Detection of Flood Inundation Areas Based on Sentinel-1 SAR Imagery in the Klawing River Watershed

Abstract In December 2020, the Klawing River overflowed, flooding hundreds of houses in six villages. To aid in evacuation, identifying affected areas is crucial. Using Sentinel-1 Synthetic Aperture Radar (SAR) satellite imagery and the Change Detection Approach with thresholding via Google Earth Engine, flood-inundated areas were mapped efficiently. The process involved detecting changes in backscatter values before and after the flood. Sentinel-1 images from December 13, 2020, were used to map the flood, while images from late 2019 and 2020 served as pre-flood references. Threshold values of 1.22 to 1.24 were applied, revealing flood areas ranging from 10.56 km 2 to 17.31 km 2 .