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Assignment 2- RORB modell ing
Due date: 26 September 2014
Weighting: 25% (250 marks)
1. Overview
This assessment is designed to test your achievement of course objectives 4 to 8 focussing on model
calibration and runoff routing modelling. This assignment is divided into three main activities:
1. Familiarisation with RORB software –described in Section 2
2. Calibration of RORB for the Spring Creek catchment – described in Section 3
3. Application of RORB to estimate design discharges at a road crossing - described in Section 4
Details of the submission requirements for Assignment 2, as well as how the assignment will be
marked, is described in Section 5.
2. Familiarisation with the RORB model
Some students may have been previously introduced to the basic principles of runoff routing in
completing ENV3105 Hydrology Module 6. Runoff routing involves the prediction of how a
discharge hydrograph is modified by storage available within the catchment and waterway system.
These hydrograph changes include potential reduction of the discharge peak (attenuation) and time
delay of the peak (lag or translation).
RORB is a runoff routing model commonly used in Australia. Download the RORB software
(Version 6) from the SKM website and install. The RORB User Guide (Laurenson et al, 2007) is
provided with the software download.
Read through the RORB User Guide, with close attention to the following Chapters:
1. Chapter 2 (and Appendix A) which present the concepts and hydrological theory behind the
RORB model
2. Chapter 3 which documents runoff generation and routing processes represented in the RORB
model
3. Chapter 7 which provides information on the operation of the RORB model
The Monte Carlo feature of the RORB model will not be utilised in this Assignment.
2.1 RORB Familiarisation Activity – South Creek
This activity is assessable and is included as a way for you to trial the RORB software before
embarking on the full calibration and application exercise (See Sections 3and 4). Refer to Section 5
on the submission requirements for this part of the assignment.
The familiarisation activity is based on the South Creek worked example outlined in Chapter 10.4 of
the RORB User Manual. A more detailed activity based on the South Creek example is provided in a
separate document prepared for ENV4107. Access the file RORB Worked Example from USQ
StudyDesk or the course CD and work through the instructions given in Section 3 of this document.
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(A technical background of the RORB model is also provided in Section 2 to supplement the material
contained in the RORB User Manual).
To demonstrate your familiarisation of the RORB model, complete the following:
1. Rerun the calibration storm using m=0.75 instead of m=0.8. Retain kc=16 and IL=0mm. Plot
the hydrograph. Describe the effect of reducing the m value. Why has this occurred?
2. Rerun the final detention basin configuration (7x2400mm pipes) with Unfiltered temporal
patterns and an Areal Reduction Factor based on AR&R. Plot the predicted hydrographs and
report the estimated peak basin water levels. Are the results significantly different to the run
using Filtered patterns and ARF=1?
3. RORB Model – Spring Creek
This part of the assignment involves the setup up and calibration of a RORB model for Spring Creek
at Killarney (GS 422321B). Details of the streamgauge can be found at the QDERM Watershed
website. The RORB model will be calibrated to flood hydrograph data obtained for a selected
historical event.
The calibrated RORB model will then be applied to estimate design discharges at a proposed road
crossing close to the streamgauge site (refer Section 4). These design discharges will be used to
provide a flood risk assessment at the road crossing as part of Assignment 3.
3.1 RORB Data and Resources
Data and resources compiled in order to complete the RORB modelling are listed in Table 1 and are
provided on StudyDesk or can be downloaded from external websites.
Table 1: Data and resources to setup and calibrate RORB model
Description File name
Extract from 1:100000 Warwick map covering
the Spring Creek region
Topographic Map available at StudyDesk
6-minute pluviograph data 41056 Killarney
Post Office
Download from StudyDesk
Daily rainfall data Download from BOM Climate Online
Streamflow discharge hydrograph data Download from QDERM Watershed
website (recommend obtain 15 minute data)
Reference is made to the Queensland Urban Drainage Manual (QUDM) which can be downloaded
from: http://www.dews.qld.gov.au/water-supply-regulations/urban-drainage
3.2 Setup and Calibration Scope
The following scope tasks are recommended to firstly setup and then calibrate the RORB model.
