Toshimitsu Takagi

Tsunami Damage Estimation in Consideration of Beach Transformation and Dike Failure

Quantitative estimation methods for tsunami damage to houses and humans are proposed in consideration of beach transformation and dike failure. Case studies were conducted for Kochi Coast, Japan, where dike subsidence caused by earthquake motions, topographical change by tsunami, and dike failure by toe scouring is expected. Damage to houses and humans on land increases with dike subsidence and dike failure, and public awareness of evacuation had a significant influence on the extent of human damage. The methods used in this study quantitatively evaluated the mitigation of tsunami damage achieved by making, coastal dikes earthquake- and tsunami-resistant, and raising the level of evacuation awareness.

Projection of Topographic Change of an Estuary Terrace by Horizontal 2-D Simulation Model, Considering Grain Size

A numerical model for estimating the terrace topography changes caused by floods is introduced, by considering grain size of sediment discharged from a river. Applying this model to Fuji river-mouth, the sediment discharged during floods can be estimated with an aspect of quantity and quality. As the result, it was obvious that the major part of sediment discharged from Fuji river-mouth at floods is flushed out offshore in deeper than 20m depth, which can not contribute as the longshore sediment transport that nourish the neighborhood of the river-mouth.