Mitigation effects of onshore perforated barriers on inundation and forces induced by tsunami and tsunami-driven objects

The hydraulic performance of onshore barriers in response to tsunami and a tsunami-driven shipping container was examined experimentally. For the barriers subjected to tsunami up to twice their designed height, experiments with various barrier permeability were conducted to assess the mitigation effect and the concurrent forces on the barrier. The perforated barrier with 30% porosity reduced the momentum flux of the inundation flow behind the barrier by 40-60% even when the water overflowed the barrier. Below the overflow limit, the barrier reduced the fluid force acting on it by 40% of the corresponding force on the impermeable barrier. The force on the perforated barrier was close to half the momentum flux of the incoming inundation. The low-permeability barrier buffered the impact of the drifting shipping container and reduced the impact force on the barrier. The total force induced by the inundation flow associated with the driftage was reduced with decreasing permeability of the barrier. The inverse relation between the impact forces acting on the high- and low-porosity barriers was in contrast to that of the fluid forces. The permeability of wall-type structures has an important influence on inundation mitigation and reduction of the fluid force and the impact force.