Effects of spatial scale on distributed flood simulation based on HEC-HMS model: A case of Jinjiang watershed, Fujian, China

Taking Jinjiang watershed of Fujian province in China as study area, this work examines the effects of DEM resolutions, ranging from 30m to 600m, on Nash efficiencies of rainstorm flood simulation based on HEC-HMS model. Another focus is the influence of sub-basin division on flood simulation results. The study indicates that, with the decreasing of DEM resolution, basin slope, among other parameters such as basin evaluation and river length, etc., is most sensitive to the change of DEM resolution. In general, the Nash efficiency would drop down if DEM resolution decreases while other parameters held constant. DEM resolution at 150m appears to play a role of critical and optimal scale. Being based on 30m DEM resolution, it is found that the change of divided sub-basin number only slightly affects the results of flood simulation.