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CRC PUBLICATIONS |
Estimation of Extreme Rainfalls for Victoria Using the CRC-Forge Method
Nanda Nandakumar,
Erwin Weinmann,
Russell Mein,
Rory Nathan
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:
Precipitation (Atmospheric)
Dams
Spillway
Design Data
Frequency Analysis
Flood Forecasting
Floods and Flooding
Rainfall/Runoff Relationship
Modelling (Hydrological)
FORGE
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Abstract / Summary:
Abstract
This report describes research work undertaken as part of Project D3 on "Probability and Risk of Extreme Floods" to develop and evaluate a methodology for estimating extreme design rainfalls. The specific range of interest is design rainfalls of one to several days duration and annual exceedance probabilities (AEPs) of 1 in 50 to 1 in 2000. The main field of application of this research relates to the design and safety assessment of dam spillways.
The CRC-FORGE method resulting from this research is a further development of the Focussed Rainfall Growth Estimation (FORGE) concept originating from the UK Institute of Hydrology (IH) [Reed and Stewart, 1989]. Modifications to the IH-FORGE methodology were necesssary to allow its application to the estimation of design rainfalls in the extreme range of AEPs.
The development and testing of the CRC-FORGE methodology was based on the analysis of daily rainfall data from more than 1400 medium to long record rainfall stations in Victoria and the bordering regions, made available by the Bureau of Meteorology.
The important questions of regional homogeneity of extreme rainfall, appropriate probability distributions, and effects of inter-site dependence of rainfall data were addressed in detail, using appropriate statistical tests and the results of rainfall data generation experiments. A method for estimating confidence limits on the estimated rainfall frequency curve was also developed.
The report concludes that the CRC-FORGE method yields consistent extreme design rainfall estimates to an AEP of 1 in 2000, and thus establishes an improved basis for the estimation of design floods in the extreme range. The method has been applied to produce design rainfall estimates for any site in Victoria for rainfall durations from 12 to 72 hours and for AEPs in the range from 1 in 50 to 1 in 2000. The CRC-FORGE method is considered suitable for application to extreme design rainfall estimation in other regions of Australia.
This report is not currently available for downloading. Printed copies may 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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