Spatial distribution of landslides in response to the geomorphometric constraints in Darma Valley, Kumaun Himalaya

The Kumaun Himalaya is well-known as a geologically and tectonically complex region that amplifies mass wasting processes, particularly landslides. This study attempts to investigate the interplay between landslide distribution and the litho-tectonic regime of Darma Valley, Kumaun Himalaya. A landslide inventory comprising 295 landslides in the area has been prepared and several morphotectonic proxies such as valley floor width to height ratio (Vf), stream length gradient index (SL), and hypsometric integral (HI) have been used to infer tectonic regime. Morphometric analysis, including basic, linear, aerial, and relief aspects, of 59 fourth-order sub-basins, has been carried out to estimate erosion potential in the study area. The result demonstrates that 46.77% of the landslides lie in very high, 20.32% in high, 21.29% in medium, and 11.61% in low erosion potential zones respectively. In order to determine the key parameters controlling erosion potential, two multivariate statistical methods namely Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC) were utilized. PCA reveals that the Higher Himalayan Zone (HHZ) has the highest erosion potential due to the presence of elongated sub-basins characterized by steep slopes and high relief. The clusters created through AHC exhibit positive PCA values, indicating a robust correlation between PCA and AHC. Furthermore, the landslide density map shows two major landslide hotspots. One of these hotspots lies in the vicinity of highly active Munsiyari Thrust (MT), while the other is in the Pandukeshwar formation within the MT's hanging wall, characterized by a high exhumation rate. High SL and low Vf values along these hotspots further corroborate that the occurrence of landslides in the study area is influenced by tectonic activity. This study, by identifying erosion-prone areas and elucidating the implications of tectonic activity on landslide distribution, empowers policymakers and government agencies to develop strategies for hazard assessment and effective landslide risk mitigation, consequently safeguarding lives and communities.