Assessment of implementation stages of submerged breakwater on the bay and shoreline at Al-Ahlam Sea Resort, Northwest Coast, Egypt

摘要

Al-Ahlam Sea Resort is located at km 92 of International Coastal Road on the Northwest Coast of Egypt. Coastal projects, such as shore-parallel breakwaters cause man-induced coastal changes. Consequently, the stages of their implementation almost affect the shoreline changes and sedimentation in the area. Hence, many problems associated with these structures induce beach erosion on down-drift side which may extend beyond the project area. The study objectives are to evaluate factors inducing the problems, assess the impact of the delay of construction phases of the breakwater on the bay and shoreline, and estimate the economic and environmental losses, hence proposing immediate and permanent appropriate measures. These have been achieved based on analyses of shoreline changes, sea level variations, waves and marine survey during the period between 2008 and 2015. The implementation plan of the submerged breakwater project was scheduled to start on 2010 and end on 2012, ignoring the periods of extreme waves, storms and summer swells. Due to difficulties facing the execution company in work in the project area during the last five years, the project is still under implementation and only about 60% of its recommended works has been achieved. The present study defines the existing conditions prevailing the project area and changes that have been instigated due to delay in the project execution schedule using field data and marine surveys performed during the period between 2010 and 2015. The study revealed that the area was subjected to sever erosion in the eastern zone and its adjacent area led to a loss in beach sand reached to 45000 m(3). Besides, in the western side, sedimentation is prevailing due to the constructed artificial lagoon used for maintenance operations of the implementation marine equipment. This sedimentation leads to difficulties in the entry and departure to and from the lagoon. The study indicated that the delay of the implementation of the breakwater caused shoreline and morphology changes. These led to economic and environmental losses exceeds 2.0 million USD about 30% of the estimated original cost. The study recommended immediate start-up dredging works in the western zone and the middle sector of the project area to facilitate the maneuvering of the marine equipment, which can speed up the implementation process in order to finalize the execution of the breakwater and to reduce the economic and environmental losses. The equilibrium of the shoreline and the bay in case of completion of the submerged breakwater has been checked by application of MIKE 21 Numerical Model.