1. Setup the RORB model
2. Select calibration flood based on data quality assessment
3. Calibrate the RORB model
4. Document your work as a report
Setup the RORB model Prepare a RORB catchment file (*.cat or *.catg) for the Spring Creek catchment upstream of the
Killarney streamgauge. It is recommended that the catchment be split into at least 8 to 12 sub-areas of
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roughly equal shape and size. The centroid of each sub-area can be located by visual estimation. If
the centroid is located substantially from the main stream, the additional overland flowpath from the
centroid must be included in the reach length estimate. Provide a catchment plan showing nodes and
subarea boundaries.
The purpose of the RORB model is to estimate design discharges at a proposed road crossing located
close to the streamgauge. You will be preparing a preliminary design of the crossing in Assignment
3.
Select Calibration Flood The Spring Creek streamgauge has operated since 1972 and has recorded discharges for many flood
events. Several top-ranking floods based on the streamflow record are summarised in Table 2.
Table 2: Recorded top-ranked floods at GS 422306A
Rank Occurred during month Peak recorded discharge (m3/s)
1 5/01/2008 142
2 11/01/2011 132
3 27/01/2013 97
4 6/05/1996 84
5 27/12/2010 63
The RORB is to be calibrated against one of the floods reported in Table 2. It is normal practice to
validate RORB (and other similar models) against a range of flood events, but this is outside the scope
of this student assignment
Select one historical flood event for RORB calibration noting:
1. Use the Killarney Post Office pluviograph data to define rainfall temporal patterns for
historical flood events (refer Table 1).
2. Daily-read rain gauge data can be used to identical the spatial distribution of total storm
rainfall across the catchment. The location and availability of local rain gauges can be
obtained from the BOM Climate Online website. Select a flood event that has a reasonable
coverage of rainfall data
3. Streamgauge data recorded for each flood has been quality coded so you should take this into
account
After selecting the historical flood, undertake the following checks on the data suitability for use in
RORB calibration:
1. Prepare timeseries plots overlaying the rainfall hyetograph and the observed streamflow
hydrograph. Visually check for any unrealistic data values or potential timing problems
within the data.
2. Estimate the average total rainfall over the catchment and the equivalent runoff depth
expressed as mm (from the streamflow hydrograph, alternatively daily streamflow volumes
can be extracted from the QDERM website) – the volumetric runoff coefficient based on the
ratio of runoff to rainfall should be a realistic figure.
Prepare a storm file (*.stm) for the selected storm event. Linear interpolation of the observed rainfall
depths may be used to estimate the total storm rainfall for each sub-area. Alternatively, prepare a
rainfall isohyetal map for the storm as a way to determine the rainfall at each subarea centroid.
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Calibrate the RORB model Utilise the FIT run feature of RORB to obtain values of kc and m that produce the best fit between
predicted and observed flood hydrographs. Use an initial and continuing loss rate that represent the
catchment conditions at the start of the storm and provides a reasonable match in recorded and
estimated flood event volume at the streamgauge.
Reporting Refer to Section 5 for reporting requirements for Assignment 2.
4. RORB Application – Proposed road crossing
4.1 Design Discharges for Proposed Road Crossing
A hydraulic analysis is to be done separately in Assignment 3 as part of a flood risk assessment of the
proposed crossing. This part of Assignment 2 is a hydrologic analysis only to establish the design
discharges for the crossing site. The following flood design discharges will apply to the road crossing:
1. A 10 year ARI Minor design event – this discharge should be able to be handled by the road
culverts without overtopping of the roadway
2. A 100 year ARI Major design event – the roadway can be overtopped during this event but
the road flow condition should be safe and trafficable
The selection of Minor and Major design floods are consistent with the recommendations in QUDM
for a minor road.
4.2 Application Scope
The following broad methodology is recommended to apply the calibrated RORB model:
1. Estimate Minor and Major design discharges at the road crossing
2. Undertake sensitivity analysis
3. Conduct a sanity check of the RORB outputs
4. Document your work as a report
Estimate Minor and Major Design Discharges The Minor and Major design flood discharges (10 year ARI and 100 year ARI, respectively) should
be estimated using the calibrated RORB model noting that:
1. Design rainfalls should be applied with an areal reduction factor at the catchment centroid.
IFD parameters can be obtained using the BOM online IFD data tool.
2. Design rainfall losses should be adopted with reference to AR&R. An extract is provided in
Appendix A.
3. A range of storm durations should be analysed to identify the critical duration for the crossing
site.
