Relationship between tsunami velocity, wave length, and water depth.

This is one of the slides from Larry Braile's PowerPoint presentation.

Tsunami wave propagation characteristics note that as water depth becomes smaller, waves slow down, become shorter wavelength, and have larger amplitude.

Larry asks: When the water is 10 m deep, what is the separation of the waves in minutes?

Here's my answer:  The formula relating the period (T) with velocity (V) and wavelenght (L) is:

T = L / V

for 10m depth, T = 10.6/36 = 0.29 hours (about 18 minutes)

From a trough, the water would rise for 9 minutes and then fall for 9 minutes to the next trough.

The velocity is given by the squareroot of (water depth X the acceleration of gravity)