PILOT PROJECT SAND GROYNES DELFLAND COAST

Roderik Hoekstra, Dirk-Jan R. Walstra, Cilia S. Swinkels

Abstract


In October and November 2009 a pilot project has been executed at the Delfland Coast in the Netherlands, constructing three small sandy headlands called Sand Groynes. Sand Groynes are nourished from the shore in seaward direction and anticipated to redistribute in the alongshore due to the impact of waves and currents to create the sediment buffer in the upper shoreface. The results presented in this paper intend to contribute to the assessment of Sand Groynes as a commonly applied nourishment method to maintain sandy coastlines. The morphological evolution of the Sand Groynes has been monitored by regularly conducting bathymetry surveys, resulting in a series of available bathymetry surveys. It is observed that the Sand Groynes have been redistributed in the alongshore, mainly in northward direction driven by dominant southwesterly wave conditions. Furthermore, data analysis suggests that Sand Groynes have a trapping capacity for alongshore supplied sand originating from upstream located Sand Groynes. A Delft3D numerical model has been set up to verify whether the morphological evolution of Sand Groynes can be properly hindcasted. Although the model has been set up in 2DH mode, hindcast results show good agreement with the morphological evolution of Sand Groynes based on field data. Trends of alongshore redistribution of Sand Groynes are well reproduced. Still the model performance could be improved, for instance by implementation of 3D velocity patterns and by a more accurate schematization of sediment characteristics.

Keywords


sand groyne; Delfland Coast; sand nourishment; sediment transport; Delft3D

References


Delta Committee, 2008. Samen werken met water, recommendations of the 2008 Delta Committee to the Dutch government.

Hoekstra, R., 2010. Pilot Sand Groynes Delfland Coast – Efficiency and practical feasibility of a pulse nourishment. MSc-thesis, Delft University of Technology (Netherlands).

Lesser, G.R., Roelvink, J.A., van Kester, J.A.T.M. and Stelling, G.S., 2004. Development and validation of a three-dimensional morphological model. Coastal Engineering 51 (8-9), 883-915.doi:10.1016/ j.coastaleng.2004.07.014.

Mulder, J., 2012. 'Sand Engine': first monitoring results of a mega-nourishment. Proceedings of the 33rd International Conference of Coastal Engineering 2012. ASCE.

Van Rijn, L.C., 1993. Principles of Sediment Transport in Rivers, Estuaries and Coastal Seas. Aqua Publications, The Netherlands

PMCid:1005200


Full Text: PDF

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.