RIPPLE GEOMETRY IN WAVE-DOMINATED ENVIRONMENTS

The wavelength, height, and steepness of ripples formed under oscillat ory flows in flume and field studies are reexamined to construct a sim ple and accurate method of predicting these ripple properties. Ripples with wavelengths proportional to near-bed wave orbital diameter (orbi tal ripples), predominant in laboratory experiments, are found to have heights in excess of the thickness of the wave boundary layer. Ripple s with wavelengths that are roughly proportional to grain size and nea rly independent of orbital diameter (anorbital ripples), which predomi nate in the field, have heights at least several times smaller than wa ve boundary layer thickness. Relating wave boundary layer height to th e generally more easily estimated wave orbital diameter, a set of expr essions are developed for predicting ripple type and geometry based on mean grain size, wave orbital diameter, and estimated anorbital rippl e height. This method provides a good characterization of ripple wavel ength and steepness for a large set of combined field and flume data.