Landslides along frontal part of eastern Himalaya in east Siang and lower Dibang districts, Arunachal Pradesh, India

Abstract

Eastern Himalayan foothills particularly between Siang and Dibang Rivers are prone to landslides. The causative factors of landslides are steep slopes, presence of major structural discontinuities, multiple joint sets, drainage density, weathered to soft nature of rocks and heavy rainfall. Most of the landslides are taking place in steep to very steep slopes. Fault gouges and brecciated rocks developed along the Main Boundary Thrust (MBT) zone have also facilitated the initiation of many landslides. Wedge analyses for sandstones and quartzites have also been carried out to determine their influence on the slope stability and potential failure. The area is also susceptible to high rate of erosion due to structurally controlled streams and gullies resulting in profuse development of fans along the foothills. Seismic condition of the region is also a major concern for the slope stability. Landslides debris usually chokes the streams, destroy the bridges, subways and roads and affect cultivated lands particularly along the mountain front. Neotectonic activity along the MBT has resulted in the development of young and steep hill-slopes, which are prone to landslides.