Identification of Erosion-Prone Areas Using Hydrologic Indices and Normalized Difference Vegetation Index: A Remote Sensing and GIS Approach

In tropical river basins such as the Ib River basin, intense rainfall, deforestation, improper agricultural practices, and cultivation exacerbate soil erosion. An SRTM DEM with a 30-m pixel size was employed in this study to determine STI, TWI, SPI and analyse topographic features. Topographical and soil-related aspects were analysed using SPI, STI and TWI, while soil and vegetation characteristics were investigated using NDVI. Using this approach, soil erosion sites were categorized into five priority levels: highest (categorized by light green vegetation), higher moderate (medium green vegetation), moderate (water bodies), lower moderate (bare soil) and lowest (swampy areas). Light green vegetation showed the highest soil erosion susceptibility (60.64%), while medium green vegetation exhibited a relatively lower susceptibility (26.78%). The first two priority categories encompass an area of 5962.337 km2, representing 98.9% of the sub-basin’s total area. This area exhibits a soil erosion rate of 434 146 t/km2. Consequently, this results in average annual sediment yield of 94 147.62 t/km2, accounting for 99.70% of the sub-basin’s total annual sediment yield. The accurate identification of these areas, based on soil erosion rate and sediment yield within appropriate priority categories, enhances the reliability of the suggested method.