A conservative diffusion wave flood routing scheme for channel networks

Abstract

For long flood waves propagating over considerable distances on relatively flat slopes, the diffusion wave is an adequate approximation to the St. Venant equations of unsteady channel flow. A relatively simple and robust computational scheme based on this approximation is presented herein. The scheme is based on mass conservation equations for discrete control volumes with unique intervolume flows which ensures overall mass conservation. Simple guidelines for determining the spatial and temporal discretizations are provided. Application to a number of test situations indicates that the scheme offers acceptable accuracy without calibration using only reach-averaged channel geometry and roughness characteristics. The scheme would be especially useful as a subcomponent of a large-scale distributed hydrologic or water resources system model. Key words: flood routing, rivers, channels, networks, computational hydraulics, diffusive wave, hydrologic modelling, St. Venant equations.