A Laboratory Study of the Effects of Groyne Height on Sediment Behavior in Rivers

Document Type

Conference Proceeding

Publication Date

2005

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

Groynes are structures that extend from riverbanks out into the flow in order to protect from bank erosion and keep sediment from depositing and thereby blocking river transportation. If there is general bed aggradation or degradation, then the relative height of the groyne is changed. Little is known about the effects of this change in height on the flow or sediment behavior. A laboratory study was performed at the Technical University at Delft, The Netherlands to examine this issue for conditions of general bed aggradation. The flume recirculated water, while sediment was fed in upstream and collected downstream. A series of groynes were installed on one side of the flume. For all test cases the Shields parameter, θ was set at a value of 0.23, and the suspension number, Z was set to 1.87, so as to guarantee suspended-load, as well as bed load, transport. The hydraulic conditions were chosen to replicate natural river conditions, i.e., constant mobility and suspension in all test cases. Furthermore, for all the test cases Froude number (Fr) was small enough (maximum = 0.28), and the Reynolds number (Re) high enough to ensure subcritical, fully-developed, turbulent flow in both the main channel (Re ≅; 1.8 x 104) and the groyne fields (Re ≅; 0.5 x 104). Results are presented for the effect of groyne height on flow patterns, velocity, sediment exchange between main channel and groyne areas, and local scour. The results demonstrate the differences between the erosion and deposition patterns in the groyne fields for the different flow conditions and the dependency of the scour geometry on the relative height of the groynes.

Publication Title

World Water and Environmental Resources Congress 2005

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