Flood Inundation Mapping in Ramganga River Basin Using Synthetic Aperture Radar (SAR) Based Sentinel-1 Data in 2018

Remote sensing data is a widely used technique in real-time flood monitoring and assessing the effects of the flood. The study focuses on the extension of the flood water at pre-flood, during flood, and post-flood events using Synthetic Aperture Radar (SAR) images, which are derived from the sensor of Sentinel-1 satellite in VV polarisation. The study also emphasizes the change of river direction during flood and helps to identify the most vulnerable zones of the study area. Identification of flooded areas and their temporal changes is calculated by the ‘Modified Normalised Differential Water Index’ (MNDWI) formula using the ‘threshold method’. Optical imagery of Sentinel-2 is used to understand the temporal changes of the river path in a better way. Daily precipitation data of the study area is acquired from ‘Tropical Rainfall Measuring Mission (TRMM)’ to assess the contribution of precipitation to the flood that occurred in August-September 2018. The study covers some selected parts of the middle-lower Ramganga river basin in Uttar Pradesh. The results indicate that the peak flood condition occurred on 02 September 2018 (54.51 Sq. Km.) due to heavy precipitation on 24th Aug 2018 (166.41 mm) and 28th Aug 2018 (46.82 mm). The findings show a negative relationship between the distance of surrounding lands from the river channel and the duration of the flood. In the study, it is also observed that the width of the river channel increases at the time of flood, which indicates the necessity of sustainable planning for the development of that area. Overall, the results help to achieve the sustainable goals, making the human and human settlements more inclusive, resilient, safe, and sustainable.