1.24 1.64 I

I 0.35 0.61 0.80 1.07 0.24 ·0.41 0.55 0.72 0.19 0.32 0.42 0.56 0.12 0.21 0:28 0.37

182

year 100 year inches 3.03 inches Delta Mass Delta 0.00 0.00 0.00 0.05 0.06 0.06 0.04 0.11 0.05 0.05 0:17 10.08 0.04 0.21 0.04 0.08 0.27 0.06 0.06 0.35 0.08 0.07 0.42 0.07 0.06 0.50 0.08 0.08 0.59 0.09 0.07 0.67 0.08 0.08 0.76 0.09 0.10 0.88 0.12 0.14 1:05 0.17 0.15 1.21 0.16 0.50 I·· 1:79 0.58 0.41 2.33 0.54 0.13 2.48 0.15 0.13 2.64 0.16 0.05 2.70 ·0.06 0.08 2.79 0.09 0.05 2.85 .0.06 0.06 2.91 0.06 0.05 2.97 0.06 0.05 3.03 0.06

0.50 0.58 0.91 1.12 1.26 1.45 1.70 1.97 1.98 2.29 2.62 3.03

2.00 2.32 1:94 2:24 1.26 1.45 0.85 0.99 0.66 0.76 0,44 0.51

25 sq. mile Time DiS!.

0:00 0.0 0:15 2.0 0:30 3.5 0:45 5.5 1:00 7.0 1:15 9.0 1:30 11.5 1:45 14.0 2:00 16.5 2:15 19.5 2:30 22.0

.

2:45 25.0 3:00 29.0 3:15 34.5 3:30 40.0 3:45 59.0 4:00 n.0 4:15 82.0 4:30 97.0 4:45 89.0 5:00 92.0 5:15 94.0 5:30 96.0 5:45 98.0 6:00 100.0





0.61 inches 1.07 inches 1.41 inches 1.96 inches 2.20 Mass Della Mass Delta Mass Delta Mass Della Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

L 0;01 0.02 0.02 0.03 0.03 0.04 1 .. 0.04 0.04 .0.01 0.02 0.01 0.04 0.02 0.05 0.02 0.07 0.03 0.08 0.03 0.01 0.06 0.02 0.08 0.03 0.10 I· 0.03 0.12 0.04 0.01 0.07 0.01 0.10 0.02 0.13 0.03 0.15 0.05 0.01 0.10 0.03 0.13 0.03 0.17 0.04 0.20 0.07 0.02 0.12 0.02 0.16 0.03 0.21 0.04 0.25 0.09 0.02 0.15 0.03 0.20 0.04 0.26 0.05 0.31 0.10 0.01 0.18 0.03 0.23 0.03 0.31 0.05 0.36 0.12 0.02 0.21 0.03 0.27 0.04 0.36 0.05 0.43 0.13 0.01 0.24 0.03 0.31 0.04 0.41 0.05 0.48 0.15 0.02 0.27 0.03 0.35 0.04 0.47 0.06 0.55 0.18 0.03 0.31 0.04 0.41 0.06 0.54 0.07 0.64

'0:21 0.03 0.37 0.06 0.49 0.08 0.64 .. 0.10 0.76 0.24 0.03 0.43 0.06 0.56 0.07 0.74 0.10 O.BB 0.36 0.12 0.63 0.20 0.83 0.27 1.10 0.36 1.30 0.47 0.11 0.82 0.19 1.09 0.26 1.43 0.33 1.69

1 0.50 0.03 0.88 0.06 1.16 0.07 1.53 0.10 1.80 0.53 0.03 0.93 0.05 1.23 0.07 1.62 0.09 1.91

. 0.54 0.01 0.95 0.02 1.25 0.02 1.66 0.04 1.96 0.56 0.02 0.98 0.03 1.30 0.05 1.71 0.05 2.02

(·0.57 .0;01 '.LOl 0.03 1.33 0.03 1.75 0.04 2.07 0.59 0.02 1.03 0.02 1.35 0.02 1.79 0.04 2.11

0:60 0.01 1'.05 0.02 1.38 0.03 I 1.82 0.03 2.16

0.61 0.01 1.07 0.02 1.41 0.03 1.86 0.04 2.20

Maximum Values (depth in inches) 0.12 0.20 0.27 0.36 0.23 0.39 0.53 0.69 0.29 0.51 0.68 0.89 .... 0.40 I 0.69 0.92 1.21 ...•.. 0.46 0.81 1.07 1.41

I 0.61 1.07 .' 1.41 1.86

Maximum Values (intensity in inches/hour) 0.48 0.80 1.08 1.44 0;46 .. 0:78 1.06 1.38 0.29 0.51 0.68 0.89 0.20 0.35 0.46 0.61 0.15 0.27 0.36 0.47 0.10 0.18 0:24 0.31

183

year 100 year inches 2.55 inches Delta Mass Delta 0.00 0.00 0.00 0.04 0.05 0.05 0.04 0.09 0.04 0.04 0.14 0.05 0.03 0.18 0.04 0.05 0.23' 0.05 0.05 0.29 0.06 0.06 0.36 0.07 0.05 0.42 0.06 0.07 0.50 0.08 0.05 0.56 0.06 0.07 0:64 0.08 0.09 0.74

10.10

0.12 0:88 I 0.14. 0.12 1.02 0.14 0.42 .. l,5.0 0.48 0.39 1.96 0.46 0.11 2;09' 0.13. 0.11 2.22 0.13 0.05 .. 2;27' . 0.05 0.06 2.35 0.08 0.05 ·····2.40 0.05 0.04 2.45 0.05 0.05 ,2.50' . 0.05 0.04 2.55 0.05

0.42 0.49 0.81 0.94

..

1.05 1.22 1.43 i.66 1.66 1.93 2.20 2.55

1.68 1.92 1.62 1:88' 1.05 1.22 0.72 o~83 0.55 0.64 0.37 0:43


0:00 0.0 0:15 2.0 0:30 3.5 0:45 5.5 1:00 7.0 1:15 9.0 1:30 11.5 1:45 14.0

I 2:00 16.5 2:15 19.5 2:30 22.0 2:45 25.0 3:00 29.0 3:15 34.5 3:30 40.0 3:45 59.0 4:00 77.0 4:15 82.0 4:30 87.0 4:45 89.0 5:00 92.0 5:15 94.0 5:30 96.0 5:45 98.0 6:00 100.0




Storm Frequency 2 year 5 -vear 10 year 25 year 50

0.51 inches 0.89 inches 1.18 inches 1.55 inches 1.83 Mass Delta Mass Delta Mass Delta Mass Oelta Mass 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0;01 0.01 0.02 0.02 0.02 0.02 0.03 ·0.03 0.04 0.02 0.01 0.03 0.01 0.04 0.02 0.05 0.02 0.06 0.03 0.01 0.05 0.02 0.06 0.02· 0:09 .0.04· I 0.10 0.04 0.Q1 0.06 0.01 0.08 0.02 0.11 0.02 0.13 0.05 0.01 0.08 0.02 0.11 0.03 0.14 0.03 0.16 0.06 0.01 0.10 0.02 0.14 0.03 0.18 0.04 0.21 0.07 0.01 0.12 0.02 0.17 0.03 0.22 0.04 0.26 0.08 0.01 0.15 0.03 0.19 0.02 0.26 0.04 0.30 0.10 0.02 0.17 0.02 0.23 0.04 0.30 0.04 0.36 0.11 0.01 0.20 0.03 0.26 0.03 0.34 0.04 0.40 0.13 0.02 0.22 0.02 0.30 0.04 0.39 0.05 0.46 0.15 0.02 0.26 0.04 0.34 0.04 0.45 0.06 0.53 0.18 0.03 0.31 0.05 0.41 0.07 0.53 0.08 0.63 0.20 0.02 0.36 0.05 0.47 0.06 0.62 0.09 0.73 0.30 0.10 0.53 0.17 0.70 0.23 0.91 0.29 t.OS 0.39 0.09 0.69 0.16 0.91 0.21 1.19 0.28 1.41 0.42 0.03 0.73 0.04 0.97 0.06 1.27 1 0.08 1.50 0.44 0.02 0.77 0.04 1.03 0.06 1.35 0.08 1.59 0.45 0.01 0.79 0.02 1.05 0.02 1.38 0.03 1.63 0.47 0.02 0.82 0.03 1.09 0.04 1.43 0.05 1.68 0.48 0.01 I 0.84 I· 0.02 1.11 0.02 1.46 10.03 1.72 0.49 0.01 0.85 1. 0.01 1.13 0.02 1.49 0.03 1.76 0.50 0.01 0.87 0.02 1.16 0.03 1.52 0.03 , 1:79 0.51 0.Q1 0.89 0.02 1.18 0.02 1.55 0.03 1.83

