An Effective Artificial Beachon Muddy Coast: the Case of Jinshan City Beach of Shanghai

The Jinshan District of Shanghai, located on the north bank of Hangzhou Bay, has a well developed silty and muddy coast with a low and smooth tidal flat covered by fine sediment in shape of a sink 0.1~0.2 m in depth. The content of sea water in the sediment is extremely high during storm surge so that the mud layers are easy to slide. In 2005, a 3.3 km closed cofferdam was constructed on the Jinshan tidal flat and a lake of 1.72 km² was formed. A sediment net was setting up and an 1.4 km long artificial beach was constructed by throwing 156 000 m³ of sand from offshore. After many times of sand replenishment and cofferdam reinforcement, the "Yellow Water covered Black Beach" finally turned into a beach of "Blue Water with Golden Sand", which is called Jinshan City Beach since then. The artificial beach is the first successful case in China to turn a muddy flat into a sand beach. After it, more than ten artificial beaches, such as the Tianjin Dongjiang Beach, Weifang Yangzi Artificial Beach, and Nantong Qidong Beach were built up successively. In the case of the Jinshan City Beach, closed cofferdam is used to eliminate wave and protect sand from erosion, make the beach more stable, keep sea water clean and prevent the deposition of beach mud with the technology of sinking sediment and clean water. The fixed mud net is strong enough to ensure the safety of visitors. Its engineering techniques, such as encircling the sea into a lake, sinking mud to clean water, sand nourishment, beach construction and keeping the mud boundary stable, etc., have provided useful samples for construction of artificial sand beaches in China.