RIPPLE GEOMETRY IN WAVE-DOMINATED ENVIRONMENTS

The wavelength, height, and steepness of ripples formed under oscillatory flows in flume and field studies are reexamined to construct a simple and accurate method of predicting these ripple properties. Ripples with wavelengths proportional to near-bed wave orbital diameter (orbital ripples), predominant in laboratory experiments, are found to have heights in excess of the thickness of the wave boundary layer. Ripples with wavelengths that are roughly proportional to grain size and nearly independent of orbital diameter (anorbital ripples), which predominate in the field, have heights at least several times smaller than wave boundary layer thickness. Relating wave boundary layer height to the generally more easily estimated wave orbital diameter, a set of expressions are developed for predicting ripple type and geometry based on mean grain size, wave orbital diameter, and estimated anorbital ripple height. This method provides a good characterization of ripple wavelength and steepness for a large set of combined field and flume data.