Mitigation of tsunami bore impact on a vertical wall behind a barrier

Since tsunamis pose a threat to many coastal areas, the mitigation of tsunami forces is important in saving lives and reducing damage when a tsunami comes. Barriers are generally constructed to protect coasts from extreme waves including tsunamis. Although extensive research has been conducted to investigate tsunami forces on coastal structures, the effectiveness of defensive structures such as barriers, seawalls and embankments in mitigating these forces has not been studied thoroughly. This paper presents a series of physical experiments to investigate the effectiveness of barriers in reducing tsunami bore impact (and associated pressures) on a vertical wall. While horizontal forces and overturning moments on the wall can be significantly reduced if the barrier is high enough, low barriers can lead to larger horizontal forces and overturning moments than if the barrier were absent. Predictive equations are proposed for reduction ratios of horizontal forces and overturning moments, as well as other methods to estimate horizontal forces.