Quantifying soil erosion dynamics in lower Subansiri Basin, Assam, India, using the RUSLE model

Soil erosion has become a significant problem due to land degradation, increased agricultural production, and other human influences. Subansiri River is one of the biggest tributaries of the River Brahmaputra. It experiences severe erosion due to high discharge, deforestation, and land use modification. The present research adopted the empirical approach revised universal soil loss equation (RUSLE) to determine soil losses along the Subansiri River of Assam, India. The RUSLE approach is formulated on the basis of assessing soil loss per unit area. It considers some different factors, including rainfall erosivity factor (R), soil erodibility factor (K), topography factor (LS), cover and management factor (C), and conservation practices factor (P). In a geographic information system (GIS) setting, the RUSLE factors were determined. It is seen that the RUSLE model yields soil erosion rate to be between 0 and 895.69 t ha⁻¹ yr⁻¹. About 20 million t yr⁻¹ of soil from the study area is lost annually. Seven categories were used to classify the different levels of soil erosion as very severe (0.02%), severe (35.14%), very high (25.16%), high (23.12%), moderate (5.02%), low (4.82%), and very low (6.73%). The final result demonstrates that the majority of soil erosion takes place in the northern and northwestern regions, which are also areas of high slope angles, and along the Subansiri River and its channels. Though the RUSLE model has been used extensively, not much research has been done on the Subansiri River in Assam, especially incorporating dynamic land use changes and high-resolution spatial data. Furthermore, little research has been done using a combination of GIS and remote sensing with other models to analyse soil erosion in this region. Therefore, controlling soil erosion in the study region would improve water quality, decrease flood risk, and support sustainable agriculture. Study shows that the RUSLE-based methodology can be adapted to different environmental settings such as high rainfall, moderate to steep slope, and alluvial soil types.