Breaking waves
Shallow water waves feel the bottom, and, because their speed depends on the water depth, slow down
Orbits of water particles near sediment water interface first become elliptical then devolve to a back-and-forth movement as waves travel to shallower water
Waves could slow by reducing wavelength (L) or increasing period (T); observe that waves reduce L but keep T constant
- Wave height is unchanged but wavelength is shorter, so waves steepen, and often take on trochoidal form
- As waves slow, their total kinetic energy remains about the same; later waves add energy to waves already slowed, so crest heights of waves may actually increase
- Energy of particles of water at different positions in wave remains as nearly constant as possible; particles in upper parts of wave less affected by bottom, so keep circular path
In response to the slowing, steepening, etc, waves eventually break, usually when wave height H = 0.8D