BEACH EVOLUTION AND SPACE-TIME DISCREPANCY OF EROSION INTENSITY AFTER NOURISHMENT——Taking Langtaosha Beach of Qinhuangdao as an example

Beach nourishment is a convenient and effective way to fight with coastal erosion, and there has been a large number of projects at home and abroad for nourishment. After every nourishment, the beach profiles will change obviously after or within three years to approach a hydrodynamic balance. In this case, we studied the natural evolution of the Langtaosha beach for two years of time after a nourishment. In the two years, the beach volume increased about 63.87m³/m, the shoreline moved seawards for about 14m, and the ratio of sand preservation of the beach reached 79.16%. The project is respected as a great success. In the process of natural evolution, the erosion intensity is significantly changed in different seasons and from place to place. Immediately after the beach nourishment, the beach erosion was very strong. It became weaker as time went on. As a result of the seasonal variation in wave direction, sea level and wind direction, the erosion intensity in summer is stronger than that in winter. Because of the headland on the eastern side of the beach and difference in sediment nourishment, the eastern part of beach, which is located at a relative concave bank and shielded from wave action, is more inclined to deposition. But the western section, which is located at a relative convex bank, is eroded seriously.