Beach recovery and non-recovery processes were examined by exposing beaches to solitary waves in combination with three kinds of regular waves. Under depositional regular waves, beach recovery processes under tsunami conditions were achieved within thirty minutes. Under erosional wave conditions, however, a beach recovery process was not observed. This is partly because a solitary wave does not break in the offshore bar crest, but does so near the shoreline.


The Great India Tsunami caused major damage to civil infrastructure. The Japanese Society of Civil Engineers (JSCE) sent teams of engineers to the disaster areas to examine the damage (JSCE, 2005). There was some damage to beaches and coastal structures due to the tsunami; i.e. beach erosion, scour and inundation. It is reported recently through the India Ocean Tsunami survey that a couple of beaches changed by the tsunami have recovered in only one month (Dalrymple and Kriebel 2005). However, not all the damaged beaches have recovered, and the actual recovery processes of beaches have not been clear. Sugahara et al. (2003) have studied sheets of sediment deposited on the land due to the tsunami. Kobayashi et al. (2004) have also carried out experiments on onshore-offshore sediment transport under positive and negative solitary waves, and showed the importance of the initial wave profile for the swash sediment dynamics. The knowledge of sediment transport processes under tsunami conditions is less than that under wind waves. Therefore a method to simulate the beach profile changes due to a tsunami has not yet been proposed. To examine the time-space variation of beach profiles, wave-number spectra of bottom profiles has often been used. Hino (1968) showed the "-3 power low" of the equilibrium spectrum of sand waves for high frequencies, based on a dimensional ground.

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