Abstract
Rapid identification of affected areas and volumes in a large-scale debris flow disaster is important for early-stage recovery and debris management planning. This study introduces a methodology for fusion analysis of optical satellite images and digital elevation model (DEM) for simplified quantification of volumes in a debris flow event. The LiDAR data, the pre- and post-event Sentinel-2 images and the pre-event DEM in Hiroshima, Japan affected by the debris flow disaster on July 2018 are analyzed in this study. Erosion depth by the debris flows is empirically modeled from the pre- and post-event LiDAR-derived DEMs. Erosion areas are detected from the change detection of the satellite images and the DEM-based debris flow propagation analysis by providing predefined sources. The volumes and their pattern are estimated from the detected erosion areas by multiplying the empirical erosion depth. The result of the volume estimations show good agreement with the LiDAR-derived volumes.
Highlights
Landslides triggered by heavy rainfalls and earthquakes have been one of the frequently occurring natural disasters in all over the world
Debris flow is a form of rapid movement of loose soil, rocks and driftwoods flowed to downstream along valleys due to slope failures
Despite the efforts by the governments, extensive damage was produced by huge number of flooding and landslides, including debris flows triggered by the heavy rainfalls, mainly in the western part of Japan
Summary
Landslides triggered by heavy rainfalls and earthquakes have been one of the frequently occurring natural disasters in all over the world. On 20 August 2014, heavy rainfall-induced debris flows hit the residential areas and produced severe structural damage including 76 fatalities in the northern part of Hiroshima city [4,5]. After these debris flow disasters in Japan, the national and local governments have undertaken the disaster mitigation measures such as new construction of debris control dams, re-identification of hazardous zones and their public disclosure to citizens. Despite the efforts by the governments, extensive damage was produced by huge number of flooding and landslides, including debris flows triggered by the heavy rainfalls, mainly in the western part of Japan. The damages in Hiroshima were caused mainly by debris flows occurred at approximately 8,000 sites
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