GIS-based Landslide Hazard Zonation in the Bhagirathi (Ganga) Valley, Himalayas

TLDR

Landslides cause widespread damage in the Himalayas, and hazard zonation is essential for rapid mitigation and strategic planning. The study mapped landslide hazard in the Bhagirathi Valley using GIS, integrating topographic, geological, satellite, and field data, applying an ordinal weighting scheme to produce a Landslide Hazard Index and delineate hazard zones. Landslide distribution is mainly controlled by proximity to thrust zones, presence of Munsiari Formation, and barren or sparsely vegetated areas.

Abstract

Landslides cause widespread damage in the Himalayas. Landslide Hazard Zonation is important to take quick and safe mitigation measures and make strategic planning for the future. A part of the Bhagirathi Valley in the Garhwal Himalaya was selected for landslide hazard zonation. The study utilized different types of data including Survey of India topographic maps, geological (lithological and structural) maps, IRS-1B and-1D multispectral and PAN satellite sensor data and field observations. The processing of multi-geodatasets was carried out in a raster GIS environment. The various data layers generated and co-registered were: landuse/landcover, buffer map of thrusts, buffer map of photo-lineaments, lithology, buffer map of drainage, slope angle and relative relief. Data integration was carried out using the ordinal scale (qualitative) relative weighting rating technique to give a Landslide Hazard Index (LHI) value. The breaks in the LHI frequency diagram were used to delineate various landslide hazard zones, namely, very low, low, moderate, high and very high. Field data on landslides were employed to evaluate and validate landslide hazard zonation map. It is interpreted that the distribution of landslides is largely governed by a combination of geoenvironmental conditions like proximity (>500 m) to the thrust zone, presence of Munsiari Formation (Higher Himalayan Crystalline) and barren or less-vegetated areas.