RORB Sensitivity Analysis A ‘one-at-a-time’ sensitivity analysis should be done to check the predicted change in 100 year ARI
discharge estimate in response to the following:
1. A +10% and -10% change in the calibrated kc and m values
2. A +20% and -20% change in the design storm loss rates (20% was selected as the magnitude
of loss rates can easily vary by at least this amount and loss rates are a major source of
uncertainty in design flood estimation)
3. The use of filtered versus unfiltered temporal patterns
4. Spring Creek has its headwaters at the Great Dividing Range and thus close to the boundary
of two design temporal pattern zones. Rerun the RORB model to check if discharge estimates
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change significantly if the alternate set of temporal patterns is used.
Make adjustments to the design discharge estimates based on the outcomes of the sensitivity analysis.
Sanity Check of RORB outputs Do you think that the Minor and Major design discharges predicted by the RORB model are
reasonable estimates? It is recommended to use an alternative method of analysis to check the
discharges. A recommended approach is to use the regional flood frequency method developed by
Palmen and Weeks (2011).
As part of the sanity check, state the aspects of the RORB analysis that you consider would contribute
most to uncertainty in the design discharge estimates.
Reporting Refer to Section 5 for reporting requirements for Assignment 2.
5. Submission
Your submission for Assignment 2 should be in the form of a single file report. The purpose of a file
report is to provide a concise record of your work that (hypothetically) can be put on file/archived so
relevant information can be recovered at a later date. It is acceptable to use dot points to describe the
analyses.
A marking scheme is provided as Table 3. Use this marking scheme to check that you have addressed
the full scope of the work. If an element of the assignment has not been documented in the file
report than no marks will be given for that element. It is recommended that you structure your report
in such a way that each element is clearly and easily identified. Key information such as the
methodology that was used, assumptions about analysis inputs and parameters, outputs and results,
interpretation of results and recommendations should be included in the file report.
A portion of the available marks has been allocated to reward reporting that is well set out and easy to
follow. Submissions that are untidy and/or poorly structured and thus difficult to assess will attract
less marks for this element.
Electronic submission of this assignment is preferred. One ZIP file will be accepted containing:
A single pdf of the report incorporating all appendices
RORB files
The following filename convention shall be used: *Ass2.zip, *Ass2.pdf and *Ass2.xlsx, where * is
your student number.
Table 3: Assignment 2 Marking Scheme
Assignment element Marks
RORB Familiarisation
Familiarisation with the RORB model algorithms (Section 2.1) 10
RORB Model – Spring Creek
Setup the RORB model
Appropriate subareas, reach lengths and node layout 20
RORB catchment map 10
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Select Calibration Flood
Appropriate flood selection based on assessment of historical data 220
Data suitability check incl. timeseries plot and volumetric runoff coefficient 220
Storm file incl. storm rainfall at each subarea and rainfall temporal pattern 10
Calibrate the RORB model
Appropriate use of FIT analysis incl. loss rates and RORB parameters 220
Demonstrated a reasonable fit between predicted and observed hydrographs 110
RORB Application – Proposed road crossing
Estimate Minor and Minor Design Discharges for no crossing conditions
Appropriate design rainfalls and areal reduction factor 110
Appropriate design storm losses 10
Critical duration analysis to establish appropriate design discharges 10
Sensitivity analysis
Sensitivity to RORB parameters 10
Sensitivity to design storm losses 10
Sensitivity to filtered versus unfiltered patterns 10
Sensitivity to temporal patterns 10
Sanity check of RORB outputs
Palmen and Weeks discharge estimates 20
Assessment of sources of uncertainty 20
Reporting
Assignment report (readability, structure and completeness) 20
TOTAL MARKS 250
6. References
Laurenson, E.M., R.G. Mein and R.J Nathan, 2007. RORB Version 6 Runoff Routing Program User
Manual, December 2007.
Palmen, L.B. and W.D Weeks, 2011. Regional flood frequency for Queensland using the quantile
regression technique. Australian Journal of Water Resources, 15 (1), 47-57 .
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Appendix A: Extracts from AR&R
3.4 MODELS OF RAINFALL EXCESS
For practical estimation of rainfall excess, numerical representations or models are required of rainfall and
losses or of the relation of runoff to rainfall.
3.4.1 Rainfall
Rainfall is virtually always represented by a hyetograph or pattern of intensity with time. Two distinct
cases are used:
(i) design rainfall with average intensity from Section 1, and pattern from Section 2. These patterns are only
applicable to the design case, and
(ii) recorded rainfall for simulating an actual hydrograph.
