EFFECTS OF CROSS SHORE PROFILES ON THE SUSTAINABLE DESIGN OF COASTAL STRUCTURES

Abstract

The performance of the existing coastal structures at different locations along Alexandria coastline, Egypt was re-examined. These coastal structures have been constructed (1998-2002) on Alexandria coastline during the phase of widening the coastal road. The constructions of these coastal structures, although protected the coastal road but didn’t maintain the sandy beaches. El-Sharnouby and Soliman (2011) studied the behaviour of these structures during a storm. This paper investigates the benefits of complementing the existing structures by adding limited modification. Three areas of different profiles and types of coastal protective works along Alexandria shoreline were selected to investigate their performance. The first area “Shatby” has a narrow sandy beach that is protected by a vertical seawall of 3-5 m above sea water level. The second area “Sporting” was protected by a revetment of 20-30 width with 10 ton concrete cubic blocks. In the third area “Loran”, revetment protected the shoreline against further erosion with beach profile completely covered by blocks,
Reeve et el. (2008) used a two dimensional Reynolds-Averaged Navier-Stokes (RANS) numerical model to obtain wave run-up and overtopping characteristics. This model was based on the work of Liu et al. (1999) and Lin and Xu, (2006). A proposed artificial offshore submerged breakwater was introduced to determine its impact on wave runup. Beach profile data were collected by Coastal Research Institute monitoring program for the Alexandria coastal area. Profiles‘surveying were carried out from a constructed land baseline to a water depth of 10.0 m below the M.W.L. The wave characteristics used at the three surveyed profiles are: significant wave height Hs = 1.00 m, dominant wave period = 6.0 sec with wave direction from N to NW.

Several coastal protection schemes were explored; submerged sills, T-groins,..etc. The objectives were to determine their effects on the reduction of wave breaking heights, wave run up as well as maintaining nourished sandy beaches.

The numerical model showed the reduction of wave runup (20%) by submerged reefs, however other design analyses would indicate that coupled systems could fulfil the sustainable design targets. However cost optimization as well as design risk level should play a rule in the final system selection. Detailed results are provided in the poster session as well as final paper.