潮滩极浅水时段潮锋动力地貌过程研究

As an active zone of interaction between land and sea, tidal flat has considerable ecological and economic benefits in maintaining the health of coastal ecosystem and improving the ability of coastal soft protection. Researches have shown that the "very shallow water" period with a water depth on the order of 10 cm occurs frequently at the beginning of the flood tide makes remarkable contribution to water-sediment transport and morphodynamical processes. However, the mechanism of the formation of velocity and suspended sediment concentration (SSC) surge, as well as their quantitative contribution to micro-morphology change are remained unclear. This project plans to explore the phenomenon of velocity surge and (SSC) surge during very shallow water periods based on methods of theory analysis and field observation. The goal includes: set up a hydrodynamic theoretical model of the tidal front during very shallow water periods on silt muddy tidal flats, clarify the controlling factors and formation mechanism of the velocity and SSC surge; quantify the contribution of tidal front to sediment resuspension and geomorphological changes, and finally illuminate the morphodynamical effects of the very shallow water periods. The expected results will deepen the understanding of the morphodynamical process of tidal flat, and enrich the connotation of coastal dynamics and sediment movement mechanics, which have important theoretical value and discipline significance.

潮滩作为海陆相互作用的活跃地带，在维持海岸生态系统健康、提高海岸软防护能力等方面有着十分可观的生态与经济效益。包括申请人在内的已有研究表明，涨潮初期“极浅水”时段（水深10厘米量级）的潮锋过程具有显著的输水输沙和动力地貌效应，但目前缺乏关于极浅水时段流速、含沙量突增现象的形成机理和定量化动力地貌效应研究。本项目拟采用理论分析结合现场观测的研究手段，建立潮滩极浅水时段潮流前锋水动力理论模型，阐明潮流前锋流速、含沙量突增现象的形成机制；量化潮流前锋对滩面泥沙再悬浮、微地貌演化的贡献，探明极浅水时段水沙关系及动力地貌效应。预期可加深对潮滩动力地貌过程的认识，丰富海岸动力学和泥沙运动力学的内涵，具有重要的理论价值和学科意义。

潮滩作为海陆相互作用的活跃地带，在维持海岸生态系统健康、提高海岸软防护能力等方面有着十分可观的生态与经济效益。本项目选取江苏中部粉砂淤泥质潮滩潮间带光滩为研究区域，开展了泥沙临界起动切应力原位观测以及潮滩近底层多点位同步水沙观测，对极浅水时段的水沙动力及泥沙输运空间分布特征进行了定量研究。研发了便携性好、准确度高的泥沙临界起动切应力原位测量装置，为潮滩动力地貌过程研究中的重要参数获取提供了有效量测手段；剖析了浅水时段流速-含沙量突增现象空间分布特征，证实了水位变化率是导致流速（含沙量）突增现象发生的重要因素，并进一步量化了极浅水时段对水沙输运和微地貌演变的贡献；通过理论分析，从水流前锋的水流结构出发建立了潮间带涨潮阶段水流前锋床面切应力的计算表达式，为解释涨潮前锋水流强烈的冲刷效应提供了理论基础。