Maximum Values (depth in inches) 0.10 0.17 0.23 0.29 0.19 0.33 0.44 0.57 0.24 0.43 0.57 0.74 0.33 0.57 0.77 1;01 0.38 0.67 0.89 1.17 0.51 0.89 1.18 1;55

Maximum Values (intensity in inches/hour) 0.40 0.68 0.92 1.16 0.38 0.66 0.88 1:14 0.24 0.43 0.57

I 0.74

0.17 0:29 0.39 0.51 . 0.13 0.22 0.30 0.39

I 0.09 0.15 0;20 0:26

184

year 100 year inches 2.12 inches Delta Mass Delta 0.00 0.00 0.00 0.04 0.04 I 0.04 0.02 0.07 0.03 0.04 0;12 I.· 0.05 0.03 O.lS 0.03 0.03 0.19 0.04 0.05 0.24 0.05 0.05 0.30 0.06 0.04 0.35 0.05 0.06 0.41 0.06 0.04 0.47 0.06 0.06 0.53 0.06 0.07 0.61 0.08 0.10 0.73 0.12 0.10 0.85 0.12 0.35 1.25 ,0,40 0.33 1.83 0.38 0.09 1.74 1 0.11 0.09 1.84 0.10 0.04 1.S9 0.05 0.05 1.95 0.06 0.04 1,99 0.04 0.04 2.04 0.05 0.03 2.08 0.04 0.04 2.12 0.04

0.35 0.40 0.68 0.78 0.88 1.02 1.19 1.37 1.38 1.60 1.83 2:12

1.40 1.60 1.36 ·'.56 0.88 1.02 O.SO ·M9 0.46 0.53 0.31 0:35

100 SQ.

TIme 0:00 0:15 0:30 0:45 1:00 1 :15 1:30 1:45 2:00 2:15 2:30 2:45 3:00 3:15 3:30 3:45 4:00 4:15 4:30 4:45 5:00 5:15 5:30 5:45 6:00


Storm Frequency 2 year 5 year 10 year 25 year 50 year 100

mile 0.39 inches 0.69 inches 0.91 inches 1.20 inches 1.41 inches 1.64 Dist. Mass Della Mass Della Mass Delta. Mass Delta Mass Delta Mass

0.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.0 I·· 0.01' 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.03 3.5 0.01 0.00 0.02 0.01 0.03 0.01 0.04 0.02 0.05 0.02 0.06 5.5 1 0.02 0.01 0.04 0.02 0.05 0.02 0.07 0.03 0.08 0.03 0.09 7.0 0.03 0.01 0.05 0.01 0.06 0.01 0:08 0.Q1 0.10 0.02 0.11 9.0 0.04 0.01 0.06 0.01 0.08 0.02 0.11 0.03 0.13 0.03 0.15

11.5 0.04 0.00 0.08 0.02 0.10 0.02 0.14 0.03 O.lS 0.03 0.19 14.0 0.05 0.01 0.10 0.02 0.13 0.03 0.17 0.03 0.20 0.04 0.23 lS.5 O.OS 0.01 0.11 0.01 0.15 0.02 0.20 0.03 0.23 0.03 0.27 19.5 0.08 0.02 0.13 0.02 0.18 0.03 0.23 0.03 0.27 0.04 0.32 22.0 0.09 0.D1 0.15 0.02 0.20 0.02 0.26 0.03 0.31 0.04 0.36

25.0 0.10 0.01 0.17 0.02 0.23 0.03 0.30 0.04 0.35 0.04 0.41

29.0 0.11 0.01 0.20 0.03 0.26 0.03 0.35 0.05 0.41 O.OS 0.48

I· 34.5 I 0.13 0.02 0.24 0.04 0.31 0.05 0.41 O.OS 0.49 0.08 0.57 40.0 0.16 0.03 0.28 0.04 0.36 0.05 0.48 0.07 0.56 0.07 0.66 59.0 0.23 0.07 0.41 0.13 0.54 0.18 0.71 0.23 0.83 0.27 0.97 77.0 0.30 0.07 0.53 0.12 0.70 0.16 0.92 0.21 1.09 0.26 1.26

82.0 I 0.32 0.02 0.57 1 .. 0•04 0.75 0.05 0.98 0.06 1.16 0.07 .. 1.34 87.0 0.34 0.02 O.SO 0.03 0.79 0.04 1.04 0.06 1.23 0.07 1.43

89.0 0.35 . 0.01 1 0.61 <0.01 I 0.81 0.02 1.07 0.03 1.25 0.02 1.46

92.0 0.36 0.01 0.63 0.02 0.84 0.03 1.10 0.03 1.30 0.05 1.51 I·· 94.0 LO:37 0.01 0.65 .. 0.02 0.86 0.02 1.13 0.03 L33 0.03 1:54

96.0 0.37 0.00 0.66 0.01 0.87 0.01 1.15 0.02 1.35 0.02 1.57

·98.0 ·0:38· 0.01 0.68 iO;02 ·0.89 0.02 1.18 0.03 1.38 0.03 1 1:61

100.0 0.39 0.01 0.69 0.01 0.91 0.02 1.20 0.02 1.41 0.03 1.64

Maximum Values (depth in inches) 15 min. 0.07 0.13 0.18 0.23 0.27

30 min. 0.14 0.25 0.34 0:44 0.53

1 hour 0.19 0.33 0.44 0.57 0.68

2 hour I 0.25 0;45· 0.59 0.78 0:92 ! .. 3 hour 0.30 0.52 0.69 0.90 1.07

6 hour 0.39 ······0.69 0.91 1:20 lAl

Maximum Values (intensity in inches/hour) 15 min. 0.28 0.52 0.72 0.92 1.08

30 min. ...

0.28 1 0.50 0.68 0.88 . 1.06 I 1 hour 0.19 0.33 0.44 0.57 0.68

2 hour 0.13 ··0.23 I 0:30 0.39 GA6

3 hour 0.10 0.17 0.23 0.30 0.36

6 hour 0.07 0;',' ....... 0:15 0;20 0.24 1

185

year inches Della 0.00 0.03 0.03 0.03 0.02 0.04 0.04 0.04 0.04 0.05 0.04 0.05 0.07 0.09 0.09 0.31 0.29 0.08 0.09

·0.03 0.05 0.03 0.03 0.04 0.03

0.31 0.60 0.78 1.07 1.24 1.64

1.24 1.20 0.78

·0.54 0.41 0.27

CRAWFORD RANCH AREA PRECIPITATION SAN BERNARDINO COUNTY DESIGN STORM

1 SQ. MI.



5-MIN. 0.13 0.22 0.29 0.38 0.45 0.52

30-MIN. 0.32 0.56 0.73 0.97 1.15 1.33

l-HR. 0.40 0.70 0.92 1.22 1.44 1.67

3-HR. 0.58 1. 01 1. 33 1. 76 2.08 2.40

6-HR. 0.73 1.27 1. 68 2.22 2.62 3.03

24-HR. 1.12 1.93 2.55 3.37 3.99 4.61



5-MIN. 0.971 0.13 0.21 0.28 0.37 0.44 0.50

3D-MIN. 0.971 0.31 0.54 0.71 0.94 1.12 1.29

l-HR. 0.971 0.39 0.68 0.89 1.18 1.40 1.62

3-HR. 0.996 0.58 1.01 1. 32 1. 75 2.07 2.39

6-HR. 0.998 0.73 1.27 1.68 2.22 2.61 3.02

24-HR. 0.999 1.12 1.93 2.55 3.37 3.99 4.61


DURATION DEPTH-AREA 2-YR. 5-YR. la-YR. 25..,YR. 50-YR. 100-YR.

