Tsunami Geomorphology: Erosion and Deposition from the 15 November 2006 Kuril Island Tsunami

The 15 November 2006 Kuril earthquake (Mw 8.1–8.4) and tsunami enabled us to collect a compelling data set of coastal geomorphic change in the Kuril Islands from ~3 months before to 9 (and 21) months after the tsunami. Our pre-tsunami and post-tsunami surveys of the islands, including four topographic profiles measured in 2006 and reoccupied in 2007, allow us the confidence to attribute many changes to the tsunami, in spite of an absence of eyewitness accounts in the central islands. Areas with low runup, <8 >m, underwent limited geomorphic change, primarily confined to beach or stream channels. Regions with high runup, >15 m, underwent massive erosion that dramatically altered the coastline. Tsunami deposits roughly corresponded with the extent of tsunami runup and inundation. The amount of sediment eroded by the tsunami far outweighed the amount deposited on land in all cases studied. The tsunami was dominantly erosive in the Kuril Islands because the high-relief topography of the coastline accelerated tsunami outflow.