Physical Modeling of Hard Structure Effects on Tsunami Force Reduction in Urban Coastal Environment

Countermeasures such as seawalls and submerged breakwaters have been constructed to protect coastal communities from extreme waves, including tsunamis. Extensive studies have been performed to examine tsunami wave forces on structures, but there are few studies to evaluate the effects of defensive structures on alleviating tsunami inundations and loadings on buildings. The current study presents a large-scale experiment to investigate the performance of seawalls and submerged breakwaters against tsunami overflows by measuring the pressures and forces on the series of building arrays at the coasts. Each defensive structure effectively reduced a cross-shore tsunami force and inland flow hydrodynamics at the low water depth cases. The impulsive force on the most seaward side building was reduced by 36% when both seawalls and submerged breakwaters were installed simultaneously. However, the high water depth cases with the submerged breakwater, the impulsive forces on the most seaward building were greater than the baseline cases (absence of countermeasure structure).