Incorporating Floodplain Functions into River Restoration Engineering: The Role of Floodplain Vegetation on Channel-Floodplain Hydrodynamics

由于洪泛区在连接河流和陆地生态系统方面的独特作用，洪泛区为自然和人类系统提供了许多好处或服务，如洪水波衰减、污染物的生物地球化学减少和营养物质的转移。这些服务依赖于洪水期间河道和洪泛区表面之间的水转移，也称为水文交换流。洪泛区植被在控制河流-洪泛区水力学和水文交换流方面起着特别重要的作用，因此可以影响许多洪泛区服务和通道稳定性。然而，大多数河流恢复工作很少考虑洪泛区植被的影响，因为我们没有充分了解植被的水力控制稳定的恢复设计，也没有植被影响交换流量和洪泛区服务的程度。因此，本研究的目标是提高我们的认识，河漫滩植被恢复蜿蜒的渠道和对河漫滩服务的重要水文交换流量的水动力学的耦合效应。为了实现上述目标，本研究的主要目标是：（1）提高对天然河床地形下弯曲河道中与动量交换相关的植被-水流动力学的概念性认识：（2）研究漫滩植被对漫滩表面水文交换流的影响;以及（3）评估河漫滩修复设计中河漫滩表面上的河道水动力和水文交换流之间的关系。本研究将使用水槽实验和数值模拟相结合，与当地河流恢复项目的特点，以解决这些目标。将进行水槽实验，以探索蜿蜒河道中漫滩水流的水动力学，同时系统地改变漫滩植被特征。水槽实验期间收集的水力测量数据将用于更好地了解漫滩流期间河漫滩植被和河道底形对河道内和河漫滩水力条件的影响，包括二次流分布、湍流特性和水文交换流。水槽实验的结果将用于通知数值模拟。数值和物理实验的补充，将收集和分析现场数据，从当地的恢复网站上的该高速缓存拉普德雷河，科罗拉多。在这项研究中进行的工作将密切涉及柯林斯堡市，它已经花费了近1000万美元对当地的Poudre河的恢复投资，并有改造Poudre河的大目标，以提供自然和人类系统之间的更大联系沿着。这项研究将通过参与众多当地的外展活动，包括Poudre River Fest和城市的“幕后科学”计划，与利益相关者进行互动。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Because of their distinct role in linking riverine and terrestrial ecosystems, floodplains provide numerous benefits or services to natural and human systems, such as floodwave attenuation, biogeochemical reduction of pollutants, and transfer of nutrients. These services rely on the transfer of water between a river channel and floodplain surface during flooding events, also known as hydrologic exchange flows. Floodplain vegetation plays a particularly important role in controlling river-floodplain hydraulics and hydrologic exchange flows, and therefore can influence many floodplain services and channel stability. However, most river restoration efforts rarely consider the influences of floodplain vegetation because we do not adequately understand the hydraulic controls of vegetation on stable restoration designs nor the degree to which vegetation influences exchange flows and floodplain services. Therefore, the goal for this research is to improve our understanding of the coupled effects of floodplain vegetation on hydrodynamics in restored meandering channels and on hydrologic exchange flows that are important for floodplain services. To meet the above stated goal, this research targets accomplishing the following core objectives: (1) advance conceptual knowledge of the vegetation-flow hydrodynamics related to momentum exchange in meandering channels with natural bed topography; (2) investigate the influence of floodplain vegetation on hydrologic exchange flows on floodplain surfaces; and (3) evaluate relationships between channel hydrodynamics and hydrologic exchange flows on floodplain surfaces pertaining to river-floodplain restoration design. This research will address these objectives using a combination of flume experiments and numerical modeling that are linked to characteristics of local river restoration projects. Flume experiments will be conducted to explore the hydrodynamics of overbank flows in meandering channels while systematically varying floodplain vegetation characteristics. Hydraulic measurements collected during the flume experiments will be used to better understand the influence of floodplain vegetation and channel bedform on in-channel and floodplain hydraulic conditions during overbank flows, including distributions of secondary currents, turbulence characteristics, and hydrologic exchange flows. Results from the flume experiments will be used to inform numerical modeling. The numerical and physical experiments will be complemented by the collection and analysis of field data from local restoration sites on the Cache la Poudre River, Colorado. Work conducted in this research will closely involve the City of Fort Collins, which has already spent nearly $10 million on restoration investments on the local Poudre River and has large goals for transforming the Poudre to provide a greater connection between natural and human systems along the river. This research will engage with stakeholders by participating in numerous local outreach events, including the Poudre River Fest and the City's "The Science Behind the Scenery" program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.