Climatic, tectonic, and fluvial controls on the origin and retreat of the Aharbal Waterfall, Himalaya

River incision is a fundamental geomorphic process in tectonically active mountain regions, influenced by structural, hydrological, lithological, and morphological factors. This process often results in formation of knickpoints along river courses. The Aharbal Waterfall (AWF) is a structural knickpoint, formed along the Vishav River in Pir Panjal Range of northwestern Himalaya. It originated through continuous erosion of glacial till down to underlying basement rocks, composed of highly jointed basalts and agglomerates. Field investigations supplemented by high-resolution drone surveys indicate that AWF has retreated by approximately 538 meters upstream from its original location subsequent to the exposure of basement rocks triggered by intensified fluvial activity in the region. The continued retreat is driven by active tectonics, river incision, and lithological controls. High SL and Ksn values concentrated along the Aharbal reach further support enhanced channel incision and indicate active tectonic forcing associated with the AWF. Numerous step-falls downstream likely mark former positions of the retreating AWF. To quantify retreat rate, we utilized Schmidt hammer (N-type) repeated impact tests and an empirical model evaluating the balance between erosive and resistant forces. Our analysis estimates retreat rate of 0.94 cm/year, which is relatively high given basaltic lithology of the site. The persistent upstream migration is primarily controlled by toppling failure of well-jointed basalts, allowing waterfall to maintain its steep gradient. However, the presence of active faults in the reach especially in vicinity and the potential for landslides in the immediate proximity pose significant geohazards, threatening both the stability of waterfall and surrounding landscape. Understanding these retreat dynamics is critical for assessing long-term landscape evolution and mitigating potential hazards in this tectonically active region.