The Effects of Tsunamis on the Land

Multiple Wave Damage

• Tsunamis arrive with multiple waves, with the stronger ones typically arriving after the first one hits. Given the shape of the underwater shore, significant amounts of water get pushed upward and higher at the coast, allowing the tidal water to flow higher than it normally would. Anything that is loose on the ground gets swept up and bounced around like cork. Because water is so heavy as a mass, it can move cars, wood, metal, cement, and debris. All of this material with the force of water acts as a grinding catalyst on anything else that gets hit next by the debris waves.

Vegetation Disappears

• Tsunami waves are so strong they frequently uproot trees, bushes and plants from affected areas, inundating them with water until the soil breaks loose as the vegetation gets pulled. Anything that remains roots becomes buried with water and dies off within hours from a lack of oxygen and sun. By the time the mass of water drains from an affected area, usually days or weeks later, the ground that remains resembles a consistency of mud and debris only.

Structural Damage

• Land structures standing in areas hit by a tsunami tend to stand for a bit but sustained pressure from waves and debris eventually collapse many structures. Most buildings are designed to hold weight pressure from above, not from the sides. Wood, stucco, and composite material walls collapse quickly under water pressure, typically being pushed off their foundations and then floating away. Cement structures can remain standing if the water finds ways to flow through the building bottom (i.e. windows, doors, garages).

Agricultural Damage

• Many agricultural zones hit by tsunamis experience significant erosion in a short amount of time. This reshaping of the land or loss of it to the ocean causes two major changes: seawater dumps high levels of salinity inland killing existing plants not wiped off by the water, and much of the loose topsoil in farming areas can be washed back out to sea making the remaining ground useless for crops. Additionally, debris can gouge the land as it gets pushed along by water, damaging canals and irrigation carefully planned for efficient water drainage in crop areas.