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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