FIELD SURVEY ON TSUNAMI-INDUCED TOPOGRAPHICAL CHANGE

Abstract

 A set of field survey including airborne laser mapping, sea bottom sounding, boring, Swedish weight sounding was conducted to measure topographical change induced by the 2011 Tohoku Earthquake and Tsunami in Takada Coast, Okirai Coast, Ryoishi Fishing Port Coast, Kanahama Coast and Otsuchi River in Iwate Prefecture. Tsunami overtopping caused scouring landward of coastal dike deeper than the height of the ground at the time of the survey. It shows that backfilling occurred with a thickness of several meters after the scouring. Scour depth at dike break was larger than that in adjacency. In Takada Coast, large-scale topographical change resulted in sediment loss of about 1.86 million cubic meters.