ASSESSMENT OF COASTAL FLOODING AT SOUTHERN MEDITERRANEAN WITH GLOBAL OUTLOOK FOR LOWLAND COASTAL ZONES

Nabil Ismail, Moheb Iskander, Walid El-Sayed

Abstract


This paper presents an assessment of the performance of a shoreline revetment; M. Ali Seawall, placed to protect the land behind against flooding and overtopping at coastal site, within Abu Qir Bay, East of Alexandria along the Nile Delta coast. Coastal zone management of the bay coastline is of utmost significance to the protection of the low agricultural land and the industrial complex located in the rear side of the seawall under the current and progressive effects of climate change. The latest storm in December 2010, which hit the Nile Delta and which was the severest in the last decades showed that generated surges, up to 1.0 m as well as a maximum of 7.5 m wave height in the offshore of Alexandria presented a major natural hazard in coastal zones in terms of wave run up and overtopping. The storm, fortunately, resulted in a partial and modest flooding of the zone behind the seawall particularly in the beach segment, located in the middle of the seawall. This research project aims to the design review of the seawall which was first constructed in 1830 to protect the lowland agricultural area, 2.0 m below mean sea level, and was rehabilitated in 1981 as part of the Master Plan of the Nile Delta Coastal Zone Management. The seawall was further upgraded in 2009; one year before the 2010 storm. The paper will give an overview of the seawall design and its upgrades and the current conducted hydrodynamic analyses to estimate wave height distributions, wave run up and overtopping over the seawall and its beach segment. Use has been made of the in-house modified ImSedTran-2D model as well as universal design standards as EurOtop (2008). Based on the results for worst design scenarios, recommendations are given to increase the height of the seawall cap, to strengthen the beach top and back slope with a facility to drain storm water to increase coastal resilience behind the seawall. Comparison of the predicted overtopping with the observed wave overtopping volumes during the 8hrs-2010 storm, allowed the verification of the used universal design tools. Impact of precise estimate of storm and barometric surge as well as seawall armor roughness and shapes on overtopping rates are highlighted.

Keywords


storm surges; coastal flooding; coastal resilience; seawalls; climate change

References


Bruce, T., van der Meer, J.W, Franco, L., and Pearson J. 2006. A comparison of overtopping performance of different rubble mound breakwater armour. ASCE, Proceedings ICCE, San Diego.

De Waal, J.P., van der Meer, J.W. 1992. Wave run-up and overtopping on coastal structures. Proceedings 23rd International Conference on Coastal Eng. ASCE, Venice, Italy, vol. 2, pp 1759–1771.

Debes, A.A.M. 2002. The study of sea level changes and currents at Rosetta and Damietta outlets and Abu Qir Bay. M.Sc. Thesis, Physical Oceanography Department, Faculty of Science, Alexandria University.

El-Sayed, M.k, and Ismail, N. 2011. Enhancement of cross-shore profile evolution models for sustainable coastal design, Proceedings of Conference on Coastal Engineering Practice, ASCE, COPRI, San Diego, California. August 21-24, pp 548-560.

El Shinnawy, I.A., Abo Zed A.I., Ali, M.A., Deabes, E.A., Abdel-Gawad, S. 2010. Vulnerability to climate changes and adaptation assessment for coastal zones of Egypt., Proceedings of the First International Journal on Coastal Zone Management of River Deltas and Low Land Coastlines, Alexandria, Egypt, ISSN 1110-4929, pp 145-160.

Fanos, A., Khafagy, A., and Dean, R. 1995. Protective works on the Nile-Delta coast, J. Coastal Research, vol.11, No. 2.

Frihy, O.E., Iskander M.M., El Sayed W.R., Abo Zed A.L., Selim M.A., Hassan M.S., Badr A.M. 2006. Environmental impacts monitoring of the emerged breakwaters at Asafra-Mandara beach, Alexandria, Egypt, The first International Environmental Forum, A New Strategy for Developing Communities and Environment, Tanta University, Tanta.

Frihy O.E., Iskander M.M., Bader A.M. 2004. Effect of shoreline and bedrock irregularity on the morphodynamics of Alexandria coast littoral cell, Egypt, Journal of Geo-marine Letters, vol. 24, No.4. pp 195-211.http://dx.doi.org/10.1007/s00367-004-0178-x

Ha, W., Kim, K., and Lim, W. and Pyum, C. 2011. An experimental study on coastal erosion protection by submerged breakwater made of Tetrapods, Proceedings of Conference on Coastal Engineering Practice, ASCE, COPRI, San Diego, California.

