Assessing tectonic influence on landscape evolution: case study of the Nandakini Watershed, Western Himalaya

Understanding the active tectonic processes in the Nandakini Watershed is imperative for evaluating geological hazards and seismic risks, as well as for informing land-use planning and natural resource management strategies in the region. Tectonic geomorphology serves as a vital tool for characterizing recent tectonic movements. This research employs GIS techniques to elucidate tectonic activity and its influence on drainage patterns in the Nandakini Watershed, utilizing morphometric parameters derived from SRTM DEM data. Morphometric indices are employed to assess the tectonic movement within drainage basins, capturing both areal and linear factors such as drainage density, texture, circulatory and bifurcation ratios, and stream length ratios. The linear and areal morphometric indices are categorized into three classes representing varying degrees of active tectonic activity. These classifications are then utilized to compute the relative active tectonic index (IRAT). In addition, geomorphic parameters include hypsometric integral, stream length-gradient index, normalized steepness index, chi gradient index, and swath profiles. The majority of the studied region is in an extremely high to moderately active tectonic zone. Large-scale faults and thrusts within the basins are closely correlated with these zones that have been identified. The integrated methodology of GIS-based morphometric analysis and geomorphic study enables the identification of deformed landforms associated with ongoing tectonic activity. Furthermore, these results offer valuable insights for informing watershed management strategies and promoting sustainable land use planning initiatives.