OCEAN DRIVEN FLOODING OF A COASTAL LAKE

David P Callaghan, Thuy T. T. Vu, David J. Hanslow, Peter Nielsen, Zai-Jin You, Ian Teakle

Abstract


Analysis of Lake Conjola flooding in April 2006, provided in this paper, attributes it to waves pumping water over a 300 m long beach berm and into Lake Conjola. This overwash, generated by the medium wave height swell occurring during this flooding, was able to lift the lake levels near the entrance, persistently over several tidal cycles, to well above the ocean water levels. The wave pump model was used to model this flooding. Lake Conjola water storage and dynamics were modelled by using a two-node continuity based model that a change in storage in time is driven by the net inflow to a node and these nodes and the ocean are linked by log-law. The extents of these two nodes were established from previous water surface measurements. While the qualitative flood behavior was reproduced by this remarkably simple model, the peak flood level was not satisfactorily predicted when using literature values for model turning parameters. One reason for this mismatch was that the waves pumped against a head including critical flow on the beach berm. Based on recent images of Lake Conjola wave overwash events, it may be concluded that pumping against critical flow is too harsh. Removing this from the model has halved the gap between the measurements and predictions. However, more research is definitely required to establish what components should be included in the hydraulic head pumped against.

Keywords


coastal flooding; wave pumping; overwash; continuity modelling

Full Text:

PDF

References


Baldock, T.E., Hughes, M.G., Day, K. and Louys, J., 2005. Swash overtopping and sediment overwash on a truncated beach. Coastal Engineering, 52(7): 633-645.

Bruun, P., F. and Viggoson, G., 1977. The wave pump: Conversion of wave energy to current energy. Journal of the Waterway, Port, Coastal and Ocean Division, 103(WW4): 449-469.

Callaghan, D.P., CIVL3141/2012, Catchment hydraulics: Open channel flow and design, Lecture Slides, 260 pp.

Callaghan, D.P., CIVL2131/2014, Fluid mechanics for civil and environmental engineers, Lecture Slides, 253 pp.

Callaghan, D.P., Nielsen, P., Baldock, T.E., Moura, T., Olfateh, M. and Golshani, A., 2013. Wave setup and tides at the trained and untrained river entrances of hastings point and pottsville, The University of Queensland, St Lucia, QLD 4072.

Callaghan, D.P., Nielsen, P., Cartwright, N., Gourlay, M.R. and Baldock, T.E., 2006. Atoll lagoon flushing forced by waves. Coastal Engineering, 53(8): 691-704.

Dunn, S.L., 2001. Wave setup in river entrances. Ph.D. Thesis, The University of Queensland, St. Lucia, Qld., 175 pp.

Dunn, S.L., Nielsen, P., Madsen, P.A. and Evans, P., 2000. Wave setup in river entrances. Proceedings of the 27th International Conference on Coastal Engineering, Sydney, Australia, 3432-3445.

Elger, D.F., Williams, B.C., Crowe, C.T. and Roberson, J.A., 2012. Engineering fluid mechanics. Wiley, Hoboken, USA, 673 pp.

Gourlay, M.R., 1996. Wave set-up on coral reefs. 1. Set-up and wave generated flows on an idealised two dimensional horizontal reef. Coastal Engineering, 27(3-4): 161-193.

Guard, P.A. and Baldock, T.E., 2007. The influence of seaward boundary conditions on swash zone hydrodynamics. Coastal Engineering, 54(4): 321-331.

Kofoed, J.P., Frigaard, P., Friis-Madsen, E. and Sørensen, H.C., 2006. Prototype testing of the wave energy converter wave dragon. Renewable Energy, 31(2): 181-189.

Moura, T., Olfateh, M., Callaghan, D.P., Nielsen, P., You, Y.G. and Baldock, T.E., 2013. Tidal amplitude and wave setup in trained and untrained river entrances, Coasts and Ports, Sydney.

Nielsen, P., 2009. Coastal and estuarine processes. Advanced series on ocean engineering. World Scientific, Singapore, 341 pp.

Nielsen, P., Brander, R., W. and Hughes, M., 2001. Rip currents: Observations of hydraulic gradients, friction factors and wave pump efficiency. Coastal Dynamics ’01, Lund, Sweden, 483-492.

Nielsen, P., Guard, P.A., Callaghan, D.P. and Baldock, T.E., 2008. Observations of wave pump efficiency. Coastal Engineering, 55(1): 69-72.

Press, W.H., Teukolsku, S.A., Vetterling, W.T. and Flannery, B.P., 1992. Numerical recipes in fortran: The art of scientific computing. Cambridge University Press, Cambridge, 1486 pp.

Sugandika, T.A.N., Callaghan, D.P. and Nielsen, P., 2013. Atoll lagoon flushing at manihiki in the cook islands, Coasts and Ports, Sydney.

Vu, T.T.T., 2014. Aspects of inlet geometry and dynamics, The University of Queensland, 343 pp.

Wilson, B., 1997. The efficiency of a wave pump, University of Queensland, Brisbane, 46 pp.




DOI: https://doi.org/10.9753/icce.v34.currents.47