A STUDY ON SOIL EROSION AND ITS IMPACTS ON FLOODS AND SEDIMENTATION

Abstract

Balanced ecosystem comprising of soil, water and plant environment is essential for survival and welfare of the mankind. However, eco-system of the earth has been disturbed in the past due to over exploration of the nature for meeting the demands generated due industrial growth etc. Activities such as deforestation, Mining, Agriculture etc., that dominantly occurred in the recent past due to developments resulted in soil on land surfaces exposed directly to the rains. This unprotected soil could be easily removed from the land surfaces by the combined action of rain and the resulting flow. Vast tracts of land have been thus irreversibly converted into infertile surfaces due to the continued soil erosion. These degraded land surfaces also become sources of pollution to the natural water. Soil eroded from the upland areas of the catchment, gets deposited in the rivers causing aggradation. This causes increase in floods plain area of the river choking of the clearance below the bridge and culverts etc. Reservoir sedimentation is the problem of prime concerns for water resources engineers and gets accelerated due to catchment soil erosion. The net amount eroded soil (sediment) reaching to the catchment outlet over a period of time is termed as sediment yield. For the project planning purpose estimates of sediment yield can be made with the available techniques by using the data on the hydrometeorology and the catchment characteristics. The tools of Remote sensing (RS) and Geographical Information Systems (GIS) are vigorously being utilized to give a Digital representation of the hydrological variables like soil erosion. For soil conservation planning however it is necessary to estimate the variation of soil erosion and sediment yield with the time during storm events or for a series of storm events. The problem of soil erosion is prevalent over about 53 % of the total land (1750000 km 2 out of the total land area of 3280000 km 2 ) area of India (Narayana & Ram Babu, 1983).The regions of high erosion include the severely eroded gullied land along the banks of the river Yamuna, Chambal and Mahi and other west flowing rivers in Western Indian states. The Himalayan and lower Himalayan regions have been greatly affected by soil erosion due to intensive deforestation, large scale road construction, mining and cultivation on steep slopes. Areas affected by soil erosion in India can be broadly grouped into two categories, representing, firstly the Himalayan and Lower Himalayan region and secondly other regions. In the present paper light is focused on erosion and its impacts on sedimentation and Floods considering relevant case studies, also some of the potential remedial measures are briefly discussed.