Damage Assessment of Debris Flow in Atami City, Japan, Based on Field Survey and High-Resolution SAR Data

In the rainy season of July 2021, debris flow suddenly occurred in Atami City, Japan, after a heavy rainfall and it caused significant impacts to human lives and houses along the Aizome river. In this study, the pre- and post-event SAR images acquired from the ALOS-2 satellite were used to extract the affected area and the results were compared with optical images and field survey data. The change detection techniques could identify the hard-hit zone to some extent. But the mountainous topography and thick vegetation cover hindered the accurate extraction of the affected area only from the SAR imagery. To interpret the SAR intensity images, a simple SAR simulation was further carried out using DSMs obtained from pre- and post-event LiDAR data.