Prioritisation of subwatersheds based on morphometric analysis of drainage basin: a remote sensing and gis approach

Abstract

Remote Sensing and Geographic Information System (GIS) techniques are being effectively used in recent times as tools in determining the quantitative description of basin geometry i.e., morphometric analysis. In the present study, each of the nine subwatersheds of the major part of Nayagram Block in the Midnapore District, West Bengal have been studied in terms of the morphometric parameters - stream length, bifurcation ratio, drainage density stream frequency, texture ratio, form factor, circularity ratio and elongation ratio and prioritised all the subwatersheds under study.

The results suggest that the ratio between cumulative stream length and stream order is constant throughout the successive orders of a basin. The morphometric parametersbifurcation ratio and drainage density, confirm that the area is under dense vegetation cover and virtually the drainage has not been affected by structural disturbances. The form factor values indicate that the basin has moderately high and short duration peak flows. It was observed from the prioritisation of subwatersheds, the subwatershed 8 has got the highest priority because of high erosion intensity considering the above mentioned morphometric parameters. The subwatersheds have been analysed through Sediment Yield Index (SYI) model also and the results tally in most of the cases with the present approach. The subwatershed 8 is coming under priority—I by SYI model also, which indicates that the morphometric analysis could be used for prioritisation of subwatersheds even without the availability of reliable soil maps of the area under study.