Morphological analysis of the Gandak River between Valmikinagar Barrage and Chakia using Google Earth Engine

The Gandak River originates in Nepal and flows into the Ganges River in India. It is undergoing substantial geomorphological transformations driven by climate change and human activities. The current study analyzed satellite imagery of 33 years (1990-2023) using the MNDWI index, leveraging platforms such as Google Earth Engine and ArcGIS to assess morphological changes between Valmikinagar barrage and Chakia, India. To scale factor correct and mitigate the impact of cloud interference, the cloudMask was applied to the satellite images. The whole river was divided into four reaches to investigate the morphological changes. In Reach 1, a significant portion of the river shifted to the left, with bifurcation and widening being the dominant features, while in Reach 3, a significant braiding pattern emerged after 1990, and the braiding index increased by 50% until 2020. The river exhibited planform variation, widening, and meandering patterns in reaches 2, 3, and 4, with a higher population density observed along the right bank. In Reach 4, the upstream region, the river shifted leftward and bifurcated. The river widened, braided, bifurcated, and merged in almost all the reaches along its stretches comparatively. This study is vital for flood mitigation strategies, riverbank stabilization, erosion control measures, and proactive actions to minimize socioeconomic losses before flooding events.