埃及阿莱曼旅游区海滩养护及硬工程作用

THE BEACH NOURISHMENT PROJECT IN EL ALAMIEN MARINA,EGYPT,AND ROLE OF HARD STRUCTURES

阿莱曼海滩位于埃及尼罗河三角洲西侧,是长约12km的平直沙坝潟湖岸,在强劲的西向常、强浪的作用下,泥沙沿岸向东运移,引起海岸长期强烈蚀退。1998—2009年分3个阶段整治和抛沙养滩,先后建成13条丁坝组成的丁坝群,丁坝效应稳定了8.5km的海滩,3个阶段共向滩肩抛沙116×104 m3,但是水下基岩陡斜地形导致严重沙流失,使海滩不能增宽,丁坝群尾闾效应也导致丁坝群下游3.5km海难侵蚀更加严重,于是先后采取了分段式岸外坝群和岸外连续长潜堤加堤内丁坝格,消除了丁坝群下游岸的侵蚀。结合我国相应案例说明在那些强烈侵蚀和严重沙流失岸段养滩,必须强调丁坝、岸外坝等硬工程的作用。这些构筑物既能消散波能,又能阻拦所抛沙的流失。对于那些水下为基岩陡斜地形的海滩,更应设计一定的硬工程,埃及阿莱曼的连续长潜堤加丁坝格的设计和我国三亚三美湾的连续岸外坝丁坝加人造沙坝的经验都是十分重要的。

The El Alamien marina is located in the west of the Nile Delta in Egypt,as a 12 km long flat sandbank along the shore of a lagoon.The coast has been eroded intensively for a long time,under the long-term action of the strong southwest wave which carries sediment moving eastwards along the coast.Three projects had been conducted in 1998—2009to protect the beach from erosion.13 groins were built to stabilize the beach of 8.5km long and 116×104 m^3 of sand have been nourished to save the beach.However,they did not work well.Then groins and continuous offshore submerged dikes plus internal groins were constructed to stop the loss of sand,and then they succeeded.Some of the domestic nourishment projects in China face similar challenges.We made an introduction to the success management experiences in the El Alamien marina to use the model to combine groins and continuous offshore submerged-dikes and the model to combine groins and double parallel offshore groins at foreshore flow-out to effectively stop sand loss with the dissipation of the offshore wave energy and then stop the littoral drift to protect the nourished beach from erosion.It is also verified that it is possible to construct a broad artificial beach at a steep rocky coast with the support of specific combination of hard structures.