Field validation of erosion hazard zones for small scale assessment using GIS

Soil erosion is one of the most serious environmental problem of agricultural based developing countries since it remove soils rich in nutrients, increase natural level of sedimentation in rivers and other water bodies and causes flood and water quality problems. The final results are the reduction of the productivity of land, which can lead to increase in expenditure in fertilizers to maintain yields and reduction in capacity of rivers increasing the risk of flooding, blocking of irrigation canals and shortening the design life of reservoirs. Soil erosion assessment for watershed management is one of the major concerns because in reality it is not possible to conserve all areas under the threat of erosion due to the financial constrains. Soil loss rate or erosion rate estimation for land parcels is of utmost importance to the effort of soil conservation work. The most common method in the world to identify land parcels which is severely eroded is Universal Soil Loss Equation (USLE). It predicts the long-term average annual rate of erosion. However the factors in this equation require field validation prior to their application for a particular region. This study was carried out for a relatively small area and this paper describes the key issues, methodology and recommendations for the process of soil erosion assessment of such an area. Erosion hazard in a watershed has spatially varying characteristics. Hence, the use of a computer tool, which can handle spatial data, is important. Geographic Information System (GIS) provides an easy solution for such spatial assessments for effective watershed management