Morphometric Analysis of Beshigram Watershed in Swat Valley, Eastern Hindukush, Using GIS and Remote Sensing Techniques

Abstract

Morphometric analysis quantitatively evaluates a drainage basin's linear, aerial, and relief parameters. This study uses various stream attributes to examine the characteristics of the Beshigram watershed, a key eastern tributary of the Swat River that joins it near Madyan. Data sources include ASTERGDEM-V3 (30m resolution) from the NASA website and toposheet 43 A/12. The Arc Hydro tool in ArcGIS 10.8.2 is employed for drainage extraction and empirical analysis. The watershed spans 151.52 km² and contains 294 streams arranged in a dendritic pattern, with the Beshigram River classified as a fifth-order stream. Key morphometric parameters include an average bifurcation ratio of 3.94, a drainage density of 1.40 km/km² (indicating moderate to sparse vegetation, impermeable rocks, and high runoff potential), a circulatory ratio of 0.623, a form factor of 0.489, and an elongation ratio of 0.8. These values suggest an oval-shaped basin with mature topography and moderate to high relief. The aerial aspects highlight the influence of relief on drainage development and the potential for prolonged high-discharge flooding. Geologically, 90% of the watershed is comprise of impermeable rocks. The DEM-derived stream network closely matches the manually digitized toposheet data. The findings demonstrate the utility of morphometric analysis in geological, hydrological, groundwater, flood forecasting, soil erosion, and flood management studies. The analysis reveals that the Beshigram watershed is vulnerable to floods and erosion, highlighting the need for management strategies like reforestation and check dams for flood risk mitigation.