GALVESTON COUNTY, TEXAS,

GALVESTON COUNTY, TEXAS, AND INCORPORATED AREAS

VOLUME 1 OF 4

Community Name Community Number

BAYOU VISTA, VILLAGE OF 481589 CLEAR LAKE SHORES, CITY OF 485461 DICKINSON, CITY OF 481569 FRIENDSWOOD, CITY OF 485468 GALVESTON, CITY OF 485469 HITCHCOCK, CITY OF 485479 JAMAICA BEACH, VILLAGE OF 481271 KEMAH, CITY OF 485481 LA MARQUE, CITY OF 485486 LEAGUE CITY, CITY OF 485488 SANTA FE, CITY OF 481562 SEABROOK, CITY OF 485507 TEXAS CITY, CITY OF 485514 TIKI ISLAND, VILLAGE OF 481585 GALVESTON COUNTY (UNINCORPORATED AREAS)

485470

REVISED: PRELIMINARY

Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER

xxxxxx

GALVESTON COUNTY

mlfuller

09 27 2012

i

NOTICE TO

FLOOD INSURANCE STUDY USERS

Communities participating in the National Flood Insurance Program have established repositories of flood

hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS)

may not contain all data available within the repository. It is advisable to contact the community

repository for any additional data.

The Federal Emergency Management Agency (FEMA) may revise and republish part or all of this FIS

report at any time. In addition, part of this FIS may be revised by the Letter of Map Revision process,

which does not involve republication or redistribution of the FIS. It is, therefore, the responsibility of the

user to consult with community officials and to check the Community Map Repository to obtain the most

current FIS components.

Selected Flood Insurance Rate Map panels for this community contain information that was previously

shown separately on the corresponding Flood Boundary and Floodway Map panels (e.g., floodways, cross

sections). In addition, former flood hazard zone designations have been changed as follows:

Old Zone(s)

New Zone

A1 through A30

AE

V1 through V30

VE

B

X

C

X

Part or all of the Flood Insurance Study may be revised and republished at any time. In addition, part of

this Flood Insurance Study may be revised by the Letter of Map Revision process, which does not involve

republication or redistribution of the Flood Insurance Study. It is, therefore, the responsibility of the user

to consult with community officials and to check the community repository to obtain the most current

Flood Insurance Study components.

Initial Countywide FIS Effective Date:

ii

TABLE OF CONTENTS

Volume 1 of 4

Page

1.0 INTRODUCTION.......................................................................................................................... 1

1.1 Purpose of Study ................................................................................................................. 1

1.2 Authority and Acknowledgements ..................................................................................... 1

1.3 Coordination ....................................................................................................................... 4

2.0 AREA STUDIED ........................................................................................................................... 5

2.1 Scope of Study .................................................................................................................... 5

2.2 Community Description ...................................................................................................... 6

2.3 Principal Flood Problems .................................................................................................... 7

2.4 Flood Protection Measures ............................................................................................... 11

3.0 ENGINEERING METHODS ..................................................................................................... 12

3.1 Hydrologic Analyses ......................................................................................................... 12

3.2 Hydraulic Analyses ........................................................................................................... 18

3.3 Coastal Analysis ............................................................................................................... 23

3.3.1 Storm Surge Analysis and Modeling ................................................................................ 24

3.3.2 Statistical Analysis ............................................................................................................ 25

3.3.3 Stillwater Elevations ......................................................................................................... 26

3.3.4 Wave Height Analysis ............................................................................................ . ........ 26

3.4 Vertical Datum .................................................................................................................. 41

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS ............................................................... 41

4.1 Floodplain Boundaries ...................................................................................................... 42

4.2 Floodways ......................................................................................................................... 42

5.0 INSURANCE APPLICATIONS ................................................................................................. 61

6.0 FLOOD INSURANCE RATE MAP .......................................................................................... 61

7.0 OTHER STUDIES ....................................................................................................................... 66

8.0 LOCATION OF DATA ............................................................................................................... 66

9.0 BIBLIOGRAPHY AND REFERENCES................................................................................... 66

iii

TABLE OF CONTENTS (Continued)

Page

FIGURES

Figure 1 – Transect Schematic .......................................................................................................................... 26

Figure 2 – Transect Location Map .................................................................................................................... 40

Figure 3 – Floodway Schematic ........................................................................................................................ 43

TABLES

Table 1 – Initial and Final CCO Meetings ......................................................................................................... 4

Table 2 – Scope of Study .................................................................................................................................... 5

Table 3 – Summary of Discharges .................................................................................................................... 15

Table 4 – Coastal Transect Data ........................................................................................................................ 29

Table 5 – Floodway Data Table ........................................................................................................................ 44

Table 6 – Community Map History................................................................................................................... 63

EXHIBITS

Exhibit 1 – Flood Profiles

Benson Bayou Panel 01P

Borden's Gully Panels 02P-03P

Cedar Gully Panel 04P

Chigger Creek Panels 05P-06P

Clear Creek Panels 07P-11P

Cowart Creek Panel 12P

Dickinson Bayou Panels 13P-17P

Gum Bayou Panel 18P

Highland Bayou Panel 19P

Lower Highland Bayou Panels 20P-21P

Magnolia Bayou Panels 22P-23P

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EXHIBITS Volume 2 of 4

Magnolia Creek Panel 24P

Marchand Bayou Panels 25P-26P

Marys Creek Panel 27P

Tributary to Gum Bayou Panel 28P

Unnamed Tributary 1 (to Lower Highland

Bayou)

Panel 29P


Bayou)

Panel 30P


Bayou)

Panel 31P

Unnamed Tributary 3 Diversion Channel

to Lower Highland Bayou

Panel 32P

Unnamed Tributary of Clear Creek Panel 33P

Unnamed Tributary to Dickinson Bayou

(East Branch)

Panel 34P

Unnamed Tributary to Dickinson Bayou

(West Branch)

Panel 35P

Upper Highland Bayou and Diversion

Channel

Panel 36P

Exhibit 2 – 0.2-Percent-Annual-Chance Wave Envelopes

Transect 1 Panel 01P






Transect 7 Panels 07P-08P

















v

EXHIBITS Volume 2 of 4 (Continued)









vi


































vii






































Exhibit 3 – Flood Insurance Rate Map Index

Flood Insurance Rate Maps

1

FLOOD INSURANCE STUDY

GALVESTON COUNTY, TEXAS AND INCORPORATED AREAS

1.0 INTRODUCTION

1.1 Purpose of Study

This Flood Insurance Study (FIS) revises and updates information on the existence and

severity of flood hazards in the geographic area of Galveston County, including Cities of

Clear Lake Shores, Dickinson, Friendswood, Galveston, Hitchcock, Kemah, La Marque,

League City, Santa Fe, Seabrook, and Texas City; Villages of Bayou Vista, Jamaica

Beach, and Tiki Island, and the unincorporated areas of Galveston County (referred to

collectively herein as Galveston County) and aids in the administration of National Flood

Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This study has

developed flood risk data for various area of the community that will be used to establish

actuarial flood insurance rates and assist the community in their efforts to promote sound

floodplain management. Minimum floodplain management requirements for participation

in the National Flood Program are set forth in the Code of Federal Regulations at 44

CFR, 60.3.

The City of Seabrook is located in Harris, Chambers and Galveston Counties, and the

Cities of Friendswood and League City are located in Harris and Galveston Counties.

Only the portions that are within Galveston County are shown in this FIS report.

In some States or communities, floodplain management criteria or regulations may exist

that are more restrictive or comprehensive than the minimum Federal requirements. In

such cases, the more restrictive criteria take precedence and the State (or other

jurisdictional agency) will be able to explain them.

1.2 Authority and Acknowledgements

The sources of authority for this Flood Insurance Study are the National Flood Insurance

Act of 1968 and the Flood Disaster Protection Act of 1973.

This FIS was prepared to include the unincorporated areas of, and incorporated

communities within Galveston County into a countywide FIS. Information on the

authority and acknowledgments for all of the incorporated communities within, and the

unincorporated areas of, Galveston County, as compiled from their previously printed

FIS reports, is shown below.

Galveston County

(Unincorporated Areas): The hydrologic and hydraulic analyses for the FIS report

dated November 2, 1982, and the Flood Insurance Rate

Map dated May 2, 1983 were prepared by Tetra Tech,

Inc., for the Federal Emergency Management Agency

(FEMA) under Contract No. H-4788. The work for the

1983 revision was completed in December 1979. For the

November 16, 1990 revision, the hydrologic and

hydraulic analyses for Magnolia Bayou were prepared

by Van Sickle, Michelson & Klein, Inc. That work was

2

completed in June 1988. For the August 18, 1992

revision, Dewberry & Davis prepared revised and

hydraulic and erosion analyses for the Gulf of Mexico.

That work was prepared for FEMA under Contract No.

EMW-89-C-2906 and was completed in January 1991.

For the July 5, 1993 revision, Dewberry & Davis

prepared the revised hydraulic and erosion analyses for

the Gulf of Mexico based on improved topographic

information. That work was prepared for FEMA, under

Contract No. EMW-89-C-2906 and was completed

August 1992.

Clear Lake Shores, City of The hydrologic and hydraulic analyses for the FIS report

dated October 4, 1982 were performed by Tetra Tech,

Inc. for the FEMA, under Contract No. H-4788. This

study was completed in April 1981.

Dickinson, City of The hydrologic and hydraulic analyses for the FIS report

dated March 4, 1991 represented a revision of the

original analyses prepared by Tetra Tech Inc., for the

FEMA, under Contract No. H-4788. The work for the

original study was completed in December 1979. The

hydrologic and hydraulic analyses for Borden’s Gully

and Magnolia Bayou in the March 4, 1991 revision were

prepared by Van Sickle, Mickelson & Klein, Inc. This

work was completed in June 1988.

Friendswood, City of The hydrologic and hydraulic analyses for the FIS report

dated September 22, 1999 were based on work prepared

by Tetra Tech, Inc., for the FEMA, under Contract No.

H-4788. This work was completed in July 1981. This

work was updated by the Galveston District of the U.S.

Army Corps of Engineers (USACE) for FEMA, under

Inter-Agency Agreement No. H-10-77, Project No. 1 and

amendments thereto; the Harris County Flood Control

District (HCFCD); and Bernard Johnson, Inc. (BJI).

These revisions took into account rapid development and

improvements that were made to the watersheds since

the completion of the original study. The tidal flooding

analysis was prepared by Tetra Tech, Inc., under

Contract No. H-4788 and amendments thereto. The

USACE and Tetra Tech, Inc. completed their work in

June 1982; the HCFCD completed their work in

December 1984; and BJI completed their work in April

1986.

Galveston, City of The hydrology and hydraulic analyses for the FIS report

dated February 15, 1983, were performed by Tetra Tech,

Inc., for the FEMA under Contract No. H-4788. The

work for the 1983 revision was completed in December

1979. For the December 6, 2002 restudy, Taylor

3

Engineering, Inc. prepared revised coastal hydrologic

and hydraulic analyses for FEMA under Contract No.

EMT-1999-RP-0004. In support of the study

contractor’s technical analyses, Continental Aerial

Surveyors, Inc, was contracted to perform surveying of

coastal profiles. The work for this restudy was

completed in July 2001.

Hitchcock, City of The hydrologic and hydraulic analyses for the FIS report


Inc., for the FEMA, under Contract No. H-4788. This

study was completed in December 1979.

Jamaica Beach, Village of The hydrology and hydraulic analyses for the FIS report

dated October 4, 1982, were performed by Tetra Tech,

Inc., for the FEMA under Contract No. H-4788. This

work was completed in December 1979. For the

December 6, 2002 revision, Taylor Engineering, Inc.

prepared revised coastal hydrologic and hydraulic

analyses for FEMA under Contract No. EMT-1999-RP-

0004. In support of the study contractor's technical

analyses, Continental Aerial Surveyors, Inc., was

contracted to perform surveying of coastal profiles. The

work for this restudy was completed in July 2001.

Kemah, City of The hydrologic and hydraulic analyses for the FIS report




La Marque, City of The hydrologic and hydraulic analyses for the FIS report

dated August 16, 1982 were performed by Tetra Tech,



League City, City of The hydrologic and hydraulic analyses for the FIS report

dated September 22, 1999 represented a revision of the

original analyses prepared by Tetra Tech, Inc., for the

FEMA, under Contract Ne. 8-4788. The work for the

original study was completed in July 1981. The

hydrologic and hydraulic analyses for Borden’s Gully

and Magnolia Bayou in that revision were prepared by

Van Sickle, Michelson & Klein, Inc. The work for this

revision was completed in July 1988.

Santa Fe, City of The hydrologic and hydraulic analyses for the FIS study

dated April 18, 1983 were performed by Tetra Tech Inc.,

for the FEMA, under Contract No. H-4788. This study

was completed in December 1979.

4

Texas City, City of The hydrologic and hydraulic analyses for this study

were performed by Tetra Tech, Inc. for the FEMA,

under Contract No. H-4788. This study was completed

in December 1979.

Tiki Island, Village of The hydrologic and hydraulic analyses for the FIS study

dated November 1, 1985 were performed by Tetra Tech,

Inc., during the course of the FIS for Galveston County,

Texas. The Galveston County study was completed in

December 1979.

Taylor Engineering, as a part of FTN/Taylor Joint Venture, completed the work for this

countywide revision in April 2012 under contract EMT-2002-CO-0050 J021.

1.3 Coordination

An initial Consultation Coordination Officer’s (CCO) meeting is held typically with

representatives of the communities, FEMA, and the study contractors to explain the

nature and purpose of the FIS, and to identify the streams to be studied by detailed

methods.

The initial and final meeting dates for previous FIS reports for Galveston County and its

communities are listed in Table 1, “Initial and Final CCO Meetings”.

Table 1 – Initial and Final CCO Meetings

Community Initial Meeting Final Meeting

CLEAR LAKE SHORES, CITY OF * April 27, 1982

DICKINSON, CITY OF * March 18, 1982

FRIENDSWOOD, CITY OF May 1, 1978 April 16, 1982

GALVESTON, CITY OF July 28, 1999 December 6, 2001

HITCHCOCK, CITY OF * April 27, 1982

JAMAICA BEACH, VILLAGE OF July 28, 1999 December 6, 2001

KEMAH, CITY OF * April 27, 1982

LA MARQUE, CITY OF * March 17, 1982

LEAGUE CITY, CITY OF * June 3, 1982

SANTA FE, CITY OF * March 18, 1982

TEXAS CITY, CITY OF * June 3, 1982

TIKI ISLAND, VILLAGE OF * November 15, 1984

GALVESTON COUNTY

(UNINCORPORATED AREAS)

February 27, 1989 April 9, 1991

*Data not available

A final CCO meeting is held with representatives of the communities, FEMA, and the

study contractors to review the results of the study.

For this countywide study, an initial CCO meeting was held on April 13, 2005 and

attended by representatives of the community, the study contractor, and FEMA.

5

The results of the study were reviewed at the final CCO meeting held on XXXX XX,

XXXX and attended by representatives of the community, the study contractor, and

FEMA. All problems raised at that meeting have been addressed.

2.0 AREA STUDIED

2.1 Scope of Study

This FIS report covers the geographic area of Galveston County, Texas, including the

incorporated communities listed in Section 1.1. The areas studied by detailed methods

were selected with priority given to all known flood hazards and areas of projected

development or proposed construction through.

Limits of detailed study are indicated on the Flood Profiles (Exhibit 1) and/or on the

FIRM (Exhibit 3).

The flooding sources previously studied by detailed riverine methods are shown in Table

2.

Table 2 - Flooding Sources Studied by Detailed Methods

Benson Bayou Magnolia Bayou

Borden’s Gully Magnolia Creek

Cedar Gully Marchand Bayou

Chigger Creek Marys Creek

Clear Creek Unnamed Tributary 1 to Lower Highland Bayou

Cowart Creek Unnamed Tributary 2 to Lower Highland Bayou

Dickinson Bayou Unnamed Tributary 3 to Lower Highland Bayou

Gum Bayou Unnamed Tributary 3 Diversion Channel to LHB

Tributary to Gum Bayou Unnamed Tributary to Clear Creek

Highland Bayou Unnamed Tributary (East Branch)

Lower Highland Bayou Unnamed Tributary (West Branch)

Upper Highland Bayou & Diversion Channel

No new detailed riverine hydrologic or hydraulic modeling was performed or incorporated as

part of this study. LOMC (Letters of Map Change) were incorporated for Magnolia Creek,

Borden’s Gully, and Unnamed Tributary 3 to Lower Highland Bayou and Unnamed Tributary

3 Diversion Channel to LHB, LOMR (Letter of Map Revision) numbers 01-06-673P, 05-06-

1666P, and 06-06-BK83P, respectively. Tropical Storm Allison Recovery Project (TSARP)

completed the 2004 Harris County FIS, which included a detailed study of Clear Creek, which

was incorporated into this FIS.

