Study of Beach Erosion and Evolution of Beach Profile Due to Nearshore Bar Sand Dredging

摘要

The sand dredging activities may cause various physical and environmental changes such as beach erosion, evolution of beach profile, change in current and wave field. To evaluate the relationship among the volume of sand dredging, method of sand dredging, time of sand dredging, shoreline retreat and evolution of beach profile, some experiments were conducted and a two-dimensional numerical model was used. The effect of sand dredging volume on shoreline retreat was investigated by dredging various amounts of sand at one time under the same regular wave condition. The results showed that the relationship between shoreline retreat and dredging volume is nonlinear. In the other considerations, sand bar was dredged as different methods i.e. periodic sand dredging method under the same regular wave condition as well as one time dredging under different regular wave conditions. The final shoreline retreat in the last two methods was nearly equal to the first method, however, the progress of shoreline retreat was slower. After sand dredging in all cases, the beach profiles were not translated to the same original form. Infill rate of the bar after sand dredging is also discussed in term of average absolute sediment transport rate.