Effects of Submerged Breakwater on Hydrodynamics and Shoreline Change of the East Beach of Beidaihe, Bohai Bay, China

The beaches in Beidaihe of Bohai Bay of China have been eroded since 1950s, clearly evidenced by sand coarsening, rock outcropping, and slope steepening. Beach nourishment is a common coastal management strategy used to protect beaches from erosion along sandy coastlines, and it has already been applied to recover several beaches of Beidaihe since 2008. In this paper, the effects of a submerged breakwater used as part of a beach nourishment project on hydrodynamics and shoreline changes of the East Beach of Beidaihe are presented. First, the brief descriptions of phase land phase II of the beach nourishment project of East Beach are given. And then numerical models, including tidal current model, wave model, and one-line model for simulating hydrodynamics (tidal currents and waves) and shoreline changes are established and verified by field measurements. These well-verified numerical models are adopted to compute the tidal current fields, wave fields, and shoreline changes of East Beach with and without the submerged breakwater. The results show that the submerged breakwater plays a very important role in protecting East Beach to a certain degree. The effects of alterations of the freeboard and the width and the length of the submerged breakwater on shoreline changes are also discussed, and the results show that increasing the above three parameters will better protect the beach. Overall, a submerged breakwater can play a certain role in protecting a beach against erosion; additional beach nourishment is needed to stabilize East Beach in long term.