Stability of laboratory scale rivers

Fluid Dynamics provides a sound insight to the geomorphologist interested in the ubiquitous formation of regular sedimentary patterns by rivers (like bars, braids and meanders). Many theoretical advances as well as laboratory experiments tend to prove that those patterns do not simply reflect a general turbulence pattern. Instead, their formation results from the interaction between a surface flow and an erodible substrate. The interface separating the sediment layer from water is found to be unstable in many cases. In particular, small laboratory flumes are able to generate regular sediment patterns, at Reynolds number of the order of, or below 100. This suggests that turbulence is not essential to bars, braids and maybe meanders formation. Laminar flumes then become simple models of their natural turbulent counterparts. This poster presents the linear stability analysis of a laminar flow confined in a slowly erodible channel. The basic state is an infinite straight river, which profile is to be determined