5-MIN. 0.971 1.51 2.56 3.38 4.43 5.24 6.06

30-MIN. 0.971 0.62 1.09 1.42 1.88 2.23 2.58

l-HR. 0.971 0.39 0.68 0.89 1.18 1.40 1.62

3-HR. 0.996 0.19 0.34 0.44 0.58 0.69 0.80

6-HR. 0.998 0.12 0.21 0.28 0.37 0.44 0.50

24-HR. 0.999 0.09 0.16 0.21 0.28 0.33 0.38

186


5 SQ. MI.



5-MIN. 0.13 0.22 0.29 0.38 0.45 0.52

30-MIN. 0.32 0.56 0.73 0.97 1.15 1.33

1-HR. 0.40 0.70 0.92 1.22 1.44 1.67

3-HR. 0.58 1. 01 1.33 1.76 2.08 2.40

6-HR. 0.7J 1.27 1.68 2.22 2.62 J.03

24-HR. 1.12 1. 93 2.55 3.37 3.99 4.61



5-MIN. 0.857 0.11 0.19 0.25 0.33 0.39 0.45

30-MIN. 0.857 0.27 0.48 0.63 0.83 0.99 1.14

l-HR. 0.857 0.34 0.60 0.79 LOS 1.23 1.43

3-HR. 0.979 0.57 0.99 1.30 1.72 2.04 2.35

6-HR. 0.989 0.72 1.26 1.66 2.20 2.59 3.00

24-HR. 0.994 1.11 1.92 2.53 3.35 3.97 4.58



5-MIN. 0.857 1.34 2.26 2.98 3.91 4.63 5.35

30-MIN. 0.857 0.55 0.96 1.25 1.66 1.97 2.28

l-HR. 0.857 0.34 0.60 0.79 1.05 1.23 1.43

3-HR. 0.979 0.19 0.33 0.43 0.57 0.68 0.78

6-HR. 0.989 0.12 0.21 0.28 0.37 0.43 0.50

24-HR. 0.994 0.09 0.16 0.21 0.28 0.33 0.38

187


10 SQ. HI.

",POINT RAINFALL DEPTHS (IN. )

DURATION 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. lOo-YR.

5-MIN. 0.13 0.22 0.29 0.38 0.45 0.52

3D-MIN. 0.32 0.56 0.73 0.97 1.15 1.33

l-HR. 0.40 0.70 0.92 1.22 1.44 1.67

3-HR. 0.58 1.01 1. 33 1.76 2.08 2.40

6-HR. 0.73 1.27 1. 6B 2.22 2.62 3.03

24-HR. 1.12 1.93 2.55 3.37 3.99 4.61


DURATION DEPTH-AREA 2-YR. 5-YR. lo-YR. 25-YR. 50-YR. loo-YR.

5-MIN. 0.750 0.10 0.17 0.22 0.29 0.34 0.39

30-MIN. 0.750 0.24 0.42 0.55 0.73 0.86 1.00

1-HR. 0.750 0.30 0.53 0.69 0.92 1.08 1.25

3-HR. 0.955 0.55 0.96 1.27 1.68 1. 99 2.29

6-HR. 0.979 0.71 1.24 1.64 2.17 2.56 2.97

24-HR. 0.987 1.ll. 1.90 2.52 3.33 3.94 4.55



5-MIN. 0.750 1.17 1.9B 2.61 3.42 4.05 4.6B

3D-MIN. 0.750 0.48 0.84 1.10 1.46 1.72 2.00

1-HR. 0.750 0.30 0.53 0.69 0.92 LOB 1.25

3-HR. 0.955 0.18 0.32 0.42 0.56 0.66 0.76

6-HR. 0.979 0.12 0.21 0.27 0.36 0.43 0.49

24-HR. 0.987 0.09 0.16 0.21 0.28 0.33 0.38

188


25 SQ. MI.



5-MIN. 0.13 0.22 0.29 0.38 0.45 0.52

30-MIN. 0.32 0.56 0.73 0.97 1.15 1. 33

I-HR. 0.40 0.70 0.92 1. 22 1.44 1. 67

3-HR. 0.58 1.01 1. 33 1. 76 2.08 2.40

6-HR. 0.73 1.27 1. 68 2.22 2.62 3.03

24-HR. 1.12 1. 93 2.55 3.37 3.99 4.61



5-MIN. 0.570 0.07 0.13 0.17 0.22 0.26 0.30

3D-MIN. 0.595 0.19 0.33 0.43 0.58 0.68 0.79

I-HR. 0.605 0.24 0.42 0.56 0.74 0.87 1.01

3-HR. 0.910 0.53 0.92 1.21 1.60 1.89 2.18

6-HR. 0.958 0.70 1.22 1.61 2.13 2.51 2.90

24-HR. 0.974 1.09 1.88 2.48 3.28 3.89 4.49

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN ./HR.)


5-MIN. 0.570 0.89 1.50 1.98 2.60 3.08 3.56

30-MIN. 0.595 0.38 0.67 0.87 1.15 1.37 1.58

I-HR. 0.605 0.24 0.42 0.56 0.74 0.S7 1. 01

3-HR. 0.910 0.18 0.31 0.40 0.53 0.63 0.73

6-HR. 0.958 0.12 0.20 0.27 0.35 0.42 0.48

24-HR. 0.974 0.09 0.16 0.21 0.27 0.32 0.37

189


50 SQ. MI.

POINT RAINFALL DEPl'HS (IN. )

DURATION 2-YR. 5-YR. 10-YR. 2S-YR. 50-YR. 100-YR.

5-MIN. 0.13 0.22 0.29 0.38 0.45 0.52

30-MIN. 0.32 0.56 0.73 0.97 1.15 1. 33

1-HR. 0.40 0.70 0.92 1.22 1.44 1.67

3-HR. 0.58 1. 01 1.33 1. 76 2. OS 2.40

6-HR. 0.73 1. 27 1.68 2.22 2.62 3.03

24-HR. 1.12 1. 93 2.55 3.37 3.99 4.61


DURATION DEP'l'H-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. lOO-YR.

5-MIN. 0.430 0.06 0.09 0.12 0.16 0.19 0.22

30-MIN. 0.468 0.15 0.26 0.34 0.45 0.54 0.62

1-HR. 0.492 0.20 0.34 0.45 0.60 0.71 0.S2

3-HR. 0.840 0.49 0.85 1.12 1.48 1. 75 2.02

6-HR. 0.929 0.68 1.18 1.56 2.06 2.43 2.81

24-HR. 0.957 1.07 1.85 <t.44 3.23 3.82 4.41

MAXIMUM ADJUSTED PRECIPITATION INTENSITIES (IN.jHR. )


5-MIN. 0.430 0.67 1.14 1.50 1.96 2.32 2.68

30-MIN. 0.468 0.30 0.52 0.68 0.91 1.08 1.24

l-HR. 0.492 0.20 0.34 0.45 0.60 0.71 0.82

3-HR. 0.840 0.16 0.28 0.37 0.49 0.58 0.67

6-HR. 0.929 0.11 0.20 0.26 0.34 0.41 0.47

24-HR. 0.957 0.09 0.15 0.20 0.27 0.32 O. J7

190


100 SQ. HI.


DURATION 2-YR. 5-YR. la-YR. 25-YR. 50-YR. lOa-YR.

