Abstract
Tsunami-induced flow fields around the landward toe of a coastal dike and the effectiveness of countermeasures against local scouring were investigated from full-scale numerical simulations. Numerical results showed that the flow fields were classified into two patterns, i.e., a submerged flow which ran down on the landward slope and submerged under a hydraulic jump, and a clockwise vortex which was formed from a flow separated at the landward edge of protection blocks and a return flow along the surface of a scour hole under the separated flow. Furthermore, the submerged flow was formed when bottom flow velocity at the landward edge of protection blocks was directed downward. This suggested that it is essential to reduce the downward component of the bottom flow velocity in order to prevent the formation of the submerged flow, which increases the depth and width of a scour hole.
