RC: Review by Chris Paola, University of Minnesota

Abstract

The paper is a straightforward, nicely presented, experimental and theoretical study of the effect on channel bars of systematically increasing water discharge. Because the experiments use a conventional vertical-wall flume, the increase in discharge translates to increasing depth and shear stress at constant width and slope. The result is a transition from emergent bars that lead to a rough meandering pattern through conventional alternate bars to a form of diagonal bar that seems to be a transition to dunes. The bars generally get lower and shorter, and move faster, as the discharge increases. The paper also shows that many of the changes are reasonably well predicted by the weakly nonlinear bar theory proposed in 1987 by Colombini and colleagues.