Spatial soil loss risk assessment for priority intervention using GIS and remote sensing techniques: A case of Neri Watershed Southwestern Ethiopia

Abstract

Soil loss by runoff is a severe and continuous ecological problem in Neri watershed. It affects agricultural production, drinking water quality, ecosystem health, and landscape aesthetics. This study was conducted to assess spatial risk of soil by estimating the average annual soil loss, and creating a soil erosion hazard map for this watershed. Revised Universal Soil Loss Equation (RUSLE) model supported by a GIS framework was used. To this end, data for the model parameters were derived from, a digital elevation model (DEM) of (30*30 m), thirty years (1988-2017) rainfall data at rain gauge stations, soil erodibility data from field soil samples, Landsat-8 satellite image for cover management and conservation support practices. Once raster layer of the input parameters created, overlay analysis was carried to assess the spatial distribution of soil loss. The estimated annual soil loss varies from 0 to 465.16 t ha−1 yr−1 with a mean annual soil loss of 9.95 t ha−1 yr−1. The empirical analysis also confirmed that the watershed losses a total of about 463365.46 t of soil annually. Out of the total area; 54.9% of the watershed was categorized below moderate classes and the remaining 45.1% of land area was classified under high to very high classes, which is about several times the maximum tolerable soil loss rate. Based on the classification of soil loss hazard map, six out of eleven Neri sub-watersheds need prior intervention in terms of integrated cover-management and mechanical conservation measures. Furthermore, model results can be refined by analyzing along with sub-watersheds level real time monitoring for conservation practices.