The effects of vegetation coverage, topography and coastal orientation on the 2011 Tohoku-Oki (Japan) tsunami inundation investigated by satellite data

Abstract

We have studied the disastrous effects of the tsunami triggered by the earthquake (M 9.0) occurred on March 11th, 2011 offshore the Honshu island (Japan). The tsunami caused a huge amount of casualties and severe damages along the coastline of most of the island. The dataset used is composed of data in the visible and thermal spectral range provided by ASTER sensors, and in the microwave range from the active SAR sensors by ENVISAT mission. The processing and the analysis of this large amount of data from different sensors was performed in order to obtain the tsunami inundation map of the Sendai coastal area. Unsupervised and supervised classification algorithms have been applied to provide land cover change detection maps. The identified classes are: stressed vegetation, infrastructure and structure damage, flooded and debris areas. A maximum value of the inundation, about 6 km, is found in the central portion of the Sendai plain and the distance drops to about 1 km at the edges of the plain. The maximum inundation line has been jointly analyzed with the ASTER DTM providing the run-up, values ranging from a minimum of few meters to a maximum of 35m. We point out that the high-relief and the slope gradient are the main inland factors influencing the inundation distance in the study sector, while the vegetation cover and the coastal strike do not significantly affect run-up and wave inundation.