MODELING LONG-TERM BEACH CHANGE UNDER INTERACTING LONGSHORE AND CROSS-SHORE PROCESSES

Hans Hanson, Magnus Larson, Nicholas C Kraus

Abstract


This paper presents mathematical formulations and a new numerical model GenCade that simulates beach and dune change in response to cross-shore processes of dune growth by wind and dune erosion by storms, and by gradients in longshore sand transport that will also alter shoreline position. The berm plays a central role since the potential for sand to be transported to the dune by wind depends on berm width, and sand lost in erosion of the dune during storms will widen the berm. Morphologic equilibrium considerations are introduced to improve reliability of predictions and stability of the non-linear model. An analytical solution is given to illustrate properties of the model under simplified conditions. Sensitivity tests with the numerical solution of the coupled equations demonstrate model performance. Finally, the numerical model is applied to examine the consequences of groin shortening at Westhampton Beach, Long Island, New York, as an alternative for providing a sand supply to the down-drift beach. Results indicate that the sand will be released over several decades as the shoreline and dune move landward in adjustment to the new equilibrium condition with the shortened groins.

Keywords


dune erosion; shoreline change; coastal evolution; numerical model; GenCade; Westhampton Beach

References


Bagnold, R. A. 1954. The physics of blown sand and desert dunes, Methuen & Co. Ltd., London, 265 pp.

Bocamazo, L.M., and Grosskopf, W.G. 1999. Shore response to groins, Westhampton, New York. Proceedings Coastal Sediments '99, ASCE, 2,073-2,089.

Camenen, B., Bayram, A., and Larson, M. 2006. Equivalent roughness height for plane bed under steady flow, Journal of Hydraulic Engineering, 132(11), 1146-1158. http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:11(1146)

Camenen, B., Larson, M., and Bayram, A. 2009. Equivalent roughness height for plane bed oscillatory flow, Estuarine, Coastal, and Shelf Science, 81, 409-422.http://dx.doi.org/10.1016/j.ecss.2008.11.019

Davidson-Arnott, R.G.D. and Law, M.N. 1990. Seasonal pattern and controls on sediment supply to coastal foredunes, Long Point, Lake Erie, In: Nordstrom, K.F., Psuty, N.P., Carter, R.W.G., (Eds.), Coastal Dunes: Form and Processes, John Wiley & Sons, 177-200.

Davidson-Arnott, R.G.D., MacQuarrie, K., and Aagaard, T. 2005. The effect of wind gusts, moisture content and fetch length on sand transport on a beach, Geomorphology, 68, 115-129.http://dx.doi.org/10.1016/j.geomorph.2004.04.008

Dean, R.G., 1977. Equilibrium beach profiles: U.S. Atlantic and Gulf coasts. Department of Civil Engineering, Ocean Engineering Report No. 12, University of Delaware, Newark, DE.

Erikson, L., Larson, M., and Hanson, H. 2005. Prediction of swash motion and run-up including the effects of swash interaction, Coastal Engineering, 52, 285-302. http://dx.doi.org/10.1016/j.coastaleng.2004.12.001

Hanson, H. 1989. GENESIS - A generalized shoreline change numerical model, Journal of Coastal Research, 5(1), 1-27.

Hanson, H., and Kraus, N. C. 1989. GENESIS: Generalized Model for Simulating Shoreline Change. Report 1: Technical Reference, Technical Report CERC-89-19, U.S. Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, Vicksburg, MS.

Hopf, F., and Sherman, D.J. 2007. Aeolian processes, coastal dunes, and the Coastal Engineering Manual Part III, Chapter 4 "Wind-Blown Sediment Transport." Proceedings Coastal Sediments '07, ASCE, 1,241-1,254.

Hotta, S. 1984. Wind blown sand on beaches. PhD dissertation. Tokyo, Japan: Department of Civil Engineering, University of Tokyo.

Kraus, N.C., and Batten, B.K. 2006. Shoreline evolution in a groin field by Reservoir Model approach.Proceedings 30th Coastal Engineering Conference, World Scientific Press, 3,886-3,898.

Kraus, N.C., Hanson, H., and Blomgren, S. 1994. Modern functional design of groins. Proceedings 24th Coastal Engineering Conference, ASCE, 1327-1342.

Larson, M., Erikson, L., and Hanson, H. 2004. An analytical model to predict dune erosion due to wave impact, Coastal Engineering, 51, 675-696. http://dx.doi.org/10.1016/j.coastaleng.2004.07.003

Larson, M. and Kraus, N.C. 1989. SBEACH: Numerical model for simulating storm-induced beach change, Report 1: Empirical foundation and model development, TR CERC-89-9, U.S. Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, Vicksburg, MS.

Larson, M., and Kraus, N.C. 1991. Mathematical modeling of the fate of beach fill. In: Niemayer, H.D van Overeem, J., and van de Graaff, J. (eds.), Artificial Beach Nourishments, Coastal Engineering, Special Issue 16, 83-114.

Larson, M., Kraus, N.C., and Hanson, H. 2002a. Simulation of regional longshore sediment transport and coastal evolution – The Cascade model, Proceedings 28th Coastal Engineering Conference, ASCE, 2612-2624.

Larson, M., Rosati, J.D., and Kraus, N.C., 2002b. Overview of regional coastal processes and controls. Coastal and Hydraulics Engineering Technical Note CHETN XIV-4, U.S. Army Engineer Research and Development Center, Vicksburg, MS.

Nersesian, G.K., Kraus, N.C., and Carson, F.C. 1992. Functioning of groins at Westhampton Beach, Long Island, New York. Proceedings 23rdCoastal Engineering Conference, ASCE, 3,357-3,370.

Psuty, N. P. 1990. Foredune mobility and stability, Fire Island, New York. In: Nordstrom, K.F., Psuty, N.P., and Carter, R.W.G. (eds.) Coastal Dunes: Form and Process, John Wiley and Sons, NY, 159-200.

Raubenheimer, B., Guza, R.T., Elgar, S., and Kobayashi, N. 1995. Swash on a gently sloping beach, Journal of Geophysical Research, 100, 8,751-8,760.

Rosati, J.D., Gravens, M.B., and Smith, W.G. 1999. Regional sand budget for Fire Island to Montauk Point, New York, USA. Proceedings Coastal Sediments '99, ASCE, 802-817.

Smith, S.J. and Kraus, N.C. 1999. Mitigation of a beach-fill hot spot, Monmouth Beach, New Jersey. Proceedings Coastal Sediments '99, ASCE, 2,102-2,117.


Full Text: PDF

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