Elkamhawy, Hamdy

Elsharnouby, Bahaa

Soliman, Akram

English

Hydraulic Engineering Repository

Conference Paper, Published VersionSoliman, Akram; Elsharnouby, Bahaa; Elkamhawy, HamdyShoreline Changes Due to Construction of AlexandriaSubmerged Breakwater, EgyptZur Verfügung gestellt in Kooperation mit/Provided in Cooperation with:Kuratorium für Forschung im Küsteningenieurwesen (KFKI)Verfügbar unter/Available at: https://hdl.handle.net/20.500.11970/99490Vorgeschlagene Zitierweise/Suggested citation:Soliman, Akram; Elsharnouby, Bahaa; Elkamhawy, Hamdy (2014): Shoreline Changes Dueto Construction of Alexandria Submerged Breakwater, Egypt. In: Lehfeldt, Rainer; Kopmann,Rebekka (Hg.): ICHE 2014. Proceedings of the 11th International Conference onHydroscience & Engineering. Karlsruhe: Bundesanstalt für Wasserbau. S. 675-684.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.Significant erosion occurs along most of Alexandria’s beaches as a result of sediment starvation, coastal processes and sea level rise. The beach widths have gradually decreased due to the action of the waves and currents. With time, some beaches have totally disappeared and the wave action has attacked the toe of seawalls (Soliman and Reeve, 2007). Flooding problems have also appeared in these eroded areas af-fecting the traffic flow. In December 2003, the shoreline of Mandara beach (Alexandria city, Egypt) had suffered serious erosion. The sand beach had disappeared is some areas,  with waves scouring and un-dermining the road and seawall. Waves and sand also overtopped the broken seawall onto the Cornice road.  There are many factors that have contributed to that severe Alexandria coastline erosion, including: • Incident waves, storm events, and the phenomena of Sea Level Rise (SLR) (Frihy, 2003).  • Instability of northern delta coast due to the lack of Nile river sedimentation (Frihy et al. , 2010). • Loss of a considerable part of the sand beach due to the enlargement of the Cornice road toward the sea (El-Sharnouby and Soliman, 2011). Several types of coastal structures had been used to protect Alexandria coastline during the last twenty years. There was no certain strategic plan for the protection of Alexandria coastline and for that each zone of Alexandria shoreline has been protected using different types of structures. These different types of shore protection structures and methods are sand nourishment, revetment, groins, sea walls, emerged and submerged breakwaters. More details of these types and their positive and negative effects can be found in (El-Sharnouby and Soliman, 2010 and 2011) .  Conventional beach protection structures, such as groins, revetments and emerged breakwaters, are be-coming increasingly unpopular, principally due to their adverse impact on beach amenity and aesthetic considerations. In contrast, submerged structures are widely perceived as capable of providing the neces-sary beach protection without a loss of beach amenity or negative aesthetic impact (El-Sharnouby et al., 2011). On the basis of the field observations, Lamberti et al., (2005) mentioned that submerged breakwa-ter work effectively under different environmental conditions, providing the opportunity to protect beach-es in the context of Integrated Coastal Management. Submerged Breakwaters present several advantages with respect to conventional structures, not only concerning the visual impact (which, from the "beach-user’s" point of view is very important), but also in that they allow more wave overtopping, enhance the water renovation rates in the sheltered area, and produce higher sediment transport rates. As a result, there is increasing community pressure on coastal management authorities and government agencies to consid-er submerged structures for beach protection. The increasing popularity of submerged structures is also due to a growing recognition that their bathymetry can be optimised to enhance local surfing conditions (Ranasinghe et al., 2006). In this paper, Summary of field observations of shoreline response to submerged structures reported in the published literature are presented in section 2. Then, details of Alexandria submerged breakwater are shown in section 3. Section 4 presents the field data and wave analysis used in the design of Alexandria submerged breakwater. Discussion of the collected data and the analysis of the results of these investiga-tions on the development of a predictive capability for shoreline response to submerged structures are il-lustrated in section 5. Finally, conclusion of the obtained results is identified in section 6. 