FRAMEWORK DEVELOPMENT FOR LANDSCAPE EVOLUTION OF THE HIMALAYAN (GANGA) RIVER BASIN IN RESPONSE TO NATURAL HAZARDS AND ASSOCIATED GEOMORPHOLOGICAL CHANGES

Abstract

The river morphologies and the associated landscape experience considerable changes in response to landslides and floods. The young and tectonically active Himalayan region is more prone to such natural hazards. The impacts of climate change and anthropogenic activities have further increased the frequency and intensity of such natural disasters in this already active region. These disasters cause vast losses of life, property, infrastructure and disturb the ecological balance. This study explores the geomorphological changes occurring in the stretch of River Ganga starting from Devprayag (Devprayag is the confluence point of the rivers Alaknanda and Bhagirathi) using the Google Earth Engine (GEE) cloud-based computing tool. We extract the active river channel width using Landsat multispectral images. The results show considerable changes in width over the years (1990-2021) and the changes start from the knickpoint continuing towards downstream. The changes in the river’s bank line indicate the bank erosion and relocation of sediments along the river, likely supplied by erosion processes at upstream reaches. Here, we try to identify the critical point where the deposition process first starts to highlight the most vulnerable zone geomorphologically. The changes obtained from Google Earth Engine is validated with geomorphological changes obtained from Digital Shoreline Analysis System which is an Arc GIS based software application. The study further focuses on whether there has been an increase in sediment deposition in recent years due to likely increased erosion related to deforestation on upstream reaches of the river system namely in Alakananda catchment and Bhagirathi catchments. We try to achieve this goal by correlating the river landform changes and land cover changes along riparian areas of the river temporally. Our overall objective is to develop a framework for studying the geomorphological changes using secondary data and correlate changes or processes in upstream reaches to depositions or erosions along the downstream sections of a high-energy river.