Author(s): Tatsuki Iida; Shuichi Kure; Keiko Udo; Akira Mano; Hitoshi Tanaka
Linked Author(s): Hitoshi Tanaka
Keywords: Tsunami; Coastal levee; Breach; Return flow; Two-dimensional finite volume method
Abstract: On March 11,2011, a tsunami hit the Sendai Bay Coast and broke 80%of the coastal levees. The areas around thebreached levees were scoured deeply, causing adverse effects thathaveimpactedpost-disaster reconstruction efforts. This motivated us to analyze the mechanism of the local scouring in the areas around thebreached levees. We collected and investigated various data such as aerial photographs and tsunami videos, and found the breach points progressing in two steps: first, the brittle upperpartofthestructure was destroyed by the first leading wave. Second, the concentration of the return flow eroded and breached thepartiallybrokenlevees from the first step. In order to understand the details of the second step, a numerical simulation was conducted using a finite volume method. Takingintoaccountthe results of the simulation, wediscussedandanalyzed thescouringmechanismaroundthebreachedlevees.