Keywords
sandbar
wave
undertow
numerical model
How to Cite
Abstract
A numerical model of beach profile evolution is developed to study the onshore and offshore sandbar migration under different wave conditions. The integrated model consists of wave model, roller model, flow model, sediment transport model and bed evolution model. In particular, the interaction between waves and wave-induced undertow current is considered in the flow model. This is achieved by adding a mean pressure gradient term into the firs-order momentum balance equation of flow. A simple empirical method is also introduced to describe the variation in eddy viscosity during one wave cycle. A preliminary application of the present model shows good agreements of both onshore and offshore sandbar migration phenomenon with the laboratory observation. It is found that the offshore sandbar migration is dominated by undertow while wave affects the transport rate. For the onshore sandbar migration, although sediment transport is mainly driven by wave and the undertow is weak, the transport pattern is considerably modified by undertow. It is shown that the combined effects of wave and undertow are important in beach profile evolution.References
Aagaard, T., and M.G. Hughes, 2010. Breaker turbulence and sediment suspension in the surf zone, Marine Geology, 271, 250-259.http://dx.doi.org/10.1016/j.margeo.2010.02.019
Battjes, J.A., 1975. Modelling of turbulence in the surf zone, Proceedings Symposium on Modeling Techniques, ASCE, 1050-1061.
Battjes, J.A., and J.P.F.M. Janssen. 1978. Energy loss and set-up due to breaking of random waves, Proceedings of 14th International Conference on Coastal Engineering, ASCE, 569-587.
Deigaard, R., 1993. A note on the three dimensional shear stress distribution in a surf zone, Coastal Engineering, 20, 157-171.http://dx.doi.org/10.1016/0378-3839(93)90059-H
Elfrink, B., D.M. Hanes, and B.G. Ruessink, 2006. Parameterization and simulation of near bed orbital velocities under irregular waves in shallow water, Coastal Engineering, 53, 915-927.
Gallagher, E.L., S. Elgar, and R.T. Guza, 1998. Observations of sandbar evolution on a natural beach, Journal of Geophysical Research, 103, 3203-3215.http://dx.doi.org/10.1029/97JC02765
Grasso, F., B. Castelle, and B.G., Ruessink, 2012. Turbulence dissipation under breaking waves and bores in a natural surf zone, Continental Shelf Research, 43, 133-141.http://dx.doi.org/10.1016/j.csr.2012.05.014
Guannel, G., H.T. Ozkan-Haller, M.C. Haller, and J.T. Kirby, 2007. Influence of velocity moments on sand bar movement during CROSSTEX, Proceedings of the 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Process, ASCE, 28-41.
Hoefel, F., and S. Elgar, 2003. Wave-induced sediment transport and sandbar migration, Science, 299, 1885-1887.http://dx.doi.org/10.1126/science.1081448
PMid:12649479
Hsu, T.J., S. Elgar, and R.T. Guza, 2006. Wave-induced sediment transport and onshore sandbar migration, Coastal Engineering, 53, 817-824.http://dx.doi.org/10.1016/j.coastaleng.2006.04.003
Janssen, T.T., and J.A. Battjes, 2007. A note on wave energy dissipation over steep beaches, Coastal Engineering, 54, 711-716.http://dx.doi.org/10.1016/j.coastaleng.2007.05.006
Maddux, T.B., E.A. Cowen, D.L. Foster, M.C. Haller, and T.P. Stanton, 2006. The Cross Shore sediment transport experiment (CROSSTEX), Proceedings of 14th International Conference on Coastal Engineering, ASCE, 2547-2559.
Nielsen, P., and D.P. Callaghan, 2003. Shear stress and sediment transport calculations for sheet flow under waves, Coastal Engineering, 47, 347-354.http://dx.doi.org/10.1016/S0378-3839(02)00141-2
Reniers, A.J.H.M., E.B. Thomton, T.P. Stanton, and J.A. Roevink, 2004. Veritcal flow structure during Sandy Duck: observations and modeling, Coastal Engineering, 51, 237-260.http://dx.doi.org/10.1016/j.coastaleng.2004.02.001
Ribberink J.S., 1998. Bedload transport for steady flows and unsteady oscillatory flows, Coastal Engineering, 34, 59-82.http://dx.doi.org/10.1016/S0378-3839(98)00013-1
Roelvink, J. A., and M.J.F. Stive, 1989. Bar-generating cross-shore flow mechanisms on a beach, Journal of Geophysical Research, 94, 4785-4800.http://dx.doi.org/10.1029/JC094iC04p04785
Ruessink, B.G., Y. Kuriyama, A.J.H.M. Reniers, J.A. Roevink, and D.J.R. Walstra, 2007. Modeling cross-shore sandbar behavior on the timescale of weeks, Journal of Geophysical Research, 112, doi: 10.1029/2006JF000730.http://dx.doi.org/10.1029/2006JF000730
Stive, M.J.F., and H.J. De Vriend. 1994. Shear stresses and mean flow in shoaling and breaking waves, Proceedings of 24th International Conference on Coastal Engineering, ASCE, 594-608.
van Rijn, L.C, D.J.R. Walstra, B. Grasmeijer, J. Sutherland, S. Pan, and J.P. Sierra, 2003. The predictability of cross-shore bed evolution of sandy beaches at the time scales of storms and seasons using process-based profile models, Coastal Engineering, 47, 295-327.http://dx.doi.org/10.1016/S0378-3839(02)00120-5
Walstra, D.J.R., A.J.H.M. Reniers, R. Ranasinghe, J.A. Roelvink, and B.G., Ruessink, 2012. On bar growth and decay during interannual net offshore migration, Coastal Engineering, 60, 190-200.http://dx.doi.org/10.1016/j.coastaleng.2011.10.002
Zhang, C., Zheng, J., Wang, Y., and Z. Demirbilek, 2011. Modeling wave-current bottom boundary layers beneath shoaling and breaking waves, Geo-Marine letters, 31, 189-201.http://dx.doi.org/10.1007/s00367-010-0224-9