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CRC PUBLICATIONS |
A Design Flood Estimation Procedure Using Data Generation and a Daily Water Balance Model
Walter Boughton,
Peter Hill
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
Flood Forecasting
Rainfall/Runoff Relationship
Modelling (Hydrological)
Design Data
Catchment Areas
Peak Flow
Frequency Analysis
Water Balance
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Abstract / Summary:
Summary
Daily rainfall records form an extensive and valuable data base in most areas of Australia. The use of these records for water supply design is well established, but little use is made of the data in design flood studies. This report describes a new design flood estimation procedure which makes use of the site-specific information in daily rainfall records as an alternative to the generalised rainfall information in Australian Rainfall & Runoff.
A daily rainfall generating model uses the relevant statistics from an actual record to generate very long sequences of daily rainfalls. The synthetic sequence becomes input into a daily rainfall-runoff model which generates a corresponding sequence of daily runoff values. Using a relationship between daily volumes of runoff and peak rates of runoff, the annual maxima values of daily runoff are used to estimate the annual maxima distribution of peak rates of runoff.
The daily rainfall generating model is a modification of the Srikanthan-McMahon (1985) model. The daily rainfall-runoff model is the AWBM water balance model (Boughton, 1993). Three methods of relating annual `maxima peak flow rates and daily volumes are tested, and a log-log relationship is selected for use. All of the components, i.e. daily rainfall generating model, rainfall-runoff model and peak/volume relationship, have been used before in separate studies. This study brings these components together into a complete design flood estimation procedure. The use of a continuous simulation rainfall-runoff model avoids the treatment of flood runoff as isolated events, and avoids any need to assume values of "losses".
The daily rainfall generating model is calibrated against available information on annual maxima daily rainfalls. If only the record of daily rainfalls is available, the model can safely extrapolate to design floods of ARI 500 years. If rainfall extrapolation techniques such as FORGE are available, then design flood estimates to ARIs of 2000 years can be made. If estimates of 24 hour PMP are available, the calibrated model can be used to generate periods of data equal in length to the assumed ARI of the PMP and so enable the distribution of flood peaks up to the PMF to be estimated.
The complete design flood estimation procedure is demonstrated using data from the 108 kilometre squared Boggy Creek catchment in Victoria.
This report is 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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