Application of GeoWEPP - TOPAZ model to delineate stream network and watershed at upper Citarum watershed - Cikeruh and Citarik sub-watershed

Abstract

GIS technology in GeoWEPP, namely TOPAZ model, was utilized to delineate network streams and watershed. The purpose of this study is to apply the TOPAZ model in GeoWEPP for watershed modeling. The research location is the Citarik and Cikeruh Sub-watershed. The TOPAZ model utilizes a DEM to generate topographic parameterization. It processed a DEM and then distinguished a hillslope, a channel based on channel network. Stream order is allocated for channel section in accordance with the watershed channel network. DEMNAS which based on the IFSAR, TERRASAR X, and ALOS-PALSAR was utilized. Network stream and watershed delineation generated by TOPAZ based on 10-meters resolution DEM, 5 ha Critical Source Area (CSA), and 100 meters Minimum Source Channel Length (MSCL). The result shows that GeoWEPP can effectively produce watershed. Compared to the traditional method of delineating by hands, GeoWEPP failed to accurately define the watershed area since it located in the downstream and paddy field. These are weaknesses in the spatial analysis of GIS since TOPAZ cannot define the existing channel and change topography easily. The solution, field surveys are needed and river basins can be accurately determined. However, TOPAZ successfully generates network streams and watersheds in the upstream area.