For design, a single hyetograph applying to the whole catchment is generally used. For simulation of an actual
hydrograph, different hyetographs may be used for different sub-areas.
3.4.2 Losses or Relations of Runoff to Rainfall
These are estimated in different ways depending on the model adopted. Some of the most frequently used
models are:
(i) loss (and hence runoff) is a constant fraction of rainfall in each time period. This is an extension of the
runoff coefficient concept;
(ii) constant loss rate, where the rainfall excess is the residual left after a selected constant rate of infiltration
capacity is satisfied;
(iii) initial loss and continuing loss, which is similar to (ii) except that no runoff is assumed to occur until a
given initial loss capacity has been satisfied, regardless of the rainfall rate. The continuing loss is at a
constant rate. A variation of this model that is sometimes recommended is to have an initial loss
followed by a loss consisting of a constant fraction of the rainfall in the remaining time periods;
(iv) infiltration curve or equation, representing capacity rates of loss varying (decreasing) with time;
(v) standard rainfall-runoff relation, such as the U.S. Soil Conservation Service relation.
Figure 3.1. Loss models used to estimate rainfall excess.
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These five models are illustrated in Figure 3.1. For any of these methods of estimating losses and hence rainfall
excess, weighted average values of losses for different conditions or land uses, such as proportions of pervious
and impervious areas, can be derived and used, as for the Rational Method.
Choice and validity of the above methods depend on the type of problem, the data available, and the
likely runoff processes. For the design case, which would usually involve the use of a large storm from which
runoff is likely to occur from the whole catchment and where the Horton process is dominant, models (ii) and
(iii) would be the most appropriate. For design, as discussed in Book I Section 1, median values of the losses
should be used, though there is little data available on median values of initial loss.
If saturated overland flow occurred from a fairly constant proportion of a catchment, model (i) involving
a constant fraction of the rainfall might be the best approach for design. This fraction would be the fraction of
the catchment producing runoff. Some studies have indicated that the runoff coefficient approach may be
better than loss rates in the south of Australia and in south west Western Australia (e.g. Harvey, 1982),
particularly during the winter wet season. However, little definite information is available, and either the loss
rate or fraction of rainfall approaches could be used.
The US Soil Conservation Service approach has given only fair results when tested in the United States.
There has been little testing of the model under design conditions though it is widely recommended in the
United States (USDA, 1972, 1975). In Australia only limited testing has been carried out, as described in
Book IV Section 1.3.5. This has shown that the results obtained from the model are very sensitive to the
choice of runoff curve number and to the method of estimating time of concentration, and often differed
markedly from observed runoffs. To obtain satisfactory results, the method would need to be calibrated with
observed data from the region of interest.
For estimating the rainfall excess from an actual storm as distinct from the design situation, allowance
must be made for the condition and wetness of the catchment immediately prior to the event. Rainfall runoff
relations such as model (v) are suitable if sufficient data are available for their derivation. Alternatively, the
Bureau of Meteorology often uses model (iii) with the initial loss being related to the antecedent rainfall.
3.5 COLLECTION OF DATA AND DATA SOURCES
From the discussion of methods of estimating losses from storm rainfall it can be seen that loss
values derived according to one of the definitions are not usable for estimating values for other
definitions. Values can be derived by analysing observed rainfall and runoff data. Since individual values
are dependent on the particular rainfall and catchment wetness characteristics of the event, individual
values have little meaning except as indicators of those particular events. For design, as discussed in
Book I Section 1, an average value is usually needed and, since there is no reason for expecting loss rate
values for a catchment to conform to any particular distribution, the median of the derived values is
probably the most appropriate for design.
In order to obtain a median loss rate value from observed data, values should be estimated from at
least three, and preferably five or more events. If it is only possible to derive one or two values from
observed data care must be exercised to avoid adopting an extreme value. Figure 3.2 shows the
distribution of all derived values from 54 Australian catchments listed in Table 3.1. The range of derived
values is large and the possibility of a single derived value being an extreme is not small. It may be
possible to compare the derived values with values from the same storms for nearby catchments where
data are available to obtain an estimate of the median. The designer would have to assume the same
relationship between the observed and median values for the catchment in question as occurred on the
nearby catchment.
