An efficient method for DEM-based overland flow routing

The digital elevation model (DEM) is frequently used to represent watershed topographic features based on a raster or a vector data format. It has been widely linked with flow routing equations for watershed runoff simulation. In this study, a recursive formulation was encoded into the conventional kinematic- and diffusion-wave routing algorithms to permit a larger time increment, despite the Courant–Friedrich–Lewy condition having been violated. To meet the requirement of recursive formulation, a novel routing sequence was developed to determine the cell-to-cell computational procedure for the DEM database. The routing sequence can be set either according to the grid elevation in descending order for the kinematic-wave routing or according to the water stage of the grid in descending order for the diffusion-wave routing. The recursive formulation for 1D runoff routing was first applied to a conceptual overland plane to demonstrate the precision of the formulation using an analytical solution for verification. The proposed novel routing sequence with the recursive formulation was then applied to two mountain watersheds for 2D runoff simulations. The results showed that the efficiency of the proposed method was significantly superior to that of the conventional algorithm, especially when applied to a steep watershed.