Analysis of the Erosion Hazard Level Using the USLE Method with the ARCGIS Application in the Upstream of the Pengga Reservoir

Abstract

This study evaluates the erosion hazard level in the upstream region of the Pengga Reservoir by applying the Universal Soil Loss Equation (USLE) method, integrated with Geographic Information System (GIS) tools in ArcGIS. Soil erosion is recognized as a critical environmental concern in upstream reservoir catchments due to its contribution to accelerated sedimentation, which in turn reduces reservoir storage capacity and operational lifespan. The research was conducted within the Dodokan Watershed, encompassing the West Lombok and Central Lombok Regencies in West Nusa Tenggara Province, Indonesia. The analysis was based on secondary data, including rainfall records from the Meteorology, Climatology, and Geophysics Agency (BMKG), soil characteristics, topographic features, and land use and vegetation cover data. The USLE model was used to calculate five contributing factors: rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover-management (C), and support practices (P), which were processed using spatial analysis in ArcGIS.

The results indicate that erosion hazard levels across the study area vary from very light to very severe. The total estimated annual soil loss is 405,204.65 tons/ha/year, with approximately 70.37% of the catchment experiencing very light erosion and 4.05% experiencing very severe erosion. The estimated sediment yield, calculated using the Sediment Delivery Ratio (SDR), is approximately 30,038.52 m³/year. These findings offer valuable insights for regional soil conservation planning and contribute to the development of sustainable reservoir management strategies.