长江河口崇明东滩周期性淹水区域水流的基本特征

潮间带周期性淹水区域水深、流速的变化过程是潮滩水动力过程的基本组成部分，也是潮流与泥沙相互作用的基础。通过2002年4月至2003年1月4个季节的野外实测，获得了平静天气条件下，崇明东滩滩面潮流水深、流速与流向的变化过程数据。结果表明，崇明东滩盐沼和邻近光滩处涨潮历时均小于落潮历时，水深过程变化呈现出“陡涨缓落”的特点。光滩与盐沼交界处光滩一侧流速过程呈“双峰型”特征，涨落潮均出现流速峰值;盐沼（植物生长期）流速过程具有“单峰型”特点，仅在涨潮初出现峰值。研究区潮流不对称性明显，主要表现为涨潮优势，且由光滩向盐沼上部不断增强，潮沼植物和地形变化是加强盐沼区涨潮优势的主要原因。流速变化过程的差异和潮流不对称性使盐沼区域发生稳定的泥沙淤积，盐沼前缘光滩则会出现较频繁的冲淤变化，平静天气条件下，它们是控制崇明东滩泥沙输移和潮滩动力地貌过程的动力基础。

An Investigation of Water Depth and Current Velocity Process in Periodic Inundation Area of East Chongming Tidal Flat, Yangtze Estuary

Water depth and current velocity,as the fundamental constituents of hydrodynamics,played an important role in sediment advection,deposition and resuspension on the intertidal flats.A field measurement of water depth,current velocity and flow direction was carried out on the East Chongming tidal flat in the Yangtze Estuary,between April 2002 and January 2003.Measurements of current velocity during semi-diurnal tidal cycles showed different shapes of the time series of velocity between saltmarsh and adjacent mudflat.On the mudflat,in general,the current velocity reached peck value during the flood and ebb phase in single tidal cycle.However,on the saltmarsh,peck current velocity values only appeared during the flood phase,except when marsh vegetation wilting.At the measurement sites,time-velocity asymmetry was significant.A duration period during flood phase was shorter than ebb phase.Current velocity during flood phase,in contrast,was larger than ebb phase.The results indicated flood current dominant in the research area.Marsh vegetation and topographty,which reduced ebb currents,enhanced flood current dominance on the saltmarsh.As a result,there was stable accumulation on the saltmarsh,compared to frequent alternation of erosion and accretion in adjacent mudflat.Overall,under calm weather condition,tidal current process and asymmetry were basic dynamic controls of sediment transport and morphodynamics process on the East Chongming tidal flat.