5-HIN. 0.13 0.22 0.29 0.38 0.45 0.52

30-MIN. 0.32 0.56 0.73 0.97 1.15 1.33

I-HR. 0.40 0.70 0.92 1.22 1.44 1.67

3-HR. 0.58 1. 01 1.33 1. 76 2.08 2.40

6-HR. 0.73 1.27 1.68 2.22 2.62 3.03

24-HR. 1.12 1.93 2.55 3.37 3.99 4.61



5-MIN. 0.300 0.04 0.07 0.09 0.11 0.14 0.16

30-MIN. 0.355 0.11 0.20 0.26 0.34 0.41 0.47

1-HR. 0.402 0.16 0.28 0.37 0.49 0.58 0.67

3-HR. 0.747 0.43 0.75 0.99 1.31 1.55 1. 79

6-HR. 0.889 0.65 1.13 1.49 1.97 2.33 2.69

24-HR. 0.935 1.05 1.80 2.38 3.15 3.73 4.31


DURATION DEPTH-AREA 2-YR. 5-YR. 10-YR. 25-YR. 50-YR. laO-YR.

S-MIN. 0.300 0.47 0.79 1. 04 1.37 1.62 1.87

30-MIN. 0.355 0.23 0.40 0.52 0.69 0.82 0.94

1-HR. 0.402 0.16 0.28 0.37 0.49 0.58 0.67

3-HR. 0.747 0.14 0.25 0.33 0.44 0.52 0.60

6-HR. 0.889 0.11 0.19 0.25 0.33 0.39 0.45

24-HR. 0.935 0.09 0.15 0.20 0.26 0.31 0.36

191


150 SQ. MI.



5-MIN. 0.13 0.22 0.29 0.38 0.45 0.52

3D-MIN. 0.32 0.56 0.73 0.97 1.15 1.33

l-HR. 0.40 0.70 0.92 1.22 1.44 1.67

3-HR. 0.58 1. 01 1. 33 1.76 2.08 2.40

6-HR. 0.73 1. 27 1. 68 2.22 2.62 3.03

24-HR. 1.12 1.93 2.55 3.37 3.99 4.61



5-MIN. 0.243 0.03 0.05 0.07 0.09 0.11 0.13

3D-MIN. 0.310 0.10 0.17 0.23 0.30 0.36 0.41

l-HR. 0.362 0.14 0.25 0.33 0.44 0.52 0.60

3-HR. 0.688 0.40 0.69 0.92 1.21 1.43 1.65

6-HR. 0.870 0.64 1.10 1.46 1.93 2.28 2.64

24-HR. 0.923 1. 03 1. 78 2.35 3.11 3.68 4.26



5-MIN. 0.243 0.38 0.64 0.85 1.11 1.31 1.52

30-MIN. 0.310 0.20 0.35 0.45 0.60 0.71 0.82

l-HR. 0.362 0.1.4 0.25 0.33 0.44 0.52 0.60

3-HR. 0.688 0.13 0.23 0.31 0.40 0.48 0.55

6-HR. 0.870 0.11 0.18 0.24 0.32 0.38 0.44

24-HR. 0.923 0.09 0.15 0.20 0.26 0.31 0.35

192

APPENDIXC

EXCERPT, U.S.G.S. WATER RESOURCES INVESTIGATION REPORT 84-4142

193

ESTIMATION OF MAGNITUDE AND FREQUENCY OF FLOODS IN

PIMA COUNTY, ARIZONA, WITH COMPARISONS OF

ALTERNATIVE METHODS

By James H. Eychaner

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 84-4142

The opinions, findings, and conclusions expressed in this report are not necessarily those of Pima County or the City of Tucson.

Prepared in cooperation with

PIMA COUNTY AND CITY OF TUCSON

Tucson, Arizona August 1984

194

Adjustment for Uncertainty

In some circumstances, the possible losses due to underdesign of channels or hydraulic structures may be high, and the designer may want better than a 50-percent chance that an estimated peak discharge is at least as large as the true discharge for a specific recurrence interval. An adjusted estimate that makes use of the standard error can be computed for any desired confidence level:

where

z(p)SI. Q* = Q (10 ), (3)

Q* is the adjusted estimate of peak discharge at confidence level p,

Q is an unadjusted estimate,

5L

is the standard error, in log units, and

z(p) is the standard normal deviate for cumulative probability p.

Equation 3 is based on the approximately log-normal error distribution associated with the regression analyses. Values of z( p) can be taken from the table below or from tables of the cumUlative normal distribution given in most statistics textbooks. The uncertainty-adjustment factor

Z(P)SL 10 is shown in figure 5 for several values of 5

L.

p, in percent 50 0.00

60 0.25

70 0.52

80 0.84

90 1.28 z(p)

For a 50-percent confidence level-an equal chance that an estimate is too high or too low-figure 5 shows that the factar is 1.0. A 25-percent increase in a peak-discharge estimate, how.ever, will improve the odds against the estimate being too low to about 2 to 1 (67 percent confidence level) for standard errors in the range of most values in tables 1,. Z, and 4. This adjustment procedure can be used with any regression equation in this report.

Example: Estimate the 100-year peak discharge in Amigo Was.h at Arivaca Road with 70-percent confidence that the true 100-year peak IS

no larger.

1. The unadjusted estimate is 2,260 ft3/s (see the previous example for ungaged rural sites).

2. The standard error is 0.205 log units (table 1).

z(P)SL From figure 5, 10 = 1.28. 3.

4. The adjusted estimate is Q* = 2,260(1.28) = 2,890 ft3/s.

195

vr--Q. --0'1 0 ~

2.0

1.8

1.6

1.4

1.28 1.2 ,

: Exampl e , 1. 0 1.o!:: __ L.. __ .!..' __ -L __ -L __ -J

50 60 70 80 90 100

CONFIDENCE LEVEL, IN PERCENT

Figure 5.--Uncertainty-adjustment factor.

196

APPENDIXD

STREAM GAUGE DATA TABULATION

197

TABLE 01

STREAMGAUGING STATIONS IN CALIFORNIA FOR MODEL CALIBRATION AND VERIFICATION

Maximum Drainage Period Discharge

USGS Area Gauge of N of Record 2 Study No. Station Name Sq. Mi. State County Type1 Record2 Years (cfs) References Comments

09428530 Arch Ck. near Earp 1.52 CA San Bernardino R 1959-1973 15 7160 3,5 a,

09428560 Colorado River Trlb. 0.42 CA Riverside 1960-1973 14 400 5, a, No. 2 near Vidal

10250600 Wildrose Ck. near 23.7 CA Inyo R 1%1-1975 15 1060 3,4 " Wildrose Station -'" 10250800 Darwin Ck. near 173 CA Inyo R 1963-1988 26 4400 3,4 a, .... Darwin

10251000 Big Dip Ck. near 0.95 CA Inyo C 1959-1963 15 199 3,5 Stovepipe Wells R 1963-1973

10251350 Horse Thiel Ck. near 3.06 CA San Bernardino R 1961-1970 10 850 3, a, Tecopa

10251400 Ibex Ck. near 0.20 CA San Bernardino 1959-1973 15 126 5, a, Tecopa

10252550 Caruthers Ck. near 1.13 CA San Bernardino R 1964-1988 25 814 3,4,5 a, Ivanpah

10253000 Gourd Ck. near 0.30 CA San Bernardino (1959-1973 (26) 125 5,6 a, Ludlow 1978-1981

1983,84 1986-1990) (6)

!Continued next Dal!:el

TABLE D1

STREAMGAUGING STATIONS IN CALIFORNIA FOR MODEL CALIBRATION AND VERIFICATION (Continued)


USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Typel Record2 Years (cfs) References Comments

---------------------------

10253350 Forty Nine Palms Ck. 8.55 CA San Bernardino 1961 18 1240 5, a, near Twenty Nine Palms 1963-1979

10253540 Com Springs Wash 24.1 CA Riverside 1964-1971 8 10,500 5, a, hi near Desert Center

10253750 Monument Wash 4.29 CA Riverside 1960-1973 14 100 3,4 a, - Desert Center '" 00

10254050 Salt Ck. near 269 CA Riverside R 1961-1988 28 9900 3,4 Mecca

10254475 Glami. Wash at 0.60 CA 6025 1960-1974 14 86 5, a, Glamis

10255700 San Felipe Ck. near 89.2 CA San Diego R 1959-1983 25 6150 3, a, Julian

10255800 Coyote Ck. near Borrego Springs

144 CA San Diego R 1951-1986 36 3890 3,

10255805 Coyote Ck. below Box 154 Canyon near Borrego Springs

CA San Diego R 1984-1988 5 67 3, h,

10255810 Borrego Palm Ck. near Borrego Springs

21.8 CA San Diego R 1951-1988 38 2640 3, a,

(Continued next page)

