Author(s): Vo Cong Hoang; Hitoshi Tanaka; Yuta Mitobe
Keywords: Tsunami; River mouth; One-line model; Diffusion coefficient; Erosion propagation
Abstract: The tsunami, which happened on March 11, 2011 in the northeast of Japan, caused significant changes of morphology on Sendai Coast, Miyagi Prefecture. The concave shoreline can be observed after the flushing of river sand spit and the sand barrier in front of the lagoon induced by the tsunami and return flow. Measured data indicating the erosion of sandy beaches, which are adjacent to the concave shoreline, were happing just after the tsunami. That erosion was propagating along the coast during the recovery process. This study investigates the erosion of shoreline on the right side of the Nanakita River mouth through the aerial photograph and the analytical solution of one-line model. The erosion propagation distance is proportional to the square root of elapsed time. Diffusion coefficient, which is an important parameter in numerical simulation of shoreline change, has been estimated from measured data of erosion propagation distance. This value is utilized to reproduce the erosion and the recovery of shoreline positions at study area. The results show good agreement between the simulation and measurement.