chapter  8
39 Pages

Prototype situations

WithG.J.C.M. Hoffmans, H.J. Verheij

In prototype situations the bed around groynes is usually protected. When the river is running high, the groynes are submerged. In this situation, scour can occur at the downstream side of the groynes. An estimate of the discharge can be obtained by using known relations for submerged weirs and for free-discharge weirs, depending on the flow situation. A discrepancy exists between the different methods of calculating the equilibrium scour depth for submerged vanes using relations for slender bridge piers. This is mainly due to the fact that hardly any experimental data are available for situations with submerged vanes. The presence of the guiding dam will cause changes in the flow profile of both water and sediment. Scour depths are only available from the study for two situations: in the first place the scour resulting from the presence of the guiding dam and a groyne, in the second place the scour in the cross-section at the end of the guiding dam.