The destructive effects of tsunamis on islands and coastal areas directly result from three factors: (1) inundation (flooding and floating debris); (2) wave impact on structures, ships, and port facilities, and (3) erosion of foundations leading to collapse of bridges, seawalls, and buildings.
Indirect factors of tsunami casualties come from (1) fires initiated in buildings, ships, oil tanks, and gas stations; (2) environmental pollution caused by sewage, oil, and dangerous chemicals; and (3) outbreak of epidemic diseases. All these lead to tragic loss of life, damage to property, and destruction of ports, towns, and villages.