9-Sources of Sediment and Process of Erosion.

Abstract

Water erosion is the most widely spread degradation process on the earth through which not only the fertility of soil greatly decreases but, in many cases, the soil is physically destroyed and disappears. Although the problem of sail erosion has been concern of mankind since the dawn of settled agriculture, an understanding of the mechanism underlying these processes is still incomplete. In the last two decades, considerable progress has been made in unfolding the basics of erosion and sedimentation phenomena. This has been made possible because of advent off ast computers, availability of better instrumentation techniques, stress on field experiments, developments of newer techniques like remote sensing, and numerical methods etc. The paper brings out the physics of erosion-sedimentation process, mechanism of water erosion and various assessment techniques of the processes. A detailed amount of various models available for erosion & sedimentation processes have been mentioned. The status of reservoir sedimentation in India and its impacts have been elucidated. The need for research in the area has been brought out pointwise. It has been concluded that there is an immediate need to use powerful newer techniques like remote sensing and digital computer for estimation and extent of water erosion in various scenarios. It has also been stressed to conduct studies on large catchments with a view to develop soil-water land-vegetation interactions. As an important conclusion it has been pointed out that before taking up any soil-water conservation programme, it would be imperative to understand erosion process, various factors influencing erosion and estimate the magnitude of erosion, This would be all the more necessary for large catchments. Transposing of results from small watersheds to large catchments is not desirable considering the implications of hydrological phenomena. This calls for the use of extension monitoring utilising the modern technologies and use of mathematical modelling.