On the prediction of geometric characteristics of dunes

A method for estimating dune steepness ìs presented by using a mechanical approach. A single dune is here considered acting independently by the others: -by usìng·the momentum conservation equation and dimensional analysis, an expression is derived for the net form drag force acting on the single dune considered as a protuberance on the stream bad. By means of the available experimental flume and field data, an empirical relationship is then derived for estimating the dune drag coefficient as a function of the dune Reynolds number. The proposed relationship allows to predict dune steepness with an order of approximation that seems to be quite encouraging. The effects of three dimensional characteristic of dune pattern on the geometrie properties are also shown by the adopted scheme.