A numerical simulation of drainage of influent water caused by Tsunami at Kawauchi, Tokushima

This study investigated the phenomena of long-term flooding during 72 hours since a tsunami in Tokushima city by using numerical analysis. We applied AFREL (Application of Flood Risk EvaLuation) software that calculates a movement of water on the ground surface, open channels and sewers. Drainage pumps can be also defined to move water outside of the levees. AFREL has been used to analyze inundation inside of the levee by river water during heavy rains. In this study, the boundary condition of heavy rains was replaced to tsunami calculated by the great Nankai earthquake. The maximum amount of flooded water in the Kawauchi area of Tokushima city was calculated to be about 3 million cubic meters after 10 hours, and 66.1 % of that could be drained at 42 hours from the earthquake with an assumption of the all 13 drainage pumps in operation. On the other hand, a calculation with top three drainage pumps stop could drain 48.3 % of the maximum amount of water. However, the flooded water stayed in low elevation areas for the both cases even after 72 hours.