Geometry of Ripples and Dunes

Abstract

A kinematic theory for lower‐regime bedform shape is presented and examined in the light of extensive bedform data observed in large prototype channels. Depending upon the extent of bedform maturity, the theory predicts uniquely defined nondimensional shapes for upstream faces. These shapes are borne reasonably well by the observed data in spite of large variation in bedform size. The length of upstream face, relative to the wavelength, is randomly distributed with most probable value of 0.614, which is close to the value 0.667 predicted by the theory for mature ripples and dunes.