现代废黄河口大规模侵蚀下沉积物源-汇作用及其机制

As a major new sediment source of the Bohai Sea, the quantity of the eroded sediment off the abandoned Shenxiangou-Diaokou river mouth of the Huanghe is more than 0.21 Gt/yr. However, the process and pathway of the resuspended sediment transport as well as its "sink" have not been well documented so far. This project aims at studying the variations of the seabed erosion, resuspended sediment transport and deposition under different time-scale hydrodynamic processes off the abandoned Shenxiangou-Diaokou river mouth, and examing their mechanisms and geomorphlogical effects as well. Based on the integrated observation of hydrography, sediment dynamics and morphology along 3 transects off the abandoned river mouth, we illustrate the seabed erosion and resuspended sediment transport during different seasons and extreme weather conditions. The seabed erosion, resuspended sediment transport and deposition are simulated using a three dimensional numerical model combined with the in-situ observational and remote-sensing data and the mechanisms of their variations under different time-scale hydrodynamic processes are examined. Moreover, the geomorphological responses of the seabed to different time-scale hydrodynamic processes are also discussed based on the simulated results and observational data. This project, as we believe, would promote the studies on the source-sink effect of the massively eroded sediment off the abandoned Shenxiangou-Diaokou river mouth in the Bohai Sea and even in the Yellow Sea, and on the theory of the evolution of river deltas. Moreover, it would be of importance for the development of the Huanghe delta and the safety in production of the Shengli Oil Field.

黄河废弃神仙沟-刁口河口每年沉积物侵蚀量达 2.1 亿吨，是渤海新的主要物源，但其输运过程、路径及归宿尚不清楚。本申请拟研究不同时间尺度动力过程作用下神仙沟-刁口废弃河口海域海底侵蚀和沉积物输运的变化过程，揭示其变化的动力机制并探讨其地貌效应。选取不同季节在废黄河口关键面进行多船同步的定点、大面观测以及海底三脚架长期观测，获取不同季节以及事件性天气过程下水文、沉积物以及地形资料，揭示该区不同时间尺度动力过程作用下海底侵蚀过程和悬浮沉积物输运变化特征；应用三维数值模型，结合现场观测、卫星遥感资料，模拟不同季节和事件性天气过程作用下海底侵蚀和再悬浮沉积物输运路径、通量及归宿，揭示不同时间尺度动力过程影响海底侵蚀和沉积物输运、沉积的动力机制及其地貌效应。本申请可推进现代废弃黄河口侵蚀过程在渤海沉积物的源-汇作用研究，丰富三角洲演变理论，还可为黄河三角洲开发、胜利油田安全生产提供科学依据。

黄河废弃神仙沟-刁口河口每年沉积物侵蚀量达2.1亿吨，是渤海新的主要物源，但其输运过程、路径及归宿尚不清楚。本项目研究不同时间尺度动力过程作用下神仙沟-刁口废弃河口海域海底侵蚀和沉积物输运的变化过程，揭示其变化的动力机制并探讨其地貌效应。选取不同季节在废黄河口关键面进行海底三脚架长期观测，获取不同季节以及事件性天气过程下水文、沉积物以及地形资料，揭示该区不同时间尺度动力过程作用下海底侵蚀过程和悬浮沉积物输运变化特征；应用三维数值模型，模拟了不同季节和事件性天气过程作用下海底侵蚀和再悬浮沉积物输运过程，揭示不同时间尺度动力过程影响海底侵蚀和沉积物输运、沉积的动力机制及其地貌效应。研究表明：冬季风暴海况下近底层垂向沉积物输送通量平均约为平静海况下的22倍，一次风暴过程导致沉积物的侵蚀量约占该区年侵蚀厚度的10%以上，对该区地形地貌塑造和沉积过程具有重要作用。风暴作用导致沉积物液化，使得海底地质灾害（如滑坡、碎屑流等）在15m以浅海域广泛发育，威胁海底管线及平台安全。夏季再悬浮沉积物主要向渤海湾内输运，仅有一小部分向渤海中部输运。冬季则主要向渤海中部和沿岸向南输运，其通量可达冬季3-4倍，其中风暴海况下高出平静海况可达1-2个数量级。废黄河三角洲水上三角洲目前已基本冲淤平衡，而水下三角洲部分由于存在大量的地质灾害，海底沉积物具有显著的跨斜坡传输过程，导致该区水下三角洲部分存在显著的上蚀下淤特征。近年来斜坡的坡度逐渐变缓和沉积物粒度粗化，三角洲海底沉积物液化程度的降低，跨斜坡传输过程不再占主导，取而代之的是波流共同作用下的再悬浮沉积物被海流沿岸长距离搬运，水下三角洲进入二次侵蚀阶段，这与渤海中部沉积记录结果一致。本项目发表学术论文12篇，其中SCI论文9篇，培养硕士研究生5名。本项目推进了现代废弃黄河口侵蚀过程在渤海沉积物的源汇作用研究，丰富三角洲演变理论，同时为黄河三角洲开发、胜利油田安全生产提供科学依据。