What is run-up and inundation?
When a tsunami approaches a coastline, the wave begins to slow down and increase in height, depending on the topography of the sea floor. Often the first signs of a tsunami are a receding water level caused by the trough of the wave. In some instances though, a small rise in the water level just before the recession, has been observed. Regardless, the incoming wave approaches much like the incoming tide though on a much faster scale. The maximum vertical height to which the water is observed with reference to sea level is referred to as run-up. The maximum horizontal distance that is reached by a tsunami is referred to as inundation.
