Spatiotemporal migration patterns of rivers in the Ganga-Brahmaputra basin

Deshpande, Rucha Sanjay (2022) Spatiotemporal migration patterns of rivers in the Ganga-Brahmaputra basin. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Deshpande Rucha Sanjay (17MS120)) 17MS120_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Rivers are one of the most dynamic natural features on the planet. Channel bank erosion, lateral accretion, and high-water discharge events lead to the migration of river channels across the floodplain slowly or quickly over time. This channel migration over time could harm human settlement, infrastructure, and natural resources in the floodplain area. The Indo-Gangetic Plain is the world's most extensive alluvial tract, drained by the Ganga, Brahmaputra, Indus rivers, and tributaries. Previous studies were devoted to understanding the spatiotemporal patterns of channel migration along individual river segments. However, regional analysis of channel migration rates and patterns is essential for understanding migration rate variability over a large scale and its control, identifying areas most vulnerable and immune to lateral migration, and execution of the floodplain management. This study uses Landsat imagery from 1990 to 2020 to map and quantify spatio-temporal migration rates of all main river systems in the Himalayan foreland basin. We created annual active channel binary masks from Landsat imagery using Google Earth Engine. We defined the centerline of channels and estimated channel migration rates over time using the RivMAP toolbox in MATLAB. We also calculated the elevation difference between the river channel and the floodplains following a swath-based method and using 30-m ALOS Digital Elevation Models. This study indicates that the channel migration rates are higher within 50-100 km from the mountain front, with the highest values observed in Gandak, Ghaghara, and Kosi rivers. The lower Ganga plain, which is defined as the region along river Ganga South of the Ganga-Ghaghara confluence is identified as the zone most susceptible to migration. The relative elevation difference between the channel and adjacent floodplain is identified as one of the spatial controls on channel migration rates in the Ganga-Brahmaputra plain.

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