Guido Wolters, Marcel R.A. Van Gent


Rubble mound coastal structures typically contain granular filters in one or more layers. These filters are normally geometrically tight (to prevent material washout), often difficult to realize in the field, and expensive. An alternative is a geometrically open filter (i.e. a large ratio of the size of toplayer material and underlayer material), designed in such a way that it fulfills its filter functions with only minimal base material loss or settlement. Potential applications of open filters include bed protections and toe & slope configurations of coastal structures. Proper guidelines on the design of open filters under wave and current loading could lead to significant cost and material savings, and to a more practical application of filters in the field. The physical model tests conducted in this study focus on granular open filters on a horizontal sand bed under wave and combined wave & current loading.


rubble-mound breakwater; open filter; transport filter; waves; currents; physical model tests


Bakker K.J., Verheij H.J., and de Groot M.B. 1994. Design relationship for filters in bed protection". J. Hydraulic Eng., 120(9), 1082-1088.

CUR report 161. 1993. Filters in hydraulic engineering, Gouda (in Dutch).

CUR report 233. 2010. Interface stability of granular filter structures, Theoretical design methods for currents, CURNET, Gouda.

Den Adel H. 1992. Transport model for filters, Deel 1-3, report C0-325970/6, Delft Hydraulics (in Dutch).

De Graauw, A., Van der Meulen, T., Van der Does de Bye, M. 1983. Design criteria for granular filters, Publication 287, Delft Hydraulics.

Dixen, F.H., Sumer, B.M. and Fredsoe, J. 2008. Suction removal of sediment from between armor blocks. II: waves, J. of Hydraul. Eng., Vol 134, no 10, October 2008, ASCE. Klein Breteler M. 1989. Sand transport in granular filters, horizontal steady current, report H869, Delft Hydraulics (in Dutch). Klein Breteler M., Den Adel H., Koenders M.A. 1992. Slope protections of set stone (revetment), Design rules for the filter layer, Report M1795/H195, XXI, Delft Hydraulics & Geo Delft (in Dutch).

Ockeloen, W.J. 2007. Open filters in breakwaters with a sand core, M.Sc. thesis, TU Delft.Sumer, B. M., Cokgor, S., and Fredsøe, J. 2001. Suction removal of sediment from between armor blocks, J. Hydraul. Eng., 127(4), 293–306.

Uelman, E.F. 2006. Geometrically open filters in breakwaters, M.Sc. thesis, TU Delft.

Van Gent, M.R.A. 1995. Wave interaction with permeable coastal structures, Ph.D.-dissertation, Delft University of Technology, ISBN 90-407-1182-8, Delft University Press, Delft.

Vroeg de J.H. and Muttray M. 2009. Stability of sand under an open filter, Desk study, Deltares, internal communication (in Dutch).

Wolters G., D. Rudolph, B. Hofland, H. Verheij. 2010. On the behaviour of Open Filters under wave loading, Proc. 5th International Conference on Scour and Erosion (San Francisco), Geotechnical Special Publication 210, ASCE.

Full Text: PDF

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