Figure 3.2. Frequency distribution of individual loss ratevalues summarised in Table 3.1.
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Table 3.1. Loss rate data for catchments with five or more derived values.
Catchment Station Catchment Loss Rate mm/h Number of
Catchment Location Index Number Size km2 Median Mean Events
Bobo R NSW 204026 80 2.2 2.3 35
Badgerys Ck NSW 212330 0.068 3.8 4.1 14
Cawleys Ck NSW 214334 5.4 2.7 3.1 15
Blicks Ck NSW 204020 252 3.3 3.4 17
Blicks Ck NSW 204021 70 2.0 2.2 9
Eastern Ck NSW 212340 25 2.0 2.4 30
South Ck NSW 212321 88 1.4 1.9 24
Lidsdale No. 1 NSW 212301 0.055 1.8 13.0 9
Lidsdale No. 5 NSW 212305 0.062 3.0 2.9 7
Lidsdale No. 6 NSW 212306 0.090 4.5 17.0 12
Lidsdale No. 9 NSW 212309 0.23 2.8 2.9 6
Pokolbin No. 1 NSW 210063 14 3.0 2.7 8
Pokolbin No. 3 NSW 210068 25 2.5 2.2 11
Research Ck NSW 214330 0.39 2.3 2.7 31
Mt. Vernon Ck NSW 212333 0.70 3.2 4.4 18
Mann R NSW 204004 7800 3.2 3.2 10
Gwydir R NSW 418010 6650 1.4 2.0 11
Namoi R NSW 419022 5180 2.0 2.6 7
Severn R NSW 416006 3010 3.8 4.4 9
Belubula R NSW 412056 1610 2.5 2.7 5
Manilla R NSW 419020 1020 3.3 2.7 5
Brogo R NSW 219013 453 2.3 2.1 6
Hunter R NSW 210015 1290 4.3 5.7 7
Cudgegong R NSW 412038 544 2.3 2.6 11
Eucumbene R NSW 222503A 743 2.3 2.1 6
Lachlan R NSW 412067 8290 1.1 1.6 14
Macquarie R NSW 421002 13900 1.9 3.7 8
Macquarie R NSW 421025 4580 3.3 3.5 5
Nymboida R NSW 204001 1660 3.3 4.2 7
Queanbeyan R ACT 410760 894 1.3 2.1 5
Molonglo R ACT 410729 1540 1.9 2.2 5
Carey Bk WA 608147 114 3.2 4.0 40
South Dandalup R WA 614022 334 4.6 - 15
Ellen Bk WA 616189 525 3.8 - 22
Jane Bk WA 616178 75 4.6 - 30
Scabby Gully WA 607052 12.7 4.3 - 9
Parwan VIC 231156 0.86 4.1 4.2 21
Stewarts Ck 4 VIC 407163 0.25 2.0 2.2 8
West Arkins Ck VIC 203205 4.2 4.8 7.0 18
Second Wannon R VIC 238214 8.8 3.3 3.6 17
Jacksons Ck VIC 230103 85 4.6 4.0 7
Stewarts Ck 5 VIC 407164 0.17 2.5 3.4 21
Avon R VIC 415224 259 1.7 1.8 10
East Tarwin R VIC 227228 44 2.4 2.0 8
Cobbannah Ck VIC 224209 104 0.9 1.9 8
Lerderberg R VIC 231213 153 1.7 1.8 5
Seven Cks VIC 405234 153 3.1 4.1 8
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Warrambine Ck VIC 233223 62 5.0 4.2 7
North Pine R QLD 142110 350 1.9 1.9 5
Gregory R QLD 137101 455 0.9 0.8 6
Mary R QLD 138110 480 8.0 10.0 7
Raglan Ck QLD 130004 390 4.5 5.9 8
Boyne R QLD 136307 4195 2.8 2.3 5
Kolan R QLD 135002 545 1.5 7.8 6
Where data are not available on the catchment of interest but are available from nearby similar
catchments, it would appear appropriate to adopt the median of these observed values. However if such
data are not available or if the project does not warrant the effort needed to estimate local values,
indications of appropriate values for various sections of the States of Australia are shown in Tables 3.1 to
3.9. Where possible the sources of the data quoted in these tables are shown. A considerable amount of
the information shown in Tables 3.2 to 3.9 is the result of fitting a flood estimation model (runoff routing
or unit hydrograph) to observed flood events. The values obtained from this type of exercise are
appropriate design values if the fitting involved reproduction of a flood peak estimated from a flood
frequency curve by means of a rainfall estimated for the same frequency from appropriate intensity-
frequency-duration data. However in many cases the loss values quoted result from model fitting for
actual observed rainfalls and the corresponding observed hydrographs. In these cases the estimates of
continuing losses will probably be appropriate for design since continuing losses in large floods are fairly
independent of catchment condition (Cordery & Pilgrim, 1983) but other loss parameters will probably
not be suitable for design. As discussed earlier, median values of the various loss parameters are probably
the most appropriate values for use in design. However values of initial loss or proportional loss obtained
by taking observed rainfall events and adjusting the loss and other parameters until good reproduction of
the corresponding observed hydrograph is obtained will not produce loss values that are suitable for direct
design application for two reasons:
i. The values obtained from fitting observed storms will be biased towards wet catchment conditions.
