Interpreting the geomorphometric indices for neotectonic implications: An example of Alaknanda valley, Garhwal Himalaya, India.

Tectonic process can influence the erosion and exert the first order impression on hydrographic network of an area. Geomorphometry, a mathematical analysis of the configuration of the landforms, allows quantifying the degree of landform evolution and is widely used as a measure of tectonic deformation/uplift. Alaknanda valley lies in the tectonically active Garhwal Himalaya which has experienced two disastrous large earthquakes in the last two decades. Morphometric analyses of the valley were carried out in a fluvial erosion dominated regime and the morphometric indices were derived from the ASTER (30 m × 30 m pixel) Digital Elevation Model (DEM) using Arc GIS. The results of the analyses reveal two zones of high deformation/uplift in the valley, viz., the zone of high deformation proximal to the Main Central Thrust (MCT) in the Inner Lesser Himalaya (ILH) and the second zone of moderate deformation/uplift in the Outer Lesser Himalaya (OLH), south of the Tons Thrust (TT). The high deformation in the ILH is ascribed to the focussed convergence and high precipitation; however, the causes for the moderate deformation in the OLH are yet to be established. [ABSTRACT FROM AUTHOR]