The following flooding sources were mapped using digital conversion of the effective special

flood hazard areas: Magnolia Bayou, Unnamed Tributary to Dickinson Bayou (East Branch),

Unnamed Tributary to Dickinson Bayou (West Branch), and Upper Highland Bayou.

In all other cases, effective water surface elevations were redelineated on updated terrain. The

following flooding sources were studied by approximate methods: Chigger Creek Tributary 1,

Chigger Creek Tributary 2, Clear Creek Tributary 4, Clear Creek Tributary 5, Dickinson

Bayou, Dickinson Bayou Tributary 2, Magnolia Bayou, and Magnolia Bayou Tributary 1.

6

All coastal areas were studied by new detailed methods. Computations for flood levels along

the rivers resulting from either coastal surges or rainfall were independently performed.

Revised coastal surge elevations were combined statistically to obtain flood levels for each

return period.

2.2 Community Description

Galveston County occupies a land area of approximately 399 square miles in southeastern

Texas. It is bordered by the incorporated areas of Harris and the unincorporated areas of

Chambers Counties to the north, Galveston Bay to the east, the Gulf of Mexico to the

south, and the unincorporated areas of Brazoria County to the west. The City of

Galveston, the county seat, is located approximately 50 miles southeast of the City of

Houston.

The 2010 population of Galveston County was 291,309 (Reference 1). The population

has increased 16.5% since 2000. During the decade from 2000-2010, League City

surpassed the City of Galveston as the most populous municipality with 83,560 compared

to 47,743.

The economy of the county is based primarily on petrochemical manufacturing,

petroleum exploration and mining, shipbuilding, shipping, public administration,

agriculture, and tourism, with its attendant commercial and service-type employment.

The major streams within the county are Highland Bayou, Dickinson Bayou, and Clear

Creek. Highland Bayou flows generally towards the southeast through Galveston County

from the vicinity of Arcadia/Alts Loma into Jones Bay, an arm of West (Galveston) Bay.

It is approximately 14 miles long, has a watershed area of approximately 38 square miles,

and is tidal for approximately 8.5 miles in its lower reaches. Dickinson Bayou,

approximately 23 miles long, flows towards the east from the Galveston County

boundary and empties into Dickinson Bay on the west side of Galveston Bay. It drains

approximately 99 square miles of land in north-central Galveston County. Clear Creek,

45 miles long, flows through the northern portion of Galveston County eastward into

Clear Lake/Galveston Bay, and drains a total of approximately 250 square miles. Along

with their tributaries, these streams provide a fairly extensive drainage system.

Galveston County is located in the humid-subtropical climatic zone, which is

characterized by mild winters and warm summers. Rainfall is abundant and quite evenly

distributed throughout the year. The heaviest rains usually occur during the hurricane

season, which extends from approximately June through October. In the City of

Galveston, which is located in the southern portion of the county, the average annual

precipitation is approximately 43 inches, and the average annual temperature is

approximately 70 degrees Fahrenheit (Reference 2). Soils in Galveston County are clayey

and loamy, and are categorized in five soil associations that have similar characteristics:

low infiltration rates and high runoff potential. All the soils are classified in SCS Group

D for hydrologic purposes.

Coastal short grass prairie is the dominant vegetation in the county. Much of this prairie

grassland is cultivated and used for agriculture, and much of the higher coastal land in the

southern portion of the county is range-pasture land. Fluvial woodland is found along the

lower reaches of the major streams. There are extensive areas of tidal marsh along the

bays and bayous (Moses Lake, Dollar Bay, Swan Lake, Jones Bay, and West Bay).

7

Vegetated barrier flats on Galveston Island and Bolivar Peninsula support a growth of

salt-tolerant weeds and grasses.

Physiographically, Galveston County lies within the Gulf Coastal Plain and is

characterized by relatively flat terrain with level or nearly level areas in the northeastern

portions of the county. The elevation in the study area ranges from sea level along most

of the coast to approximately 50 feet. On the east, the coastal area of Galveston Bay near

Bacliff, extending north from Dickinson Bay to approximately Kemah, is characterized

by cliffed bay margins at an elevation of 10 feet or more. In the south, Galveston Island

and part of Bolivar Peninsula form a barrier to the mainland.

2.3 Principal Flood Problems

Flooding in Galveston County results primarily from overflow of the streams (caused by

rainfall runoff), ponding, and sheet flow, and from tidal surge and associated wave action

(caused by hurricanes and tropical storms). Wave action that accompanies wind-

generated tides can cause flood, erosion, and structural damage, particularly on the

offshore islands. Rainfall that usually accompanies hurricanes can aggravate the tidal

flood situation. Because of the flatness of the terrain, many inland areas experience

shallow flooding during heavy rainfalls. Additionally, land surface subsidence in

mainland Galveston County is causing many areas that were previously non-floodprone

to be subject to inundation by high tides, and further lowering land already in the

floodplain (Reference 3).

Not all storms that pass close to the county produce extremely high tides. Similarly,

storms that produce extreme conditions in one area may not necessarily produce critical

conditions in other portions of the county. Storms passing Texas in the vicinity of

Galveston County have produced severe floods as well as structural damage. Brief

descriptions of several significant tropical storms follow; these provide historical

information to which flood hazards and the projected flood depths can be compared

(References 4, 5, 6, 7, 8, 9, 10, and 11).

September 7-10, 1900

This severe hurricane, which had a radius of approximately 16 miles, crossed the Texas

coastline near San Luis Pass, approximately 20 miles south of the City of Galveston.

Storm surge generated by this hurricane was estimated to be between 14.2 feet and 14.5

feet mean sea level (msl). Maximum wind velocity was estimated to be between 110 and

120 miles per hour (mph). The beachfront at the City of Galveston was badly eroded to

300 feet inland, and the first two to five blocks of the eastern, southern, and western

sections of the city were swept by the storm surge and shorn of buildings. Water in the

Kinkhead addition just beyond the corporate limits was reported to be ten feet deep. At

Bolivar Point, wharves were gone and buildings were crushed. All of the Gulf, Colorado,

and Santa Fe Railway bridges across Galveston Bay were destroyed. On the mainland, all

houses at Virginia Point were reported washed and blown away; Dickinson was reported

to be almost completely demolished. This storm killed an estimated 6,000 of Galveston

Island's inhabitants, and destroyed 3,600 homes. Property damages were estimated to be

30 million dollars. In 1902, Galveston County began construction of a seawall to protect

the city against future tropical storms.

8

August 16-17, 1915

The hurricane, which had a radius of 32 miles, made landfall near Matagorda,

approximately 40 miles southwest of the City of Galveston. Tides at Galveston were

estimated to be 12.7 feet msl, with 16.1 feet at the causeway, and storm tides inundated

the area for more than 40 hours. It was estimated that crests of breaking waves reached

21 feet at the seawall, which protected the city. Great quantities of water were thrown

over the wall and scour of pavement and building foundations caused extensive damage.

In the area of the City of Texas City, many houses were swept away from their

foundations, docks were damaged, and brick structures caved in. The area from La

Marque to Galveston was flooded. Clear Creek was reported to be 1.5 miles wide, and the

Kemah area was seriously damaged. This storm caused 275 fatalities and a total of $56

million in damages.

September 14, 1919

This hurricane, which practically paralleled the coast, passed approximately 140 miles

south of the City of Galveston. Maximum winds of 53 mph and tides of 8.8 feet above

normal were recorded in Galveston, whose downtown area was flooded by three feet of

water. In the northern portion of Galveston Bay, water was reported to be five feet deep

in the area between Clear Lake and Seabrook.

August 30-31, 1942

Although this hurricane passed 120 miles west of Galveston, it caused wind speeds of 50

mph and tides of 5.3 feet at Galveston. The southwestern portion of Galveston Island was

inundated, and some residential and business sections of the City of Galveston were

flooded.

October 2-3, 1949

This storm originated in the Pacific Ocean near El Salvador, crossed Guatemala, moved

northward across the Gulf of Mexico, and made landfall near Freeport. Storm surge

reached 11.5 feet at Freeport and Velasco, 9 feet at Anahuac, 7 feet at Galveston, and 8.5

feet at Kemah. The Weather Bureau reported highest sustained wind at 67 mph with gusts

between 80 and 90 mph at Galveston. State Route 75 at Wye was reported to be under

four feet of water. In the area of the City of Texas City, the golf course area between the

bay and the seawall was covered with water. Total property damage in Texas was $1

million, of which $800,000 was in damage to oil rigs off the Texas coast.

June 27, 1957 (Hurricane Audrey)

This first hurricane of the season crossed the coast near the Texas Louisiana border,

approximately 60 miles east of Galveston. Tides of 6.0 feet were reported at Galveston

Island two to three hours before the center of the hurricane passed inland and almost all

downtown streets were flooded. In the Offatt's Bayou area, winds of 70 mph and tides of

8 feet were reported. Tides of 6.6 feet were observed at Texas City and did considerable

damage. The San Leon area reported winds of 45 to 50 mph and tides of 4 feet above

normal. State Route 146 along Galveston Bay between Texas City and Seabrook was

flooded, and a 54-foot tug sank in Galveston Bay near Dickinson Bayou.

9

September 11, 1961 (Hurricane Carla)

The 30- to 40-mile-diameter eye of this large, slow-moving hurricane crossed the Texas

shoreline more than 100 miles below Galveston, near Port O’Connor. Minimum

barometric pressure in Galveston was recorded at 29.24 inches and at Texas City was

recorded at 29.26 inches. Maximum winds were an estimated 80 mph at Galveston,

where the four-day rainfall was 15.32 inches and maximum tide recorded in the Gulf at

Galveston was 9.3 feet msl. The entire western two thirds of Galveston Island was

inundated with still high water elevations ranging from 10.5 to 12.1 feet msl. This

hurricane also spawned a rash of 26 tornadoes that caused several fatalities in Texas and

caused dramatic damage. At least three of these tornadoes crossed the City of Galveston.

Water surface elevations along the western shore of Galveston Bay reached

approximately 14 feet msl. Areas around Kemah, La Marque, Hitchcock, and Texas City

were hard-hit and heavily damaged. This hurricane flooded approximately 2 16 square

miles of Galveston County (approximately 50 percent of the county's total land area). The

total damages to the county were estimated to be $84,499,000, of which $61,860,000

were due to tidal overflow.

September 5-22, 1967 (Hurricane Beulah)

This hurricane flooded the bay side of Galveston Island and Bolivar Peninsula, the

mainland side of West Bay, and areas along Highland Bayou to approximately the Texas

City Terminal Railroad. High-water marks recorded were 4.4 feet at Seabrook, 3.2 feet at

the Texas City dike, 3.7 feet gulfside at Galveston, and 3.8 feet in West Bay, 3.3 feet

bayside off Bolivar Peninsula, and 3.0 feet at Marsh Point.

August 2-5, 1970 (Hurricane Celia)

Hurricane Celia originated in the Caribbean Sea near Cuba struck the Texas coast and

moved inland at Corpus Christi. Highest tide at Galveston was recorded at 3.0 feet msl.

There was minor damage to piers and small boats, and Stewart Road was closed from the

corporate limits to San Luis Pass. In the northern portion of the county, residents left the

low-lying areas. This storm destroyed an estimated $500 million worth of property in

Texas. However, nearly all of the damage was from wind, not flooding or storm surge.

July 25, 1979 (Tropical Storm Claudette)

Tropical Storm Claudette, an upper air low pressure cell, originated in the Atlantic Ocean

near Puerto Rico and moved towards the west, into the Gulf of Mexico. It brought gale-

force winds and heavy rainfall to many parts of southeastern Texas, causing severe

flooding along streams and coastal areas. Estimated tides were between four and five feet

in Galveston Bay and its upper reaches, and approximately three feet along Galveston

Island and Bolivar Peninsula. Rainfall ranged from 14 to 24 inches in some areas of

Galveston County. Winds of 25 to 30 mph were reported, with gusts clocked as high as

55 mph. Low-lying areas between the Gulf Freeway and Galveston Bay were evacuated.

Flooding was reported also in the southwestern portion of the county along State Route 6

just north of West Bay in Hitchcock, Algoa, Arcadia, and Alta Loma. The Gulf Freeway

at Clear Creek was flooded, as were State Routes 6 and 146 along Upper Galveston Bay.

Dickinson Bayou and Clear Creek, as well as the smaller creeks, were out of their banks

and flooded large portions of nearby communities. On Galveston Island, many streets

10

were closed because of high water, and the highway to West Galveston Island was

closed. Bolivar Peninsula was evacuated. In Galveston County, an estimated 2,500 homes

suffered major damage, and 500 homes suffered minor damage from this storm. An

estimated 85-percent of northern Galveston County was affected by flooding.

September 19, 1979

This storm brought torrential rainfall to the Galveston County area. Officials at Texas

City reported 19 inches of rain in 72 hours. The areas around Dickinson Bayou, Clear

Creek, and Highland Bayou were inundated, and streets and homes were flooded.

October 15, 1989 (Hurricane Jerry)

Hurricane Jerry hit the Texas coast at Jamaica Beach. The flood elevations experienced

along the Gulf Coast at the Galveston Point Pleasant gage (No. 877 15 10) were

comparable to a 10-year flood. The elevations observed on the bayside of the barrier

island at the Galveston gage (No. 8771450) and Sabine Pass, North gage (No. 8770570)

were comparable with 5-year and 2-year flood elevations, respectively.

July 30-31, 1995 (Tropical Storm Dean)

This storm formed in the north-central Gulf of Mexico, made landfall near San Luis Pass

around 8:30 pm Central Daylight Time on July 30, and moved inland. Peak winds

recorded on Galveston Island were 51 mph, and the lowest barometric pressure recorded

was 1003.4 mb. Tides were 3 to 3.5 feet (NAVD88) above normal, and ranged from 3.3

feet above mean lower low water (MLLW) at Morgans Point to 4.8 feet at Pleasure Pier.

Minor storm-surge flooding of Highway 87 occurred. Tropical Storm Dean caused about

$450,000 in damage, mainly due to rainfall-related flooding in inland counties (Reference

12).

August 21-22, 1998 (Tropical Storm Charley)

Tropical Storm Charley made landfall on the middle Texas coast with peak recorded

gusts of 69 mph in Matagorda County. Most locations along the coast experienced winds

of less than 46 mph. Tidal surge was between 2 and 3 feet (NAVD88) and caused

significant beach erosion (Reference 12).

September 7-12, 1998 (Tropical Storm Frances)

This tropical storm formed slowly about 250 miles south of Galveston Island and moved

inland over a period of 5 days. As the storm made landfall near Port O’Connor,

approximately 120 miles southwest of Galveston, it stalled and remained on the coast for

most of a day. Peak wind gusts of 54 mph, with sustained winds of 30 to 40 mph, were

recorded in Galveston. Storm surge and high tides persisted for 2 days and caused major

damage in the Galveston area. More than 10 inches of rainfall was measured in most

coastal counties, exacerbating surge-related coastal flooding. The water level gage at the

Galveston Pleasure Pier measured tides of more than 4 feet above MLLW for 36 to 48

hours, and a peak of 7 feet above MLLW, equivalent to a storm surge of about 4.5 feet

(NAVD88) above predicted tides. Storm surge combined with sustained winds to create

significant wave action and cause extensive property damage. More than 100 single-

11

family homes were completely destroyed, and estimated property damage in Galveston

and surrounding counties totaled $286 million. Three deaths were attributed to the storm,

with all three people drowning while swimming or surfing off of Galveston Island

(Reference 12).

September 13-14, 2008 (Hurricane Ike)

Hurricane Ike was the ninth named storm, fifth hurricane, and third major hurricane of

the 2008 Atlantic hurricane season. Ike made its final landfall near Galveston, Texas as a

strong Category 2 hurricane, on September 13, 2008. Hurricane-force winds extended

120 miles (195 km) from the center and tropical storm-force winds extended far beyond

that. Ike was blamed for 112 people deaths in the United. Damages from Ike in U.S.

coastal and inland areas are estimated at $29.6 billion (2008 USD). Ike was the second

costliest Atlantic hurricane of all time, only surpassed by Hurricane Katrina of 2005. The

hurricane also resulted in the largest evacuation of Texans in that state's history.

2.4 Flood Protection Measures

There are many existing and planned structural flood protection measures in the county.

In the vicinity of the City of Texas City on Galveston Bay, there is an elaborate flood

protection system that consists of earthen levees, concrete floodwalls, drainage and

closure structures, tidal control and navigation structures, and pump stations. In the

Hitchcock-La Marque area, a diversion dam has been placed in Highland Bayou to divert

flood flows through the Basford Bayou watershed (a poorly defined drainage course

south of Highland Bayou) to Jones Bay via a diversion channel. Also, Highland Bayou

will be enlarged and rectified from the diversion dam upstream of Avenue J. Throughout

the county, local and private interests have constructed levees and other structures to

protect limited areas. Nonstructural flood protection measures in the unincorporated areas

of Galveston County consist of building regulations.