TABLE 01



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Type1 Record2 Years (cis) References Comments

10255850 Vallecito Ck. 39.7 CA San Diego R 1964-1983 20 1160 3, a, near Julian

10255885 San Felipe Ck, near 1693 CA 6025 1961-1988 28 100,000 4, Westmoreland

10256000 Whitewater R. at 57.4 CA Riverside R 1938-1979 31 42,000 3, Whitewater

- 10256500 Snow Ck. near 10.8 CA Riverside R 1961-1988 28 13,000 3, '" '" near Whitewater

10257600 Mission Ck. near 37.5 CA Riverside R 1968-1988 21 1750 3, a, Desert Hot Springs

10257710 Chino Canyon Ck. 3.88 CA Riverside R 1975-1984 10 247 3, near Palm Springs

10257800 Long Ck. near Desert Hot Springs

19.4 CA Riverside R 1963-1979 17 9270 3, a,

10258000 Tahquitz Ck. near 16.9 CA Riverside R 1948-1982 40 2900 3, Palm Springs 1984-1988

10258500 Palm Canyon Ck. 93.1 CA Riverside R 1930-1941 54 7000 3, near Palm Springs R 1947-1988

(Continued next val!e)

TABLE D1



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Type1 Record2 Years (Cfs) References Comments

10259000 Andreas Ck. near 8.65 CA Riverside R 1950-1988 39 1960 3, Palm Springs

10259200 Deep O. near 30.6 CA Riverside R 1963-1988 26 7100 3, Palm Desert

10259500 Thermal Canyon trib. 0.18 CA Riverside 1960-1973 14 128 5, a, near Mecca

10259600 Cottonwood Wash near 0.71 CA Riverside R 1960-1973 14 34 3, a, '" Cottonwood Springs 0 0

10260200 Pipes Ck. near 15.1 CA San Bernardino R 1959·1971 21 350 3, a, Yucca Valley C 1971-1979

10260400 Cushenbury Ck. 6.36 CA San Bernardino R 1958-1971 20 530 3, a, near Lucerne C 1971-1976

C 1979

10261800 Beacon Ck. at 0.72 CA San Bernardino 0959-1969 (26) 360 5, 6, Helendale 1978,1980-85

1987-1990) (6)

10260500 Deep O. near 134 CA San Bernardino R 1906,07,09,10, 70 46,600 3, Hesperia 1911,14,15,16,

1918,20,21 1930-1988

(Continued next vaee)

TABLE D1




10260620 Houston Ck. above 0.35 CA San Bernardino R 1980-1988 9 295 3, h, Lake Gregory at Crestline

10261000 W. Fk. Mojave River 70.3 CA San Bernardino R 1907,09,10,11 63 26,100 3, near Hesperia 1914-1916

1930-1971 1975-1988

10262600 Boom Ck. near 0.24 CA San Bernardino (1959-1973 (27) 125 3,5,6, Barstow 1978-1981

N 19R3-1990)(6) 0 -10263100 Zzyzx Ck. near 0.23 CA San Bernardino 1959-1969 11 46 5, a,

Baker

10263500 Big Rock Creek near 22.9 CA Los Angeles R 1923-1988 66 8300 3, Valyermo

10264560 Spencer Canyon Ck. 3.60 CA Los Angeles 1959-1973 21 430 5, near Fairmont 1978-1981

1983,1986

10264600 Oak Ck. near Mojave 15.8 CA Kern R 1958-1986 29 1740 3, a,

10264605 Joshua Ck. near 3.83 CA Kern 1959·1973 15 2540 5, Mojave

(Continued next pa£e)

TABLE 01



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Type1 Record2 Years (ds) References Comments

10264750 Pine Ck. near Mojave 33.5 CA Kern R 1959-1973 20 30,000 3, a, 1975-1979

10264878 Nine Mile Ck. near 10.4 CA Inyo 1962-1976 15 437 3,4, near Brown

10264900 Salt Wells Ck. 61.6 CA San Bernardino 1959-1973 15 612 4, near Westend

'" 0

'" 10285780 Owens Lake \rib. 7.18 CA Inyo 1965-1973 9 68 5, a, hr near Keeler

10287240 Dry Ck. near June lake 2.33 CA 6051 1964-1%9 6 12 5, h,

11136450 Dry Canyon trib. near Stauffer

0.15 CA 6083 1960-1973 14 14 5.

11136500 Cuyama River near 89.9 CA 6111 1946, 12 7210 ~ ~,

Ventucopa 1948-1958

11194200 Wagon Wheel Ck. 1.38 CA Kern 1959-1973 15 338 5, near Reward

(Continued next page)

'" 8

USCS No.

11195000

Footnotes:

TABLE D1

STRF.AMGAUGING STATIONS IN CALIFORNIA FOR MODEL CALIBRATION AND VERIFICATION (Continued)


Area Cauge of N of Record2 Study Station Name Sq. Mi. State County Type! Record2 Years (cfs) References

Oil Creek near Taft 0.35 CA Kern 1959-1%9 11 11 5,

I. Gauge Type, R = stage recorder; C = crest gauge.

Conunents

2. Streamgauge data obtained from HYDRO DATA, 1991 by Earth Info. Periods of record and maximum discharges of record obtained from HYDRODATA unless otherwise indicated by alternative reference in parentheses.

3. Desert Rainfall Study, Report No.2, George V. Sabol Consulting Engineers and URS Consultants, Inc., October 26, 1990. 4. Regional discharge frequency analysis, HydrologiC Documentation Feasibility Study, Las Vegas Wash and Tributaries, Clark County, NV,

U.S. Army Corps 01 Engineers, Los Angeles, CA, April, 1988. 5. Regional Arid S-graph Development, see Section 1l.3 of the Main Report. 6. Transmittal dalecf August 2, 1991 from Dennis Marfiee, U.S. Army Corps of Engineers, Los Angeles, 10 Bob Corchero, San Bernardino County. Comments: a . Low flow events and zero flow years> 25% of record. b. Removed from consideration in 1988 COE study due to mountainous nature of watershed and significant snowpack. c. Removed from consideration in 1988 COE study due to upstream ponding or diversion. d. Removed from consideration in 1988 COE study due to gauge data yielding low standard deviation, not indicative of study area. e. No gauge record available. f: Gauge located in HYDR0-40 region B or D. g. Gauge located in Arizona Rood Frequency Region 3, 4 or 5 (ref, Methods for Estimating the Magnitude and Frequency of Floods in Arizona,

Arizona Department of Transportation, September 1978). h. Gauge has less than 10 years of data available.

TABLE D2

STREAMGAUGING STATIONS IN ARIZONA FOR MODEL CALIBRATION AND VERIFICATION


USGS Area Gauge of N of RecordZ Study No. Station Name Sq. Mi. State County Typel Record2 Years (els) References Comments

09383400 Little Colorado R. 30.9 AZ Apache R 1961-1984 23 615 3, f, g, at Greer

09390500 Show Low Ck. near 68.6 AZ Navajo Lakeside

R 1954-1989 36 5550 3, g

09398500 Clear Ck. below Willow 317 AZ Coconino R 1948·1989 42 19,700 3, Ck, near Winslow

... 09403800 Bi Iter Seeps Wash 2.85 AZ Mohave C 1963-1976 14 1950 3, 0 ... trib. near Fredonia

09423820 Sacramento Wash 787 AZ Mohave 1965-1976 12 13,000 4, nearYueca

09424700 Iron Spring Wash trib. 0.64 AZ Yavapai C 1964-1979 15 180 3, near Bagdad

09419590 Detrital Wash trib. 1.23 AZ Mohave C 1963-1980 15 470 3,4 a, near Chloride

09423760 Little Meadow Ck. 8.47 AZ Mohave C 1965-1976 12 869 3,4 a, near Oatman

09423780 Walnut Ck. near 31.3 AZ Mohave C 1965-1976 12 n5 3,4 d, l<ingman

(Continued. next oal!:e)

