Estimation of Soil Erosion Hazard in The Simpo Subwatershed, Indonesia

Abstract

River siltation caused by sedimentation in the downstream area of Simpo River, Juli Sub-district, Bireuen Regency, is suspected to occur due to increased land erosion. The siltation leads to a decrease in river capacity and triggers overflow (flooding) during the rainy season. This affects residential areas, plantations, and tourist areas around the river. This research aims to estimate the rate of land erosion and map the Erosion Hazard Level (EHL) occurring in the Simpo Subwatershed. The estimation is carried out with the Universal Soil Loss Equation (USLE) method based on the Geographic Information System (GIS). The data used includes 10 years of monthly rainfall data, soil type maps, Digital Elevation Model (DEM) data, and land cover maps. Based on the calculation results, the rate of land erosion is found to be 52592.9 tons/ha/year. Furthermore, the erosion hazard in the Simpo Subwatershed ranges from low to high levels. The EHL in the subwatershed is dominated by the High-Moderate category, reaching 38.1%. Most of the areas affected by this erosion category are spatially located in the upstream area with moderately steep slopes (15–25%), primarily consisting of plantation areas. This indicates that soil conservation measures need to be adopted in the region.