Accessing the soil erosion rate based on RUSLE model for sustainable land use management: a case study of the Kotmale watershed, Sri Lanka

Water based soil erosion is a serious socio-economic and environmental problem across the world especially in the tropical region. Assessing the soil erosion quantitatively and spatially provides information to prioritize the soil conservation area in sustainable land management view point. Among the other soil erosion approaches, erosion modeling has been playing a significant role and provides an accurate result in a cost-effective manner. In this study, revised universal soil loss equation (RUSLE) was integrated with remote sensing (RS) and geographic information system (GIS) to analyse the quantitative and spatial distribution of soil erosion across the entire Kotmale watershed which is located in the western part of the central mountain region in Sri Lanka. In the methodology, the parameters of the RUSLE model were estimated using pixel overlay method in ArcGIS software, both spatial data and remote sensing data facilitated with appropriate calibration. From the analysis, the annual soil erosion ranges from 0 to 472 t ha − 1 year − 1 with the mean and standard deviation 9.8 t ha − 1 year − 1 and 15.7 t ha − 1 year − 1 respectively. The mean erosion rate of the model was correlated with ground based data. After the final model was established, conservation priority area was identified by using hot and cold spot analysis. Here “hot spots” shows the area with high soil erosion clustering value, while “cold spot” refers to area with low soil erosion clustering. The soil conservation priority map has been produced and the result shows that approximately 25% represents hot sport. The result would be an aid and sources for soil and water conservation in the Kotmale watershed.