CS(AR)-38/96-97 : Sediment yield estimation and watershed prioritization in Shakkar river

Abstract

Soil erosion occurs by both wind and water as agent of erosion. In humid areas water is a main cause of erosion. An area in Narmada basin namely Shakkar catchment is selected. Areal extent of the catchment is 2236 sq. Km. This lies in humid climatic region and is mainly forest covered mountainous catchment. IRS LISS I digital data are used to obtain land use and land cover map. The data are digitally processed by sequential clustering technique in PC ERDAS and themes are identified through color in GIS and classes in collateral data. Subwatersheds (89) are delineated from a report on Watershed prioritization. Areal extent of subwatersheds varies between 5077 Ha to 588 Ha. Erosion intensity mapping units (EIMU) are extracted by using GIS operations on collateral data and maps produced from remote sensing data and GIS. Various operations of map overlay, classification, reclassification are used. There are differences in EIMU extent. This is concluded based on general observation of EIMU derived here and that in collateral data. GIS operation has also been useful for extracting eroded stream bank area in northern plain region. Softwares used are PC ERDAS and ILWIS. There are 3, 50, 36 subwatersheds classified with very low, low and medium priority classes, respectively. Values of sediment yield indices for these classes are respectively 900- 1000, 1000- 1100 and 1100- 1200. Medium priority subwatersheds are located in alluvium, shale/ sandstone and basalt geology areas. In alluvium and shale/ sandstone areas of the northern plain, river bank erosion is a main cause for 'medium' priority class. 'Medium' priority areas are also located in hilly and upland areas due to higher slopes and open land class. For Other area of 'low' priority effort should be made to reduce soil loss from bare land, cultivated land and river banks. The sediment load transported at Gadarwara is estimated as 2121964 tonnes year-1. The sediment yield from the catchment is 949 tonnes km-² year This is the yield from Upper Narmada upto Jamatara.