黄河三角洲强侵蚀岸段海域的悬沙输运机理研究

Study on suspended sediment transport in sea area off the heavy erosion coast of the Yellow River Delta

基于2010年10月黄河三角洲强侵蚀岸段海域各站位的现场水文观测资料,分析了各站位流速和悬沙浓度的垂向分布,并采用水深对瞬时物质输移量分解法,估算了各站位的余流、单宽净输水量和悬沙单宽净通量以及潮流输沙各影响项的贡献。结果表明:研究海域潮流为流向与岸线大致平行的往复流,各站位潮周期内垂向流速的空间分布表现为十八井外海域的最大,其次为刁口河外海域,最小的为五号桩外海域。潮周期内单宽输水量的空间分布为十八井和五号桩外海域的较大,刁口河外海域的较小,且输水方向与欧拉余流方向一致。悬沙输移量分解计算表明各站位潮流输沙的主要贡献项为平均流输移项(T1)和斯托克斯漂移项(T2)。研究海域13m水深以浅区域的底沙可在相应区域的常见波浪作用下起动、悬浮,被潮流输运,造成水下三角洲侵蚀,这与根据1976-2005年的实测水深资料分析的结果相吻合。

Based on hydrological data at observation station in sea area off the heavy erosion coast in the Yellow River Delta in October 2010,vertical profiles of current velocity and suspended sediment concentration are analyzed. By method of instantaneous sediment transport decomposition,it is analyzed to estimate the residual current,the net water transport of unit width and the net suspended sediment flux of unit width,and contributions of suspended sediment transport impact factors. Results show that the tidal current in study area is reciprocating flow with running direction roughly parallel to coastline. In a tidal cycle the spatial distribution characteristics of vertical suspended sediment concentration profiles at each station consist with the vertical profiles of current velocity,and that is maximum occurred in the sea area off Shi Bajing,second in the sea area off Diao Kouhe,and minimum in the sea area off Wu Haozhuang. The larger of the net water transport of unit width occurred in the sea area off Wu Haozhuang and Shi Bajing,the smaller occurred in the sea area off Diaokouhe in a tidal cycle. Suspended sediment transport decomposition indicated that the main contributions of suspended sediment transport in study area are the Euler residual current and the Stokes drift. Bottom sediment in the sea area shallower than 13 m can be started and suspended by the common wave in the corresponding region,and transported by the tidal current,which caused erosion in the subaqueous delta,this phenomenon agrees with result that analyzed from the measured bathymetric data from 1976 to 2005.