长江河口泥沙再悬浮研究

As we know, the Yangtze river-borne sediment has been decreasing sharply in recent years, the water-sediment relationship and flux equilibrium in the estuary will probably be influenced, leading to the resuspension of sediment in the estuary, as well as the variations of estuarine sediment transport and land-sea interaction processes. This project will mainly explore the distributions of particle sizes for suspended sediment and bedload in the Yangtze estuary in the context of sharp reduction in river sediment supply, and the sediment resuspension processes and variations in different estuarine channels, and also the dynamic mechanism and quantity of interchanges between suspended sediment and bedload, as well as the influences to the vertically uneven distributions of the sediment concentration resulting from the resuspended sediment. In the context of new water-sediment relationship in the estuary, the project will be based on the latest field data, lay emphasis on the measurements of first-hand in situ material, apply multi-disciplinary various research methods to explore the dynamic mechanism of interchanges between suspended sediment and bedload in different channels of Yangtze estuary. This is also the focus and new issue of the LOICZ. The research achievements will provide scientific reference for the solution of the siltation in the Deep Navigation Channel (DNC), so the project is significant both in theory and practice.

近年来长江流域来沙锐减，势必会影响到进入河口区的水沙关系及通量的平衡，由此带来河口区域的河床泥沙再悬浮，以致河口陆海动力相互作用关系和泥沙输移过程发生改变。 本项目主要研究流域来沙锐减背景下，长江河口悬沙、床沙颗粒径分布特征；不同河道泥沙再悬浮过程及时空变化；不同河道悬沙-底沙交换动力机制；流域来沙锐减背景下，河口再悬浮泥沙对含沙量不均衡分布格局及变化过程的影响及贡献作用。 本项目针对流域和河口新水沙环境，以大量最新实测数据为基础，注重现场第一手原型资料的观测。采用多学科交叉和多种研究手段，开展新水沙环境下长江河口不同河道悬沙-底沙交换动力机制研究。这是国际陆海相互作用计划关注的焦点和核心研究中的新课题。其成果可为河口航槽淤积泥沙来源的判断提供科学依据，在理论上和应用上都具有重要现实意义。

近年来三峡工程拦沙而导致流域来沙锐减和河口众多大型涉水工程建造的影响环境下，河口和邻近海域悬浮泥沙分布及河床泥沙再悬浮必将对此所做出响应。基于河口大量现场开展的实测水沙、沉积物和地形数据，着重在对近年来流域和河口水沙数据分析的基础上。开展了长江入海来沙锐减过程及其影响因素分析、近期北支河道冲淤变化与泥沙再悬浮过程、近期南支河道冲淤变化与泥沙再悬浮、近期南、北港河道泥沙特性变化与泥沙再悬浮过程、近期不同典型河道泥沙再悬浮过程及影响因素等科学问题的研究。确定2003年以来河口含沙量的锐减是受控于三峡大坝的蓄水拦沙所致，南支河道、南港河道和北港河道中上段含沙量减少 40%～60%。而最大浑浊带发育的北支中下游河道、北港下段河道，以及南、北槽拦门沙河道实测含沙量仍较高，含沙量减少不明显；阐述了长江流域入海悬浮泥沙和河口细颗泥沙行为、水沙输运过程，河口不同河道河床沉积物组成、悬浮泥沙和河床沙交换的动力机制，以及不同河道泥沙再悬浮对水体含沙量不均衡分布贡献及变化过程的多因素互相影响的内在关系；在对人类活动强烈干扰下的河口不同河道含沙量分布和变化规律取得了新的认识。为河口潮滩发育和航槽淤积泥沙来源的判断可提供科学依据。