Following the massive devastation of the September 1900 hurricane, the City of

Galveston constructed a 17-foot high, 10-mile long seawall that protects over one-third of

the island’s area, principally the highly developed central business district. It is a gravity-

type, pile-supported concrete wall, extending westward from the foot of the South Jetty

on the east end of the island to approximately 3 miles west of 61st Street.

The seawall has been extended and redesigned numerous times, but the western two-

thirds of the island remains unprotected from storm surges and waves from the Gulf of

Mexico. The city and county have enforced flood damage prevention by requiring

buildings to be elevated to or above an elevation of 13 feet (NAVD88). The county has

followed building regulations required by the National Flood Insurance Act, Title 42,

since December 31, 1971.

The City of Kemah has built a tide barrier with a barrier crest about 7 feet MSL in the

Highway 146 drainage ditch west of 2nd Street, and installed pumps to pump out rainfall

runoff which backs up behind the barrier. This measure is effective for protecting the

low-lying downtown area against the more frequent tidal floods, such as the 100-year

event, but would be inconsequential for the 100-year event.

12

The City of La Marque has a diversion channel along Highland and Basford Bayous,

through the Basford Bayou watershed to Jones Bay, and a diversion dam across Highland

Bayou at mile 8.56. A 255,000 gallons per minute (gpm) pumping station at La Marque

(Palm Street outfall) and 2.6 miles of earthen levee extending up to 15- 19 feet

(NAVD88) provide protection from hurricane surges up to the 500-year return interval.

The City of Texas City includes an elaborate system of flood measures. On Galveston

Bay there are 13.6 miles of earthen levees varying in elevation from 15 to 23 feet, 1.3

miles of concrete floodways with elevations from 2 1 to 23 feet; drainage and closure

structures to direct drainage into ponding areas, tide control and navigation structures

across the entrance to Moses Lake and Dollar Point, interior drainage pumping stations

with a combined capacity of 1,000,000 gallons per minute. These systems protect the

eastern and southwestern portions of Texas City from interior drainage problems and

hurricane surge up to the 500-year recurrence interval.

3.0 ENGINEERING METHODS

For the flooding sources studied in detail in the county, standard hydrologic and hydraulic study

methods were used to determine the flood hazard data required for this study. Flood events of a

magnitude that are expected to be equaled or exceeded once on the average during any 10-, 50-,

100-, or 500-year period (recurrence interval) have been selected as having special significance

for floodplain management and for flood insurance rates. These events, commonly termed the

10-, 50-, 100-, and 500-year floods, have a 10-, 2-, 1-, and 0.2-percent-annual-chance flood,

respectively, of being equaled or exceeded during any year. Although the recurrence interval

represents the long-term, average period between floods of a specific magnitude, rare floods

could occur at short intervals or even within the same year. The risk of experiencing a rare flood

increases when periods greater than 1 year are considered. For example, the risk of having a

flood that equals or exceeds the 1-percent-annual-chance flood in any 50-year period is

approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60

percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions

existing in the community at the time of completion of this study. Maps and flood elevations will

be amended periodically to reflect future changes.

3.1 Hydrologic Analyses

Hydrologic analyses were carried out to establish peak discharge-frequency relationship

for each flooding source studied by detailed methods affecting the community.

The following descriptions of riverine hydrology analysis have been sourced from each

community’s effective FIS report when applicable. These analyses have been carried

forth and applied to this countywide study. While no new study was completed for this

countywide FIS, the new detailed study on Clear Creek (The Harris County TSARP

developed data) was incorporated. Also, updated USACE Hydrologic Engineering Center

Flood Hydrograph Package HEC-1 models for Borden’s Gully, Magnolia Creek,

Unnamed Tributary 3 to Lower Highland Bayou and Unnamed Tributary 3 Diversion

Channel to Lower Highland Bayou from 2006, 2001, and 2007 LOMR’s, respectively,

were incorporated (Reference 13).

13

City of Dickinson

Flood magnitude and frequency values for Benson Bayou, Dickinson Bayou, Gum

Bayou, Magnolia Bayou, Tributary to Gum Bayou, Unnamed Tributary to Dickinson

Bayou (East Branch), and Unnamed Tributary to Dickinson Bayou (West Branch), were

estimated using HEC-1 (Reference 13). Regionalized unit hydrograph and rainfall loss

rate parameters were developed by hydrograph reconstitution studies using 30 storms in

six gaged basins. The transposition of the HEC-1 model parameter from gaged to

ungaged basins was based on hydrologic similarity as assessed from soil maps, US

Geological Survey (USGS) topographic maps, recent aerial photographs, and field

reconnaissance (References 14, 15, 16, and 17). Urbanized watersheds were studied using

methodology developed by Beard (References 18 and 19). Rainfall data were developed

from hourly rainfall records from the National Climatic Center and from Technical Paper

40 (References 20 and 21). The storms used to generate peak discharges of selected

frequency have depth-area- duration characteristics consistent with the Texas Gulf Coast

area.

City of Friendswood

Flood magnitude and frequency values for Chigger Creek, Cowart Creek, and Marys

Creek were obtained from the USACE publication, Clear Creek Flood Control Study,

Development of Existing Watershed Conditions, Hydrology, and Hydraulics (Reference

22). Peak discharges for Marys Creek at the corporate limits were obtained from

Woodward-Clyde Consultants in conjunction with the Flood Insurance Study for the

unincorporated areas of Brazoria County (Reference 23). Flood magnitude and frequency

values for Chigger Creek, Cowart Creek, and Marys Creek were updated by BJI in 1986

using a revised hydrologic analysis for Clear Creek developed by the HCFCD in 1984.

The 0.2-percent-annual-chance discharge values were determined by extrapolation of the

discharge-frequency curves as described in the HCFCD analysis.

HCFCD developed revised methodologies for Cedar Gully to reflect rapid development

that has occurred in the area since 1979 (Reference 13). The Clark's unit hydrograph

parameters of time of concentration (Tc) and attenuation constant (R) were optimized

from a regression analysis evaluating the storm events obtained at various gages. Percent

of urbanization was taken into account by separating the above data into three categories:

(1) undeveloped, (2) partially developed, and (3) developed conditions.

The above regression analysis showed the equation for Tc to be a function of overbank

slope, length to centroid of area, urbanization, and weighted channel slope; while, the

equation for T+R was found to be a function of the length of the watershed to the divide,

the weighted channel slope, urbanization, and channel conveyance. Ponding, caused by

extensive rice farming in the southern and western portions of the county, was taken into

account by developing a relationship between percent ponding and R. This relationship

was obtained from the SCS publication Technical Release 55, Urban Hydrology for

Small Watersheds (Reference 24). The SCS methodology that incorporates the use of

runoff curve numbers and soil type was used to estimate loss rates (Reference 25).

14

City of Hitchcock

HEC-1 was used to estimate the flood magnitude and frequency for areas subject to

flooding from Highland Bayou (Reference 13). Regionalized unit hydrograph and rainfall

loss rate parameters were developed by hydrograph reconstitution studies using 30 storms

in six gaged basins. The transposition of the HEC- 1 model parameter from gaged to

ungaged basins is based on hydrologic similarity as assessed from soil maps (References

21 and 22), USGS topographic maps (Reference 16), recent air photos (Reference 26)

and field reconnaissance. Urbanized watersheds were studied using methodology

developed by Beard (References 27 and 19). Rainfall data were developed from hourly

rainfall records from the National Climatic Center (Reference 16) and from TP-40

(Reference 21). The storms used to generate peak discharges of selected frequency have

depth area duration characteristics consistent with the Texas Gulf Coast area.

City of La Marque

HEC-1 was used to estimate the flood magnitude and frequency for areas subject to

freshwater flooding from Highland Bayou and its tributaries (Reference 13).

Regionalized unit hydrograph and rainfall loss rate parameters were developed by

hydrograph reconstitution studies using 30 storms in six gaged basins. The transposition

of the HEC-1 model parameter from gaged to ungaged basins is based on hydrologic

similarity as assessed from soil maps (Reference 14 and 15), U. S. Geological Survey

topographic maps (Reference 16), recent air photos (Reference 22) and field

reconnaissance. Urbanized watersheds were studied using methodology developed by

Beard (Reference 27 and 19). Rainfall data was developed from hourly rainfall records

from the National Climatic Center (Reference 28) and from TP-40 (Reference 21). The

storms used to generate peak discharges of selected frequency have depth area duration

characteristics consistent with the Texas Gulf Coast area.

City of League City

For Magnolia Bayou in the September 22, 1999 revision, flood-frequency discharge

values were determined using the USACE HEC-1 computer program (Reference 13).

City of Texas City

Flood magnitude and frequency for areas subject to flooding from Dickinson Bayou,

Gum Bayou, and Moses Lake were estimated using the HEC-1 Flood Hydrograph

Package (Reference 13). Regionalized unit hydrograph and rainfall loss rate parameters

were developed by hydrograph reconstitution studies using 30 storms in six gaged basins.

The transposition of the HEC-1 model parameters from gaged to ungaged basins is based

on hydrologic similarity as assessed from soil maps (Reference 14), USGS topographic

maps (Reference 16), air photos (Reference 17) and field reconnaissance. Urbanized

watersheds were studied using methodology developed by Beard (References 27 and 19).

Rainfall data were developed from hourly rainfall records from the National Climatic

Center (Reference 20) and from TP- 40 (Reference 21). Ponding elevations in Moses

Lake were estimated using the modified Puls reservoir routing capability of the HEC-I

computer program. The storms used to generate peak discharges of selected frequency

have depth area duration characteristics consistent with the Texas Gulf Coast area.

15

Galveston County (Unincorporated Areas)

For the Galveston County 1983 and 1990 revisions, flood frequency discharge values for

the streams studied by detailed methods were estimated using the HEC-1 Flood

Hydrograph Package (Reference 13). Regionalized unit hydrograph and rainfall loss rate

parameters were developed by hydrograph reconstitution studies using 30 storms in six

gaged basins. The transposition of the HEC-1 model parameter from gaged to ungaged

basins is based, on hydrologic similarity as assessed from soil maps, USGS topographic

maps, aerial photographs, and field reconnaissance (References 14, 15, 16, and 17).

Urbanized watersheds were studied using methodology developed by Beard (References

19 and 20). Rainfall data were developed from hourly rainfall records from the National

Climatic Center and from Technical Paper No. 40 (References 20 and 21). The storms

used to generate peak discharges of selected frequency have depth-area duration

characteristics consistent with the Texas Gulf Coast area. Peak Discharges are listed in

Table 3, “Summary of Discharges”.

Table 3 – Summary of Discharges

Peak Discharge (cubic feet per second)

Flooding Source and Location

Drainage Area

(square miles)

10-Percent- 2-Percent- 1-Percent- 0.2-Percent-

Annual

Chance

Annual

Chance

Annual

Chance

Annual

Chance

BENSON BAYOU

At League City corporate limits 3.2 1,215 1,550 1,670 2,000

At FM 517 6.2 1,470 1,920 2,080 2,500

BORDEN’S GULLY At Calder Road 1.1 446 636 740 *

At mouth 2.8 1,003 1,383 1,587 *

CEDAR GULLY At stream mile 0.08 1.1 580 790 880 1,100

CLEAR CREEK At confluence of Halls Road Ditch 67.2 4,361 6,766 7,901 10,572

At confluence of Turkey Creek 77.3 6,876 10,632 12,282 17,205

At confluence of Marys Creek 95.6 9,343 14,080 16,162 22,566

At confluence of Cowart Creek 118.5 11,700 17,710 20,329 28,726

At confluence of Chigger Creek 139.1 13,201 19,868 22,891 30,896

At confluence of Magnolia Creek 144.9 13,407 20,253 23,340 31,269

At confluence of Landing Ditch 150.0 13,563 20,518 23,660 31,516

At confluence of Tributary

A111-00-00 154.0 13,729 20,766 23,940 31,637

At confluence of Cow Bayou 166.2 14,051 21,317 24,557 32,750

At confluence of Robinson Bayou 172.8 14,229 21,633 24,879 33,496

At confluence of Armand Bayou 231.9 20,938 35,377 42,013 64,427

16



Drainage Area

(square miles)


Annual

Chance

Annual

Chance

Annual

Chance

Annual

Chance

CLEAR CREEK (Continued)

At confluence of Taylor Bayou

250.8

22,481

38,995

47,042

72,745

At mouth 260.0 21,618 38,098 46,341 71,847

CHIGGER CREEK At the confluence with Clear Creek 16.7 2,125 3,077 3,764 5,200

COWART CREEK At the confluence with Clear Creek 20.0 2,851 4,116 4,774 6,200

DICKINSON BAYOU At Interstate Route 75 43.0 3,710 5,240 5,920 7,490

At its confluence with Benson

Bayou 70.0 7,880 10,800 12,000 14,800

At its confluence with Gum Bayou 89.0 11,100 15,300 17,100 21,000

At State Route 146 99.0 14,600 19,800 22,000 26,900

UNNAMED TRIBUTARY 3

DIVERSION CHANNEL TO LHB

Just downstream of its confluence

with Unnamed Tributary 3 2.7 1,200 1,560 1,700 2,100

GUM BAYOU At Farm Road 517 13.5 1,940 2,680 3,000 3,740

HIGHLAND BAYOU ABOVE

DIVERSION DAM

At Old Camp Wallace Road 17.0 4,970 6,500 7,010 8,800

LOWER HIGHLAND BAYOU At Marchand Bayou 8.5 2,360 3,130 3,460 4,100

At Highway 6 18.0 4,970 6,500 7,010 8,800

MAGNOLIA BAYOU

At its confluence with Dickinson

Bayou 5.8 1,820 2,280 2,530 3,200

MAGNOLIA CREEK At mouth 4.8 1,669 2,298 2,579 3,200

MARCHAND BAYOU At State Route 519 3.8 1,390 1,770 1,900 2,300

17



Drainage Area

(square miles)


Annual

Chance

Annual

Chance

Annual

Chance

Annual

Chance

MARYS CREEK

At the corporate limits 19.0 1,750 2,400 2,750 3,650

At the confluence with Clear Creek 20.0 2,014 2,741 3,054 3,800

TRIBUTARY TO GUM BAYOU At its confluence with Gum Bayou 5.7 1,500 2,000 2,200 2,500

UNNAMED TRIBUTARY TO

CLEAR CREEK

At mouth 3.1 890 1,220 1,390 2,150


DICKINSON BAYOU (EAST

BRANCH)

Above Second Street 4.6 1,380 1,770 1,900 2,300


DICKINSON BAYOU (WEST

BRANCH)

At its confluence with Unnamed

Tributary to Dickinson Bayou (East

Branch)

2.5 1,170 1,440 1,530 1,800

UPPER HIGHLAND BAYOU At Diversion Dam 17.0 3,140 4,340 4,815 5,910

UNNAMED TRIBUTARY At Delaney Road 1.6 1,080 1,280 1,380 1,610

UNNAMED TRIBUTARY 1 TO

LOWER HIGHLAND BAYOU

At Gulf Freeway 1.6 1,120 1,320 1,440 1,560



At Gulf Freeway 1.1 780 920 1,020 1,120



At FM 1765 1.1 990 1,270 1,400 1,730

At Temple Road 2.4 1,490 1,990 2,230 2,790

18



Drainage Area

(square miles)


Annual

Chance

Annual

Chance

Annual

Chance

Annual

Chance



(Continued)

Just upstream of its confluence with

Diversion Channel 2.7 1,600 2,130 2,350 2,950

Just downstream of its confluence

with Diversion Channel 2.7 400 570 650 850

UNNAMED TRIBUTARY 4 At Highway 6 1.2 1,000 1,160 1,250 1,420

* Data not available

3.2 Hydraulic Analyses

Analyses of the hydraulic characteristics of flooding from the sources studied were

carried out to provide estimates of the elevations of floods of the selected recurrence

intervals. Users should be aware that flood elevations shown on the Flood Insurance

Rate Map (FIRM) represent rounded whole-foot elevations and may not exactly reflect

the elevations shown on the Flood Profiles or in Table 5, Floodway Data Table. Flood

elevations shown on the FIRM are primarily intended for flood insurance rating purposes.

For construction and/or floodplain management purposes, users are cautioned to use the

flood elevation data presented in this FIS report in conjunction with the data shown on

the FIRM.

Locations of selected cross sections used in the hydraulic analyses are shown on the

Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed

(Section 4.2), selected cross-section locations are also shown on the FIRM.

