DEMs Resolution Effect on SCS Curve Number Derived through WI_CN Method Based on Saturation Excess Concept

The effects of DEM resolution on the curve number values as. Based on WI_CN method is addressed in the present research. This method, due to a use of TOPMODEL’s excesses saturation concept, is considerably dependent on the topographic index and subsequently on DEM cell sizes. The results of WI_CN method application in the Kasilian watershed for different DEM cell sizes indicated that the watershed averaged curve number in DEMs with resolutions of 50 and 300 meters amount to 59.8 and 71.8, respectively, which means when DEM resolution gets coarser the difference between WI_CN method and common methods (derived CN using GIS and RS techniques) increases. For instance the maximum differences observed between the two methods (in 50 and 300 meter cell sizes) are 8.3% and 29.9%, respectively. Therefore, when making use of the saturation excess based methods for deriving curve number raster maps, especially in ungauged watersheds, DEM resolution effects should be defined with respect to data resolution.