2 LITERATURE REVIEW OF SUBMERGED BREAKWATERS The most important objectives of submerged breakwater construction are as follows (Burcharth and Lam-berti, 2004): • Protection of land and infrastructure by prevention or reduction of coastal erosion. • Improvement of recreational conditions. • Minimizing impacts on cultural and natural heritage of the coastline. • Minimizing and / or mitigating impacts of submerged breakwater on species, habitats and ecosys-tems. • Enhancing natural living resources for food and recreation. The review of the available published literature of submerged breakwaters is presented with the aim of investigating the environmental and structural parameters governing shoreline response to submerged structures, gleaned from the results of field, laboratory and numerical studies undertaken to date. Sub-merged structures constructed to date range from single, shore-parallel breakwaters to large, multi-functional surfing reefs with complex design configurations. Ranasinghe and Turner (2006) presented the main features of the engineering projects involving ten submerged structures reported to date as summa-rized in Table 1. Alexandria submerged breakwater with three other sites has been added to their table, 676raising the number to fourteen submerged structures. It is of particular note that, of the fourteen sub-merged structures, net erosion was reported at seven of the sites. For convenience, the investigations de-scribed here are sub-divided into those associated with shore-parallel structures, multi-functional struc-tures, and natural reefs, and are introduced in the chronological order of publication date.  Table 1. Features of the sites and the submerged coastal structures reported in the published literature. (B =length of struc-ture, S =distance from undisturbed shoreline to structure, W=crest width, h =water depth at structure, hc=water depth at crest of the structure, tanβ =bed slope in the vicinity of the structure), (Adopted from Ranasinghe and Turner, 2006). Location Reference Structure Shoreline Nour-ish. Long shore transport rate (m3/year) B (m)  S (m) W (m)  h (m)  hc (m)  tan β type response   Delaware Bay, Douglass and Single Erosion  Y Negligible 300 75 Not 1 at MLW  Not USA Weggel,  breakwater          report-ed     reported   1987 +2 end groins                 Keino- Deguchi and Single Erosion Y Not  re-ported 80 85 20 4 2m be-low 0.1 Matsubara Sawaragi,  breakwater              MLW near shore Beach, Ja-pan 1986                 and 0.03                     offshore Niigata, Ja-pan  Funakoshi Single Erosion N Exists, 540 400 20 8.5 1.5 m below 0.02   et al.,  breakwater     but not         MLW     1994 +2 groins     quantified            Lido di Os-tia, Tomassicchio, Single Erosion Y 50,000 3000 100 15 4 1.5 m below 0.05 Italy (#1) 1996 breakwater              MSL   Lido di Os-tia, Tomassicchio,  Single Accretion N 50,000 700 50 15 3-4 0.5 m below 0.1 Italy (#2) 1996 breakwater              MSL   Lido di Dante, Lamberti and Single Accretion Y Negligible 770 150 12 3 0.5 m below 0.02 Italy Mancinelli , 1996 breakwater              MSL   Marche, It-aly Lamberti and Multiple Erosion N Negligible  Not 100-200 10-12 3 0.5 m below  Not   Mancinelli  segmented      reported       MSL Reported   , 1996 breakwaters                 Palm Beach, Dean et al., Single Erosion N 100,000 1260 70 4.6 3 0.7 m below 0.04 FL, USA 1997 breakwater              MLLW   Vero Beach, Stauble et al., Segmented Erosion N 30,000 915 85 4.6 2.1-2.7 0.25-0.35 m  0.03 FL, USA 2000 breakwater              below MLLW   Gold Coast, Jackson et al., Multi-function Accretion Y 500,000 350 100-600 2 2-10 1.0 m below 0.02 Australia 2002 surf reef              MLW   Mount Reef, Maun-ganui, New Zealand Black and Mead, 2009  Multi-function surf reef Not re-ported N Not reported 80 - 90 3-3.5 0.5 m Below CD 0.02 Pratte's Reef, El Segundo,  CA,USA Jackson and Corbett, 2007  Multi-function surf reef Not re-ported N Not reported 56 30-40 3-12 1.8 m  (MLLW) - 0.05 Boscombe Reef, UK Mead et al., 2010 Multi-function surf reef Accretion N Not reported 80 280 100 3-5 0.5 m  Above CD 0.05 Alexandria El-Sharnouby & Segmented Accretion N Not  report-ed 2555 150-300 36-46 2.5-8.5 0.5 m below 0.025 Egypt Soliman, 2010 breakwater               MLW     677 Table 4. The design water levels according to tide range, extreme water level and sea level rise. 100 Years 50 Years 1 Year Operational Event 1.11 1.06 0.76 0.50 EWL [m CD ] 0.06 0.06 0.06 0 SLR [m] 1.17 1.12 0.82 0.50 DWL [m CD ]   Table 5 presents the values of significant wave height, peak wave period and wave direction in water depths 14, 10 and 6 m for 1, 50 and 100 years return period (El-Sharnouby et al., 2007).   