The hydraulic analyses for this study were based on unobstructed flow. The flood

elevations shown on the Flood Profiles (Exhibit 1) are thus considered valid only if

hydraulic structures remain unobstructed, operate properly, and do not fail.

Below is a summary of the hydraulic studies previously published and adapted for this

countywide study. While no new study was completed for this countywide FIS, the new

detailed study on Clear Creek (The Harris County TSARP developed data) was

incorporated. Also, updated USACE HEC-RAS models for Borden’s Gully, Magnolia

Creek, Unnamed Tributary 3 to Lower Highland Bayou and Unnamed Tributary 3

Diversion Channel to Lower Highland Bayou from 2006, 2001, and 2007 LOMR’s,

respectively, were incorporated (Reference 29).

City of Dickinson

Cross sections for the backwater analyses were obtained from field surveys and USGS

topographic maps (Reference 16). All bridges, dams, and culverts were field-checked to

19

obtain elevation data and structural geometry. Releveling of all bench marks along

Dickinson Bayou was performed by Tetra Tech Inc., during field surveys in 1978. The

channel cross sections, therefore, actually reflect the subsidence effect up to 1978. Cross

sections for the restudy of Magnolia Bayou were taken from USACE surveys performed

November 1984 through January 1985. Cross section elevations were corrected to the

National Geodetic Vertical Datum of 1929 (NGVD) 1984 adjustment.

Water-surface elevations of floods of the selected recurrence intervals were computed

using the USACE HEC-2 step-backwater computer program (Reference 29). Starting

water-surface elevations for Dickinson Bayou were set equal to mean high tide. Starting

water-surface elevations for the remaining streams were set equal to the elevation of the

main stream at their confluence. Flood profiles were drawn showing computed water-

surface elevations of floods of the selected recurrence intervals.

Channel roughness factors (Manning's "n") used in the hydraulic computations were

chosen by engineering judgment and based on field observations and aerial photographs

of the streams and floodplain areas, and USGS Water-Supply Paper 1849 (Reference 30).

Channel "n" values for the streams studied by detailed methods ranged from 0.020 to

0.080, and the overbank "n" values ranged from 0.060 to 0.130.

City of Friendswood

Cross sectional information in this study was obtained from the Galveston District of the

USACE based on field survey data taken in 1976 and tied to National Geodetic Survey

(NGS) bench marks releveled in 1973. The HCFCD, in updating the analyses for Cedar

Gully, utilized field survey data based on USACE marks that also tied into the NGS

bench marks releveled in 1973. The updated analysis of Marys Creek, Cowart Creek, and

Chigger Creek, performed by BJI, incorporated updated field surveys and as-built plans

based on the 1978 releveling of NGS datum. The cross sections were located at close

intervals above and below bridges and culverts and supplemented with information from

USGS topographic maps in order to compute the significant backwater effects of these

structures (Reference 16).

Water-surface elevations of floods of the selected recurrence intervals were computed

using the USACE HEC-2 step-backwater computer program (Reference 29). Flood

profiles were drawn shoving computed water-surface elevations for floods of the selected

recurrence intervals. The starting water-surface elevations for Cedar Gully, Chigger

Creek, Cowart Creek, and Marys Creek were calculated by the slope/area method taking

elevations at the mouth of each stream.


chosen by engineering judgment based on field observations, aerial photographs of the

streams and floodplain areas, and USGS Water Supply Paper 1849 (References 17 and

30). For Chigger Creek, Cowart Creek, and Marys Creek, channel "n" values ranged from

0.013 to 0.040, and overbank "n" values ranged from 0.080 to 0.150. The Cedar Gully

Channel "n" ranged from 0.035 to 0.070 and overbank "n" values ranged from 0.035 to

0.150.

In the watersheds of these streams, flat terrain makes definition of the watershed divides

difficult. The discharges in Table 3 that are identified as being adjusted for basin

20

overflow reflect the final discharges used in the hydraulic backwater model and have

already had the basin overflow discharge subtracted from the total discharge computed by

hydrologic methods. The three hydraulic methods used to calculate basin overflow are

Manning's Equation, the Weir Equation, and a known stage-discharge curve.

Manning’s Equation and the Weir Equation methods both contain many similarities and

will be discussed jointly. The equations for these methods are as follows:

Manning’s Equation: Q = 1.49/n AR.67

S.5

Weir Equation: Q = CLH1.5

Where:

Q = overflow discharge

N = Manning’s “n” value

A = area

R = hydraulic radius

S = slope in direction of overflow

C = weir coefficient

L = weir length

H = energy head assuming negligible velocities

The Manning's "n" values were determined from field inspection. The weir coefficient

was determined from the Handbook of Applied Hydrology and was set at 2.8 (Reference

31).

The third method used to predict the amount of basin overflow was from a known stage-

discharge curve. This method was used to evaluate some of the diversion channels. The

stage-discharge relationship was developed from multiple backwater computations.

The computation procedure for all methods is as follows: 1) the basin divide line is

plotted using the ground elevations at the "ends" of the cross sections used in the

backwater computations; 2) an overflow discharge is assumed for each reach (the area

between two points of the basin divide) in the overbank areas; 3) each overflow discharge

is subtracted from the total discharges for all downstream cross sections to determine the

amount of discharge left in the stream; 4) backwater computations are performed using

the adjusted stream discharges; and 5) the elevations computed by the backwater analysis

are compared to the elevations needed to produce the assumed overflow discharges. A

revised overflow discharge is obtained by either averaging the new overflow discharge

with the previously assumed discharge or by using the computed overflow discharge

directly. This process is repeated with the newly assumed overflow discharges until the

assumed and calculated discharges converge, or until the profile elevations show little

change. These computations were performed by hand or by the split flow option of the

HEC-2 program (Reference 29).

City of Hitchcock

For areas that are affected by stream overflow, water-surface elevations of floods of the

selected recurrence intervals were computed through use of USACE HEC-2 water-

surface profile computer programs (Reference 29). Starting water-surface elevations for

21

Highland Bayou were set equal to mean high tide. Starting water-surface elevations for

Marchand Bayou and Unnamed Tributary 4 were set equal to the backwater elevation of

Highland Bayou.

Cross sections for the backwater analysis of Highland Bayou, Marchand Bayou,

Unnamed Tributary 4 were obtained from field surveys and USGS 7.5-minute

topographic maps (Reference 16). All bridges, dams, and culverts were field checked to

obtain elevation data and structural geometry. Re-leveling of all benchmarks along

Highland Bayou was performed by Tetra Tech, Inc. during field surveys in 1978. The

channel cross sections, therefore, actually reflect the subsidence effect up to 1978.


chosen by engineering judgment and based on field observations and aerial photo of the

streams and flood plain areas and on U.S. Geological Supply Paper 1849 (Reference 30).

Roughness values used for Highland Bayou and its tributaries in the Hitchcock area range

from 0.33 to 0.04, with flood plain roughness values ranging from 0.06 to 0.1 for all

floods.

City of La Marque

For areas subject to stream overflow, water-surface elevations of floods of the selected

recurrence intervals were computed through use of the USACE HEC-2 water-surface

profile computer program (Reference 29). Starting water-surface elevations for Highland

Bayou were set equal to mean high tide. Starting water-surface elevations for Marchand

Bayou and Unnamed Tributary 3 were set equal to backwater elevations of Highland

Bayou at their respective confluences. The starting water- surface elevations for

Unnamed Tributaries 1 and 2 were estimated to be the maximum rainfall ponding levels

behind the southwest levee.

Cross sections for the backwater analysis of Highland Bayou, Marchand Bayou,

Unnamed Tributary 1, Unnamed Tributary 2, and Unnamed Tributary 3 were obtained

from field surveys and U.S. Geological Survey 7.5-Minute Topographic Maps (Reference

16). All bridges, dams, and culverts were field checked to obtain elevation data and

structural geometry. Releveling of all benchmarks along Highland Bayou was performed

by Tetra Tech during field surveys in 1978. The channel cross sections, therefore,

actually reflect the subsidence effect up to 1978.

Channel roughness factors (Manning's "n”) used in the hydraulic computations were

chosen by engineering judgment and based on field observations and aerial photos of the

streams and flood-plain areas and on U.S. Geological Survey Water Supply Paper 1849

(Reference 30). Roughness values used for Highland Bayou and its tributaries in the La

Marque area range from 0.025 to 0.040, with flood plain roughness values ranging from

0.060 to 0.10 for all floods.

City of League City

For the streams studied by detailed methods in the original study and in the September

22, 1999 revision, water-surface elevations of floods of the selected recurrence intervals

were computed using the USACE HEC-2 step-backwater computer program (Reference

29). Starting water-surface elevations for Benson Bayou, and Unnamed Tributary of

22

Clear Creek were set equal to normal depth. Cross sectional data for Unnamed Tributary

of Clear Creek was obtained from the Galveston District of the USACE. Cross sectional

data for Benson Bayou were obtained from field surveys and USGS topographic maps

(Reference 16). For Magnolia Bayou in the 1999 revision, starting water-surface

elevations were determined from the backwater elevation of Dickinson Bayou. Cross

sectional data used in this revision were obtained from field surveys; elevations were

adjusted to the 1984 vertical datum due to subsidence. Flood profiles were drawn

showing computed water-surface elevations for floods of the selected recurrence

intervals. Flood profiles for Clear Creek were obtained from the Harris County FIS

(Reference 22).


chosen by engineering judgment based on field observations, aerial photographs of the

streams and floodplain areas, and USGS Water Supply Paper 1849 (Reference 30). For

the streams studied by detailed methods, the channel "n" values ranged from 0.020 to

0.080, and overbank "n" values ranged from 0.080 to 0.150.

City of Santa Fe



profile computer programs (Reference 29). Starting water-surface elevations for the reach

of Highland Bayou downstream of the diversion darn were set equal to the mean high

tide. Starting water-surface elevations for the tributaries of Highland Bayou were set

equal to the elevation of the mainstream at their confluence. The starting elevations for

Highland Bayou above the Diversion Dam were estimated at normal depth.

Cross sections for the backwater analysis of Highland Bayou and tributaries were

obtained from field surveys and U.S. Geological Survey 7.5-minute topographic maps

(Reference 16). All bridges, dams, and culverts were field checked to obtain elevation

data and structural geometry. Releveling of all bench marks along Highland and

Dickinson Bayous was performed by Tetra Tech during field surveys in 1978. The

channel cross sections, therefore, actually reflect the subsidence effect up to 1978.

Channel roughness factors (Manning's “n”) used in the hydraulic computations, were

chosen by engineering judgment and based on field observations and aerial photos of the

streams and floodplain areas and on U.S. Geological Survey Water Supply Paper 1849

(Reference 30). Roughness values used for the main channel of Highland Bayou and its

tributaries range from 0.025 to 0.080, with flood plain roughness values ranging from

0.060 to 0.120 for all floods.

City of Texas City



profile computer programs (Reference 29). Starting water-surface elevations for

Dickinson Bayou were set equal to mean high tide. Starting water-surface elevations for

Gum Bayou were set equal to the backwater elevations at its confluence with Dickinson

Bayou.

23

Cross sections for the backwater analysis of Dickinson Bayou and Gum Bayou were

obtained from field surveys and U.S. Geological Survey 7.5-minute topographic maps

(Reference 16). All bridges, dams, and culverts were field checked to obtain elevation

data and structural geometry. Releveling of all benchmarks along Dickinson Bayou was

performed by Tetra Tech during field surveys in 1978. The channel cross sections,

therefore, actually reflect the subsidence effect up to 1978. Channel roughness factors

(Manning's "n”) used in the hydraulic computations were chosen by engineering

judgment and based on field observations and aerial photos of the streams and floodplain

areas and on U.S. Geological Survey Water Supply Paper 1849 (Reference 30).

Roughness values used for the main channels of Dickson Bayou and Gum Bayou range

from 0.030 to 0.040, with flood plain roughness values ranging from 0.060 to 0.100 for

all floods.

Galveston County (Unincorporated Areas)

In the 1983 revision and in the November 16, 1990, revision, water surface elevations of

floods of the selected recurrence intervals were computed using the USACE HEC-2 step-

backwater computer program (Reference 29). Starting water-surface elevations for

Dickinson Bayou and the portion of Highland Bayou downstream of the diversion dam

were set equal to mean high tide. Starting water surface elevations for the remaining

streams were set equal to the elevation of the main stream at their confluence. Starting

water surface elevations for Highland Bayou above the diversion dam were estimated at

normal depth. Flood profiles were drawn showing computed water-surface elevations of

floods of the selected recurrence intervals.

Cross sections for the backwater analysis of Dickinson Bayou and tributaries, and

Highland Bayou and tributaries, were obtained from field surveys and USGS topographic

maps (Reference 16). All bridges, dams, and culverts were field- checked to obtain

elevation data and structural geometry. Releveling of all benchmarks along Highland and

Dickinson Bayous was performed by Tetra Tech, Inc., during field surveys in 1978. The

channel cross sections, therefore, actually reflect the subsidence effect up to 1978. Cross

sections for the November 16, 1990, restudy of Magnolia Bayou were taken from

USACE surveys performed between November 1984 and January 1985.


chosen by engineering judgment and based on field observations and aerial photographs

of the streams and floodplain areas, and USGS Water-Supply Paper 1849 (Reference 30).

Channel "n" values for the streams studied by detailed methods ranged from 0.025 to

0.080, and the overbank "n" values ranged from 0.060 to 0.120.

Locations of selected cross sections used in the hydraulic analyses are shown on the

Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed

(Section 4.2), selected cross-section locations are also shown on the Flood Insurance Rate

Map (Exhibit 2).

3.3 Coastal Analysis

The hydraulic characteristics of coastal flood sources were analyzed to provide estimates

of flood elevations for selected recurrence intervals. Users should be aware that flood

elevations shown on the FIRM represent rounded whole-foot elevations and may not

24

exactly reflect the elevations shown in the coastal data tables and flood profiles provided

in the FIS Report.

3.3.1. Storm Surge Analysis and Modeling

For areas subject to coastal flood effects, the 10-, 2-, 1-, and 0.2-percent-annual-

chance stillwater elevations were taken directly from a detailed storm surge study

documented in Flood Insurance Study: Coastal Counties, Texas Intermediate

Submission 2 – Scoping and Data Review prepared by the USACE. This storm

surge study was completed in November 2011.

The Advanced Circulation (ADCIRC) model for coastal ocean hydrodynamics

developed by the USACE was applied to calculate stillwater elevations for

coastal Texas. The ADCIRC model uses an unstructured grid and is a finite

element long wave model. It has the capability to simulate tidal circulation and

storm surge propagation over large areas and is able to provide highly detailed

resolution in areas of interest along shorelines, open coasts and inland bays. It

solves three dimensional equations of motion, including tidal potential, Coriolis,

and non-linear terms of the governing equations. The model is formulated from

the depth-averaged shallow water equations for conservation of mass and

momentum which result in the generalized wave continuity equation.

In performing the coastal analyses, nearshore waves were required as inputs to

wave runup and overland wave propagation calculations, and wave momentum

(radiation stress) was considered as contribution to elevated water levels (wave

setup). The Steady State Spectral Wave (STWAVE) model was used to generate

and transform waves to the shore for the Texas Joint Storm Surge (JSS) Study.

STWAVE is a finite difference model that calculates wave spectra on a

rectangular grid. The model outputs zero-moment wave height, peak wave

period (Tp), and mean wave direction at all grid points and two-dimensional

spectra at selected grid points. STWAVE includes an option to input spatially

variable wind and storm surge field. Storm surge significantly alters wave

transformation and generation for the hurricane simulations in shallow-flooded

areas.

STWAVE was applied on five grids for the Texas JSS: NE, CE, SW, NEn, and

CEn. Three large grids (NE, CE, SW) with offshore boundaries at depths near

100 feet (30 meters) encompassed the entire coast of Texas and applied the

efficient half-plane version of STWAVE (which must approximately align with

the shoreline). Two nested grids (NEn and CEn) covered Galveston Bay and

Corpus Christi Bay and applied the fullplane version of STWAVE to allow

generation of wind waves in all directions. Notably, memory requirements for

the full-plane model precluded its use for the large grids with offshore

boundaries. The input for each grid includes the bathymetry (interpolated from

the ADCIRC domain), surge fields (interpolated from ADCIRC surge fields), and

wind fields (interpolated from the ADCIRC wind fields, which apply land effects

to the base wind fields). The wind and surge applied in STWAVE are spatially

and temporally variable for all domains. STWAVE was run at 30-minute

intervals for 93 quasi-time steps (46.5 hours).

