THE INFLUENCE OF SAND-MUD INTERACTIONS ON MIXED SEDIMENT DYNAMICS

河口和近岸海岸带是世界上最具生产力、最具活力和最复杂的生态系统之一。它们的高环境、社会和经济价值反映在欧盟和英国政府的政策中，通过立法以可持续和综合的方式管理这些资产。这一政策的任务是平衡持续的人类活动（如港口、航运、海洋可再生能源）带来的未来经济增长，日益增加的海岸侵蚀和洪水风险带来的社会经济影响，以及保护和增强敏感栖息地和生态系统。在这些相互竞争的需求下，迫切需要为英国河口和沿海地区制定协调一致的沉积物管理计划，以确保实施可持续的做法，并在未来的规划战略中提高恢复力。为了实现这些具有挑战性的目标，工程师和科学家必须对控制河口和海岸系统中沉积物动态行为的物理过程及其在大规模形态进化中的作用有基本的了解。然而，最大的挑战之一是目前缺乏对混合床沉积物的行为的了解，混合床沉积物包含非粘性砂和粘性泥浆。当前河口和海岸模拟系统的关键缺陷通常与它们对与这些沙泥混合物相关的重要小规模动力过程的描述不足有关，包括侵蚀、夹带、絮凝、沉降和沉积。因此，许多河口和近岸沿海地区对气候变化和人为开发的未来影响的敏感性目前处于高度不确定性之中。拟议的项目将以系统的方式解决这些缺点。研究方案包括在复杂的沉降柱和底栖环形水槽设施中进行基础实验研究，以比以前进行的更详细的定量调查这些混合沉积物过程。这项实验工作将由新的分析模型的发展来补充，通过更多的基于物理的描述所涉及的重要的沙-泥相互作用，来更好地理解混合沉积物絮凝和差异沉降过程。这项研究的一个关键成果将是首次建立混合沉积物悬浮物中这些沙-泥相互作用与由此产生的混合沉积物床层的结构和成分特征之间的重要联系。该项目的综合实验数据和分析模型输出将为今后制定更可持续和更有弹性的河口和沿海沉积物管理战略所需的先进数值模型的发展提供基础。

Estuaries and near-shore coastal zones are amongst the most productive, dynamic and complex ecosystems in the world. Their high environmental, social and economic value is reflected in EU and UK government policy through legislation targeted at managing these assets in sustainable and integrated ways. This policy is tasked with balancing future economic growth from continued human activities (e.g. ports, navigation, marine renewables), socio-economic impacts from increasing coastal erosion and flood risk, and the protection and enhancement of sensitive habitats and ecosystems. Under these competing demands, there is an urgent need for coordinated sediment management plans for UK estuaries and coastal regions to ensure sustainable practices are implemented and improved resilience in future planning strategies is realised. To achieve these challenging goals, it is vital that engineers and scientists have the fundamental understanding of physical processes controlling the dynamic behaviour of sediments in estuarine and coastal systems and their role in large-scale morphological evolution. One of the biggest challenges to this, however, is a current lack of knowledge on the behaviour of mixed bed sediments that contain both non-cohesive sands and cohesive muds. Critical shortcomings in current estuarine and coastal modelling systems typically relate to their inadequate representation of important small-scale dynamical processes associated with these sand-mud mixtures including erosion, entrainment, flocculation, settling and deposition. As a consequence, the sensitivity of many estuaries and near-shore coastal regions to future impacts from climate change and anthropogenic development is currently subject to a high degree of uncertainty. The proposed project will address these shortcomings in a systematic way. The research programme includes fundamental experimental studies in sophisticated settling column and benthic annular flume facilities to investigate these mixed sediment processes in greater quantitative detail than previously undertaken. This experimental work will be complemented by novel analytical model developments to provide better understanding of mixed sediment flocculation and differential settling processes through more physics-based descriptions of the important sand-mud interactions involved. A key outcome from this research will be to establish, for the first time, important linkages between these sand-mud interactions within mixed sediment suspensions and the resulting structural and compositional characteristics of mixed sediment bed deposits. The combined experimental data and analytical model outputs from this project will underpin the development of advanced numerical models required for the development of more sustainable and resilient estuarine and coastal sediment management strategies in the future.