Evaluating Soil Erosion within the Neyyar Basin in Kerala through RUSLE and Geospatial Analysis

Abstract

Soil erosion represents a significant issue in the Western Ghats, especially within the Neyyar river basin in the southern region of Kerala. To address this problem, a research project was conducted in three sub-watersheds of the Neyyar river basin, specifically Neyyar, Mullayar, and Chittar, with the primary goals of quantifying annual loss of soil and creating erosion maps. To predict this, researchers employed the Revised Universal Soil Loss Equation (RUSLE) in conjunction with Geographic Information System (GIS). To compute the RUSLE factors viz., R, K, LS, C and P for these sub-watersheds, monthly and yearly rainfall, soil texture and organic matter content, length and steepness of slope, crop cover and conservation practices data were used.The results showed that the extent of soil loss varied among the three watersheds. Soil loss ranged from 0 to 92, 257, and 28 tons per hectare per year for Chittar, Mullayar, and Neyyar sub-watersheds, respectively. In 38% of Mullayar, 41% of Chittar, and 45% of Neyyar watersheds, soil loss was relatively low, being less than 10 tons per hectare per year. However, in 35% of Mullayar, 30% of Chittar, and 25% of Neyyar sub-watersheds, soil loss was moderate to very high, ranging from 15 to over 40 tons per hectare per year. These variations in soil loss were attributed to factors beyond just rainfall, such as slope (LS) and soil erodibility (K), indicating that other elements influenced the soil erosion risk. Moreover, it was observed that Mullayar had the highest erosion risk, followed by Chittar watershed, highlighting the significance of factors like slope and soil erodibility in contributing to the loss of soil.