Evaluation of overland flow models using laboratory catchment data II. Parameter identification of physically based (kinematic wave) models

Abstract

Using the Imperial College laboratory catchment facility data from96 experiments on a slightly-roughened varnished strip catchment(1 m x 9.925 m) are used to investigate the performance of numericalmodels of overland flow based on the kinematic wave approximation.A simple four-parameter model incorporates the Darcy-Weisbach laminarflow and Manning turbulent flow friction relationships, with differentvalues of the friction parameter permitted under "rain" and "no-rain"flow states. The optimization strategy combines grid-search and gradient-searchalgorithms. Model fits are good by conventional standards and theeffect of raindrop impact on effective roughness is clearly identified.However, the Manning relationship is not valid in the zone of transitionto rough turbulent flow and somephysical inconsistencies in optimal parameter values are apparent.Incorporation of a Colebrook-White friction relationship gives similargoodness of fit, but identified parameters conform more closely toexpectation from hydraulic theory.