Structural control of landslides in Eastern Kumaun Himalaya: Case study from Sukhidhang-Ladhiya section

Landslides are the most common hazards which modify the surface morphology of the orogenic belts. Structural conditions and nature of slope forming material play a vital role in the development of surface morphology. The paper highlights the influence of structure on slope morphology and consequent instability pattern in Sukhidang-Ladhiya section in Eastern Kumaun Himalaya. Rocks of lesser Himalayan sequences, Siwalik Group and veneer of Quaternary deposits occur in the area. The area is punctuated by many landslides of various dimensions affecting all the lithological units present; however, study is based on three major landslides occurring along the Main Boundary Thrust (MBT) and Himalayan Frontal Thrust (HFT) zone. Structural data shows that thrusts environment has manifested in crushing and shearing of rocks, which play an important role in landslide proneness along with the rainfall intensity. Evidences of active tectonics such as triangular facets (flatirons), tilting river terraces and active landslides zones have been noticed in the study area. Limited data on temporal details of landslide morphology (perimeter and area) from remote sensing and topographical sheets indicate that perimeters and area of active scars of landslides in the area are gradually expanding, probably associated with tectonic movements in proximal areas of thrusts.