8. Delineation of Waterlogged Areas Using Geospatial Technologies and Google Earth Engine Cloud Platform

The plethora of remotely sensed datasets, specifically the Sentinel-2 data, provides an opportunity for assessment of waterlogging areas. Surface waterlogging is one of the main hazards in north Bihar, specifically in Gandak and Kosi command areas, which necessitates to map and monitor the waterlogging situation accurately at a fine scale. Present study is carried out with an objective of mapping the permanent and seasonal waterlogging areas in a flood-prone Vaishali district, Bihar state using Sentinel-2 multi-spectral data available at 10 m spatial resolution for 2020. The permanent and seasonal waterlogged area mapping were carried out using two approaches, namely spectral index (NDWI) and Otsu method based on the wetness of KT transformed images. The result suggests that both techniques could identify similar spatial patterns of waterlogged areas, while differed on area statistics. The total area under permanent and seasonal waterlogging using NDWI was less compared to the Otsu-KT approach. The higher estimate of Otsu-KT approach could be related to saturated areas, where pixels with higher moisture content during the binary thresholding approach may get classified. Although Otsu algorithm proved to be effective for delineation of water bodies and river network, its efficacy for delineation of waterlogged areas with saturated areas needs to be studied extensively.