Characterizing the physical drivers of vegetation-forced bar evolution in gravel-bed streams

河岸植被斑块迅速殖民暴露的酒吧在砾石河床的河流，影响附近的流动水力学和随后的侵蚀沉积过程中洪水事件。这种植被造成的砾石坝侵蚀和沉积非常重要，因为它改变了河床沉积物的大小和组成，影响水生和河岸生境质量，推动地下水力学和相关水质的变化，并影响水流输送和社区洪水风险。该项目旨在了解水力学和泥沙输运能力如何通过植被斑块变化，以解释所观察到的河床沉积物的空间格局和由此产生的砾石坝形状。预计变化的幅度取决于斑块内的植被密度。结果可以帮助指导水机构在决定什么样的植被种植密度是必要的，在河流恢复活动，以达到预期的进化结果。此外，预计结果将帮助洪水管理人员预测砾石酒吧尺寸从现有的植被密度，并确定是否植被稀疏或删除是必要的公共safety.Predicting植被酒吧演变是困难的，因为当地的水力学和泥沙流动性（泥沙运动的开始）是空间可变的，通过植被补丁。目前，没有一个单一的参数可用于预测粗泥沙的流动性在开放和植被的渠道。在这里，结合实地考察和大型水槽实验与植被模拟物将被用来开发一个机械驱动器的粗泥沙流动性，适用于植被和无植被的条件。在计划的实验中，植被密度将有所不同，以确定一个密度阈值，启动粒度变化，空间分选，并在砾石床河流酒吧的演变。此外，植被密度和平衡杆尺寸之间的预测关系将被开发。该项目由地貌学和土地利用动力学（GLD）和刺激竞争研究的既定计划（EPSCoR）共同资助。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。

Riparian vegetation patches rapidly colonize exposed bars in gravel-bed rivers, impacting the nearby flow hydraulics and subsequent erosional-depositional processes during flood events. This vegetation-forced erosion and deposition on gravel bars is important as it alters the size and composition of the bed sediments that affects aquatic and riparian habitat quality, drives changes in subsurface hydraulics and associated water quality, as well as impacts flow conveyance and community flood risk. This project seeks to understand how the hydraulics and sediment transport capacity change through vegetation patches to explain the spatial patterns of observed bed sediments and resultant shape of gravel bars. The magnitude of changes is expected to depend on the vegetation density within a patch. Results can help guide water agencies in deciding what vegetation planting densities are necessary during river restoration activities to achieve the desired evolutionary outcomes. Additionally, results are expected to help flood managers predict gravel bar dimensions from existing vegetation densities and determine if vegetation thinning or removal is necessary for public safety.Predicting vegetated bar evolution is difficult because the local hydraulics and sediment mobility (initiation of sediment motion) are spatially variable through a vegetation patch. Currently, no single parameter is available to predict coarse-sediment mobility in both open and vegetated channels. Here, a combination of fieldwork and large-scale flume experiments with vegetation simulants will be used to develop a mechanistic driver of coarse-sediment mobility that is applicable in both vegetated and unvegetated conditions. In the planned experiments, vegetation density will be varied to identify a density threshold that initiates grain-size changes, spatial sorting, and bar evolution in gravel-bed rivers. Further, a predictive relation between vegetation density and equilibrium bar dimensions will be developed.This project is jointly funded by Geomorphology and Land-use Dynamics (GLD) and by the Established Program to Stimulate Competitive Research (EPSCoR).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.