ABSTRACT: New Wave Parameters Due To Shoaling

TANNER, WILLIAM F.

Deep-sea wave height, length and period each may have a Gaussian distribution. However, deep-sea wave height and length can't be used in shoaling depths, where sand is moved on the bed, and there is no simple equation which gives modified parameters at each point during shoaling: they must be calculated step-by-step over a bathymetry of some kind.

Shoaling over real-world profiles yields complicated distributions of these parameters, due to bottom irregularities. Shoaling on most profile equations also makes complicated distributions, even without irregularities, showing a bad match with hypothetical dynamic-equilibrium profiles.

One result is that nearshore wave parameters may have polymodal distributions, commonly with two-to-six Gaussian components. Any one component of one parameter may be truncated at either end, hence even the wave period may not be constant from deep water to the beach.

The initial wave period, the deep-water wave height, and the modal inshore wave length can be related in a simple equation for algebraic profiles but not for most examples of natural bathymetry. Therefore one uses iteration (computer simulation) to track deep-sea waves across real-world bathymetry, to the beach. This must be done with many deep-water wave periods & wave heights, to produce a realistic variety of results at the outer edge of the surf zone. The result provides for a more accurate assessment of wave energy expenditure along the wave ray, and hence of the energy available in the breakers.

This is particularly important for sediment transport studies.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana