# 10.2: Wave Speed and Energy and Wave Base

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## Wave Speed and Wave Energy

Wave speed is a function of wavelength and wave period, and is related to the wind velocity where the waves form.

Wave speed (c) is the distance the wave travels divided by the time it takes to travel that distance. Wave speed is determined by dividing the wavelength (L) by the wave period (T). [c = L/T]. Wave period is the average of how many seconds pass between a series of wave crests moving past a stationary object in the water, such as a post on a pier or a buoy.

What is important is the combination of the wave height and wave period. Wave period is directly related to the speed the wave is traveling. The longer the period, the faster the wave, and the more energy in contains.
The greater the period the faster the wave moves (Figure 10.5). Also, the greater the period, typically the higher the wave breaks as it approaches the shore. Figure 10.5. Comparison of wavelength to wave speed and wave period.

## Wave Base

Wave base is the depth of influence of a passing water wave—it is about half the wavelength of passing water waves (Figure 10.16). At depths greater than half the wavelength wave motion dies out—the water motion is less than 4% of its value at the water surface and is generally insignificant.