25

The ADCIRC model computational domain and the geometric/topographic

representation developed for the Joint Coastal Surge effort was designated as the

TX2008 mesh. This provided a common domain and mesh from the Texas-

Mexico border to western Louisiana, extends inland across the floodplains of

Coastal Texas (to the 30- to 75-foot contour NAVD88), and extends over the

entire Gulf of Mexico to the deep Atlantic Ocean. The TX2008 domain

boundaries were selected to ensure the correct development, propagation, and

attenuation of storm surge without necessitating nesting solutions or specifying

ad hoc boundary conditions for tides or storm surge. The TX2008 computational

mesh contains more than 2.8 million nodes and nodal spacing varies significantly

throughout the mesh. Grid resolution varies from approximately 12 to15 miles in

the deep Atlantic Ocean to about 100 ft. in Texas. Further details about the

terrain data as well as the ADCIRC mesh creation and grid development process

can be found in Flood Insurance Study: Coastal Counties, Texas Intermediate

Submission 2 – Scoping and Data Review (Reference 40).

3.3.2. Statistical Analysis

The Joint Probability Method (JPM) is a simulation methodology that relies on

the development of statistical distributions of key hurricane input variables such

as central pressure, radius to maximum wind speed, maximum wind speed,

translation speed, track heading, etc., and sampling from these distributions to

develop model hurricanes. The resulting simulation results in a family of

modeled storms that preserve the relationships between the various input model

components, but provides a means to model the effects and probabilities of

storms that historically have not occurred.

Due to the excessive number of simulations required for the traditional JPM

method, the JPM-Optimum Sampling (JPM-OS) was utilized to determine the

stillwater elevations associated with tropical events. JPM-OS is a modification

of the JPM method and is intended to minimize the number of synthetic storms

that are needed as input to the ADCIRC model. The methodology entails

sampling from a distribution of model storm parameters (e.g., central pressure,

radius to maximum wind speed, maximum wind speed, translation speed, and

track heading) whose statistical properties are consistent with historical storms

impacting the region, but whose detailed tracks differ. The methodology

inherently assumes that the hurricane climatology over the past 60 to 65 years

(back to 1940) is representative of the past and future hurricanes likely to occur

along the Texas coast.

A set of 446 storms (two sets of 152 low frequency storms + two sets of 71

higher frequency storms) was developed by combining the “probable”

combinations of central pressure, radius to maximum winds, forward speed,

angle of track relative to coastline, and track. Tracks were defined by five

primary tracks and four secondary tracks. Storm parameters for synthetic storms

are provided in Table 11 of Flood Insurance Study: Coastal Counties, Texas

Intermediate Submission 2 – Scoping and Data Review (Reference 40). The

estimated range of storm frequencies using the selected parameters was between

the 10%- and 0.2%-annual-chance storm events. The ADCIRC-STWAVE

26

modeling system was validated using five historic storms: Hurricanes Carla

(1961), Allen (1980), Bret (1999), Rita (2005), and Ike (2008).

3.3.3 Stillwater Elevations

The results of the ADCIRC model and JPM-OS provided 10-, 2-, 1-, and 0.2-

percent-annual-chance stillwater elevations which include wave setup effects.

Stillwater elevations are assigned at individual ADCIRC mesh nodes throughout

the Texas coast. Triangular Irregular Networks (TINs) and raster datasets were

built from these nodes for use in wave analysis and floodplain mapping.

An Independent Technical Review (ITR) was performed on the overall storm

surge study process. This review process was performed in accordance with

USACE regulations. The ITR team was composed of experts in the fields of

coastal engineering and science, and was engaged throughout the study.

Appendix K of Flood Insurance Study: Coastal Counties, Texas Intermediate

Submission 2 – Scoping and Data Review includes all comments received from

the ITR panel, as well as responses to those comments (Reference 40).

3.3.4 Wave Height Analysis

FEMA has defined coastal high hazard zones as coastlines subject to significant

wave affects (defined by wave heights that equal or exceed 3-feet). To determine

overland wave heights, and define the coastal high hazard zones, Taylor

Engineering applied the 1-percent-annual-chance-stillwater elevations, LiDAR

topographic data, and land-use data to model the waves as they propagate

landward of the shoreline.

Figure 1 shows a profile for a typical transect, illustrating the effects of energy

dissipation and regeneration on a wave as it moves inland. This figure shows the

wave crest elevations being decreased by obstructions, such as buildings,

vegetation, and rising ground elevations, and being increased by open,

unobstructed wind fetches. Figure 1 also illustrates the relationship between the

local stillwater elevation, the ground profile, and the location of the V/A

boundary. This inland limit of the coastal high hazard area is delineated to

ensure that adequate insurance rates apply and appropriate construction standards

are imposed, should local agencies permit building in this coastal high hazard

area.

27

Figure 1 – Transect Schematic

Laboratory tests and field investigations have shown that wave heights as little as

1.5 feet can cause damage to and failure of typical Zone AE construction.

Therefore, for advisory purposes only, a Limit of Moderate Wave Action

(LiMWA) boundary has been added in coastal areas subject to wave action. The

LiMWA represents the approximate landward limit of the 1.5-foot breaking

wave.

The effects of wave hazards in the Zone AE between the Zone VE (or shoreline

in areas where VE Zones are not identified) and the limit of the LiMWA

boundary are similar to, but less severe than, those in Zone VE where 3-foot

breaking waves are projected during a 1-percent-annual chance flooding event.

In areas where wave runup elevations dominate over wave heights, such as areas

with steeply sloped beaches, bluffs, and/or shore-parallel flood protection

structures, there is no evidence to date of significant damage to residential

structures by runup depths less than 3 feet. However, to simplify representation,

the LiMWA was continued immediately landward of the VE/AE boundary in

areas where wave runup elevations dominate. Similarly, in areas where the Zone

VE designation is based on the presence of a primary frontal dune or wave

overtopping, the LiMWA was also delineated immediately landward of the Zone

VE/AE boundary.

Transect locations and spacing is determined by considerations of physical and

land-use characteristics of the coast. The transects are located to adequately

represent the dominate direction of overland wave propagation. The transects are

closely spaced in areas of changing topography or land use and, conversely,

spread further apart in areas of similar topography or land use. Transects are also

located in areas where unique flooding existed and in areas where computed

wave heights varied significantly between adjacent transects. Where transects

28

crossed, the largest wave height value was delineated on the FIRM panel.

Transects are shown on the respective FIRM panels for the county.

This study applied topographic data from LiDAR data collected by FEMA in

2006 under a subcontract with Sanborn (Reference 35). In 2011 NOAA modified

and updated some areas of the data (Reference 36). The topographic data is

referenced to NAVD88.

The combination of three land use data sources comprised the data used to

identify areas of vegetative cover (forest, marsh grass, etc), buildings (density

and spacing), and open water. The three sources are: aerial photos from 2010

(Reference 36), U.S. Fish and Wildlife Service, National Wetland Inventory,

2006 (Reference 37), and NOAA Coastal Change Analysis Program (C-CAP)

data, 2006 (Reference 38). In addition, Taylor Engineering collected detailed

information about the features, such as building types, density, and vegetation

types during a ground field reconnaissance.

No storm-induced erosion analysis was performed for this study. Primary frontal

dune mapping was not applied.

Wave height calculation used in this study follows the methodology described in

the Atlantic Ocean and Gulf of Mexico Coastal Guidelines Update, 2007.

Calculations of overland wave height propagation, using WHAFIS 4.0, included

both the 1- and 0.2-percent-annual-chance events. The 0.2-percent wave height

results are not included on the FIRMs but are provided as wave-transect profiles

in Exhibit 2 of the FIS.

Each transect calculates wave heights based on stillwater elevations (from the 1-

percent surge modeling), ground elevations at each station along a transect, and

land-use properties. Wave setup was not calculated separately because wave

setup was included in the base stillwater elevations from the storm surge

analysis.

This study used default WHAFIS initial wave conditions based on fetch for each

transect. Open water transects (primarily along the open Gulf) used the maximum

24 miles of open fetch and interior transects used measured fetch lengths

(Reference 34).

Figure 2 on page 41, “Transect Location Map” shows the transect layout used for

the overland wave analyses. Along each transect, wave envelopes were computed

considering the combined effects of changes in ground elevation, stillwater

surface elevation (including wave setup), vegetation, and physical features.

Between transects, elevations were interpolated using LiDAR topographic data,

land-use and land-cover data, and engineering judgment to determine the aerial

extent of flooding. The transect data for each transect in the county, including

the flood hazard zone, base flood elevations, transect location description, 10-,

2-, 1-, and 0.2-percent annual chance stillwater elevations at the start of the

transect and the range found along the length of the transect is provided in Table

4.

29

Taylor Engineering applied the Technical Advisory Committee for Water

Retaining Structures (TAW) method and Coastal Engineering Design & Analysis

System (ACES) to calculate runup for transects 30, 33, 36, 77, 80, 81, 83, 85, 87,

108, 109, 110, and 111 along the Texas City Hurricane Protection Levee;

transects 100 and 101 for the Texas City Rainwater Levee; and transects 31, 35,

38, and 40 for the Galveston Seawall. For non-levee areas affected by runup,

transects 93, 97, 103, 104, 105, 106, 107, the TAW method was used. The 2%

runup height was added to the stillwater elevation to compute a BFE. If the runup

BFE exceeded the WHAFIS computed BFE, the map was adjusted to reflect the

runup elevation (Reference 32 and 33).

