Optimum flood inundation mapping in mountainous regions using Sentinel-1 data and a GIS-based multi-criteria approach: a case study of Tlawng river basin, Mizoram, India.

Floods pose a significant global threat, impacting populations and infrastructure worldwide. However, mapping flood inundation solely with SAR data faces challenges in hilly terrain. To address this, the study integrates SAR data with a GIS-based multi-criteria approach (MCA), incorporating various indices and parameters, to enhance the accuracy of identifying potential flood zones. The findings demonstrate the effectiveness of this approach, with high accuracy validated using GPS data and a physics-based 3-step method. The results also indicate a high level of accuracy, with an area under the curve (AUC) value of 0.92 when comparing Sentinel-1 SAR and optical data during the process of extracting permanent water bodies. The Sentinel-1 SAR-derived flood extent was found to be 9.56 m horizontally distant from the observed maximum flood mark, while the physics-based 3-step approach estimated the inundation extent to be 9.28 m away. However, both methods accurately matched the vertical elevation of 40 m above mean sea level (MSL). The findings underscore the effectiveness of SAR data and GIS-based MCA in monitoring and mapping floods in challenging terrains, offering practical implications for flood management strategies in Tlawng river basin.