Disentangling anthropogenic and geological drivers of morphodynamics change in a Himalayan river: The Yamuna River, India

River processes and its morphodynamics are shaped by a combination of geological, climatic, and human-driven factors. Recently, increasing population pressures, rapid urbanization, and related stresses, such as large-scale water diversions by dams and sediment mining activities, have begun to disrupt riverine systems, raising concerns about their long-term sustainability.

This study investigates the impact of human activities and geological controls on geomorphic change in the Yamuna River, a major Himalayan system that originates from the Yamunotri Glacier at an elevation of 6,387 m and drains a basin of 3.66x10⁵ km² over a distance of 1,376 km. The river flows through the Delhi megacity, which is home to approximately 11 million people. Besides the pressure from the megacity, the presence of the dams and sand mining from the channel bed causes intense anthropogenic stress, making it an ideal system for assessing human impacts on the channel form of a major Himalayan river. Downstream of Delhi, the river is further influenced by three major tributary confluences, which introduce significantly more water and sediment flux into the Yamuna River channel, making it a suitable location to study the natural reference stage of the river.

To evaluate these driving factors, we extracted the active floodplain using the Global Surface Water maximum water extent dataset (1984–2021) and applied the Fluvial Corridor Toolbox to segment the river into discrete geomorphic objects. Using Landsat and Sentinel-2 imagery (1984–2024), we quantified object-based geomorphic parameters, including active channel width, water width, braiding index, and vegetation width, for a 1100 km long part of the river.

Results indicate that human activities, such as dam construction, sand mining, and urban expansion, have significantly altered channel structure across multiple scales, particularly in upstream reaches and within the Delhi region. In the detailed analysis, it was found that the impact of sand mining and the pressure exerted by the Delhi megacity were more prominent than that of the dam.  In contrast, the downstream reaches of Delhi reflect a dominant tributary contribution, where these tributaries drive the geomorphic recovery and reorganization of channel form. Together, these patterns demonstrate that the Yamuna is shaped by a complex interplay between human-induced disturbances and natural fluxes from tributaries. Recognizing this dual influence is essential for designing reach-specific, sustainable river management strategies that address both immediate anthropogenic pressures and longer-term geomorphic controls.