The obtained values result from situations where significant floods occurred. However there is
probably an equal number of large rainfall events from which very small floods resulted, because the
catchment was dry, with very large potential loss values at the time of the rain. These small runoff
events are usually ignored in any parameter fitting exercise. This is certainly the case for the data
shown in Table 3.8 for the Northern Territory (Northern Territory Dept of Mines and Energy, 1986)
and is probably also true for all other actual event fitting situations. This means that the loss values
obtained in this way are towards wet catchment conditions and will tend to be considerably lower
than the median potential loss values which should be used in design.
ii. Initial loss values obtained from fitting actual storms will be too high, compared with the values that
should be used in assessing the median value for use in design. Design rainfalls are obtained from
the intensity-frequency-duration data given in Section 1. The design rainfalls are not complete
storms, and on average there would have been some low intensity rain within a total storm before the
occurrence of the intense bursts used to derive the design data given in Section 1 (Cordery, 1970a).
This problem relates only to the initial loss and is not of any importance when considering
proportional loss values. It means that initial loss values obtained from fitting rainfall and runoff data
from observed events will be larger than is appropriate for use with design rainfalls.
It is possible that the two problems with loss parameters obtained by fitting actual storms will cancel each
other in the case of initial losses, but proportional losses will tend to be underestimated. An attempt has
been made in Tables 3.2 to 3.9 to indicate the data which have been obtained by fitting actual observed
events.
Table 3.2. Design loss rates for New South Wales.
Location Loss Model Median Value of Parameters References
East of the western slopes Initial loss - Initial loss 10 to 35mm, varying with Cordery (1970a), Cordery
continuing loss catchment size and mean annual rainfall. and Webb (1974) and
Continuing loss 2.5mm/h Avery (1986)
Arid Zone, mean annual Initial loss - Initial loss 15mm
rainfall 300mm continuing loss Continuing loss 4mm/h Cordery et al. (1983)
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Table 3.3. Design loss rates for Western Australia.
Location Loss Model and Parameters References
SOUTH WEST
Jarrah Forest Proportional losses Source of all W.A.
with loam soils, data in this Table is location shown L2 = 400x10-0.0012CL
P-0.22 Flavell & Belstead
on Figure 5.7 L2 = 2 year av. recurrence interval percentage loss (1986, 1987) CL = Percentage of catchment cleared of forest
P = Average annual rainfall (mm)
Multipliers to obtain losses of other av. recurrence
intervals are
Av. recurrence interval (Y) 2 5 10 20 50
Multiplier 0% clearing 1.00 0.97 0.95 0.93 0.91
50% clearing 1.00 0.90 0.82 0.74 0.65
100% clearing 1.00 0.84 0.71 0.59 0.43
Jarrah Forest Proportional losses
with lateritic
soils, location L2 = 780x10-0.0015CLP-0.31
shown on L2 = 2 year av. recurrence interval percentage loss Figure 5.7 CL and P as defined above Multipliers to obtain losses of other av. recurrence intervals are Av. recurrence interval (Y) 2 5 10 20 50
Multiplier 1.00 0.98 0.97 0.94 0.90
Low Jarrah Forest Proportional losses
sandy soils,
location shown Av. recurrence interval (Y) 2 5 10 20
on Figure 5.7 Mean proportional loss (%) 88 86 86 84
Karri Forest, Proportional losses
loamy/sandy soils,
location shown Av. recurrence interval (Y) 2 5 10 20
on Figure 5.7 Mean proportional loss (%) 82 80 79 77
WHEATBELT
Loamy soils, Initial loss - continuing loss