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

7.5

*10.2

*12

.6*

16

.3*

7.3

- 7

.49.9

- 1

0.0

12.0

- 1

2.5

15

.6 -

16

.2V

E1

6

7.6

10.3

12

.61

6.3

7.0

- 7

.79.5

- 1

0.4

11.6

- 1

2.5

15

.3 -

16

.2V

E1

6 -

VE

19

7.9

10.8

13

.11

6.8

AE

10

- A

E1

6

5.7

- 8

.08.8

- 1

1.0

11.1

- 1

3.2

14

.7 -

18

.0V

E1

2 -

VE

17

8.0

10.8

13

.21

6.8

AE

10

- A

E1

7

6.3

- 8

.08.2

- 1

1.0

10.9

- 1

3.4

14

.6 -

17

.0V

E1

2 -

VE

20

8.0

10.8

13

.21

6.7

AE

10

- A

E1

7

6.5

- 8

.08.7

- 1

0.9

11.0

- 1

3.2

14

.6 -

16

.8V

E1

2 -

VE

20

8.0

10.8

13

.21

6.7

AE

10

- A

E1

7

6.5

- 8

.18.6

- 1

0.8

11.0

- 1

3.1

14

.6 -

16

.7V

E1

2 -

VE

20

8.0

10.8

13

.21

6.7

AE

10

- A

E1

7

5.7

- 8

.18.1

- 1

1.0

11.0

- 1

3.4

14

.5 -

17

.4V

E1

2 -

VE

20

8.1

10.8

13

.21

6.7

AE

10

- A

E1

7

6.3

- 8

.18.2

- 1

0.8

11.0

- 1

3.2

14

.6 -

16

.7V

E1

2 -

VE

20

8.1

10.9

13

.31

6.8

AE

10

- A

E1

7

6.3

- 8

.18.6

- 1

1.0

11.0

- 1

3.4

14

.5 -

17

.4V

E1

2 -

VE

20

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°3'2

5.6

74"W

29

°46

'25.8

79"N

5F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°4'3

0.2

26"W

29

°41

'59.8

13"N

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

3F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°6'4

.294"W

29

°34

'29.7

78"N

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°6'5

1.0

56"W

29

°30

'20.4

43"N

86

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

9F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°3'8

.257"W

29

°47

'34.8

28"N

7F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°3'4

4.9

65"W

29

°45'7

.782"N

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

2 4F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°5'1

5.3

85"W

29

°38'4

4.9

8"N

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°4'3

.445"W

29

°43

'52.2

66"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.1

10.8

13

.31

6.8

AE

10

- A

E1

7

6.5

- 8

.18.6

- 1

0.9

11.0

- 1

3.3

14

.5 -

16

.8V

E1

2 -

VE

20

8.1

10.9

13

.41

6.8

AE

10

- A

E1

7

6.4

- 8

.17.8

- 1

0.9

10.2

- 1

3.5

14

.4 -

17

.8V

E1

2 -

VE

20

8.2

10.9

13

.41

6.9

AE

10

- A

E1

7

4.0

- 8

.27.8

- 1

1.2

10.7

- 1

3.9

14

.3 -

19

.5V

E1

2 -

VE

20

8.2

10.8

13

.41

6.8

AE

10

- A

E1

7

6.2

- 8

.28.3

- 1

1.0

10.8

- 1

3.9

14

.4 -

19

.7V

E1

2 -

VE

20

8.2

10.8

13

.41

6.9

AE

10

- A

E1

7

6.4

- 8

.28.4

- 1

1.0

10.8

- 1

4.2

14

.4 -

20

.0V

E1

2 -

VE

20

8.3

10.8

13

.41

7.0

AE

10

- A

E1

7

6.1

- 8

.38.4

- 1

1.4

10.8

- 1

4.2

14

.4 -

20

.5V

E1

2 -

VE

20

8.3

10.8

13

.41

7.0

AE

13

- A

E1

6

6.2

- 8

.38.3

- 1

1.6

10.6

- 1

4.5

14

.4 -

18

.9V

E1

4 -

VE

19

8.3

10.7

13

.41

7.0

AE

13

- A

E1

6

6.4

- 8

.38.3

- 1

1.4

10.7

- 1

4.3

14

.4 -

18

.6V

E1

4 -

VE

19

8.3

10.7

13

.41

7.1

AE

11

- A

E1

6

6.6

- 8

.38.4

- 1

1.4

10.8

- 1

4.5

14

.4 -

19

.9V

E1

4 -

VE

19

16

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°59

'7.9

94"W

29

°62

'25.0

63"N

17

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°58

'42.9

5"W

29

°63

'54.0

53"N

18

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°58'2

2.2

45"W

29

°65

'11.4

83"N

13

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

95

°1'5

.844"W

29

°55

'10.1

53"N

14

95

°0'2

2.5

21"W

29

°57

'49.8

89"N

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

15

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°59'3

5.6

07"W

29

°60

'43.1

52"N

12

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°1'3

3.9

37"W

29

°53

'28.9

75"N

10

11

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°2'6

.542"W

29

°51

'29.3

88"N

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°2'3

4.6

62"W

29

°49

'40.2

72"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.3

10.7

13

.41

7.1

AE

13

- A

E1

6

6.3

- 8

.38.4

- 1

1.2

10.7

- 1

4.3

14

.4 -

20

.0V

E1

4 -

VE

19

8.3

10.7

13

.41

7.1

AE

10

- A

E1

7

6.3

- 8

.48.3

- 1

1.3

10.6

- 1

4.8

14

.4 -

20

.2V

E1

2 -

VE

20

8.3

10.6

13

.41

7.2

AE

12

- A

E1

6

6.4

- 8

.37.6

- 1

1.0

10.7

- 1

4.6

14

.4 -

20

.3V

E1

3 -

VE

19

8.3

10.5

13

.41

7.3

AE

12

- A

E1

6

6.3

- 8

.38.3

- 1

1.1

10.8

- 1

4.8

14

.6 -

20

.7V

E1

3 -

VE

19

8.3

10.5

13

.41

7.3

AE

10

- A

E1

7

6.4

- 8

.38.4

- 1

1.4

10.6

- 1

4.8

14

.5 -

20

.7V

E1

2 -

VE

20

8.3

10.5

13

.41

7.3

AE

12

- A

E1

7

6.0

- 8

.38.1

- 1

1.7

10.8

- 1

5.1

14

.7 -

20

.2V

E1

4 -

VE

19

8.3

10.4

13

.41

7.4

AE

12

- A

E1

7

5.9

- 8

.38.0

- 1

1.2

10.7

- 1

4.9

14

.7 -

20

.0V

E1

4 -

VE

19

8.3

10.4

13

.41

7.5

AE

10

- A

E1

7

6.1

- 8

.38.2

- 1

1.0

10.7

- 1

4.6

14

.7 -

20

.6V

E1

2 -

VE

20

8.3

10.3

13

.31

7.5

AE

10

- A

E1

7

6.4

- 8

.48.6

- 1

1.4

10.8

- 1

5.2

14

.7 -

20

.5V

E1

2 -

VE

20

25

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°54'2

0.8

58"W

29

°79'2

9.8

1"N

26

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°53'4

2.5

99"W

29

°81'5

1.1

1"N

27

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°53

'0.8

73"W

29

°84

'22.0

79"N

22

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°55'4

4.9

88"W

29

°74

'27.6

66"N

23

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°55'3

2.0

57"W

29

°75

'16.8

93"N

24

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°55

'3.2

12"W

29

°76

'58.1

11"N

19

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°57

'51.4

2"W

29

°67'1

.958"N

20

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°57'1

0.1

94"W

29

°69

'26.4

02"N

21

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°56'1

9.1

06"W

29

°72

'25.3

72"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.3

10.2

13

.21

7.3

AE

10

- A

E1

7

6.3

- 8

.38.6

- 1

0.8

11.0

- 1

4.3

14

.5 -

19

.2V

E1

2 -

VE

20

8.2

9.9

13

.31

7.7

AE

10

- A

E1

6

6.6

- 8

.38.7

- 1

0.3

10.8

- 1

3.7

14

.3 -

19

.3V

E1

4 -

VE

19

7.9

9.5

13

.31

7.7

AE

10

- A

E1

6

6.0

- 8

.66.4

- 1

1.2

9.9

- 1

4.5

13

.8 -

19

.4V

E1

4 -

VE

19

7.6

9.8

13

.31

7.8

AE

11

- A

E1

6

5.7

- 9

.38.6

- 1

1.8

10.8

- 1

4.3

14

.2 -

19

.1V

E1

4 -

VE

19

7.7

9.5

13

.51

7.9

AE

10

- A

E1

7

3.5

- 9

.27.8

- 1

1.6

9.9

- 1

4.2

13

.6 -

18

.8V

E1

2 -

VE

20

7.8

9.7

13

.41

7.8

AE

10

- A

E1

6

4.7

- 9

.17.1

- 1

1.4

8.3

- 1

4.1

13

.1 -

19

.3V

E1

3 -

VE

19

8.1

9.8

13

.41

7.9

AE

10

- A

E1

7

5.5

- 8

.97.8

- 1

1.2

10.4

- 1

3.9

14

.3 -

18

.2V

E1

2 -

VE

20

8.3

10.3

13

.41

8.0

AE

10

- A

E1

7

5.6

- 8

.47.9

- 1

0.7

10.3

- 1

3.4

13

- 1

8V

E1

2 -

VE

20

8.3

10.3

13

.31

7.9

AE

10

- A

E1

7

5.8

- 8

.47.9

- 1

0.4

9.1

- 1

3.3

13

.7 -

18

.4V

E1

2 -

VE

20

34

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°49'2

1.9

01"W

29

°96

'33.2

56"N

35

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°48'4

4.7

01"W

29

°98

'39.2

73"N

36

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°47'5

7.4

34"W

29

°10

1'3

1.2

59"N

31

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°50'5

5.1

82"W

29

°91

'17.6

33"N

32

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°50'2

2.3

83"W

29

°93

'14.4

94"N

33

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°50

'4.8

08"W

29

°94

'11.9

77"N

28

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°52'3

5.6

11"W

29

°86

'30.9

95"N

29

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°52

'2.3

96"W

29

°87

'19.1

31"N

30

Fro

m G

ulf

of

Mex

ico

cross

es W

est

Bay

an

d

exte

nd

s in

lan

d

94

°51'3

7.4

41"W

29

°88

'48.1

61"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.2

10.0

13

.41

8.1

AE

11

- A

E1

4

6.6

- 8

.48 -

10.5

9.8

- 1

3.4

13

.7 -

18

.1V

E1

4 -

VE

19

8.2

9.9

13

.21

7.9

AE

11

- A

E1

4

6.1

- 8

.38.0

- 1

0.3

10.2

- 1

3.2

14

.3 -

17

.9V

E1

3 -

VE

20

8.3

10.2

13

.11

7.9

AE

10

- A

E1

7

7.0

- 8

.48.2

- 1

0.5

11.1

- 1

3.3

14

.7 -

17

.9V

E1

2 -

VE

20

8.3

10.2

13

.11

7.8

AE

11

, A

E1

4

6.5

- 8

.48.7

- 1

0.5

10.6

- 1

3.7

14

.5 -

18

.6V

E1

3

VE

16

-

VE

20

8.3

10.2

13

.01

7.7

AE

10

- A

E1

7

7.3

- 8

.58.9

- 1

0.9

11.1

- 1

3.5

14

.5 -

18

.5V

E1

2 -

VE

20

8.3

10.2

12

.91

7.6

AE

13

7.2

- 8

.38.7

- 1

0.5

10.8

- 1

3.0

14

.3 -

17

.7V

E1

4 -

VE

20

8.3

10.5

13

.01

7.5

7.2

- 8

.38.7

- 1

0.5

10.7

- 1

2.9

14

.3 -

17

.4V

E1

4 -

VE

20

8.8

11.2

13

.91

8.6

AE

10

- A

E1

7

7.0

- 8

.88.6

- 1

1.3

10.6

- 1

3.8

14

.1 -

18

.6V

E1

2 -

VE

20

43

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°45'1

2.9

25"W

29

°13

2'3

0.3

99"N

44

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°43'3

4.9

63"W

29

°13

5'1

1.1

78"N

40

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°45'4

9.8

26"W

29

°11

0'4

8.2

01"N

41

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°45

'3.8

78"W

29

°11

3'5

1.8

01"N

42

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°44'1

3.2

21"W

29

°11

7'6

.319"N

37

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and e

xte

nd

s to

Dik

e

Ro

ad

94

°47

'8.4

33"W

29

°10

4'5

3.1

82"N

38

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°46'3

8.8

13"W

29

°10

7'1

9.7

26"N

39

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°46'1

3.2

41"W

29

°10

9'1

5.9

5"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.8

11.3

13

.91

8.8

AE

12

- A

E1

5

6.8

- 8

.98.2

- 1

1.5

9.9

- 1

41

3.4

- 1

8.8

VE

12

- V

E2

0

8.7

11.3

13

.91

8.8

AE

12

- A

E1

5

6.0

- 9

.07.4

- 1

1.4

9.3

- 1

3.9

13

.1 -

18

.8V

E1

2 -

VE

20

8.7

11.2

13

.91

8.7

AE

10

- A

E1

7

6.1

- 8

.87.6

- 1

1.5

9.2

- 1

4.2

12

.8 -

19

.3V

E1

2 -

VE

20

8.7

11.2

13

.81

8.6

AE

11

- A

E1

3

5.3

- 9

.07.6

- 1

1.4

8.9

- 1

3.8

12

.7 -

18

.6V

E1

2 -

VE

19

8.6

11.2

13

.81

8.6

AE

10

- A

E1

7

5.4

- 8

.87.2

- 1

1.3

9.3

- 1

4.0

12

.5 -

18

.9V

E1

2 -

VE

20

8.6

11.2

13

.71

8.5

AE

11

- A

E1

3

5.3

- 8

.77.7

- 1

1.3

7.7

- 1

3.9

12

.5 -

18

.9V

E1

2 -

VE

19

8.6

11.1

13

.71

8.3

AE

10

5.6

- 8

.67.6

- 1

1.2

9.1

- 1

3.6

12

.5 -

18

.3V

E1

2 -

VE

19

8.6

11.1

13

.71

8.3

AE

10

- A

E1

7

5.4

- 8

.67.6

- 1

1.3

9.1

- 1

3.7

12

.4 -

18

.3V

E1

2 -

VE

20

8.5

11.1

13

.61

8.1

AE

10

, A

E1

2-A

E1

5

5.1

- 8

.66.3

- 1

1.3

8.7

- 1

3.8

12

.0 -

18

.7V

E1

2 -

VE

19

52

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°39'3

7.2

73"W

29

°15

7'1

2.4

98"N

53

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°38'3

9.5

48"W

29

°16

0'1

6.2

27"N

49

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°41'3

1.0

21"W

29

°15

0'0

.801"N

50

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°40'5

5.1

31"W

29

°15

2'3

5.0

92"N

51

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°40

'4.6

77"W

29

°15

5'4

1.4

46"N

46

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°42'5

3.6

43"W

29

°14

1'5

2.7

1"N

47

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°42'2

1.6

45"W

29

°14

5'3

6.9

75"N

48

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

to

the

cou

nty

bo

un

dar

y

94

°41'5

4.9

53"W

29

°14

8'0

.309"N

45

Fro

m G

ulf

of

Mex

ico

cross

es G

alves

ton

Bay

and

ex

ten

ds

inla

nd

94

°43'1

4.8

82"W

29

°13

8'4

6.3

66"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.5

11.1

13

.61

8.0

AE

10

- A

E1

4

5.4

- 8

.56.9

- 1

1.3

9.0

- 1

3.7

12

.1 -

18

.4V

E1

3 -

VE

19

8.5

11.1

13

.61

7.8

AE

11

5.6

- 8

.56.8

- 1

1.2

9.0

- 1

3.6

12

.0 -

18

.1V

E1

2 -

VE

19

8.4

11.1

13

.61

7.7

AE

10

- A

E1

7

5.3

- 8

.57.3

- 1

1.2

9.1

- 1

3.6

12

.0 -

17

.7V

E1

2 -

VE

20

8.4

11.1

13

.61

7.5

AE

10

- A

E1

7

4.8

- 8

.46.9

- 1

1.3

9.1

- 1

3.7

12

.3 -

17

.9V

E1

2 -

VE

20

8.3

11.1

13

.61

7.4

AE

10

- A

E1

7

5.3

- 8

.47.4

- 1

1.3

9.3

- 1

3.8

12

.5 -

17

.8V

E1

2 -

VE

20

8.3

11.1

13

.61

7.3

5.2

- 8

.37.5

- 1

1.2

9.5

- 1

3.6

12

.8 -

17

.5V

E1

2 -

VE

19

8.3

11.1

13

.71

7.2

AE

10

- A

E1

7

4.8

- 8

.37.6

- 1

1.1

9.6

- 1

3.6

13

.0 -

17

.2V

E1

2 -

VE

20

8.2

11.0

13

.61

7.2

5.2

- 8

.27.8

- 1

19.9

- 1

3.6

13

.3 -

17

.1V

E1

4 -

VE

19

8.2

11.0

13

.61

7.1

5.2

- 8

.28 -

11

10.1

- 1

3.6

13

.6 -

17

.1V

E1

4 -

VE

19

61

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°30'1

9.3

81"W

29

°18

1'4

9.2

59"N

62

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°29'4

3.6

28"W

29

°18

3'9

.895"N

58

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°33'1

4.7

48"W

29

°17

4'4

4.9

86"N

59

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°32'1

9.1

76"W

29

°177'2

.33"N

60

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°31'1

3.2

78"W

29

°17

9'4

0.2

42"N

55

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°36

'57.5

8"W

29

°16

5'1

4.4

35"N

56

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°35'4

9.6

11"W

29

°16

8'1

7.9

63"N

57

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°34'2

4.1

18"W

29

°17

1'5

6.6

45"N

54

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°37'5

8.3

75"W

29

°16

2'2

2.8

93"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.2

10.9

13

.61

7.1

5.1

- 8

.27.9

- 1

110.1

- 1

3.5

13

.6 -

17

VE

14

- V

E1

9

8.2

11.0

13

.71

7.2

AE

10

- A

E1

7

5.1

- 8

.27.5

- 1

110 -

13

.61

3.6

- 1

7.2

VE

12

- V

E2

0

8.1

11.0

13

.71

7.3

AE

10

- A

E1

7

5.2

- 8

.18.2

- 1

110.3

- 1

3.6

14

.1 -

17

.3V

E1

2 -

VE

20

8.1

11.0

13

.81

7.4

AE

11

- A

E1

2

5.1

- 8

.18.3

- 1

1.0

10.5

- 1

3.7

14

.3 -

17

.3V

E1

7 -

VE

19

7.5

10.6

13

.71

7.5

AE

10

- A

E1

7

5.0

- 8

.18.3

- 1

1.1

10.5

- 1

3.7

14

.4 -

17

.4V

E1

2 -

VE

20

7.3

10.5

13

.71

7.5

AE

10

- A

E1

7

5.0

- 8

.18.1

- 1

1.2

10.8

- 1

3.6

15

- 1

7.6

VE

12

- V

E2

0

7.4

10.8

13

.81

8.3

4.9

- 8

.17.8

- 1

1.1

10.6

- 1

3.7

14

.8 -

18

.5V

E1

3 -

VE

19

69

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

94

°23'4

4.5

65"W

29

°19

6'4

1.7

26"N

67

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

94

°25

'43.5

2"W

29

°19

2'1

1.8

62"N

68

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

94

°24'4

4.4

61"W

29

°19

4'2

4.6

96"N

64

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°28'2

4.0

86"W

29

°18

6'1

4.0

19"N

65

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°27'3

2.3

82"W

29

°18

8'1

.713"N

66

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

94

°26'4

3.7

35"W

29

°18

9'5

4.2

73"N

63

Fro

m G

ulf

of

Mex

ico

cross

es E

ast

Bay

to

th

e

cou

nty

bo

un

dar

y

94

°29

'7.9

31"W

29

°18

4'3

3.7

02"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

7.9

11.3

14

.11

8.1

AE

12

- A

E1

5

5.0

- 8

.08.4

- 1

1.4

10.8

- 1

4.3

14

.9 -

18

.8V

E1

4 -

VE

19

8.1

11.2

14

.01

7.8

AE

10

- A

E1

7

4.7

- 8

.18.1

- 1

1.2

10.8

- 1

4.1

15

.3 -

18

.5V

E1

2 -

VE

20

8.0

*11.0

*13

.8*

17

.8*

6.4

- 6

.410.2

- 1

0.2

12.6

- 1

2.7

16

.6 -

16

.7V

E1

5

8.0

10.1

12

.51

6.0

AE

12

- A

E1

6

7.1

- 8

.79.5

- 1

1.4

11.3

- 1

5.2

15

.9 -

20

.3V

E1

5 -

VE

18

8.2

10.4

12

.71

6.2

AE

12

- A

E1

6

6.5

- 9

.29.5

- 1

1.6

11.9

- 1

5.2

16

.1 -

20

.2V

E1

6 -

VE

18

8.5

10.6

13

.01

6.7

AE

12

- A

E1

6

7.4

- 9

.39.9

- 1

1.8

12.2

- 1

4.5

16

.6 -

18

.8V

E1

5,

VE

17

, V

E1

8

8.8

11.0

13

.51

7.4

AE

14

- A

E1

5

4.7

- 9

.110.0

- 1

