开敞式潮滩-潮沟系统发育演变动力机制——Ⅰ.物理模型设计及潮沟形态

Mechanisms underlying the dynamic evolution of an open-coast tidal flat-creek system: Ⅰ: physical model design and tidal creek morphology

为研究潮沟发育演变动力机制,建立了以江苏中部粉砂淤泥质潮滩-潮沟系统为原型的降比尺物理模型,模拟在潮汐作用下,潮沟系统从平坦滩面逐渐形成、发育演变至动态平衡状态的过程,并分析了潮沟系统在不同阶段的形态特征。研究结果表明:潮沟系统发育速率先快后慢,最终达到动态平衡状态。采用潮沟发育各阶段潮沟系统的总长度与终态潮沟总长度的比值以及潮沟及其相邻处潮滩的高程变化速率两种方法,均可以衡量潮沟系统的发育程度。潮沟系统发育达到动态平衡后,各级潮沟个数占潮沟总数量的比例基本固定。潮沟的宽度、深度、宽深比均符合对数正态分布。潮沟的宽度与宽深比、深度与宽深比之间均具有幂函数关系。

To deepen the understanding of the dynamics underlying tidal creek evolution, a reduced-scale physical model was established based on the prototype of muddy silt tidal fiat-creek system on the central Jiangsu coast. Driven by tidal currents, the evolution of tidal creeks was simulated starting from initial uniform bed level to a dynamic equilibrium state, and the morphology of tidal creeks was analyzed. The results showed that the tidal creek system developed with a sharp and later a smooth increasing rate. Finally, the tidal creek system achieved a dynamic equilibrium state. The development stages of the tidal creek system could be evaluated with two methods. The first index was the ratio between the total length of the tidal creek system in different experimental stages and the total length at the dynamic equilibrium state. The other was the comparison between the elevation-changing rate of tidal creeks and its adjacent tidal fiat at each experimental stage. When the dynamic equilibrium state was reached, the number of ordered tidal creeks kept a substantially constant proportion in comparison to the total number of tidal creeks. The width, depth and the width-to-depth ratio of tidal creeks were in line with a lognormal distribution. It showed a power function exists between the width and the width-to-depth ratio, as well as the depth and the width-to-depth ratio.