A regionalisation technique for urban ungauged catchments - A case study from Norway
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Accurate estimation of rainfall-runoff in an urban area is essential for flood disaster prevention and control. A Storm Water Management Model was therefore applied to four small urban catchments in Damsgård, Bergen, Norway. In an effort to extend the modelling works to the ungauged parts of Damsgård, a technique that integrates a regionalisation concept into model calibration was tested. The SWMM parameters were calibrated along regionalisation-parameters that establish certain mathematical relationships (transfer functions) between selected SWMM parameters and catchment characteristics. The Shuffle Complex Evolution algorithm was integrated into the calibration of the model to estimate the parameters of the model, with the Nash-Sutcliffe Efficiency criterion as an objective performance measure. The calibrated model predicted the observed outputs with reasonable accuracy. Hence, the parameters derived from the transfer functions could be further used to test the applicability of the proposed methodology. A pattern between the catchments physiographic characteristics and the parameter sets of the transfer functions was observed. The two characteristics identified to affect the transferability the most were the number of residents, and the length to outlet. The results demonstrate that it is possible to combine the regionalisation of an ungauged catchment with the calibration of SWMM.