淤长型潮滩剖面形态演变模拟:以江苏中部海岸为例

Modeling the Shore-Normal Profile Shape Evolution for an Accretional Tidal Flat on the Central Jiangsu Coast

在泥质、砂质物质共存的淤长型潮滩,其剖面的塑造受到潮流作用下堆积过程的控制.为探讨这种潮滩剖面的演变过程,以江苏中部海岸为研究对象建立了大小潮周期性作用下的潮滩剖面演变模型,模拟了潮滩均衡态剖面形态与初始坡度、潮差、沉积物供应量之间的关系及潮滩的持续淤长剖面.模拟结果表明:(1)淤长型潮滩剖面达到均衡态时的形态是上凸的,且与初始形态无关;(2)在外源一定的条件下,潮滩的宽度与潮差呈正相关;(3)外源物质供应越丰富,潮滩宽度越大;(4)潮滩的冲淤状态由沉积物的供应量决定;(5)对大潮高潮位附近的无沉积带进行充填可实现对其长期持续淤长剖面的模拟;(6)有丰富沉积物来源的潮滩,在调整至均衡态后仍持续向海淤长,并在淤长过程中保持均衡态;(7)当在模型中输入有关江苏海岸的参数时,模拟的潮滩宽度和坡度与江苏海岸的潮滩一致.

The evolution of the shore-normal profile shape of an accretional tidal flat is controlled by the transport of muddy and sandy sediments by tidal currents. To understand the evolution processes, a model is established to simulate the tidal flat profile changes in response to spring-neap tidal eycles, and it is applied to the aecretional tidal flat on the central Jiangsu eoast to investigate the interrelationships between the initial profile shape of the intertidal flat, tidal range, sediment supply, the equilibrium profile shape of the intertidal flat, and the long-term behavior of a prograding profile. The modeling output indicates that： （1） the shape of the accretional tidal flat tends to be convex when reaching its equilibrium state; （2） equilibrium of the intertidal flat morphology is independent of the initial profile shape; （3） if the sediment supply remains stable, then the width of the intertidal flat is positively correlated to tidal range; （4） the width of the intertidal flat increases with sediment supply and the accretion or erosion status of the intertidal flat is determined by sediment supply; （5） there is a need to design an algorithm to treat the area close to high water on springs to simulate long-term growth of the tidal flat; （6） the intertidal flat associated with abundant sediment supply will progradeg towards the sea, and at the same time its equilibrium shape will be maintained; and （7） the width and gradient of the intertidal flat from the model output are consistent with those of the Jiangsu coast, when inputting parameters derived locally for the model.