The Great East Japan Tsunami in March, 2011 caused the significant changes of morphology on Sendai Coast. The flushing of sand spit in front of Nanakita River mouth and the breaching at Akaiko area can be observed. This study investigates the erosion of shoreline on the right side of Nanakita River mouth and the recovery of the breaching after the tsunami. Estimation of diffusion coefficient, which is an important parameter in numerical simulation of shoreline change, has been carried out for both study areas from measured data of erosional area propagation. These values of diffusion coefficient have been used to reproduce the erosion and the recovery of shoreline positions at study areas. The results show good agreement between the analytical result and measurement.