Delineating changes in soil erosion risk zones using RUSLE model based on confusion matrix for the Urmodi river watershed, Maharashtra, India

Soil loss by water erosion is a common type of land degradation issue in the hilly regions of the world. The present study investigates the soil erosion risk due to change in Land Use Land Cover (LULC) brought in by the construction of dam in a hilly watershed of the River Urmodi embracing Kaas Plateau, a world heritage site. The Revised Universal Soil Loss Equation (RUSLE) model was used with change detection analysis for soil erosion estimation. Thematic layers required for the computation of factors required in RUSLE were gathered using remote sensing (RS) and Geographical Information Science techniques. The changes in LULC affect the soil erosion phenomena and therefore, the present study analyzes drastic alteration in the hydrological nature of the watershed brought by the construction of reservoir through damming the Urmodi River. For assessment of the impact of the dam we have used RS data with 30 m spatial resolution, which includes Digital Elevation Model and Landsat TM and Landsat 8 bands. Using RUSLE, soil risk zone was mapped and the Change Detection in zones were computed. The very simple logic of 'soil erosion class as a type of land cover' was successfully applied to perform the change transition for the Urmodi river watershed. Confusion matrix technique used for analyzing the change, has the ability to show the previous and next condition of zone type very affectively with good precision. Along with Change Detection technique, soil erosion class transition operation was also performed to assess the conversion of zones. This gave the important output regarding increased conversion from very slight to very severe risk zone by 70.22 km(2). The investigation concludes that there was extensive change in very severe (> 80 ton ha(-1)year(-1)) soil vulnerable risk zone in the last 17 years with the rise of 14.87%. The conversion of lower risk category areas to higher risk category areas of soil erosion was detected all over the watershed. Undertaking such studies revealed the changes brought in the soil erosion susceptible zones by building of dams. This study will be a crucial help to policy and decision makers for proper planning of watershed with consideration to LULC in the event of dam construction on the rivers flowing in hilly terrain.