TABLE D2

STREAMGAUGING STATIONS IN ARIZONA FOR MODEL CALIBRATION AND VERIFICATION (Continued)



09423900 Sacramento Wash trib. 14.7 AZ Mohave C 1963-1976 14 1030 3,4 a, near Topock

09429400 Indian Wash trib. 2.56 AZ Yuma C 1963-1980 15 98 3,4 d, near Yuma

0942880 Tyson Wash trib. 13.7 AZ Yuma C 1963,1968 9 12100 3,4 h, near Quartzite 1970-1976

"" 09442680 San Francisco River 350 NM Catron R 1959-1989 31 9830 3, c '" near Reserve, NM

09470500 San Pedro River at 741 AZ Cochise 1926 52 22,000 5, f, g, PaIominas 1930-1933

1935-1941 1950-1989

09470900 San Pedro River trib. 5.25 AZ Cochise 1%3-1976 16 1460 5, f, gl near Bisbee 1978-1979

9471000 San Pedro River 1219 AZ Cochise 1916-1989 74 98,000 5, f, g, at Charleston

09471080 Walnut GuIdI (63.010) 6.42 AZ Cochise 1967-1981 15 2200 5, f, g, near Tombstone

(Continued next oaee)

TABLE D2



USGS Area Gauge of N of RecordZ Study No. Station Name Sq. Mi. State County Type1 Record2 Years (cfs) References Comments

09471087 Walnut Gulch (63.111) 0.22 AZ Cochise 1962-1981 20 541 5, f, g, near Tombstone

09471090 Walnut Gulch (63.009) 9.11 AZ Cochise near Tombstone

1967-1981 15 2640 5, f, g,

09471110 Walnut Gulch (63.015) 9.24 AZ Cochise R 1955-1981 27 5290 3, f, g, near Tombstone

09471120 Walnut Gulch (63.01 J) 3.18 AZ Cochise R 196.>-191\1 19 4190 3, S, f, g, '" 0 near Tombstone '"


09471140 Walnut Gulch (63.006) 36.70 AZ Cochise R 1962-1981 20 490 3, 5, f, g, near Tombstone

09471170 Walnut Gulch (63.004) 0.88 AZ Cochise R 1954-1977 24 1270 3, 5, f, g, near Tombstone


09471185 Walnut Gulch (63.103) 0.01 AZ Cochise R 1963-1981 19 31 3,5, f, g, near Tombstone

(Continued next lJaee)

TABLE D2



USGS Area Gauge of N of RecordZ Study No. Station Name Sq. Mi. State County Type! Record2 Years (cfs) References Comments

09471190 Walnut Gulch (6~.OO2) 4:1.9 AZ Cochise R 1954-1981 28 19,200 3, f, g, near Tombstone

09471195 Walnut Gulch (63.007) 5.22 AZ Cochise R 1966-1981 16 2590 3,5, f, g, near Tombstone

09471200 Walnut Gulch (63.00]) 57.7 AZ Cochise R 1957-1981 25 11,500 3,5, f, g, near Tombstone

N 09471550 San Pedro River 1740 AZ Cochise 1967-1986 20 24,200 5, f, g, 0 near Tombstone -.\

09471700 Fenner Wash near 2.71 AZ Cochise 1962-1976 16 950 5, f, gf Benson 1978

09472000 San Pedro River 2939 AZ Cochise 1926, 59 90,000 5, f, g, near Redington 1931-1941

1943-1989

09472100 Peck Canyon trib. 8.02 AZ Pima 1968-1981 14 4340 5, f, g, neare Redington

D9472400 Mammoth Wash 2.40 AZ Pinal 1956, 15 3200 5, f, g, near Mammoth 1963-1976

09473000 Aravaipa Ck. 541 AZ Pinal 1919-1921 39 70,800 5, f, g, near Mammoth 1931-1941

(Continued nexLoa£ci

TABLE D2



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. Sta te County Type! Record2 Years (cfs) References Comments

09473200 Green Lantern Wash 3.63 AZ Pinal 1964-1976 14 3700 5, f, g, near Winkleman 1981

1965-1989

09473500 San Pedro River at 4471 AZ Pinal 1919,26,30, 27 135,000 5, f, g, Winkleman 1935,40

1963-1984

09473600 Tam O'Shanter Wash 4.37 AZ Pinal 1963-1976 15 1570 5, f, g,

~ near Hayden 1981 00

09478200 Durham Wash near 15.6 AZ Pinal 1954-1957 19 3500 5, f, g, Florence 1963-1976

1980

09478500 Queen Ck. at Whitlow 144 AZ Pinal 1917-1920 17 42,900 5, Damsite near Superior 1939, 1948-1959

09478600 Queen Ck. trib. No.3 0.37 AZ Pinal C 1966-1979 14 280 3, 5, at Whitlow Dam

09479200 Queen Ck. trib. at 0.51 AZ Pinal R 1961-1973 19 262 3,5, Apache Junction C 1973-1979

09480000 Santa Cruz River near 82.2 AZ Santa Cruz R 1949-1989 41 12,000 3, 5, f, g, Lochiel

(Continued next paee)

TABLE D2



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Type! Record2 Years (cis) References Comments

09480500 Santa Cruz River 533 AZ Santa Cruz 1930-1989 60 31,000 5, f, g, near Nogales

09481S00 Sonoita Ck. near 209 AZ Santa Cruz 1930-1972 45 16,000 5, f, g, Patagonia 1978,84

09481700 Calabasas Canyon 10.3 AZ Santa Cruz 1963-1965 14 1200 5, f, g, near Nogales 1967-1976

1978

'" 0

'" 09481750 Sopori Wash at 176 AZ Santa Cruz 1948, 20 26,000 5, f, gl Amado 1954-1958

1964-1976 1978

09481800 Demetrie Wash trib. 0.15 AZ Pima 1963·1976 14 110 5, f, g, near Continental

09482000 Santa Cruz River 1662 AZ Pima 1940·1947 46 26,500 5, f, g, at Continental 1952·1989

09482200 Flato Wash near 665 AZ Pima 1955,1961 19 4500 5, f, g, Sahuarita 1965·1980

1984

09482330 Pumping Wash near 0.81 AZ Pima C 1966·1981 16 337 3, 5, f, g, Vail

(Continued next val!:e)

TABLE D2



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Typel Record2 Years (ds) References Cnmrnents

09482350 S. Fork Airport Wash 9.78 AZ Pima C 1966-1980 15 1890 3,5, f. g, near Tucson (4.38)(5)

09482370 N. Fork Aiport Wash 5.28 AZ Pima 1961, 17 1350 5, f, g, near Tucson 1965-1980

09482400 Airport Wash at 23.0 AZ Pima R 1966-1981 18 2900 3,5, I, g, TU<IDn 1984-1988

N - 09482410 Rodeo Wash at Tucson 7.24 AZ Pima C 1970-1981 12 898 3,5, f, g, 0

09482420 Julian Wash at Tucson 26.5 AZ Pima C 1970-1981 12 1270 3,5, t, g,

09482450 W. Br. Santa Cruz 23.6 AZ Pima C 1966-1981 16 910 3,5, f, g, River at Tucson

09482480 Big Wash at Tucson 2.94 AZ Pima C 1965-1981 17 3000 3,5, a, f, g,

09482500 Santa Cruz River at 2222 AZ Pima 1915-1981 73 52,700 5, f, g, Tuaon 1984-1989

09483000 Tucson Arroyo at 8.2 AZ Pima R 1940, 40 5000 3, t, g, Vine Ave., Tucson 1943-1981

09483025 Silvercroft Wash 2.74 AZ Pima 1965, 14 1500 5, f, g, at Tucson 1969-1981

(Continued lIeM. 11a2:e)

TABLE D2



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Type1 Record2 Years (ds) References Comments

