The direction of current flow over the beach surface may be determined from the shape of rhomboid ripple marks. Characteristically these ripples are bowed in the direction of current flow and are pointed up-current. They are formed on the foreshore beach by wave backwash and by washover of low bars. The washover ripples result from thin sheets of water moving shoreward over the bars. At Sapelo Island, Georgia, rhomboid ripples are best developed on slopes of 1/2 degrees to 2 degrees . The beach material is predominantly fine sand. There is a direct relation between the length-width ratio of rhomboid ripples and the slope of the beach surface.