Table 5. Values of significant wave height, peak wave period and wave direction in water depths 14, 10 and 6 m for 1, 50 and 100 years return period. Wave Results  RP (yr) -6 CD -10 CD -14 CD Dir. Tp Hs Dir. Tp Hs Dir. Tp Hs deg. sec. M deg. sec. m. deg. sec. m. 267 4.6 1.1 261 4.6 1.2 255 4.6 1.4 1 289 10.3 3.0 286 10.3 3.2 282 10.3 3.6 1 300 11.1 3.6 300 11.1 5.0 299 11.1 6.0 1 315 10.3 3.5 317 10.3 4.4 321 10.3 4.6 1 289 12.6 3.6 287 12.6 4.6 282 12.6 6.2 50 299 14.6 4.0 299 14.6 5.5 299 14.6 6.5 50 316 13.2 4.0 318 13.2 5.4 321 13.2 6.2 50 269 6.2 2.1 262 6.2 2.4 255 6.2 2.6 100 290 14.0 4.0 288 14.0 5.4 289 14.0 6.7 100 299 16.1 4.4 299 16.1 5.9 298 16.1 7.0 100 316 15.0 4.4 318 15.0 5.7 321 15.0 6.9 100 328 13.0 4.0 326 13.0 5.3 331 13.0 5.6 100 338 12.5 3.9 338 12.5 4.6 352 12.5 5.1 100  El-Sharnouby et al., (2007) calculated the wave heights after the construction of the submerged breakwa-ter using Delft-3D numerical model. Transmission coefficients values (Kt) were calculated using the em-pirical formulae of Ghalayini et al., (2003); Friebel et al., (2000) and Seabrook and Hall, (1998). Values of Kt were found to range from 0.31 to 0.6 for 1, 50 and 100 years return period and the values of wave heights behind the breakwater during the summer session (May to October) will not exceed 0.55 meter.  5 FIELD OBSERVATIONS AND SHORELINE ANALYSIS:    The submerged breakwater system showed more efficiency during storm times than was anticipated by all means of transmission analysis which has been conducted in the design phase.  The water mass between the submerged breakwater and the beach circulates well with very gentle and light waves even under storm conditions. In December 27th, 2010, the submerged breakwater segment of 220 meters long, in 8.5 meters water depth and with 46 meters crest width (Figure 3) was hit by the highest wave recorded on Al-exandria coastline in the last 50 years (7.0 meter wave height in deep water). The approaching high waves were broken over the submerged breakwater with good transmission efficiency as can be seen from Fig-ure 6. The adequate water area behind the breakwater contributed well in dissipating the transmitted ener-gy. The shoreline and sea-wall remained safe along the 220 meters breakwater segment during all storms with noticeable good quality of water on the leeside in summer time.    680Lw   Incident wave length  S   Offshore distance  W   Crest width  REFERENCES Allsop, N., Cork, R., Verhagen, H. (2009). A database of major breakwaters around the world. Proceeding of the Institution of Civil Engineers Conference: Coasts, Marine Structures & Breakwaters, Edinburgh, Scotland, UK, pp. 676-679. Black, K., Mead, S. (2009). Design of Surfing Reefs. Reef Journal  1, No. 1, pp.177-191. Burcharth, H., Lamberti, A. (2004). Design guidelines for low crested structures. Proceedings of the 29th International Confer-ence on Coastal Engineering, Lisbon, Portugal. Church, J. A., White, N. J., Aarup, T., Wilson, W. S., Woodworth, P. L., Domingues, C. M., Hunter, J. R., Lambeck, K. (2008). Understanding global sea levels: past, present and future. Sustainability Science 3, No. 1, pp. 9-22. El-Sharnouby, B., Nagy, H., Abdrabbo, F. (2007). Stability of shoreline for Miami –Montaza area.  Technical note, Faculty of Engineering, Alexandria University, Egypt. El-Sharnouby, B., Soliman, A. (2010). Shoreline response for long wide and deep submerged breakwater of Alexandria city, Egypt. Proceeding of 26th International Conference on Seaports and Maritime Transport, Alexandria, Egypt, Arab Academy for Science, Technology & Maritime Transport. El-Sharnouby, B., Soliman, A. (2011). Behavior of Shore Protection Structures at Alexandria, Egypt, during the Storm of De-cember 2010. Proceedings of Coastal Engineering Practice, San Diego, California, USA, American Society of Civil Engi-neering, pp. 780-792. El-Sharnouby, B., Soliman, A., El-Nagar, M., El-Shahat, M. (2011). Study of Environmental Friendly Porous Suspended Breakwater for the Egyptian Western North Coast. 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R., Himmelstoss, E. A., Zichichi, J. L., Ergul, A. (2009). Digital Shoreline Analysis System (DSAS) version 4.0- An ArcGIS extension for calculating shoreline change, U.S. Geological Survey, Open-File report 2008-1278, version 4.2.  684

Shoreline Changes Due to Construction of Alexandria Submerged Breakwater, Egypt

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Shoreline Changes Due to Construction of Alexandria Submerged Breakwater, Egypt

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