Tsunami/Phase 1/Lesson1 5

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Height and Run Up

Tsunami waves are described by both their height and their “run-up”.
Tsunami run-up is the maximum height that the tsunami reaches on land above normal sea level at the time (see diagram). For example, if there is a house across the street from the beach that sits 5 metres above the sea level at high tide: a tsunami, occurring at high tide, would have 5 metres run-up if the water reached the doorstep of that house. Run-up is dependent on the type and size of tsunami, as well as coastal landscape and how the land is being used. Run-up is a more useful measure than tsunami height as it relates more closely to the onshore effects of a tsunami. Run-up is the most visibly destructive part of the tsunami as the water picks up debris along its way and with great force swamps the coastal landscape: causing damage to anything in its path (buildings, etc).

Source: NZ Ministry of Civil Defence & Emergency Management