Tidal resonance

In oceanography, a tidal resonance occurs when the tide excites one of the resonant modes of the ocean. The effect is most striking when a continental shelf is about a quarter wavelength wide. Then an incident tidal wave can be reinforced by reflections between the coast and the shelf edge, the result producing a much higher tidal range at the coast.The speed of long waves in the ocean is given, to a good approximation, by g h {displaystyle scriptstyle {sqrt {gh}}}  , where g is the acceleration of gravity and h is the depth of the ocean.For a typical continental shelf with a depth of 100 m, the speed is approximately 30 m/s. So if the tidal period is 12 hours, a quarter wavelength shelf will have a width of about 300 km.