The Yamamoto coast over five years; The reconstruction of an embankment with tsunami-induced embayment

The incident waves and return flow of the 2011 tsunami caused severe damages to the coastal morphology and the embankment along Yamamoto Coast, Miyagi, Japan. This study investigates the damages and recovery of coastal morphology and the reconstruction of the coastal embankment along the coast, based on satellite images. During the recovery process, full recovery of breaching was observed at the areas with sufficient sediment supply from adjacent sandy coasts. However, in the areas without adjacent sandy coasts, the formation of tsunami embayment was found. The relationship between the measured area of adjacent sandy coasts, A_S, and the measured area of breaching of the sandy coast, A_B, indicates that the formation of tsunami embayment takes place in case A_B greater than in A_S and vice versa. There are two types of cross sections of reconstructed embankment. Due to the formation of a tsunami embayment in several areas, a setback of approximately 30 m of the reconstructed embankment has been made. At the areas without the formation of tsunami embayment, the reconstructed embankment is elevated above the level of the embankment before the tsunami.