Amaia Ruiz de Alegria-Arzaburu, Jon J Williams, Gerhard Masselink


The process-based XBeach numerical model has been used to simulate storm-induced morphological response on a macrotidal gravel barrier located in southwest UK. Using well-established parameterisation to define all relevant hydrodynamic, groundwater and sediment processes, the model was applied in 1D mode to simulate observed storm-induced beach profile responses. Investigations showed that the morphological response of the beach was best modelled using a total drag coefficient, CD, of 0.007, and a hydraulic conductivity, K, of 0.05ms-1. Results obtained from simulations with and without beach groundwater highlighted the need to account for groundwater effects when modelling morphological changes on gravel beaches. The model has been found unable of reproducing the formation of a berm, thus, beach recovery conditions cannot be modelled. This is mainly attributed to the fact that XBeach models long waves rather than individual waves, and thus it cannot simulate individual swash events that contribute to onshore sediment transport and berm accretion. However, the model is shown to provide good estimates of post-storm gravel beach/barrier profiles, and to define the threshold for overwash occurrence. Both attributes have utility in a range of practical coastal engineering and management applications.


XBeach; gravel barrier; modelling; storm response; barrier overwash; morphodynamics

Full Text:



Austin, M. and Masselink, G. 2005. Infiltration and exfiltration on a steep gravel beach: implications for sediment transport, Coastal Dynamics, ASCE p. 13.

Austin, M., Masselink, G., Turner, I., Buscombe, D. and Williams, J. 2009. Groundwater seepage between a gravel barrier beach and a freshwater lagoon, International Conference on Coastal Engineering 2008, pp. 4572–4584.

Barnes, G. 1995. Soil mechanics principles and practice, Macmillan Press Ltd. ISBN 0-333-59654-4.

Bradbury, A. 2000. Predicting breaching of shingle barrier beaches-recent advances to aid beach management, Proceedings of 35 th Annual MAFF Conference of River and Coastal Engineers, 1. 3.1–05.3.13.

Bradbury, A. and Powell, K. 1992. The short term profile response of shingle spits to storm wave action, Proceedings of the International Conference on Coastal Engineering, ASCE, 2694–2707.

Brampton, A. and Motyka, J. 1994. Modelling the plan shape of shingle beaches, Lecture Notes in Coastal Engineering Studies, 12 Offshore and Coastal Modelling' 85 pp. 219–234.

Chadwick, A. J. 1989. Field measurements and numerical model verification of coastal shingle transport, BHRA, The Fluid Engineering Centre, Cranfield, Bedford 27.

Chadwick, A. J., Karunarathna, H., Gehrels, W. R., O'Brien, D. and Dales, D. 2005. A new analysis of the Slapton barrier beach system, UK', Proceedings of the Institution of Civil Engineers-Maritime Engineering 158(4), 147–161.

Clarke, S. and Damgaard, J. 2002. Applications of a numerical model of swash zone flow on gravel beaches, Proceedings of 28 th International Conference on Coastal Engineering.

Galapatti, R. 1983. A depth-integrated model for suspended transports, Report 83- 7. Faculty of Civil Engineering, Delft University of Technology. Delft. The Netherlands.

Haigh, I., Nicholls, R. and Wells, N. 2009. Mean sea level trends around the English Channel over the 20th century and their wider context, Continental Shelf Research 29(17), 2083–2098.

Hails, J. R. 1975. Offshore morphology and sediment distribution, Start Bay, Devon, Philosophical Transactions of the Royal Society of London Series -Mathematical Physical and Engineering Sciences 279(1288), 221–228.

Holthuijsen, L. H., Booij, N. and Herbers, T. H. C. 1989. A prediction model for stationary, shortcrested waves in shallow water with ambient currents, Coastal Engineering 13(1), 23–54.

Job, D. 1993. The Start Bay barrier beach system, FSC occasional publication 27 of a field guide of the geomorphology of the Slapton region. Field Studies Council (Slapton Ley Field Studies Centre). U.K. PMCid:1134443

Lindemer, C.A., Plant, N.G., Puleo, J.A., Thompson, D.M., Wamsley, T.V. 2010. Numerical simulations of a low-lying barrier island's morphological response to Hurricane Katrina. Coastal Engineering 57, 985–995.

Lopez de San Roman-Blanco, B., Coates, T. T., Holmes, P., Chadwick, A. J., Bradbury, A., Baldock, T. E., Pedrozo-Acuna, A., Lawrence, J. and Grune, J. 2006. Large scale experiments on gravel and

Stive, M. J. F. and Dingemans, M. 1984. Calibration and verification of a one dimensional wave energy decay model. Report on investigation, Delft Hydraulics, Delft, The Netherlands.

Sutherland, J., Peet, A. H. and Soulsby, R. L. 2004. Evaluating the performance of morphological models, Coastal Engineering 51(8-9), 917–939.

Takada, I. and Sunamura, T. 1982. Formation and height of berms, Transactions Japanese Geomorphological Union 3, 145–157.

Van Dongeren, A., Benavente, J., Balouin, Y., Ciavola, P., Taborda, R., Furmanczyk, K., Haerens, P., Roelvink, D., Trifonova, E. and Williams, J. 2009. Micore: Dune erosion and overwash model validation with data from nine European field sites, Proceedings of 6 th International Conference on Coastal Dynamics 2009, 166–167.

Van der Meer, J. 1988. Rock slopes and gravel beaches under wave attack, Delft Hydraulics Publications 396.

Van Rijn, L. C., Walstra, D. J. R., Grasmeijer, B., Sutherland, J., Pan, S. and Sierra, J. P. 2003. The predictability of cross-shore bed evolution of sandy beaches at the time scale of storms and seasons using process-based profile models, Coastal Engineering 47(3), 295–327.

Van Rijn, L. C. 2007. Unified view of sediment transport by currents and waves: Initiation of motion, bed roughness, and bed-load transport, Journal of Hydraulic Engineering, 133(6), 649–667.

Van Wellen, E., Chadwick, A. J. and Mason, T. 2000. A review and assessment of longshore sediment transport equations for coarse-grained beaches, Coastal Engineering 40(3), 243–275.

Walstra, D., Roelvink, J. A. and Groeneweg, J. 2000. Calculation of wave-driven currents in a 3D mean flow model, 27 th International Conference on Coastal Engineering, pp. 1050–1063.

Williams, J., Masselink, G., Buscombe, D., Turner, I., Matias, A., Ferreira, O., Bradbury, A., Metje, N., Coates, L., Chapman, D., Thompson, C., Albers, T. and Pan, S. 2009. BARDEX (Barrier Dynamics Experiment): Taking the beach into the laboratory, Journal of Coastal Research 1, 158–2. 10th International Coastal Symposium, ICS 2009, Lisbon, Portugal, Sp. Iss. 56.