Identification the effect of spatial land use variability using gis at the upstream ciliwung watershed

The impact of spatial land use variability on the accuracy of runoff simulation was investigated in order to define the optimal spatial discretization of the watershed to be adopted in rainfall-runoff modeling. The correlation between the types of land cover, soil characteristic and soil humidity on the runoff coefficient determining is very important. Using SCS-CN model and GIS we try to indentify the effect of spatial land use on the runoff simulation. The case study presented is located in the upstream Ciliwung watershed; it is based on the detailed information from the Geographic Information System (GIS) available for upstream Ciliwung Watershed. We made the limitation on the soil humidity, we choose directly CN with the normal condition. The comparison between the averaged and distributed CN will calculate in order to analyze the effect of spatial land use variability on the surface runoff. The result is highly depends on the level of organization of land use. According to the model, the behavior of the studied watersheds may sometimes remain very similar with a homogeneous CN input, whereas for some cases the differences in the peak discharges can give the important indication of the influence of spatial land use variability.