09483030 Anklam Wash at 2.11 AZ Pima C 1%5-1981 17 2420 3~ 5~ t, g, Tucson

09483040 W. Speedway Wash 0.46 AZ Pima C 1%5-1981 17 238 3, 5, f, g, near Tucson

09483100 Tanque Verde Ck. 43.0 AZ Pima R 1960-1974 26 8600 3, 5, f, g, near Tucson C 1975-1985

09483200 Aqua Caliente Wash 2.04 AZ Pima C 1965-1980 16 430 3, 5, f, g,

'" trib. near Tucson --09484000 Sabino CIe.. near 35.50 AZ Pima R 1932-1989 58 7730 3, 5, E, g,

Tucson

09484200 Bear Ck. near 16.3 AZ Pima 1960-1974 16 1400 5, f~ g, Tucson 1979

O9484S00 Tanque Verde Cr. at 219 AZ Pima R 1940-1945 24 12,700 3, 5, f, g, Tucson C 1966-1981

C 1988,1989

09484510 Ventana Canyon Wash 6.46 AZ Pima e 1965-1981 17 260 3, f, g, near

09484560 aenega Ck. near 289 AZ Pima R 1958, 15 20,000 3, 5, f, g, Pantano 1965-1981

(Continued __ next t>ae!U

TABLE D2



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Typel Record2 Years (efs) References Comments

09484570 Mescal Arroyo near 38.4 AZ Pima C 1958, 19 27,000 3,5, f, g, Pantano 1965--1981

09484580 Barrel Canyon near 14.1 AZ Pima C 1962-1976 15 1900 3,5, f, S' Sonoita

09484590 Davidson Canyon 50.5 AZ Pima R 1968-1975 14 6860 3,5, f, g, Wash near Vail C 1976-1981 ..., -'" 09484600 Pantano Wash near 457 AZ Pima R 1958-1974 32 38,000 3, 5, f, g, Vai I C 1975-1989

09485000 Rincon Ck. near 44.8 AZ Pima 1953-1989 37 9660 5, f, g, Tucson

09485500 Pantano Wash at 602 AZ Pima 1940,1958 18 20,000 5, f, g, Tu=n 1965-1976

1979-1981 1984

09485950 Geronimo Wash 2.15 AZ Pima 1964-1981 18 705 5, f, g, near TUCliOn

09486000 Rillito Creek near 918 AZ Pima 1915-1981 68 29,700 5, f, g, 1\1cson 1984

<Continued next paee)

TABLE 02



USGS Area Gauge of N of Record2 Study Nu. Sta tion Name Sq. Mi. Slale County Typel Rerord2 Years (cis) References Comments

09486300 Canada del Oro near 250 AZ Pima 1959,61,64 20 17,000 5, f, gr Tucson 1966-1981

1984

09486500 Sanla Cruz River 3503 AZ Pima 1940-1947 44 65,000 5, f, g, at Cortaro 1950-1985

09486800 Altar Wash near 463 AZ Pima 1966-1980 15 22.000 5, f,g. Three Points

...., 09487000 Brawley Wash near 776 AZ Pima 1940,1962, 19 19,100 5, f, g. -<..>

Three Points 1966-1981 1984

09487100 Little Brawley Wash 11.9 AZ Pima 1962, 15 13,800 5, f, g, near Three Points 1968-1981

09487140 San Joaquin Wash 0.45 AZ Pima 1969-1981 13 520 5, f, g, near Tucson

09487400 Quijoto. Wash trib. 2.44 AZ Pima C 1963-1975 13 715 3r 5,

09488500 Santa Rosa Wash near 1782 AZ Pinal 1955-1980 27 53,100 5, Vaiva Vo 1984

09488600 Silver Reef Wash near 12.8 AZ Pinal 1950, 14 1400 5, Casa Grande 1963-1975

(Continued next pa!!e)

TABLE D2



USGS Area Gauge of N ofRecord2 Sludy No. Station Name Sq. Mi. State County Typel Reeord2 Years (ds) References Comments

09489200 Pacheta Ck. at 14,8 AZ Apache Maverick

R 1958-1980 23 323 3, f, g,

09492400 E. Fk. White near 38,8 AZ Apache R 1958-1989 32 2700 3, f, g, Ft Apache

09505300 Rattlesnake Canyon 24,6 AZ Yavapai R 1958-1980 23 4000 3,

09505350 Dry Beaver Ck. near 142 AZ Yavapai R 1961-1989 29 26,600 3, Rimrock

tv -'" 09505800 W, Clear Ck. near 241 AZ Yavapai R 1965-1989 25 22,400 3, Campe Verde

09508300 Wet Bottom Ck, 36.4 AZ Gila R 1968-1989 22 6830 3, g. near Childs

09510100 E. Fk, Sycamore Ck. 4.49 AZ Maricopa R 1961-1986 26 1940 3, near Sunflower

09510200 Sycamore Ck. near 164 AZ Maricopa R 1960-1989 30 24,200 3, Ft McDowell

09512200 Salt River trib. in 1.75 AZ Maricopa R 1961-1986 28 670 3, a, S. MIn, Park at Phoenix 1988-1989

09512300 Cave Creek near 121 AZ Maricopa R 1958-1979 30 12,400 3, Cave Creek C 1981-1989

(Conti!ll1ed next Da!!e)

TABLE D2



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Type1 Record2 Years (cfs) References Comments

09512400 Cave Ck. at Phoenix 252 AZ Maricopa R 1943, 33 4080 3, 1958-1989

09512500 Agua Fria R. near 588 AZ Yavapai R 1940-1989 50 33,100 3, Mayer

09513700 Agua Fria R. trib. at Youngtown

0.13 AZ Maricopa R 1961-1%8 8 73 3, h,

'" 09513800 New River at New 83.3 AZ Maricopa R 1961-1982 22 19,500 3, u: River

09513835 New River at Bell 187 AZ Maricopa C 1963 21 14,600 3, Road near Peoria C 1965-1%7

R 1967-1984

09513780 New River near 67.3 AZ Maricopa C 1962-1964 28 18,600 3, Rock Springs R 1965-1989

09513860 Skunk Creek near 64.6 AZ Maricopa C 1960-1967 30 11,500 3, Phoenix R 1968-1989

09513910 New River near 323 AZ Maricopa 1943,55 22 3620 3, Glendale 1960-1979

09514200 Waterman Wash 403 AZ Maricopa 1964-1978 25 6300 5, near Buckeye 1980-1989

(Continued next Dal!.e)

TABLE D2



USGS Area Gauge of N of Record 2 Study No. Station Name Sq. Mi. State County Typel Rerord2 Years (ds) References Comments

09515500 Hassayampa R. at Box 417 AZ Yavapai R 1925,27, 41 58,000 3, Damsite near Wickenburg 1937-38

1946-1982

09517200 Centnennial Wash trib. 2.79 AZ Yuma C 1963-1979 17 720 3, near Wenden

09519600 Rainbow Wash trib. 3.45 AZ Maricopa C 1963-1979 17 1430 3, 5, near Buckeye (2.43)(5)

.., 09519750 Bender Wash near 68.8 AZ Maricopa C 1963-1979 17 2670 3, 5, ~ Gila Bend '"

09519760 Sauceda Wash near 126 AZ Maricopa C 1963-1979 17 3150 3, 5, Gila Bend

09519780 Windmill Wash near 12.9 AZ Maricopa C 1964-1978 15 4430 3, 5, a, Gila Bend

09520100 Mili tary Wash near 8.7 AZ Maricopa C 1963-1979 17 1200 3,5, Sentinel

09520110 Hot Shot Arroyo near 0.44 AZ Pima e 1966-1981 16 240 3, 5, Ajo

09520130 Darby Arroyo near 4.72 AZ Pima C 1966-1981 16 1670 3, 5, Ajo

(Continued next pae:e)

TABLE 02



USGS Area Gauge of N of Record2 Study No. Slation Name Sq. Mi. State County Type! Record2 Years (ds) References Comments

09520160 Gibson Arroyo a I 2.18 AZ Pima C 1967-1981 15 1800 3, 5, Ajo

09520170 Rio Comez near Aio 243 AZ Pima 1967-1980 14 8030 5,

09520200 Black Gap Wash near 12.1 AZ Maricopa C 1962-1979 18 940 3, 5, tv Ajo --.>

09520230 Craler Range near Aio 1.49 AZ Maricopa 1963-1979 17 590 5,

09520300 Alamo Wash Trib. 0.90 AZ Maricopa 1963-1980 25 510 5, near Aio 1982-1989

09520350 Mohawk Pass Wash al 0.09 AZ Yuma 1963-1976 15 117 5, Mohawk 1980

09535100 San Simon Wash near 569 AZ Pima 1972-1989 18 12,500 5, Pisinimo

09535200 Sells Wash Irib. al 12.2 AZ Pima 1962-1976 15 2800 5, f, g, Sells

(Continued nexl pae:e)

..., -00

USGS No.

