Modelling soil erosion using rusle and GIS for Kadalundi river basin

Abstract

Soil is the uppermost layer of the earth surface. All life on earth depends on soil, but at present soil degradation is increasing at an alarming rate and the principal reason for this is soil erosion. Erosion is a noticeable intrinsic natural process, but in many places it is increased by anthropogenic activities. Erosion assessment has a major role in deciding the proper land management measures. To overcome the limitations of conventional erosion assessment methods, researchers usually go for modelling. Empirical models like USLE and RUSLE are widely used for soil erosion prediction. However, soil erosion always results in sedimentation and empirical models do not account for sediment deposition. A comparison of estimated soil erosion and observed sediment yield can be done with the help of a SRC and SDR. The main objective of the study was to model the potential average annual soil loss from Kadalundi river basin using RUSLE and to map the spatial distribution of soil erosion hazard using GIS to suggest suitable soil conservation and management protocol for the basin and compare the results with sediment yield data from outlet gauging stations. The morphometric characteristics of the basin were analysed under linear, areal and relief aspects to assess the erosion vulnerability of the basin. Soil erosion in the basin was estimated by RUSLE model and spatial distribution map was generated. The SRC for high flow, low flow and medium flow conditions were plotted for the basin by using the sediment yield data and stream flow data collected from CWC gauging station, Karathode for 21 years. The SDR was calculated for the Kadalundi basin using the sediment yield data from CWC gauging station, Karathode and soil erosion estimated by RUSLE. Erosion field studies were conducted at Anakkayam region of Kadalundi river basin. Sediment sampling for Kadalundi river was done at Chittathupara gauging station for one year (November 2021 to December 2022) to estimate the sediment yield. The SRC was plotted for Anakkayam region. By using sediment yield data estimated by sediment sampling and soil erosion estimated for Anakkayam region for 2021 by RUSLE model the SDR was computed. The depth of soil lost was also measured by using erosion pins installed in two trial plots of at ARS, Anakkayam. The zonal statistics was calculated for slope and land use with respect to soil erosion, to suggest suitable soil conservation and management protocol for the basin. The overall results of morphometric analysis revealed that the basin is erosion prone. The average annual soil erosion estimated by RUSLE for Kadalundi basin is 5.48 t•ha-1•yr-1 and 5.92 t•ha-1•yr-1 for Anakkayam region. Majority of the area of basin and Anakkayam region falls under slight erosion class (40 t•ha-1•yr-1). The SRC developed for high flow, low flow and medium flow can be used for future predictions of sediment yield for similar conditions. The SDR for Kadalundi basin and Anakkayam region were 0.10 and 0.98 respectively, which indicates sediment deposition is high for Kadalundi basin and very low for Anakkayam region. Erosion pin results indicate the mean depth of soil lost during one year, for a slope of 32 per cent is 18.4 mm and 16 per cent slope is 16.4 mm. Since larger part of the basin is having slight erosion, most of the erosion problems can be controlled by simple agronomical measures. Bunds, trenches and terraces were suggested to the areas having moderate erosion and slope stabilization and drainage line treat ments can mitigate the erosion problems in the areas in severe and very severe erosion classes in the basin.