Inman, D.L., and Jenkins, S.A. 1984. The Nile Delta littoral cell and man"s impact on the coastal zone of the southeastern Mediterranean. Proceedings 19th International Conference on Coastal Engineering, ASCE, Houston, Texas, vol. 2. pp 1600-1617.

Iskander, M.M. 2005. Simulating some coastal problems in Egypt using numerical modeling, Ph.D. thesis, Faculty of Engineering, Alexandria University, 170p.

Iskander, M., Frihy, M., Omran E., El Ansary, A.E., Abd El Mooty, M., Nagy, H.M. 2007. Beach impacts of shore-parallel breakwaters backing offshore submerged ridges, Western Mediterranean Coast of Egypt, Journal of Environmental Management, vol. 85, Issue 4, pp 1109-1119.http://dx.doi.org/10.1016/j.jenvman.2006.11.018

PMid:17239517

Ismail, N. M. 2011. Assessment of recent coastal flooding in Alexandria and future outlook for the Nile Delta, Geophysical Research Abstracts, vol. 13, EGU2011-13656, EGU General Assembly, Vienna, Austria, April 3-8.

Ismail, N., and El-Sayed, W. 2007. Coastal processes at Rosetta-Headland and seawall-beach interaction, Proceedings of International Conference on Coastal Structures, ASCE, Venice, Italy, July 2-4, vol. 1, pp 490-501.

Ismail, N.M. and Wiegel, R.L. 2003. Secondary flows and sediment problems near coastal marine outfalls. Proceedings 3rd International Conference on. Coastal Structures, ASCE, Portland, Oregon, USA, pp 764-776.

Ismail, N.M. 1982. Effect of wave-current interaction on littoral drifts, Shore and Beach, J. American Shore & Beach Preserv. Assoc., vol. 50, No. 1, pp 35-38.

Kadib, A.L., Shak, A.T., Mazen, A.A. and Nadar, M.K. 1986. Shore protection plan for the Nile Delta coastline. Proceedings 20th International Conference on Coastal Engineering, Taipei, Taiwan, vol. 3, pp 2530-2544.

Kraus, N.C. 1984. Estimate of breaking wave height behind structures. Journal of Waterway, Port, Coastal, and Ocean Engineering, ASCE, vol. 110, pp 276–282.http://dx.doi.org/10.1061/(ASCE)0733-950X(1984)110:2(276)

Perlin, M., Dean, R.G. 1983. A numerical model to simulate sediment transport in the vicinity of coastal structures. Miscellaneous Report No. 83-10, US Army, Corps of Engineers, CERC, Fort Belvoir, 199p.

Pullen, T Allsop, N.W.H., Bruce, T., Kortenhaus A, Schüttrumpf H., van der Meer, J.W. 2009. EurOtop – overtopping and methods for assessing discharge, Flood Risk Management: Research and Practice – Samuels et al. (eds), Taylor & Francis Group, London.

Shankar N.J., Jayaratne, M.P.R., 2003. Wave run-up and overtopping on smooth and rough slopes of coastal structures, Ocean Engineering, Elsevier, vol. 30, pp 221–238.http://dx.doi.org/10.1016/S0029-8018(02)00016-1

U.S. Army Coastal Engineering Research Center, Shore Protection Manual. 1984-2002, U.S. Government Printing, Office, Washington, D.C., vol. 2.

Van der Meer, J.W., and Janssen, J.P.F.M. 1994. Wave run-up and wave overtopping at dikes, ASCE. In: Wave forces on inclined and vertical wall structures, Ed. by N. Kobayashi and Z. Demirbilek.

Wiegel, R.L. 2005. Oceanographical Engineering, Dover Publications, NY.

Zanuttigh, B., van der Meer, J. W. 2008. Wave reflection from coastal structures in design conditions, Journal of Coastal Engineering, vol. 55, pp 771-779.

Zanuttigh, B., van der Meer, J. W., Andersen, T.L., Lara, J.L., Losada, I.J. 2008. Analysis of wave reflection from structures with berms through an extensive database and 2DV numerical modeling, Proceedings International Conference on Coastal Engineering, Hamburg, Germany, pp 3285-3297.

Zanuttigh, B., and van der Meer, J.W. 2007. Wave reflection from composite slopes, Proceedings of International Conference on Coastal Structures, ASCE Venice, Italy, pp 749-759.


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