SOIL EROSION MODELLING USING REMOTE SENSING AND GIS: A CASE STUDY OF JHIKHU KHOLA WATERSHED, NEPAL

摘要

In the process of soil erosion, nutrients rich top fertile soil is lost and it also causes environmentalrnproblems due to siltation of lakes, reservoirs and rivers. Inventory on soil loss and prediction of soilrnerosion hazard is vital for effective soil conservation planning of a watershed for sustainablerndevelopment. Soil conservation is now a necessity in almost every country of the world under virtuallyrnevery type of land use.rnInformation obtained using remotely sensing techniques can help decision makers to prepare resourcernmap accurately in less time and cost. GIS, in other hand, helps in linking those maps with otherrninformation related to geographic location and helps modelling, analysing and solving complex problems.rnA case study describes and assesses soil erosion in a watershed belonging to the river Jhikhu Khola, inrnthe middle mountain region of Nepal. Using ERDAS Imagine and ILWIS software, a landuse map wasrngenerated from satellite imagery of the study area.rnFor the estimation of Soil loss by Morgan approach, the various factor maps like kinetic energy of rainfall,rnTop soil rooting depth, percentage rainfall contributing to permanent interception and stream flow, Croprncover management factor, Ratio of actual to potential evapotranspiration, Soil moisture storage capacityrnwere generated to get final output maps like Volume of overland flow; Rate of soil detachment byrnraindrop impact, Transport capacity of overland flow. Annual soil loss estimation is calculated byrncomparing two maps of soil detachment rate and transport capacity and taking the minimum value fromrnthem. Results provided by running a soil erosion model show that, rainfed agriculture is contributingrnmaximum soil losses, 32.5 t/ha/yr. The lower soil losses are recorded under forest cover (0.01 - 0.4rnt/ha/yr) and irrigated agricultural land (0.9 t/ha/yr). Average estimated annual soil loss of the study area isrn12.6 t/ha.