Stability of Composite Breakwaters under Tsunami Attack

Breakwaters are effective structures for mitigating tsunami-induced damage. However, pieces of the breakwater can be displaced by the turbulent tsunami flow, which undermines the stability of the breakwater and reduces its mitigation effectiveness. Assessing the damage to breakwaters in tsunami-prone coasts is, therefore, valuable for the port authority, cargo owners, and coastal residents. Physical experiments were conducted to assess potential damage to a typical composite breakwater in New Zealand due to tsunamis. Higher breakwaters can resist a stronger bore impact and experience delayed initiation of the same damage. A new parameter is proposed to assess the damage in the armor layer, which takes into account the size and density of armor units, the height of the breakwater, and the tsunami bore depth.