De Roo, Sieglien

Troch, Peter

Vanhaute, Lisa

English

Ghent University Academic Bibliography

Geophysical Research AbstractsVol. 14, EGU2012-10453, 2012EGU General Assembly 2012© Author(s) 2012How ship wave action influences the sediment budget of a nature friendlybank protection in a confined, non-tidal waterwayS. De Roo, L. Vanhaute, and P. TrochHydraulics Laboratory, Department of Civil Engineering, Ghent University, Ghent, Belgium (Sieglien.DeRoo@UGent.be)Failure of the concrete slab revetment resulted in progressive bank erosion along the Lys (Belgium), a confined,non-tidal waterway subject to heavy shipping traffic. In an attempt to reconcile both the technical and environ-mental requirements related to a river bank, restoration was carried out using a more ecologically sound, ‘soft’engineering method. A nature friendly bank protection, consisting of off-bank timber piling in combination with(reed)vegetation in the shallow water zone behind, was installed.As a consequence of this effort towards a more sustainable and ecological design of the waterway, sedi-ment redistribution and transport processes are however altered distinctly. Being a waterway subject to heavyshipping traffic (on monthly average 1700 ship passages), hydrodynamic ship wave action on this open, semi-natural bank protection also induces sediment (re)suspension and acts as a main contributor to sediment transport(in normal weather conditions). In order to identify the relevant transport processes caused by ship-generated waveforcing, a field measurement campaign took place in April 2011. By measuring instantaneous water velocities,suspended sediment concentrations and wave hydrodynamics with a high temporal resolution, the effects on thesediment budget were quantified.It is found that the driving forces for these processes are the ship’s speed, its blockage coefficient and thedistance of the sailing ship to the timber piling. Bottom shear stresses significantly increase to values up to 10N/m2 during a ship passage. Being much higher than the critical shear stress of 1.5 N/m2 and lasting for severalminutes, the fine as well as coarser fractions of bottom sediment are dislodged and (re)suspended. Wave heightalso correlates well with the amount of sediment suspension. The best predictor for bank erosion is the velocity atwhich the displaced water mass hits the river bank.These experimental results indicate a reduced yet continuing erosion process in spite of the installation ofthe nature friendly bank protection. A dynamic sediment equilibrium, indispensable for optimal ecologicalconditions in the transitional zone between land and water while maintaining efficiently the goods traffic in thefairway, is not established.

How ship wave action influences the sediment budget of a nature friendly bank protection in a confined, non-tidal waterway

https://biblio.ugent.be/publication/2096642/file/2096643

How ship wave action influences the sediment budget of a nature friendly bank protection in a confined, non-tidal waterway

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