1.6

12.1

- 1

4.3

17

.3 -

19

.6V

E1

5,

VE

17

, V

E1

8

8.4

10.5

13

.01

6.8

AE

10

- A

E1

7

6.9

- 8

.510 -

10.7

11.8

- 1

3.4

16

.8 -

17

.6V

E1

2 -

VE

20

8.3

10.4

12

.81

6.7

AE

14

8.3

- 8

.510.4

- 1

0.8

12.2

- 1

3.2

16

.7 -

17

.5V

E1

4,

VE

20

71

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

94

°22'1

9.8

51"W

29

°19

9'4

8.3

14"N

70

94

°53'4

2.3

15"W

29

°11

1'4

9.6

6"N

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

73

94

°21'2

2.7

61"W

29

°20

1'5

5.3

96"N

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

72

Fro

m G

ulf

of

Mex

ico

cro

sses

In

trac

oas

tal

Wat

erw

ay t

o t

he

cou

nty

bo

un

dar

y

94

°22'5

9.4

77"W

29

°19

8'2

3.0

77"N

74

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53'3

3.2

53"W

29

°11

3'5

3.6

18"N

75

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53'5

3.6

26"W

29

°11

9'2

5.8

76"N

76

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°54'2

5.5

15"W

29

°12

6'2

9.7

99"N

77

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53'3

0.4

98"W

29

°12

7'1

.014"N

78

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°52'5

7.6

62"W

29

°12

9'3

6.5

49"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

8.2

10.1

12

.51

6.3

AE

12

, A

E1

4,

AE

15

5.9

- 8

.39.4

- 1

0.5

11.1

- 1

3.0

16

.2 -

21

.9V

E1

5,

VE

19

8.1

10.1

12

.51

6.2

AE

5

8.0

- 8

.19.9

- 1

0.1

10.8

- 1

2.5

16

.2 -

16

.2V

E1

5,

VE

17

7.8

9.8

12

.21

5.9

AE

10

- A

E1

7

7.8

- 8

.09.7

- 9

.911.5

- 1

2.2

15

.9 -

15

.9V

E1

2 -

VE

20

7.9

9.7

12

.21

5.6

AE

10

- A

E1

7

7.7

- 7

.92.0

- 9

.82.4

- 1

2.2

15

.6 -

15

.7V

E1

2 -

VE

20

7.8

9.4

11

.91

5.5

AE

10

- A

E1

7

7.7

- 7

.92.0

- 9

.62.3

- 1

1.9

15

.5 -

15

.5V

E1

2 -

VE

20

7.7

8.9

11

.81

5.2

AE

14

, A

E1

5

7.6

- 7

.82.1

- 9

.62.5

- 1

4.0

15

.2 -

18

.7V

E1

7 -

VE

19

7.8

8.3

11

.91

5.3

AE

5

7.8

- 7

.92.0

- 9

.62.1

- 1

1.9

15

.3 -

15

.3V

E1

7 -

VE

18

8.0

9.6

12

.01

5.4

AE

5

7.9

- 8

.02.1

- 9

.82.5

- 1

2.0

15

.4 -

15

.4V

E5

, V

E6

,

VE

17

-VE

18

8.0

9.8

12

.21

5.6

AE

5

8.0

- 8

.19.8

- 1

0.0

3.1

- 1

2.4

15

.6 -

15

.8V

E1

7,

VE

19

, V

E2

0

8.4

10.5

13

.01

6.6

AE

10

- A

E1

7

7.0

- 8

.69.3

- 1

1.1

11.8

- 1

4.3

16

.6 -

19

.5V

E1

2 -

VE

20

8.3

10.3

12

.91

6.4

AE

10

- A

E1

7

8.0

- 8

.39.0

- 1

0.5

11.1

- 1

3.1

15

.7 -

18

.1V

E1

2 -

VE

20

7.8

9.5

11

.91

5.4

AE

12

- A

E1

3

7.4

- 8

.08.4

- 9

.910.9

- 1

2.6

14

.5 -

16

.7V

E1

7 -

VE

19

7.5

9.3

11

.41

4.6

AE

12

- A

E1

6

7.5

- 8

.96.5

- 1

1.2

10.8

- 1

3.9

14

.6 -

19

.2V

E1

5 -

VE

17

79

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°51'5

2.2

14"W

29

°13

3'3

2.7

05"N

80

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53'1

3.9

59"W

29

°14

2'4

1.0

00"N

81

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53'1

9.4

33"W

29

°14

8'2

5.7

45"N

82

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53'2

1.3

06"W

29

°15

2'4

.351"N

83

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°53

'28.0

4"W

29

°15

4'1

.151"N

84

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°54

'49.4

5"W

29

°15

9'4

4.9

21"N

85

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°54'5

4.9

36"W

29

°16

0'1

.913"N

86

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°55'1

9.2

87"W

29

°16

1'1

4.8

58"N

87

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°55'3

9.3

36"W

29

°16

4'2

0.1

46"N

88

Fro

m D

ickin

son

Bay

exte

nd

s in

lan

d

94

°57'1

5.8

82"W

29

°16

8'3

5.7

48"N

89

Fro

m D

ickin

son

Bay

exte

nd

s in

lan

d

94

°56'3

1.0

23"W

29

°17

2'3

0.4

66"N

90

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°54'4

6.5

35"W

29

°17

6'1

.668"N

91

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°55

'3.4

15"W

29

°17

8'5

9.4

6"N

Tab

le 4

- C

oast

al

Tra

nse

ct D

ata

(C

on

tin

ued

)

10%

-Annual

-

Chan

ce

2%

-Annual

-

Chan

ce

1%

-An

nu

al-

Ch

ance

0.2

%-A

nn

ual

-

Ch

ance

Sta

rtin

g S

till

wat

er E

levat

ions

(fee

t N

AV

D 8

8)

Zo

ne

Des

ign

atio

n

and

BF

E (

feet

NA

VD

88

)

Ran

ge

of

Sti

llw

ater

Ele

vat

ions

(fee

t N

AV

D 8

8)

Tra

nse

ctD

escr

ipti

on

Lat

itu

de

& l

ongit

ude

at S

tart

of

Tra

nse

ct

1F

rom

Gu

lf o

f M

exic

o

cross

es W

est

Bay

to

th

e

cou

nty

bo

un

dar

y

95

°7'1

3.8

"W

29

°4'3

7.3

47"N

7.7

9.5

11

.81

5.2

AE

12

- A

E1

6

7.3

- 8

.68.8

- 1

1.1

10.8

- 1

4.4

15

.1 -

19

.7V

E1

6 -

VE

17

7.9

9.8

12

.11

5.4

AE

13

- A

E1

6

7.9

- 7

.99.8

- 9

.89.4

- 1

4.5

15

.3 -

19

.6V

E1

7

8.1

10.1

12

.41

5.6

AE

13

- A

E1

5

8.1

- 8

.110.1

- 1

0.1

12.3

- 1

4.4

15

.4 -

20

.1V

E1

9

8.2

10.3

12

.71

5.9

AE

10

- A

E1

7

8.2

- 8

.210.3

- 1

0.3

12.5

- 1

4.0

15

.9 -

17

.6V

E1

2 -

VE

20

8.3

10.5

12

.91

6.1

AE

13

- A

E1

4

8.3

- 8

.310.5

- 1

0.5

12.9

- 1

4.0

16

.1 -

16

.1V

E1

9

8.4

10.6

13

.11

6.4

AE

10

- A

E1

7

8.4

- 8

.410.6

- 1

0.6

12.6

- 1

3.1

16

.4 -

16

.4V

E1

2 -

VE

20

8.5

10.8

13

.41

6.9

AE

13

- A

E1

5

7.3

- 8

.510.4

- 1

1.3

12.8

- 1

4.3

16

.0 -

19

.7V

E1

9

8.6

10.5

13

.61

7.2

AE

10

- A

E1

7

8.3

- 9

.010.5

- 1

1.9

13.5

- 1

4.5

16

.5 -

18

.1V

E1

2 -

VE

20

*S

tart

ing s

till

wat

er e

levat

ion

fo

r tr

anse

ct d

oes

not

lie

wit

hin

this

county

92

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°56

'22.9

9"W

29

°18

0'4

3.8

62"N

93

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°57

'35.0

5"W

29

°18

2'2

9.7

2"N

94

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°58'3

5.5

28"W

29

°184'6

.58"N

98

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

95

°0'5

7.5

52"W

29

°19

5'1

6.2

72"N

99

Fro

m G

alves

ton

Bay

cro

sses

Cle

ar L

ake

exte

nd

s in

lan

d

95

°1'1

5.6

89"W

29

°19

9'2

5.9

7"N

95

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

94

°59'2

2.7

26"W

29

°18

6'1

0.3

7"N

96

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

95

°0'2

.289"W

29

°18

8'4

9.2

38"N

97

Fro

m G

alves

ton

Bay

exte

nd

s in

lan

d

95

°0'3

3.0

76"W

29

°19

1'4

3.9

65"N

Galveston

Bay

East

Bay

Gulf

of

Mexico

West

Bay

Ha

rris

Co

un

ty

Bra

zori

a

Co

un

ty

Ga

lves

ton

Co

un

ty

Ch

am

ber

s

Co

un

ty

Ch

am

ber

s

Co

un

tyJef

fers

on

Co

un

ty

Ga

lves

ton

Co

un

ty

Ga

lves

ton

Co

un

ty

� � �45

Je

ffers

on

!(44!(4

5

!(41

!(40

!(42

!(24

!(23

!(22

!(21

!(25

!(39

!(26

!(12

!(17

!(16

!(15

!(27

!(28

!(14

!(19

!(43

!(20

!(30

!(47

!(49

!(73

!(31

!(34

!(32

!(35

!(75

!(36

!(33

!(93

!(50

!(94

!(91

!(95

!(83

!(37

!(82

!(51

!(84

!(92

! (88

!(53

!(54

!(55

!(56

!(59

!(57

!(58

!(60

!(96

!(76

!(110

!(86

!(85

!(79

!(69

!(70

!(87

!(98 !(1

1

!(71

!(99

!(10

!(72

!(65

!(61

!(64

!(66

!(9

!(62

!(67

!(8

!(63

!(78

!(77

!(68

!(7

!(90

!(108

!(6

!(109

!(97

!(5

!(4

!(3

!(89

!(2

!(1

!(81 !(80

!(101

!(100

!(38

!(13

!(46

!(29

!(18

!(74

!(48

!(52

!(111

!(102

!(107

!(104

!(106

!(105

!(103

FIGURE 2

FE

DE

RA

L E

ME

RG

EN

CY

MA

NA

GE

ME

NT

AG

EN

CY

GA

LV

ES

TO

N C

OU

NT

Y, T

X

AN

D I

NC

OR

PO

RA

TE

D A

RE

AS

TR

AN

SE

CT

LO

CA

TIO

N M

AP

05

10

15 M

iles

Sh

ore

line

Note

: T

ranse

cts

10

0 -

111 w

ere

in

clu

ded

fo

r ru

nup c

alc

ula

tions o

nly

an

d a

re n

ot

inclu

ded

in th

e 0

.2%

annu

al-

chan

ce a

na

lysis

.

41

3.4 Vertical Datum

All FIS reports and FIRMs are referenced to a specific vertical datum. The vertical

datum provides a starting point against which flood, ground, and structure elevations can

be referenced and compared. Until recently, the standard vertical datum in use for newly

created or revised FIS reports and FIRMs was the National Geodetic Vertical Datum of

1929 (NGVD29). With the finalization of the North American Vertical Datum of 1988

(NAVD88), many FIS reports and FIRMs are being prepared using NAVD88 as the

referenced vertical datum.

Flood elevations shown in this FIS report and on the FIRM are referenced to the NAVD.

These flood elevations must be compared to structure and ground elevations referenced to

the same vertical datum. Some of the data used in this revision were taken from the prior

effective FIS reports and FIRMs and adjusted to NAVD88. The datum conversion factor

from NGVD29 to NAVD88 in Galveston County is (+) 0.01 feet.

For additional information regarding conversion between the NGVD and NAVD, visit

the National Geodetic Survey website at www.ngs.noaa.gov, or contact the National

Geodetic Survey at the following address:

Vertical Network Branch, N/CG13

National Geodetic Survey, NOAA

Silver Spring Metro Center 3

1315 East-West Highway

Silver Spring, Maryland 20910

(301) 713-3191

Temporary vertical monuments are often established during the preparation of a flood

hazard analysis for the purpose of establishing local vertical control. Although these

monuments are not shown on the FIRM, they may be found in the Technical Support

Data Notebook associated with the FIS report and FIRM for this community. Interested

individuals may contact FEMA to access these data.

To obtain current elevation, description, and/or location information for benchmarks

shown on this map, please contact the Information Services Branch of the NGS at

(301) 713-3242, or visit their website at www.ngs.noaa.gov.

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS

The NFIP encourages State and local governments to adopt sound floodplain management

programs. To assist in this endeavor, each FIS report provides 1-percent-annual-chance

floodplain data, which may include a combination of the following: 10-, 2-, 1-, and

0.2-percent-annual-chance flood elevations; delineations of the 1- and 0.2-percent-annual-chance

floodplains; and a 1-percent-annual-chance floodway. This information is presented on the FIRM

and in many components of the FIS report, including Flood Profiles, Floodway Data tables, and

Summary of Stillwater Elevation tables. Users should reference the data presented in the FIS

report as well as additional information that may be available at the local community map

repository before making flood elevation and/or floodplain boundary determinations.

http://www.ngs.noaa.gov/

http://www.ngs.noaa.gov/

42

4.1 Floodplain Boundaries

To provide a national standard without regional discrimination, the 1-percent-annual-

chance flood has been adopted by FEMA as the base flood for floodplain management

purposes. The 0.2-percent-annual-chance flood is employed to indicate additional areas

of flood risk in the community. For each stream studied by detailed methods, the 1- and

0.2-percent-annual-chance floodplain boundaries have been delineated using the flood

elevations determined at each cross section. Between cross sections, the boundaries were

interpolated using LiDAR collected by Sanborn (Reference 35).

The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the FIRM

(Exhibit 3). On this map, the 1-percent-annual-chance floodplain boundary corresponds

to the boundary of the areas of special flood hazards (Zones A, AE, AO, VE); and the

0.2-percent-annual-chance floodplain boundary corresponds to the boundary of areas of

moderate flood hazards. In cases where the 1- and 0.2-percent-annual-chance floodplain

boundaries are close together, only the 1-percent-annual-chance floodplain boundary has

been shown. Small areas within the floodplain boundaries may lie above the flood

elevations but cannot be shown due to limitations of the map scale and/or lack of detailed

topographic data.

For the streams studied by approximate methods, only the 1-percent-annual-chance

floodplain boundary is shown on the FIRM (Exhibit 3).

4.2 Floodways

Encroachment on floodplains, such as structures and fill, reduces flood-carrying capacity,

increases flood heights and velocities, and increases flood hazards in areas beyond the

encroachment itself. One aspect of floodplain management involves balancing the

economic gain from floodplain development against the resulting increase in flood

hazard. For purposes of the NFIP, a floodway is used as a tool to assist local communities

in this aspect of floodplain management. Under this concept, the area of the 1-percent-

annual-chance floodplain is divided into a floodway and a floodway fringe. The

floodway is the channel of a stream, plus any adjacent floodplain areas, that must be kept

free of encroachment so that the 1-percent-annual-chance flood can be carried without

substantial increases in flood heights. Minimum Federal standards limit such increases to

1.0 foot, provided that hazardous velocities are not produced. The floodways in this

study are presented to local agencies as minimum standards that can be adopted directly

or that can be used as a basis for additional floodway studies.

The floodways presented in this study were computed for certain stream segments on the

basis of equal-conveyance reduction from each side of the floodplain. Floodway widths

were computed at cross sections. Between cross sections, the floodway boundaries were

interpolated. The results of the floodway computations are tabulated for selected cross

sections (see Table 5, Floodway Data on page 44). In cases where the floodway and 1-

percent-annual-chance floodplain boundaries are either close together or collinear, only

the floodway boundary has been shown.

The area between the floodway and 1-percent-annual-chance floodplain boundaries is

termed the floodway fringe. The floodway fringe encompasses the portion of the

floodplain that could be completely obstructed without increasing the water-surface

43

elevation of the 1-percent-annual-chance flood more than 1.0 foot at any point. Typical

relationships between the floodway and the floodway fringe and their significance to

floodplain development are shown in Figure 3.

Figure 3 – Floodway Schematic

CR

OS

S S

EC

TIO

ND

IST

AN

CE

1W

IDT

H

(FE

ET

)

SE

CT

ION

AR

EA

(SQ

UA

RE

FE

ET

)

ME

AN

VE

LO

CIT

Y

(FE

ET

PE

R

SE

CO

ND

)

RE

GU

LA

TO

RY

(FE

ET

NA

VD

)

WIT

HO

UT

FL

OO

DW

AY

(FE

ET

NA

VD

)2

WIT

H

FL

OO

DW

AY

(FE

ET

NA

VD

)

INC

RE

AS

E

(FE

ET

)

Ben

son

Bay

ou A

2,9

32

58

38

35

.41

4.4

***

**

**

B4

,27

7

76

71

62

.91

4.5

***

**

**

C5

,62

8

52

60

93

.41

4.6

***

**

**

D7

,04

9

72

51

03

.31

4.7

***

**

**

E9

,80

0

73

49

23

.41

5.8

***

**

**

F1

4,1

50

4

20

1,4

17

1.2

18

.0*

**

**

**

Bo

rden

's G

ull

y A2

,56

55

84

81

2.6

14

.4*

12

.21

2.5

0.3

B3

,97

51

30

61

22

.01

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22

.62

2.6

23

.61

.0

Up

per

Hig

hla

nd

Bay

ou

A1

7,5

00

22

31

46

10

.51

4.9

*1

3.9

31

4.2

0.3

B1

8,9

04

27

54

45

3.3

20

.72

0.7

21

.00

.3

C1

9,9

04

24

42

57

5.5

21

.42

1.4

21

.90

.5

D2

0,2

30

24

73

16

4.4

22

.92

2.9

23

.20

.3

E2

2,9

30

26

12

84

4.4

25

.22

5.2

25

.50

.3

F2

3,6

30

28

22

19

5.7

26

.22

6.2

26

.50

.3

G2

4,5

30

26

13

07

4.1

28

.42

8.4

29

.30

.9

H2

5,5

01

21

86

68

31

.82

9.2

29

.23

0.2

1.0

3 E

levat

ion

com

pu

ted

wit

hou

t co

nsi

der

atio

n o

f b

ack

wat

er e

ffec

ts

*In

clu

des

coas

tal

com

bin

ed p

rob

abil

ity

FL

OO

DIN

G S

OU

RC

EF

LO

OD

WA

YB

AS

E F

LO

OD

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

1 D

ista

nce

in

fee

t ab

ove

mou

th

F

ED

ER

AL

EM

ER

GE

NC

Y M

AN

AG

EM

EN

T A

GE

NC

Y

GA

LV

ES

TO

N C

OU

NT

Y,

TX

AN

D I

NC

OR

PO

RA

TE

D A

RE

AS

FL

OO

DW

AY

DA

TA

UN

NA

ME

D T

RIB

UT

AR

Y T

O D

ICK

INS

ON

BA

YO

U (

WE

ST

BR

AN

CH

)

UP

PE

R H

IGH

LA

ND

BA

YO

U

2 F

eet

above

Sta

te H

igh

way

6.

