三大河口典型潮滩表层沉积物侵蚀特性分析

Analysis of sediment erosion characteristics of typical tidal flats in three estuaries

采用U-GEMS微观侵蚀系统对三大河口典型潮滩表层沉积物进行侵蚀实验,研究了典型潮滩表层沉积物的侵蚀过程、运动形式和影响因素。结果表明:三大河口典型潮滩沉积物侵蚀特性差异显著,侵蚀速率在0.002~0.064 g/m^(2)·s之间,其中刁口河潮滩沉积物侵蚀速率自陆向海逐渐减小,崇明东滩和鸡啼门潮滩沉积物侵蚀速率自陆向海逐渐增大;崇明东滩沉积物以悬移质侵蚀为主,鸡啼门潮滩沉积物主要为推移质侵蚀,刁口河潮滩沉积物侵蚀方式介于两者之间。另外,潮滩沉积物侵蚀特性受生物和水动力作用的影响。贝壳影响局部的水动力过程,从而增加沉积物的侵蚀性,使累计侵蚀量增大,例如贝壳的存在分别使刁口河潮滩和鸡啼门潮滩沉积物累计侵蚀量提高402.5%和18.4%。潮滩所处区域的水动力条件决定了沉积物的侵蚀特性差异。

The U-GEMS micro-erosion system was used to conduct erosion experiments on surface sediments to understand the erosion processes,movement patterns and influencing factors of three typical estuarine tidal flats.Significant differences of erosion characteristics were found in three different tidal flats with the sediment erosion rate in the range of 0.002-0.064 g/m^(2)/s.The erosion rate in Diaokouhe tidal flat decreases from land to sea,while it is opposite to that in eastern Chongming Island and Jitimen tidal flats.The eastern Chongming Island sediment is dominated by suspended load erosion,Jitimen tidal flat sediment is mainly eroded by bed load,the sediment movement in Diaokouhe tidal flat is in the middle.In addition,the erosion characteristics of tidal flat sediments are affected by biological and hydrodynamic effects.Shells increase the erosion of sediments by affecting local hydrodynamic processes and increased cumulative erosion mass.Specifically,the existence of shells increased the cumulative erosion masses of sediments in Diaokou tidal flat and Jitimen tidal flats by 402.5%and 18.4%,respectively.The hydrodynamics of tidal flats determine the erosion characteristics of the sediment.