Remote Sensing Approach for Mapping and Monitoring Tsunami Debris

In the 2011 Great East Japan Earthquake and Tsunami Disaster, approximately 23 million tons of debris was estimated over wide areas caused by the tsunami damage. Quantitative estimation of tsunami debris is essential from disaster response point of view. In this study, a novel remote sensing method has been developed for directly measuring the amount of debris in the affected areas and for mapping the results. Specifically, two methods are integrated. The first extracts spatial extent of debris areas using optical sensor data (digital aerial photos and satellite images) obtained immediately after tsunami disaster. The second determines the amount of debris on the ground and quantitatively estimates its amount (volume, weight) by integrating analysis that uses the height of the debris obtained by airborne light detection and ranging (LiDAR).The analysis was conducted in Onagawa town, Miyagi Prefecture, one of the most severely affected by the 2011 event, including the ground truth data acquisition. The horizontal mapping of tsunami debris in Onagawa town was performed through object-based image analysis of aerial and satellite images. Integration of horizontal mapping of tsunami debris and the analysis of digital surface model (DSM) of LiDAR data yields an estimate of the volume of the debris to be used as the observation of debris removal efforts.