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Influence of the Macro-Roughness of a Bank Protection by Rip-Rap on Bed Load Transport and Local Scouring in River Bends

Author(s): Ph. Chevre; A. J. Schleiss

Linked Author(s): Anton J. Schleiss

Keywords: Scouring and flow in curved channels; Rip-rap bank protection; Macro-roughness; Mountains rivers

Abstract: Fluvial hydraulic engineering was considered for a long time from a functional point of view exclusively, with regard to flood protection. Hydraulic-engineering measures must also integrate the environmental, social and economic aspects today. In this context, experiments on a physical model were carried out to determine the influence of the geometry of a rip-rap on a curved flow. Two geometries were tested, the first with a bank with regular slope as reference situation, the second with an undulated bank, with the purpose to improve the hydro-morphological conditions of the river. The studied parameters are the flow discharge, the transport of the sediments, the scouring of the bed and the stability of the riprap. Compared to a rip-rap with uniform slope, the undulated rip-rap strongly increases the variability of flow velocities and creates therefore favorable conditions for fish biotopes. Nevertheless the undulated rip-rap reduces somewhat the discharge capacity of the flow section and consequently increases water depth. Thus the sediment transport capacity in the bend is increased but without producing more severe scour than for the uniform bank slope. On the basis of experimental results and observations of the flow behavior, conclusions and recommendations are given in view of practical application of the new type of bank geometry.


Year: 2005

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