Quantitative Morphometric Characteristics of the Varthur Catchment Area, Bangalore Urban District, Karnataka, Using Geospatial Techniques

Abstract

The Varthur Catchment area lies in the southern part of Bangalore Urban District, Karnataka, between 12˚48'24.52"N to 12˚53'59.85"N and 77˚24'59.95"E to 77˚30'6.72"E, covering an area of 284 km 2 . Drainage characteristics were extracted from SRTM DEM and IRS P6 LISS III imagery using ArcGIS 10.2.2, and the catchment was delineated into ten sub-watersheds. The catchment is a 5th-order basin with a dendritic drainage pattern. The mean bifurcation ratio is 3.1, total stream length is 327 km, and mean drainage density is 1.31 km/km 2 , indicating moderate permeability. The elongation ratio (0.064) and circularity ratio (0.53) reflect a structurally controlled, elongated basin. Hypsometric analysis yields an integral of 0.46, placing the basin in the mature stage of geomorphic development, with about 54% of the original landmass already eroded. Sub-watershed prioritisation using the composite parameter method identifies SWS-1 and SWS-7 as high-priority zones requiring urgent soil conservation measures and SWS-2, SWS-3, SWS-4, SWS-5, SWS-6, SWS-9, and SWS-10 are classified as moderate priority, indicating moderate infiltration capacity, while SWS-8 shows the lowest erosion risk. The findings provide a baseline for watershed management and sustainable land- and water-resource planning.