Beach effects on waves
From KayakWiki
Wave propagation deals with the formation of deep water waves where the only parameters are within the air/water interface. As a wave nears shore, it begins to feel the effect of the bottom and becomes a shallow water wave. (Deep water and shallow water have nothing to do with the actual depth of the water, but the relationship between wave height and water depth).
When a deep water wave meets the beach with enough energy, it can no longer maintain a 1:7 height to wavelength ratio. Think of the wave as a runner. Its 'feet' begin to slow down in the sand; its 'head', unrestrained by land begins to fall forward and 'trip' or break.
When deep water ocean swells meet a coastal beach, surf results. Beach slope effects surf type, either gently breaking or dumping. Dumping waves are found on steep beaches while gradually breaking waves are found on gently sloping beaches. Think of our hypothetical runner--they fall down slowly on gradual beaches, and do a faceplant on steeper beaches.
Often dumping waves and breaking waves can be found on the same beach, depending on time of year or tidal height.
At higher tides, the beach profile is often steeper, producing "dumpers"; whereas the profile is more gradual at lower tides, resulting in "breakers".
In the summertime, when wave energy is lower, there is more gradual erosion of the beach face, and sand is carried out in a gradual slope seaward. Conversely, in the stormy winter season, there is a great deal more wave energy picking up sand particles and depositing them higher on the beach face. The result is dumping winter waves and breaking summer waves.
High-tide winter beaches will predictably have lots of dumping waves.
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