85-100% Median continuing loss – 3mm/h
cleared IL5 = 700 P-0.47 L-0.08
IL5 = 5 year av. recurrence interval initial loss, (mm)
L = Length of main stream, (km)
Multipliers to obtain initial loss values of other av. recurrence
intervals are -
Av. recurrence interval (Y) 2 5 10 20 50
Multiplier 0.78 1.00 1.09 0.95 1.00 NORTH WEST
Pilbara - loam Initial loss - continuing loss
soils Median continuing loss = 5mm/h
Av. recurrence interval (Y) 2 5 10 20 50
Mean initial loss (mm) 22 40 52 47 32
KIMBERLEY
Kimberley - * Initial loss - continuing loss
shallow sand Median continuing loss = 5mm/h
over rock
(sandstone
and granite) Av. recurrence interval (Y) 2 5 10 20 50
Mean initial loss (mm) 30 50 60 47 47
Kimberley - * Constant loss rate
bare rock (basalt
and granite) Av. recurrence interval (Y) 2 5 10 20 50
with some Av. constant loss (mm/h) 2.5 4.0 4.8 3.5 3.5
shallow sand
Kimberley- * Initial loss - continuing loss
loam soils Median continuing loss = 3mm/h
Av. recurrence interval (Y) 2 5 10 20 50
Mean initial loss (mm) 27 45 54 42 27
Mitchell Plateau - * Initial loss - continuing loss
sandy soils Median continuing loss = 5mm/h
Av. recurrence interval (Y) 2 5 10 20 50
Mean initial loss (mm) 50 82 98 78 70
Mitchell Plateau - * Initial loss - continuing loss
laterite with Median continuing loss = 5mm/h
some sand and
bare rock
(sandstone) Av. recurrence interval (Y) 2 5 10 20 50
Mean initial loss (mm) 42 70 84 66 66 ARID INTERIOR
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Eastern Goldfields - * Initial loss - continuing loss
loamy soil Median continuing loss = 3mm/h
Av-recurrence interval (Y) 2 5 10 20
Initial loss (mm) 20 31 38 38
* Note: When using this information reference should be made to cautionary statements given by Flavell and Belstead (1986)
or to details of the catchments used to derive the tabulated loss values which are given by Flavell and Belstead (1987).
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Table 3.4. Design loss rates for South Australia.
Location Loss Model and Design Parameters References
Humid Zone Initial loss - continuing loss WBCM Pty. Ltd.
(Mediterranean) Winter Drainage Study,
Median initial loss = 10mm Brownhill Glen
Median continuing loss = 2.5mm/h Osmond, Parklands
Summer & Keswick Creeks
Median initial loss = 25mm Vol 2, 1984
Median continuing loss = 4mm/h
Initial loss - continuing loss
Median initial loss = 30mm from fitting design B.C. Tonkin
Median continuing loss = 1mm/h values to frequency & Associates
curves of observed data (1985)
Arid Zone Initial loss - continuing loss
Median initial loss = 15mm Cordery, Pilgrim &
Median continuing loss = 4mm/h Doran (1983)
Initial loss 15-40mm from subjective fitting of Lipp (1983)
Continuing loss 1-3mm/h runoff routing model -
no data available
Table 3.5. Design loss rates for Victoria.
Location Loss Model and Design Parameters
References
South and east Initial loss - continuing loss
of the Great Median continuing loss = 2.5mm/h Cordery & Pilgrim (1983)
Dividing Range Initial loss = 25-35mm MMBW
Initial loss = 15-20mm Rural Water Commission
North and West Probably as for similar areas of NSW Information provided
of the Great verbally at seminar in
Dividing Range Melbourne, August 1985
Table 3.6. Design loss rates for Queensland.
Location Loss Model and Design Parameters
References
Eastern Queensland Initial loss - continuing loss
Median continuing loss = 2.5mm/h Cordery & Pilgrim (1983)
Median initial loss = 15-35mm Cordery (1970b)
Initial loss = 0-140mm. Higher values were from Queensland Water
rainforest areas. All values obtained by fitting Resources Commission (1982)
runoff routing model to observed floods
Western Queensland As for Northern Territory
Recommended