离岸沙坝-潟湖海岸拦门沙航道回淤——以渤海湾曹妃甸海域老龙沟拦门沙为例

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

渤海湾曹妃甸老龙沟海区属于典型的离岸沙坝-潟湖海岸体系,口门处发育有拦门沙。采用实测资料分析和二维波流泥沙数学模型计算研究了拦门沙成因及其开挖后的回淤情况。研究表明,涨落潮流路不一致、落潮流扩散是老龙沟拦门沙形成的主要原因。针对该海区波浪、潮流、泥沙及海床演变特点,进行了2006年、2007年大小潮潮流泥沙的验证及2008年8～12月试挖槽回淤的验证,在此基础上,预测了拦门沙航道正常情况下的泥沙回淤和大风天骤淤。试挖槽监测资料分析及数学模型计算表明,风浪掀沙是影响老龙沟拦门沙回淤的重要因素。

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.