61

5.0 INSURANCE APPLICATIONS

For flood insurance rating purposes, flood insurance zone designations are assigned to a

community based on the results of the engineering analyses. These zones are as follows:

Zone A

Zone A is the flood insurance risk zone that corresponds to the 1-percent-annual-chance

floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic

analyses are not performed for such areas, no BFEs or base flood depths are shown within this

zone.

Zone AE

Zone AE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance

floodplains that are determined in the FIS by detailed methods. In most instances, whole-foot

BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this

zone.

Zone AO

Zone AO is the flood insurance risk zone that corresponds to the 1-percent-annual-chance

shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and

3 feet. Average whole-foot base flood depths derived from the detailed hydraulic analyses are

shown within this zone.

Zone VE

Zone VE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance coastal

floodplains that have additional hazards associated with storm waves. Whole-foot BFEs derived

from the detailed hydraulic analyses are shown at selected intervals within this zone.

Zone X

Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percent-annual-

chance floodplain, areas within the 0.2-percent-annual-chance floodplain, areas of 1-percent-

annual-chance flooding where average depths are less than 1 foot, areas of 1-percent-annual-

chance flooding where the contributing drainage area is less than 1 square mile, and areas

protected from the 1-percent-annual-chance flood by levees. No BFEs or base flood depths are

shown within this zone.

6.0 FLOOD INSURANCE RATE MAP

The FIRM is designed for flood insurance and floodplain management applications.

For flood insurance applications, the map designates flood insurance risk zones as described in

Section 5.0 and, in the 1-percent-annual-chance floodplains that were studied by detailed

methods, shows selected whole-foot BFEs or average depths. Insurance agents use the zones and

62

BFEs in conjunction with information on structures and their contents to assign premium rates for

flood insurance policies.

For floodplain management applications, the map shows by tints, screens, and symbols, the 1-

and 0.2-percent-annual-chance floodplains, floodways, and the locations of selected cross

sections used in the hydraulic analyses and floodway computations.

This FIRM presents flooding information for the entire geographic area of Galveston County.

This FIRM also includes flood-hazard information that was historically presented separately on

Floodway Maps (FBFMs), where applicable. Historical data relating to the maps prepared for

each community, prior to the initial FIRM, are presented in Table 6, “Community Map History”.

CO

MM

UN

ITY

NA

ME

IN

ITIA

L ID

EN

TIF

ICA

TIO

N

FLO

OD

HA

ZA

RD

B

OU

ND

AR

Y M

AP

R

EV

ISIO

N D

AT

E(S

)

FLO

OD

IN

SU

RA

NC

E R

AT

E

MA

P E

FF

EC

TIV

E D

AT

E

FLO

OD

IN

SU

RA

NC

E R

AT

E

MA

P R

EV

ISIO

N D

AT

E(S

)

B

ayou V

ista

, V

illage o

f T

o B

e D

ete

rmin

ed

N

/A

To B

e D

ete

rmin

ed

N

/A

C

lear

Lake S

hore

s, C

ity o

f O

cto

ber

23,

19

70

N

/A

Octo

ber

23,

19

70

July

1, 1

974

A

pri

l 1

8, 1

975

A

ug

ust 4,

198

3

D

ickenson, C

ity o

f A

pri

l 8,

19

71

N

/A

Apri

l 8,

19

71

July

1, 1

974

June 2

4, 1

977

F

ebru

ary

16,

19

83

M

arc

h 4

, 199

1

F

riendsw

ood,

City o

f M

arc

h 3

, 197

2

N/A

M

arc

h 3

, 197

2

July

1, 1

974

D

ecem

ber

19, 19

75

A

pri

l 1

8, 1

983

June 3

, 19

88

S

epte

mber

22, 1

999

G

alv

esto

n C

ou

nty

A

pri

l 8,

19

71

N

/A

Apri

l 9,

19

71

M

ay 5

, 198

3

(U

nin

corp

ora

ted A

reas)

N

ovem

ber

16, 19

90

A

ug

ust 18,

19

92

July

5, 1

993

D

ecem

ber

6, 200

2

N/A

= N

ot A

pp

licab

le

TABLE 6

FE

DE

RA

L E

ME

RG

EN

CY

MA

NA

GE

ME

NT

AG

EN

CY

Galv

es

ton

Co

un

ty, T

X

An

d I

nco

rpo

rate

d A

reas

C

OM

MU

NIT

Y M

AP

HIS

TO

RY

CO

MM

UN

ITY

NA

ME

IN

ITIA

L I

DE

NT

IFIC

AT

ION

F

LO

OD

HA

ZA

RD

B

OU

ND

AR

Y M

AP

R

EV

ISIO

N D

AT

E(S

)

FL

OO

D I

NS

UR

AN

CE

RA

TE

M

AP

EF

FE

CT

IVE

DA

TE

F

LO

OD

IN

SU

RA

NC

E R

AT

E

MA

P R

EV

ISIO

N D

AT

E(S

)

G

alves

ton,

Cit

y o

f M

ay 2

6,

19

70

N

/A

May 2

6,

19

70

Ju

ly 1

, 1

97

4

O

cto

ber

3, 1

975

Ju

ne

13

, 1

980

A

ugu

st 1

5,

19

83

D

ecem

ber

6,

20

02

H

itch

cock

, C

ity o

f N

ovem

ber

17

, 1

970

N

/A

No

vem

ber

17

, 1

970

Ju

ly 1

, 1

97

4

O

cto

ber

31,

197

5

A

pri

l 4

, 1

98

3

Ja

mai

ca B

each

, V

illa

ge

of

Ap

ril

8,

19

71

N

/A

Ap

ril

8,

19

71

Ju

ly 1

, 1

97

4

Ju

ne

24

, 1

977

A

pri

l 4

, 1

98

3

D

ecem

ber

2,

20

02

K

em

ah,

Cit

y o

f Ju

ne

5,

19

70

N

/A

June

5,

19

70

Ju

ly 1

, 1

97

4

A

ugu

st 2

2,

19

75

A

pri

l 4

, 1

98

3

L

a M

arq

ue,

Cit

y o

f M

ay 2

6,

19

70

N

/A

May 2

6,

19

70

Oct

ob

er 1

6,

197

0

Ju

ly 1

, 1

97

4

O

cto

ber

17,

197

5

A

ugu

st 2

6,

19

77

O

cto

ber

6, 1

978

F

ebru

ary 1

6,

19

83

N/A

= N

ot

Ap

pli

cab

le

TABLE 6

777877

FE

DE

RA

L E

ME

RG

EN

CY

MA

NA

GE

ME

NT

AG

EN

CY

Ga

lves

ton

Co

un

ty, T

X

An

d I

ncorp

ora

ted

Area

s C

OM

MU

NIT

Y M

AP

HIS

TO

RY

CO

MM

UN

ITY

NA

ME

IN

ITIA

L I

DE

NT

IFIC

AT

ION

F

LO

OD

HA

ZA

RD

B

OU

ND

AR

Y M

AP

R

EV

ISIO

N D

AT

E(S

)

FL

OO

D I

NS

UR

AN

CE

RA

TE

M

AP

EF

FE

CT

IVE

DA

TE

F

LO

OD

IN

SU

RA

NC

E R

AT

E

MA

P R

EV

ISIO

N D

AT

E(S

)

L

eague

Cit

y,

Cit

y o

f Ju

ne

5,

19

70

N

/A

June

5,

19

70

Ju

ly 1

, 1

97

4

S

epte

mb

er 1

2,

197

5

Ju

ne

17

, 1

977

M

ay 2

, 1

98

3

S

epte

mb

er 2

2,

199

9

S

anta

Fe,

Cit

y o

f A

pri

l 8

, 1

97

1

N/A

A

pri

l 8

, 1

97

1

July

1,

19

74

Ju

ne

24

, 1

977

S

epte

mb

er 2

, 1

980

O

cto

ber

18,

198

3

T

exas

Cit

y,

Cit

y o

f Ju

ne

5,

19

70

N

/A

June

5,

19

70

Ju

ly 1

, 1

97

4

N

ovem

ber

5,

19

76

M

ay 2

, 1

98

3

M

ay 4

, 1

99

2

T

iki

Isla

nd

, V

illa

ge

of

Ap

ril

8,

19

71

N

/A

Ap

ril

8,

19

71

Ju

ly 1

, 1

97

4

Ju

ne

24

, 1

977

M

ay 2

, 1

98

3

N

ovem

ber

1,

19

85

N/A

= N

ot

Ap

pli

cab

le

TABLE 6

FE

DE

RA

L E

ME

RG

EN

CY

MA

NA

GE

ME

NT

AG

EN

CY

Ga

lves

ton

Cou

nty

, T

X

An

d I

ncorp

ora

ted

Area

s C

OM

MU

NIT

Y M

AP

HIS

TO

RY

66

7.0 OTHER STUDIES

This FIS report either supersedes or is compatible with all previous studies on streams studied in

this report and should be considered authoritative for purposes of the NFIP. This FIS is

compatible at the county boundary with new FIS in neighboring Harris County and Chambers

County, as well as, with Brazoria County with is currently being studied.

8.0 LOCATION OF DATA

Information concerning the pertinent data used in the preparation of this study can be obtained by

contacting Federal Emergency Management Agency, Region VI, Flood Insurance and Mitigation

Division, 800 North Loop 288, Denton, TX 76209.

9.0 BIBLIOGRAPHY AND REFERENCES

1. U.S. Census Bureau. State and County QuickFacts.

http://quickfacts.census.gov/qfd/states/48/48167.html. 27 Oct. 2011.

2. U.S. Department of Commerce, National Oceanic and Atmospheric Administration,

Climatography of the United States No. 81, Monthly Normals of Temperature, Precipitation,

and Heating and Cooling Degree Days 1941 - 1970, Asheville, North Carolina, National

Climatic Center, August 1973.

3. U.S. Department of the Interior, Geological Survey, Texas Water Development Board Report

No. 188, Land-Surface Subsidence in the Houston-Galveston Region, Texas, February 1975,

Second Printing January 1977.

4. U. S. Army Corps of Engineers, Galveston District, Texas Coast Hurricane Study, March

1979.

5. U.S. Army Corps of Engineers, Galveston District, Report on Hurricane Carla, 9-12

September 1961, January 1962.

6. Federal Emergency Management Agency, Flood Insurance Study, City of Galveston,

Galveston County. Texas, Washington, D. C., May 4, 1992.

7. University of Texas, Bureau of Economic Geology, Natural Hazards of the Texas Coastal

Zone by L. F. Brown, Jr., et al., in cooperation with the Texas Coastal Marine Council,

Austin, Texas, 1974.

8. Galveston Daily News, Houston Chronicle, Houston Post, news clippings compiled for

storms of 1900, 1915, 1919, 1942, 1949, 1957, 1961, 1970, and 1979.

9. U.S. Army Corps of Engineers, Galveston District, Texas City. Texas. Hurricane Flood

Protection, Various Design Memoranda and Operation and Maintenance Manuals; various

dates.

10. University of Texas, Bureau of Economic Geology, Environmental Geologic Atlas of the

Texas Coastal Zone: Galveston-Houston Area, 1972.

http://quickfacts.census.gov/qfd/states/48/48167.html

67

11. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Weather

Bureau, Technical Paper No. 48, Characteristics of the Hurricane Storm Surge, by D. Lee

Harris, Washington, D.C., 1963.

12. National Oceanic and Atmospheric Administration, http://www.ncdc.noaa.gov.

13. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-1 Flood Hydrograph

Package, Davis, California, January 1973.

14. U.S. Department of Agriculture, Soil Conservation Service, Generalized Soils Map for

Galveston County, Washington, D. C., November 1970.

15. U.S. Department of Agriculture, Soil Conservation Service, Generalized Soils Map for

Brazoria County, Washington, D. C., June 1977

16. U.S. Department of the Interior, Geological Survey, 7.5-Minute Series Topographic Maps,

Scale 1:24,000, Contour Interval 5 Feet: Friendswood, Texas, 1943-55, Photorevised 1969;

Algoa, Texas, 1956, Photorevised 1974; Bacliff , Texas, 1956, Photorevised 1969; Caplen,

Texas, 1954, Photorevised 1969; Dickinson, Texas,1955, Photorevised 1974; Friendswood,

Texas, 1955, Photorevised 1969; Frozen Point, Texas, 1962; Galveston, Texas, 1954,

Photorevised 1974; High Island, Texas, 1962; Hitchcock, Texas, 1964, Photorevised 1974;

Lake Como, 1954, Photorevised 1974; League City, 1953, Photorevised 1969; Mud Lake,

Texas, 1961; Mustang Bayou, Texas, 1963, Photorevised 1974; Pitchcock, Texas, 1964,

Photorevised 1974; Port Bolivar, 1954, Photorevised 1974; San Luis Pass, Texas, 1963; Sea

Isle, Texas, 1963, Photorevised 1974; Texas City, Texas, 1954, Photorevised, 1974; the

Jetties, Texas, 1954, Photorevised 1974; Unpublished; League City, Texas, Unpublished;

Pearland, Texas, Unpublished; Virginia Point, Texas, 1954, Photorevised, 1974.

17. Tetra Tech, Inc., Aerial Maps, Scale 1:9,600, December 1978.

18. University of Texas, Department of Civil Engineering, Technical Report CRWR-160, An

Urban Runoff Model for Tulsa, Oklahoma by L. R. Beard and S. Chang, Austin, Texas,

August 1978.

19. Beard, Leo R., and S. Chang, "Urbanization Impact on Streamflow," in Journal of the

Hydraulic Division, ASCE, HY6, June 1979.

20. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Deck

488, Hourly Precipitation 1948-1975, Asheville, North Carolina, National Climatic Center.

21. U.S. Department of Commerce, Weather Bureau, Technical Paper No. 40, Rainfall Frequency

Atlas of the United States, Washington, DC, 1961.

22. U.S. Army Corps of Engineers, Galveston District, Clear Creek Flood Control Study,

Development of Existing Watershed Conditions, Hydrology and Hydraulics, Galveston,

Texas, July 1981.

23. Federal Emergency Management Agency, Flood Insurance Study, Unincorporated Areas of

Brazoria County, Texas (Unpublished).

http://www.ncdc.noaa.gov/

68

24. U.S. Department of Agriculture, Soil Conservation Service, Technical Release No. 55, Urban

Hydrology for Small Watersheds, Washington, D. C., January 1975.

25. U.S. Department of Agriculture, Soil Conservation Service, National Engineering Handbook,

Section 4, Hydrology, Washington, D. C., August 1982.

26. Tetra Tech, Inc., Aerial Maps, Scale 1:9600, December 1978.

27. Beard, L.R. and S. Chang, An Urban Runoff Model for Tulsa, Oklahoma, Technical Report

CRW R-160, Department of Civil Engineering, University of Texas, Austin, Texas, August

1978.

28. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National

Climatic Center, Deck 488, Hourly Precipitation, 1948- 1975.

29. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-2 Water Surface

Profiles, Generalized Computer Program, Davis, California, April 1984.

30. U.S. Department of the Interior, Geological Survey, Water-Supply Paper 1849, Roughness

Characteristics of Natural Channels by Harry H. Barnes; Jr., Washington, D. C. 1967.

31. Ernest F. Brater and Horace Williams King, Handbook of Applied Hydrology, Sixth Edition,

New York, McGraw-Hill, 1976.

32. Technical Advisory Committee for Water Retaining Structures, Technical Report – Wave

Run-up and Overtopping at Dikes, Van der Meer, J.W., Delft, The Netherlands, May 2002.

33. ACES, Coastal Engineering Design & Analysis System, Version 4.03, integrated collection

of coastal engineering design and analysis software. Veri-Tech, 2012.

34. Federal Emergency Management Agency (FEMA) Wave Height Analysis for Flood

Insurance Study (WHAFIS) program, Version 4.0, August 10, 2007.

35. LiDAR Data. Collected by Sanborn, 2005.

36. U.S. Department of Agriculture, Farm Service Agency, National Agriculture Imagery

Program, (NAIP), 2010.

37. U.S. Fish and Wildlife Service, National Wetland Inventory, 1:65,000m scale, 1992; 1:1m

scale, 2006, http://www.fws.gov/Wetlands/Data/Products.html

38. National Oceanographic and Atmospheric Administration, Coastal Change Analysis

Program (C-CAP), 2005, http://www.csc.noaa.gov/digitalcoast/data/ccapregional/

39. Federal Emergency Management Agency, Atlantic Ocean and Gulf of Mexico Coastal

Guidelines Update, Final Draft, Washington, D.C., 2007.

40. U.S. Army Corps of Engineers. Flood Insurance Study: Coastal Counties, Texas Intermediate

Submission 2 – Scoping and Data Review. November 15, 2011.

http://www.fws.gov/Wetlands/Data/Products.html

http://www.csc.noaa.gov/digitalcoast/data/ccapregional/

Documents

GALVESTON COUNTY, TEXAS,