09536100

Footnotes:

TABLE D2



Area Gauge of N of Record2 Study Station Name Sq. Mi. State County Type! Record2 Years (cfs) References

Pitchford Canyon trib. 0.81 AZ Graham C 1963·1976 14 375 3,5, near Ft. Grant

Comments

f, g,

1. Gauge Type: R = stage recorder; C = crest gauge. 2. Streamgauge data obtained from HYDRODAT A, 1991 by Earth Info. Periods of record and maximum discharges of record obtained from

HYDRODATA unless otherwise indicated by alternative reference in parentheses. 3. 4.

Desert Rainfall Study, Report No.2, George V. Sabol Consulting Engineers and URS Consultants, Inc., October 26, 1990. Regional discharge frequency analysis, Hydrologic Documentation Feasibility Study, Las Vegas Wash and Tributaries, Clark County, NV, U.S. Army Corps of Engineers, Los Angeles, CA, April, 1988.

5. Regional Arid S·graph Development, see Section 11.3 of the Main Report. 6. Transmittal dated August 2, 199! from Dennis Marfice, U.s. Army Corps of Engineers, Los Angeles, to Bob Corchero, San Bernardino County. Comments: a. Low flow events and zero flow years> 25% of record. b. Removed from consideration in 1988 COE stUdy due to mountainous nature of watershed and significant snowpack. c. Removed from consideration in 1988 COE.study due to upstream ponding or diversion. d. Removed from consideration in 1988 COE study due to gauge data yielding low standard deviation, not indicative of study area. e. No gauge record available. f. Gauge located in HYDR0-40 region B or D. g. Gauge located in Arizona Flood Frequency Region 3,4 or 5 <ref: Methods for Estimating the Magnitude and Fr .. quency of Floods in Arizona,


TABLE D3

STREAMGAUGING STATIONS IN NEVADA FOR MODEL CALIBRATION AND VERIFICATION


USGS Area Gauge 01 N 01 Record2 Study No. Sta tion Name Sq. Mi. Stale County Type! Record2 Years (ds) References Comments

09417100 Dry Lake trib. 10 NV Clark 1964·1975 12 180 4, a, near Nellis AFB

09419610 Lee Canyon near 9.2 NV Clark 1961·1988 28 880 4, a, b, Charleston Park

'" - 09419620 Mormon Wells Wash 115 NV Clark C 1962·1988 27 480 3,4 '" near Las Vegas

09419623 Deer Ck. near 1.27 NV Clark 1967·1981 15 50 4, b, Charleston Park

09419630 Telephone Canyon 7.2 NV Clark 1962·1988 27 2500 4, a, b, near Charleston Park

09419640 Kyle Canyon near 35.9 NV Clark 1961·1988 28 1660 4, a, b, Charleston Park

09419647 Las Vegas Wash trib. 62 NV Clark C 1963·1988 26 5130 3,4, a, near N. Las Vegas

09419650 Las Vegas Wash at 693 NV Clark 1963·1978 23 12,010 4, N. Las Vegas 1982·1988

(Continued next pa"e)

TABLE D3

STREAMGAUGING STATIONS IN NEVADA FOR MODEL CALIBRATION AND VERIFICATION (Continued)


USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Typel Record2 Years (efs) References Comments

09419660 Las Vegas Wash 18.1 NV Clark 1961-1984 27 618 4, a, trib. near Nellis 1986-1988

09419663 Las Vegas Wash 1.2 NV Clark 1963-1988 25 296 4, a, trib. S. Nellis AFB

09419670 Redrock Wash near 8.09 NV Clark 1962-1988 27 7470 4, a, Blue Diamond .... ....

0 09419675 Flamingo Wash at 86 NV Clark C 1966-1981 20 3910 3,4, Las Vegas 1985,

1986-1988

09419677 Flamingo Wash at 106 NV Clark C 1969-1987 19 4700 3, 4, Maryland Pkwy. at Las Vegas

09419678 Flamingo Wash near 117 NV Clark C 1978, 18 4000 3,4, mouth at Las Vegas 1980-1987

09419680 Cottonwood Valley 18.3 NY Clark 1961-1988 28 1100 4, a, near Blue Diamond

09419690 Duck C. at Whitney 239 NY Clark 1961-1988 28 3570 4, a,

09419697 Las Vegas Wash trib. 1.17 NY Clark C 1967-1981 20 1950 3, 4, a, near Henderson 1984-1988

(Continued next paee)

TABLE D3




09419700 Las Vegas Wash near 1518+ NV Clark 1957-1983 31 6510 4, c, Henderson 1985-1988

09419800 Las Vegas Wash near 1586+ NV Clark 1964-1965 17 7760 4, c, BouldeT City 1970-1984 ..., ..., - 09423300 Piute Wash .trib. 3.4 NV Clark C 1967-1982 17 400 3,4, a, a t Searchlight 1984

10248490 Indian Springs Valley 29 NV Clark C 1964-1982 23 497 3, 4, a, lrib. near C 1984-1987 Indian Springs

10251220 Amargosa River 3090 NV Nye 1964-1981 19 16,000 4, a, near Beatty 1983

10251270 Amargosa River trib. ltD NV Nye C 1964-1981, 19 16,000 3, 4, a, near Mercury 1983

10251271 Amargosa River Irib. 2.21 NV Nye C 1967-1981 19 350 3,4, a, No.1 near Johnnie C 1984-1987

10251272 Amargosa River Irib. 2.49 NV Nye C 1968-1981 18 125 3, a, No.2 near Johnnie C 1984-1987

(Continued next Daee)

'" I::l

TABLE 03



USGS Area Gauge of N of Record2 Study No. Station Name Sq. Mi. State County Typel Record2 Years (crs) References Comments

10251400 0.20 5, e,

10251890 Peak Spg. Canyon near Charleston Park

3.09 NV Clark 1978-1985 9 228 4, b, h,

10251980 Lovell Wash near 52.8 NV Clark 1965-1981 18 4150 4, a, near Hlue Diamond

Footnotes: 1. Gauge Type: R = stage recorder; C = crest gauge. 2. Streamgauge data obtained from HYDRODATA, 1991 by Earth Info. Periods of record and maximum discharges of record obtained from

HYDRODATA unless otherwise indicated by alternative reference in parentheses. 3. Desert Rainfall Study, Report No.2, George V. Sabol Consulting Engineers and URS Consultants, Inc., October 26, 1990. 4. Regional discharge frequency analysis, Hydrologic Documentation Feasibility Study, Las Vegas Wash and Tributaries, Clark County, NV,

U.S. Army Corps of Engineers, Los Angeles, CA, April, 1988. 5. Regional Arid S-graph Development, see Section 11.3 of the Main Report. 6. Transmittal dated August 2, 1991 from Dennis Marfice, U.s. Army Corps of Engineers, Los Angeles, to Bob Corchero, San Bernardino County. Comments: a. Low flow events and zero flow years> 25% of record. b. Removed from consideration in 1988 CaE study due to mountainous nature of watershed and significant snowpack. c. Removed from consideration in 1988 CaE study due to upstream ponding or diversion. d. Removed from consideration in 1988 CaE study due to gauge data yielding low standard deviation, not indicative of study area. e. No gauge record available. f. Gauge located in HYDR040 region B or D. g. Gauge located in Arizona Flood Frequency Region 3, 4 or 5 (ref: Methods for Estimating the Magnitude and Frequency of Floods in Arizona,


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