Soil erosion and sediment yield modeling in a tropical mountain watershed of the southern Western Ghats, India using RUSLE and Geospatial tools

The development of comprehensive soil conservation strategies, based on the soil erosion risk, is one of the critical components of sustainable river basin management, especially in tropical mountainous regions. The present study computes the spatially distributed longtime average annual soil loss (A) and sediment yield (SY) and prioritizes the soil erosion risk in a tropical mountain river basin. The Revised Universal Soil Loss Equation (RUSLE) and the sediment delivery distributed model (SEDD) models were coupled in the GIS environment to predict the intra-basin variability of the A and SY of the Karimpuzha River Basin (KRB) of the southern Western Ghats (in Kerala, India). The results indicate that, on an average basis, 9.3 t of soil has been eroded per hectare per year, whereas the SY is 6.3 t ha⁻¹ y⁻¹ (i.e., approximately two-thirds of the gross soil erosion). The SY of the majority (74.2%) of the basin area is low (i.e., ≤5.0 t ha⁻¹ y⁻¹), whereas the soil erosion and transport processes are a major concern in some areas (ca. 6.3 km²). The results imply the significance of land use/land cover, rainfall, and topography in controlling the soil erosion risk of the basin. The study demonstrates the advantages of the delineation of the critical erosion areas, based on the hydrologic response units (HRUs) of the basin, to implement appropriate soil erosion management options for conservation of the soil resources.