潮间带短期冲淤过程的横向差异及其定量表达——以长江口南汇滨海岸段的观测分析为例

根据1999年4月～2000年4月对长江口滨海某研究断面上24个观测点的定期(每周一次)滩面高程测量结果的分析,定量化地探讨了滩面垂直淤积速率和稳定性的横向差异。结果表明:(1)滩面的年垂直淤积速率在淹没机率为30%左右的沼泽中下部(位于平均小潮高潮线与平均高潮线之间)达到49.5cm/a的最大值。自这点向岸和向海垂直淤积速率逐渐降低,向岸在近堤处(接近平均大潮高潮位)达到最小值2.2cm/a(仅为最大值的1/22),向海在光滩—沼泽交界处出现另一低值,而在光滩上又有所增大。(2)由于植被的抗冲护滩功能,沼泽带滩面的相对稳定性远大于光滩带。分析认为:上述滩面冲淤过程的差异是潮水淹没机率、波浪和潮流能量以及植被分布上横向差异的综合体现。

Cross-shore diference in short-term evolution of muddy intertidal flat using a quantificational method --Taking the eastern shore of Nanhui as an example

Based on the data, which were obtained weekly at 24 sites along a transection set up in the Eastern Shore of Nanhui from Apr 1999 to Apr. 2000, this article quantificationally examines the cross shore differences of annual vertical accretion rate, absolute and relative stabilities of sediment surface. The results are as follows: (1) The annual vertical accretion rates are distinctly different at each site along the transection with a maximum of 49.5 cm/a at the site where the submergence probability is about 30% (between the average neap high water level and the average high water level) and a minimum of 2.2cm/a at the site near the seawall. The maximum is 22 times of the minimum. The annual vertical accretion rate is comparatively low where the marsh and the bare flat meets. Totally, the annual vertical accretion rates are lower at sites on the bare flat than those at sites on the marsh. (2) The absolute stabilities of the sediment surface are different at each site along the transection. Because it indicates the same phenomenon as the annual vertical accretion rate does, the difference of absolute stability is in accordance with the difference of the annual vertical accretion rate along the trasection. (3) The relative stabilities of the sediment surface are different at each site along the transection. The relative stabilities are much stronger at sites on the marsh than those at sites on the bare flat. (4) Vegetation plays an important role in protecting the shore from erosion and stimulating accretion It also enhances the relative stability of sediment surface The difference in short term evolution of intertidal muddy flat is a compositive reflection of the submergence probability, energy of the wave and tide as well as the distribution of vegetation along the transection