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CRC PUBLICATIONS |
Empirical Analysis of Data to Derive Losses for Design Flood Estimation in South-Eastern Australia
Peter Hill
Upula Maheepala
Russell Mein
Erwin Weinmann
Publication Type:
Technical Report
This is a publication of the initial CRC for Catchment Hydrology
CRC Program:
Flood Hydrology (Previous CRC)
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Publication Keywords:
Floods and Flooding
Design Data
Areal Reduction Factor
Rainfall/Runoff Relationship
Catchment Areas
Modelling (Hydrological)
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Abstract / Summary:
Summary
This report presents some of the significant outcomes from a major research project "Improved Loss Modelling for Design Flood Estimation and Flood Forecasting" undertaken by the CRC for Catchment Hydrology. It details the work undertaken to derive improved design losses from the empirical analysis of data.
A methodology has been outlined in this report for deriving design losses which overcomes the basic incompatibility between design rainfalls and losses used for design flood estimation. Losses have been calculated for rainfall bursts (not complete storms) which have been selected in a manner consistent with that used to select the rainfall bursts used to derive the design rainfall temporal patterns in Australian Rainfall and Runoff, 1987.
Prediction equations have been developed for the losses for use in south-eastern Australia. The baseflow index (the fraction of the total streamflow which is baseflow) was found to be significant in explaining the variability in the calculated losses. The geology-vegetation index defined by Lacey (1996b)is recommended for estimating the baseflow index for ungauged catchments.
When applied in conjunction with unfiltered temporal patterns, the new areal reduction factors (Siriwardena and Weinmann, 1996) and a non-linear runoff-routing model, the losses have shown to produce peak flows that are consistent with the results of flood frequency analysis. However, the verification of design losses is dependent upon the choice of all of the key inputs in the modelling process. Different assumptions about any of the key inputs, such as the filtering of temporal patterns, areal reduction factors or runoff-routing model characteristics, could affect the conclusions.
The new design losses are recommended for design flood estimation for south-eastern Australia on the basis that:
they are based on a detailed study using methodology that is consistent with the derivation of design rainfalls;
they incorporate plausible relationships with catchment and climatic characteristics, and rainfall duration;
they produce satisfactory results when tested on 11 representative catchments in the region
The losses are recommended for use with unfiltered temporal patterns and the new areal reduction factors for long duration with the interim recommendations for short durations (Siriwardena and Weinmann, 1996)
It is recommended that a similar methodology as detailed in this report be applied to derive design loss values for other parts of Australia.
This report is not currently available for downloading. Printed copies can be purchased from the Centre Office
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Centre Office:
CRC for Catchment Hydrology
Dept of Civil Engineering
Building 60
Monash University Vic 3800
Tel: +61 3 9905 2704
Fax: +61 3 9905 5033
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