【作者】 李占海；

【导师】 沈焕庭；

【作者基本信息】 华东师范大学 ， 地理学， 2005， 博士

【摘要】 根据现场观测资料，本文从底质粒径组成、潮流边界层、悬沙剖面、悬沙级配特征、沉积物输运等方面探讨了江苏大丰潮滩的沉积动力特征。 大丰潮滩的底质粒径组成具有明显的空间差异，由海向陆底质的砂含量减小、粉砂含量和粘土含量增加。盐蒿滩和互花米草滩沉积物主要来源于悬沙沉降，悬沙粒径组成和沉降特点决定了表层底质的粒径组成。在泥砂混合滩、粉砂细砂滩和细砂滩上，推移质物质是影响表层底质粒径组成的重要因素。 低潮位附近的细砂滩滩面的涨潮流以逆时针方向旋转为主，落潮流以顺时针方向旋转为主，涨潮流的流向范围和潮流旋转幅度均大于落潮。落潮历时一般大于涨潮历时，而落潮流速明显大于涨潮；落潮单宽净输水量明显大于涨潮，涨潮净输水方向以平行海岸为主，落潮以垂直海岸向海为主，全潮单宽净输水量主要受落潮流控制。这种水文特征是潮沟和／或平面环流(涨、落潮流路不一致)的影响所造成的。在低潮位附近，涨、落潮周期中只出现一个明显的流速高峰，出现在落潮中期，高水位时不存在明显的憩流。 一个潮周期内，符合对数分布的流速剖面一般占总数的42-96％，各潮周期差别较大。影响流速剖面非对数分布的因素主要有风、波浪、流速的非恒定性、悬沙浓度等。受悬沙浓度和流速垂向变化的影响，水体密度层化参数R_f具有明显的时间变化和垂向变化。悬沙浓度能够减弱水体垂向上的动能量交换，使摩阻流速或剪切力减小。根据对摩阻流速与推移质输运率关系的分析，Hardisty(1983)的推移质输运率公式可导致较大的误差。 悬沙浓度在潮周期内的变化很大，涨潮平均悬沙浓度大于落潮，悬沙浓度及其垂向梯度具有明显的空间差异。从流速与悬沙浓度的关系以及悬沙粒径组成来看，位于细砂滩的测站处没有发生明显的再悬浮和悬沙沉降，悬沙浓度的变化主要与悬沙平流输运和悬沙浓度的空间梯度有关。在有明显再悬浮和沉降的情况下，悬沙粒径组成在潮周期内具有明显的时间变化和垂向变化，再悬浮量越大，悬沙粒径越粗，悬沙沉降量越大，悬沙粒径越细，底层悬沙粒径明显粗于上层悬沙粒径。在没有明显再悬浮和沉降的情况下，悬沙粒径组成在潮周期内的时间变化和垂向变化都很小，随潮周期的变化也很小。更多还原

【Abstract】 The thesis deals with the sediment dynamic processes of intertidal flats at Dafeng, northern Jiangsu, in terms of. sediment grain-size variability, benthic boundary layer properties and suspended sediment concentration profiles, sediment transport rate, on the basis of in situ measurements and laboratory analyses.Grain size distributions of the seabed sediment have marked spatial variations on the intertidal flat, with the sand content decreasing and silt and clay contents increasing from the lower part towards the upper part of the intertidal zone. On the Sueada salsa and Spartina alterniflora flats, materials from settling of suspended sediment are the main source for seabed sediment; hence, the grain size distribution of seabed sediment is determined by the characteristics of suspended sediment. On other parts of the flat, the seabed sediment originates largely from bedload transport.Near the lower part of the fine sandy flat, the tidal current rotates in an anticlockwise manner during the flood phase of the tide, whereas during the ebb the current rotates in a clockwise pattern; the range and rotation during the flood is larger than during the ebb. Ebb duration is longer than flood duration, but the ebb current velocity is stronger than the flood. Net water transport during the ebb is stronger than during the flood; net water transport direction during the flood is parallel to the shoreline, but it is towards the sea during ebb (perpendicular to the shoreline). Such hydrodynamic patterns result from the influences of the presence of tidal creek systems and/or the residual circulation over the intertidal zone. During the entire tidal cycle, there is only one current velocity peak that occurs at the middle ebb, and there is almost no slack water (i.e. zero current velocity) during the high water periods.On the intertidal flat, suspended sediment concentrations (SSCs) vary considerably during the tidal cycle; time averaged SSCs during the flood are higher than during the ebb, with remarked temporal and spatial variations in the SSC and its vertical gradient. Based upon the information on current velocity, SSC and variations of grain size distribution of suspended sediment, there is no intensive resuspension and settling at the measurement station during the survey period. Advection and spatial gradient of SSC is the main reason of CCS changes in the tidal cycle; in this case, the temporal variation in the SSC is a reflection of the spatial variation. Resuspension and settling更多还原