The importance of spatial resolution in hydraulic models for floodplain environments

For many numerical modelling applications the problem of specifying an optimum mesh resolution remains unbounded and for mesh construction objective a priori rules do not exist. By contrast, the problem of specifying model parameter surfaces is largely bounded within known physical error distributions. In this paper we thus investigate the impact of varying mesh resolution on a typical non-linear finite numerical solver. Specifically, a two-dimensional finite element code which solves the Shallow Water equations was used to simulate unsteady flows in a meandering compound channel. A range of different mesh resolutions and parameter surfaces were simulated to determine relative dominance and, unlike previous studies, the effect on both bulk flow and distributed outputs were analysed. The results showed a wide variation in performance for mesh discretizations which fulfilled traditional length scale-based construction. Mesh resolution effects were at least as important as a typical calibration parameter and model response was shown to be highly complex. (C) 1999 Elsevier Science B.V. All rights reserved.