Morphometric analysis of the Pabbar River Basin in Himachal Pradesh and Uttarakhand, India

Morphometric analysis offers a quantitative framework essential for comprehending basin geometry, geomorphic evolution, and drainage characteristics, which are crucial for effective watershed management. The Pabbar River Basin, a Lesser Himalayan tributary of the Yamuna River system in Himachal Pradesh and Uttarakhand, is studied using Copernicus GLO-30 Digital Elevation Model (COP-DEM) data at 30 m resolution. Linear, areal, and relief parameters from ArcGIS 10.8’s standard hydrologic modelling (fill sinks, flow direction, flow accumulation, raster thresholding, and pour point demarcation) show that the basin’s sixth-order dendritic drainage network has a uniform lithological character and moderate structural control. A slope-based drainage network with limited tectonic control has been revealed by linear analysis, having a mean bifurcation ratio of 4.31. Form factor, elongation ratio, and circulatory ratio point to a moderately elongated shape of the basin. A low drainage density (Dd) of 1.22 km/km² and stream frequency (Fs) of 1.28 km⁻² are indicative of a permeable subsurface, high infiltration, and restrained surface runoff capacity of the basin. Relief parameters like dissection index (0.82) and ruggedness index (5.25) reflect active vertical erosion and dissection across the basin. The basin has been identified in the equilibrium stage of geomorphological development, witnessing majorly balanced constructive and destructive processes, with a hypsometric integral (HI) of 0.49 and an S-shaped curve. Integrating morphometric parameters indicates the level of geomorphic maturity and suggests a moderate susceptibility to erosion. These key results establish a robust scientific foundation for sustainable land-use planning and efficient watershed management in the Himalayan region.