TSUNAMI-INDUCED SEDIMENT TRANSPORT SIMULATION USING BEDROCK DISTRIBUTION UNDER SEAFLOOR - CASE STUDY OF KESENNUMA BAY -

Abstract

 Field survey of bathymetry, sediment and bedrock of the narrow in Kesennuma Bay have been investigated. Numerical simulations of tsunami-induced sediment transport during the 2011 Tohoku tsunami were also improved by using the bedrock and sediment dataset. After the tsunami, depositions at the center of the narrows, erosions at the sides and the north area, and depositions at the south area were confirmed. By utlizing the bedrock data, the reproducibility of the field modeling was improved although the erosion of the narrows was limited to the bedrock distribution. It was found that the introduction of the bedrock is important to prevent underestimation of flow velocity and topographic changes. Furthermore, the simulations with simple consideration of erosion resistance due to the geology showed that the effect of erosion resistance was small and within the range of conventional modeling. The erosion speed in the narrows was characterized during the rising and the stationary period of the Shields parameter.