Geomorphic signatures of active tectonics in Subansiri River Basin, eastern Himalayas

The Subansiri, a major tributary of the Brahmaputra with its catchment area (35763 km(2)) spreading almost entirely in the Eastern Himalayas across almost all the major and local tectonic features in the area witnesses large numbers of seismic events. Active tectonic indices like relief and slope, drainage pattern, longitudinal profile, valley profile, hypsometry, valley asymmetry factors and transverse topographic symmetry index, stream length gradient, valley floor-height ratio extracted from SRTM 3 arc-second data prove that the evolving basin morphology has substantial contribution from the Himalayan tectonics. Seismic data are incorporated in the study to establish the potentially active tectonic elements in the catchment area. The study shows that the western part of the Subansiri River Basin is profoundly tilted towards north in the upper catchment and towards east in the lower and middle part of the catchment. The predominant tectonic movements in the western part of the basin caused the tilting of the basin towards north in the upstream and towards east in the middle and lower parts.