Author(s): Yudan Liang; Heide Friedrich; Asaad Shamseldin; Bodo Hellberg
Keywords: Catchment size; Stormwater modelling
Abstract: Stormwater management design in the Auckland Region is currently based on Guidelines for stormwater runoff modelling in the Auckland Region, Technical Publication No. 108 (TP108). These guidelines were produced based on Technical Release No. 55 (TR55) prepared by the U. S. Soil Conservation Services (SCS) and the U. S. SCS rainfall-runoff model was applied to catchments in the Auckland Region. It has been used as a standard design tool in catchment modelling by different users. These guidelines were prepared for the Auckland Regional Council (ARC) by Beca Carter Hollings&Ferner Ltd. BCHF selected, calibrated and validated the SCS rainfall-runoff model for these guidelines based on the evaluation of gauged catchments in Auckland. However, there are a number of limitations associated with the use of these guidelines and the SCS model. One of the major concerns of these limitations is the maximum catchment size to be used in conjunction with the rainfall-runoff model. Once the maximum catchment size is determined, large catchments can be subdivided into smaller subcatchments in order to calculate the generated runoff. Flows generated from subcatchments routed to the catchment outlet using an unsteady hydraulic model, and an estimation of accuracy would be essential. The purpose of this study is to review the TP108guidelines; and to investigate the impacts of catchment size in stormwater runoff modelling in the Auckland Region by carrying out desktop modelling simulation of the Papakura Stream Catchment.