Tsunami inundation area and run-up height in the Iwate coastal region following the Great East Japan Earthquake as estimated from aerial photographs and digital elevation data

Abstract

The Great East Japan Earthquake of 11 March 2011 unleashed a powerful tsunami that struck the coastal region and left death and extensive destruction in its wake. This event prompted many investigations to assess the damage and the extent to which the tsunami affected areas along and adjacent to the coast. In this paper, we use aerial photography and a digital elevation model to assess the inundation extent and run-up height of the tsunami along the coast of Iwate prefecture. First, the size of the area affected by the tsunami was calculated by using the observed borderline trace of its farthest reach inland. Then, elevations above sea level were determined for various points along the trace. This required a variety of approaches because of the variation in the topography and gradient of the slope along the coastline from flat to very steep. The results of our investigation showed that aerial photography can be used successfully to obtain a broad approximate assessment of the reach of a tsunami and associated damage, thereby avoiding the need for immediate on-site inspections. Furthermore, our results suggested that the tsunami run-up height in 2011 could have reached more than 40 m at places scattered along the Iwate coast.