The effect of eelgrass meadows on the morphodynamics of coastal sedimentary systems

鳗草草甸对滨海沉积体系形态动力学的影响

• 批准号: RGPIN-2019-04588
• 负责人: Kwoll, Eva
• 金额: $ 1.82万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737719
• 关键词: effect; eelgrass; meadows; morphodynamics; coastal

The goal of this proposal is to advance our understanding of the role of vegetation in coastal geomorphological change, by studying eelgrass meadows along the Fraser River, BC. The world's coastlines are highly dynamic systems that form the battleground of various socio-economic and ecological stakeholders and are experiencing increased pressure through ongoing anthropogenic alteration and accelerated sea-level rise. Conventionally, geomorphologists have examined coastal landscape evolution as a function of adjustments of flow, sediment transport and seabed morphology. More recently, it has been acknowledged that this conventional approach fails to integrate the influence of aquatic vegetation such as eelgrass meadows in coastal morphodynamics. Yet, the presence of vegetation is known to alter fluid dynamics by providing resistance to the flow and causing turbulence production. Vegetation is often referred to as a `geomorphic engineer', due to propensity to cause sediment deposition. However, a process-based understanding of the sediment dynamics around vegetation is still lacking. Building on my previous work on flow and sediment transport in sand-bedded environments, the specific objective of this proposed program is therefore to examine how the presence of eelgrass influences spatio-temporal variations in turbulent flow structure, bed shear stress, and sediment dynamics from an individual eelgrass patch to the large-scale dynamics of coastal bays. The work takes on an end-to-end approach starting with initial direct field observations in Years 1-3, systematic laboratory experiments in Year 3, through to regional-scale numerical simulations using industry-leading modelling suites in Years 3-5. Field campaigns comprise ship- and lander-based hydro-acoustic surveys using our own instrumentation over the eelgrass system of the Fraser River Delta, the largest continuous eelgrass system in BC. The field experiments will inform systematic laboratory experiments using simulated eelgrass blades and sandy sediment to arrive at parameterizations of bed shear stress and reduced settling velocities for implementation in numerical models. Our modelling effort will begin with a critical test of current formulations for vegetation and will systematically test and implement our new parametrization. The models will then be used to examine the effect of changes in vegetation on tidal flat drainage and sediment transport environment of tidal flats. Our ultimate aim is to adequately represent coastal vegetation in these model suites, which will allow a more accurate prediction of coastal change following development or climatic changes. The proposed work is therefore timely and of immediate interest to a number of coastal stakeholders, including developers, consultants, engineers, environmentalists, and coastal communities. Our usage of industry-leading, open-soure modelling software will ensure valuable contribution and lasting impact for potential end-users.

这个建议的目标是通过研究不列颠哥伦比亚省弗雷泽河沿着的鳗草草甸，来促进我们对植被在沿海地貌变化中的作用的理解。世界海岸线是高度动态的系统，是各种社会经济和生态利益攸关方的战场，并因持续的人为改变和海平面加速上升而承受越来越大的压力。传统上，地貌学家研究沿海景观的演变作为调整的流量，沉积物运输和海底形态的功能。最近，人们已经认识到，这种传统的方法未能整合水生植被的影响，如沿海形态动力学的鳗草草甸。然而，已知植被的存在通过提供对流动的阻力并引起湍流产生来改变流体动力学。由于植被有造成沉积物沉积的倾向，因此常常被称为“地貌工程”。然而，仍然缺乏对植被周围沉积物动力学的基于过程的理解。建立在我以前的工作在砂层环境中的流动和沉积物输运，因此，这个拟议中的计划的具体目标是研究如何存在的鳗鱼草影响时空变化的湍流结构，床剪切应力和沉积物动力学从一个单独的鳗鱼草补丁的大尺度动态的沿海海湾。这项工作采用端到端的方法，从第1-3年的初始直接实地观察开始，第3年进行系统的实验室实验，到第3-5年使用行业领先的建模套件进行区域规模的数值模拟。现场活动包括使用我们自己的仪器在弗雷泽河三角洲的鳗草系统上进行基于船舶和陆地的水声调查，这是不列颠哥伦比亚省最大的连续鳗草系统。现场实验将告知系统的实验室实验，使用模拟的鳗草叶片和桑迪沉积物，以达到参数化的床面剪切应力和减少沉降速度的数值模型中实施。我们的建模工作将开始，对目前的植被公式进行严格测试，并将系统地测试和实施我们新的参数化。模型将用于研究植被变化对潮滩排水和泥沙输运环境的影响。我们的最终目标是充分代表这些模型套件中的沿海植被，这将允许更准确地预测沿海发展或气候变化后的变化。因此，拟议的工作是及时的，对一些沿海利益攸关方，包括开发商，顾问，工程师，环保主义者和沿海社区的直接利益。我们对行业领先的开源建模软件的使用将确保为潜在的最终用户做出有价值的贡献和持久的影响。