Zonation of Landslide Susceptibility and Risk Assessment in Serchhip town, Mizoram

Abstract

A landslide is the downward-slope movement of soil, rock or organic material under the influence of gravity. It can be caused by a variety of reasons like intense or prolonged rainfall, earthquakes, geomorphology, slope variations and human activities. Landslides include debris flow, slide, toppling or falling movements, and many landslides exhibit a combination of two or more types of movements. Mizoram is one of the most disastrous landslide-prone areas in India. The state experienced landslides yearly during monsoon season. Landslides are a natural disaster. Though landslide occurs naturally, one of the main factors contributing to landslide in city and township can be credited to human interference. The topography of Mizoram is being relatively young; landslide can be a very major economic setbacks. Mostly there are N–S-trending anticlinal strike ridges with steep slopes and narrow intervening synclinal valleys with series of parallel ridges or topographic highs. The other landforms of the state are dissected ridges with deep gorges, spurs, keels, etc. Faulting has produced steep fault scarps. Thus, Mizoram, being a hilly terrain, is extremely prone to landslides. The extent of damage caused varies considerably from place to place, which is mainly caused by human activities and by geological processes assisted by environmental processes. The study area lies in the southern part of the Aizawl district. Remote sensing and GIS techniques are used. Recent advances of satellite remote sensing technology and geographical information system techniques have provided us a more in-depth approach to study landslide phenomena. In the present study, high-resolution satellite data such as QuickBird, IRS and Cartosat-I data were utilized to map the different landslide hazard zones of Serchhip town for undertaking mitigation measures and to identify potential zones of occurrences. Satellite data are utilized for mapping and preparing landslide hazard zones. An in-depth study of slope stability within Serchhip township was also carried out, and it was found that this locality of the town has been severely affected by subsidence and landslides, endangering the lives and property of the people. It was also found that the area comprises very soft shale and interbedded, weathered sandstone and siltstone, which belongs to the Middle Bhuban Formation of Surma Group of Tertiary age. Landslide risk assessment determines the expected degree of loss to landslide and its disruption of economic activities. The correlation of landslide susceptibility with major assets in the region helps to determine the risk assessment. Risk assessment is the final goal. The main objectives are to assess the risk, vulnerability of landslides and mapping, classify the zones of landslide hazards and suggest preventive and remedial measures, methods involving extensive fieldworks and data collections, creation of thematic layers and data analysis. From the present study, it is observed that human activities paired with natural factors have made many parts of Serchhip highly prone to landslides.