Case study of siltation in channel-mouth bar in offshore barrier-lagoon coast

The Laolonggou sea area in Caofeidian of Bohai Bay is a typical offshore barrier-lagoon coastal district with a mouth bar at the inlet region.The formation and the back-silting problem of the bar are studied using the data analysis technique and a 2-D mathematical model for sediment transport under the condition of co-action of waves and tidal currents.The back silting data collected during August-December 2008 is used to validate the 2D model simulation.The model simulates the formation of the mouth bar with regard to the observed waves condition in 2006-2007,tidal currents,sediment,and seabed evolution in Laolonggou sea area.The result shows that the difference in flood and ebb stream paths and the divergent ebb flow are two major factors for forming the bar.The back silting in the channel-mouth bar is further predicted for normal hydrological conditions and sudden siltation due to typhoon.Wave-induced sediment suspension is mainly responsible for the back-silting problem of the Laolonggou mouth bar.