Detection of landslides due to the 2013 Thypoon Wipha from high-resolution airborne SAR images

A strong typhoon hit the Pacific coast of Japan from the night of October 15th to the morning of 16th, 2013, and caused huge damages, especially in Izu-Oshima island, Tokyo. Synthetic aperture radar (SAR), which can observe the earth surface despite of weather conditions, is an effective tool to grasp damage situation caused by typhoons. In this study, pre-event Pi-SAR-L and post-event Pi-SAR-L2 airborne radar images with full polarizations were used to detect landsides and debris flows in Izu-Oshima. First, the extraction of potential landslide areas was carried out using only the post-event image by land-cover classification and from the standardized difference polarization index (NDPI). Then the difference of backscattering intensity between the pre- and post-event SAR images was calculated to extract potential landslides. In addition, a 5-m resolution digital elevation model (DEM) was introduced to remove errors. Finally, the results were verified through the comparison with the result from visual interpretation.