An effective depression filling algorithm for DEM-based 2-D surface flow modelling

摘要

The surface runoff process in fluvial/pluvial flood modelling is oftensimulated employing a two-dimensional (2-D) diffusive wave approximationdescribed by grid based digital elevation models (DEMs). However, thisapproach may cause potential problems when using the 2-D surface flow modelwhich exchanges flows through adjacent cells, with conventional sink removalalgorithms which also allow for flow exchange along diagonal directions, dueto the existence of artificial depression in DEMs. In this paper, we proposean effective method for filling artificial depressions in DEM so that theproblem can be addressed. We firstly analyse two types of depressions inDEMs and demonstrate the issues caused by the current depression fillingalgorithms using the surface flow simulations from the MIKE SHE model builtfor a medium-sized basin in Southeast England. The proposeddepression-filling algorithm for 2-D overland flow modelling is applied andevaluated by comparing the simulated flows at the outlet of the catchmentrepresented by DEMs at various resolutions (50 m, 100 m and 200 m). Theresults suggest that the existence of depressions in DEMs can substantiallyinfluence the overland flow estimation and the new depression fillingalgorithm is shown to be effective in tackling this issue based upon thecomparison of simulations for sink-dominated and sink-free DEMs, especiallyin the areas with relatively flat topography.