A simple method is presented of applying synoptic wave and current data, collected within the natural environment, to the generation of intertidal ripple marks. Initially data was collected during two summer seasons across an intertidal sand flat of The Wash, Lincolnshire, U.K. The bedforms, interpreted on the basis of morphology, were considered current formed on the lower sand flat, intermediate on the middle sand flat, and wave formed on the inner sand flat. The limits in the spatial occurrence of these variously formed ripples were then related to a computed dimensionless ratio of wave and tidal flows at the bed. Results indicate that at ratios greater than approximately 10, wave-generated ripples occurred, below a ratio of 1 current-generated ripples predominated, and between these values an intermediate ripple type was generated. Computation of ratios of various stages of the tide gives an indication of the type of bedform to be occurring on the bed at that time.