Geographic information system-based morphometric characterization of sub-watersheds of Meenachil river basin, Kottayam district, Kerala, India

The study areas Tikovil and Payppara sub-watersheds of Meenachil river cover 158.9 and 111.9 km(2), respectively. These watersheds are parts of Western Ghats, which is an ecologically sensitive region. The drainage network of the sub-watersheds was delineated using SOI topographical maps on 1: 50,000 scale using the Arc GIS software. The stream orders were calculated using the method proposed by Strahler's (1964). The drainage network shows that the terrain exhibits dendritic to sub-dendritic drainage pattern. Stream order ranges from the fifth to the sixth order. Drainage density varies between 1.69 and 2.62 km/km(2). The drainage texture of the drainage basins are 2.3 km(-1) and 6.98 km(-1) and categorized as coarse to very fine texture. Stream frequency is low in the case of Payappara sub-watershed (1.78 km(-2)). Payappara sub-watershed has the highest constant of channel maintenance value of 0.59 indicating much fewer structural disturbances and fewer runoff conditions. The form factor value varies in between 0.42 and 0.55 suggesting elongated shape formed for Payappara sub-watershed and a rather more circular shape for Tikovil sub-watershed. The mean bifurcation ratio (3.5) indicates that both the sub-watersheds are within the natural stream system. Hence from the study it can be concluded that GIS techniques prove to be a competent tool in morphometric analysis.