Neotectonic appraisal of Ramganga River basin, Eastern Kumaun, Himalaya, India

The Ramganga River flows from north to south and drains the northeastern (Lesser Himalaya) of the Himalaya. It transects with numerous active faults, thrusts, and litho-tectonic units before the confluence with the Saryu River at Rameshwar.The present study aimed to determine the virtue of geomorphic indices in appraising the status of neotectonic activity in the Ramganga River Valley, Eastern Kumaun, Himalaya. The watersheds and drainage network were extracted using the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) DEM at 50000 and 100 Pixels threshold, derived18 sub-watersheds and detailed drainage network. Further, this study deciphered the relative neo-tectonic activity of the Ramganga river using the Index of Relative Active Tectonics (IRAT) based on various geomorphic indices Bifurcation Ratio (Br), channel sinuosity (Cs), Asymmetry Factor (Af), Hypsometric Integral (HI), Basin Elongation Ratio (Re), Drainage Density (Dd), Drainage Texture (Dt), and Stream Length Gradient (SL). These indices were classified into high, moderate and low to provide a rank to sub-basin for deriving the IRAT. The northeastern bank of Ramganga River shows high neo-tectonic activity, viz., stream length gradient (500- 1688), channel sinuosity (1.41- 1.48), and valley floor width to height ratio (0.11- 0.34) than southwestern parts.