Geomorphic indices based topographic characterization of Alaknanda catchment, Western Himalaya using spatial data

Morphometry is an important method for understanding geomorphic processes, such as drainage development, impact of tectonics on the landscape, differential erosion, and categorizing the erosion stages of a varied topographic relief. The precision of a morphometric analysis depends on the high-resolution digital elevation models and a powerful estimation tool. The purpose of the study is to calculate the geomorphic indices such as Stream length gradient Index & SL-Hot Spot, Topographic swath profile, Transverse topographic symmetry factor, Channel Steepness Index, Hypsometry, and Erosion-Uplift Rate. The comparative analysis was done for the 3 sub-catchments of the Alaknanda Basin namely Upper Alaknanda, Dhauli and Middle Alaknanda. The results obtain from each of the catchment shows the spatial distribution of hot and cold spot that helps to select the zone with high SL anomalous values and principal knickzones. This information is associated with major thrusts such as the South Tibetan Detachment System (STDS), Main Central Thrust (MCT), Vaikrita Thrust (VT) of Munsiari group, Alaknanda Fault (AF) and other minor faults with the proof of landscape signature. Various knickpoints were found along the trunk stream and have been precisely analyzed using the SL-HCA approach, validated through aerial imagery and, finally, through the detailed field observations. The study also found that convexity in the river profile and knickpoints around Karnaprayag, Nandaprayag, and Joshimath, the uplift rate exceeds the rate of incision. Further, the findings show that these outputs are used in geomorphological investigations like tectonic activity, rock differential erosion, and hillslope formation.