1. Direct estimation of catchment response time in medium to large catchments
- Author
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Gericke, J., Pietersen, J., Smithers, J., and Du Plessis, K.
- Abstract
Event-based estimates of design floods in ungauged catchments are generally based on a single catchment response time parameter as input, expressed as either the time of concentration (TC), lag time (TL) and/or time to peak (TP). In small catchments, a simplified convolution process between a single observed hyetograph and hydrograph is generally used to estimate these time parameters. This simplification is neither practical nor applicable in medium to large heterogeneous catchments where antecedent moisture from previous rainfall events and spatially non-uniform rainfall hyetographs can result in multi-peaked hydrographs. This paper presents the further development and verification of the approach developed by Gericke and Smithers (2017) by using only observed streamflow data to estimate the catchment response time parameters and to derive a regional empirical catchment response time parameter equation. Flood event and catchment response time characteristics using primary streamflow data from 51 flow-gauging sites located in Primary Drainage Region X in South Africa were extracted and analysed using three different methods: (i) duration of total net rise of a multi-peaked hydrograph, (ii)triangular-shaped direct runoff hydrograph approximations, and (iii) linear catchment response functions. The combined use of the latter methods not only ensured that the high variability of event-based catchment responses is considered, but the estimated catchment TPvalues are also well within the range of other uncertainties inherent in design flood estimation. It is recommended that for design hydrology and for the calibration of empirical time parameter equations, that Method (iii) be adopted internationally., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)
- Published
- 2023
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