Drainage Morphometric analysis of Yagachi watershed area, Karnataka State, India

Abstract

The Yagachi River watershed in Karnataka State has been chosen for a thorough analysis to recognize the drainage system, morphometric features, and vulnerability of the watershed area to erosion. As a prerequisite to the analysis of morphometric features utilizing ArcGIS software, the stream networks and sub-watersheds (viz., SW01, SW02, SW03 and SW04) were delineated by making use of topographic sheets and the Digital Elevation Model (DEM). Yagachi watershed covers an area of 551.45 sq. km and observed predominant drainage patterns are sub-parallel and dendritic with sixth-order drainage. Higher stream orders (U=6), implying greater surface runoff and sediment load, and low mean stream length values in the upper reaches, signifying youthful morphological development and strong erosion potential, are characteristics of streams in the watershed. Drainage density values (1.262 to 1.930 km/km2), particularly at upper reaches in the NW part of the watershed, fine to very fine drainage texture values (7.572 and 8.337), moderate to high values of length of overland flow (Lg) and constant of channel maintenance (CCM) indicate steep to moderate slopes, fairly significant surface runoff, and high erosive power of the streams and greater sediment load. The elongated form of the watershed is shown by the computed lower form factor (Ff) and elongation ratio (Re) values. Relief characteristics of the watershed area, although suggest that the study area is vulnerable to erosion and in youth stage, in reality, the area is characterised more by the features of the late mature stage of landform development. The observed anomaly is attributed to the mountain-plain environment as the steeply sloped hill ranges of Bababudan formations are located in the northwestern parts of the Yagachi watershed area. However, the sub-watershed SW03 with high stream length, drainage density and relief value with fine drainage texture is relatively more susceptible to erosion.