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© 2024. This work is published under http://www.wrc.org.za/water-sa/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Event-based estimates of the design flood in ungauged catchments are normally based on a single catchment response time parameter expressed as either the time of concentration (TC), lag time (TL) and/or time to peak (TP). In small, gauged catchments, a simplified convolution process between a single observed hyetograph and hydrograph is generally used to estimate these time parameters. In medium to large heterogeneous, gauged catchments, such a simplification is neither practical nor applicable, given that the variable antecedent soil moisture status resulting from previous rainfall events and spatially non-uniform rainfall hyetographs can result in multi-peaked hydrographs. In ungauged catchments, time parameters are estimated using either empirical or hydraulic methods. In South Africa (SA), unfortunately, the majority of the empirical methods recommended for general use were developed and verified in catchments < 0.45 km2 without using any local data. This paper presents the further development and verification of the streamflow-based approach developed by Gericke (2016) to estimate observed TP values and to derive a regional empirical TP equation in Primary Drainage Region X, SA. A semi-automated hydrograph analysis tool was developed to extract and analyse complete hydrographs for time parameter estimation using primary streamflow data from 51 flowgauging sites. The observed TP values were estimated using three 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 these methods incorporated the high variability of eventbased time parameters, and Method (iii), in conjunction with an ensemble-event approach sampled from the time parameter distributions, should replace the event-based approaches to enable the improved calibration of empirical time parameter equations. The conceptual approach used to derive the regional empirical TP equation should also be adopted when regional equations need to be derived at a national scale in SA.

Details

Title
Alternative streamflow-based approach to estimate catchment response time in medium to large catchments: case study in Primary Drainage Region X, South Africa
Author
Gericke, O J 1 ; Pietersen, J P J 1 ; Smithers, J C 2 ; du Plessis, J A 3 

 Department of Civil Engineering, Central University of Technology, Free State, Bloemfontein, South Africa 
 Centre for Water Resources Research and School of Engineering, University of KwaZulu-Natal, Pietermaritzburg, KwaZulu-Natal, South Africa 
 Department of Civil Engineering, Stellenbosch University, P/Bag X1, Matieland 7602, South Africa 
Pages
20-31
Section
Research paper
Publication year
2024
Publication date
Jan 2024
Publisher
Water Research Commission
ISSN
03784738
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2955678283
Copyright
© 2024. This work is published under http://www.wrc.org.za/water-sa/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.