UNSTEADY-FLOW IN STRAIGHT ALLUVIAL STREAMS - MODIFICATION OF INDIVIDUAL DUNES

Changes in dune properties due to a sudden change in the water discharge are analysed. The transport of sediment is assumed to occur mainly as bed load and the square of the Froude number must be much smaller than unity. The theory is based on similarity in the bed-shear distribution close to the dune top just before and just after the change in the water discharge. The model is found to agree with laboratory experiments. Further, by use of this model, flow in a river where the water discharge oscillates weakly around a constant mean value has been treated. Hereby the variation in the phase differences between sediment transport, water depth and water discharge with the period of the oscillation is calculated. The results agree qualitatively with observations. © 1979, Cambridge University Press. All rights reserved.