Predicting In-Canopy Velocity and Retention Time for Aquatic Canopies

预测植被对流速异质性和交通的影响Heidi尼泊尔水生植被对水和栖息地质量的影响有多种方式。水生植物吸收营养物质并产生氧气。它们创造了床面应力减小的区域，促进了颗粒的保留并影响了形态演变。众所周知，淹没的树冠和浮现的树冠都能抑制海浪，减少海岸和岸边的侵蚀。最后，通过在速度场中引入空间异质性，植被增加了栖息地多样性，从而增加了物种多样性。由于PI具有许多优点，一些研究人员现在提倡大范围补种和基于生态的河道和海岸植被管理。在以前的拨款(EAR0309188，EAR0125056)中，PI描述了长的、新生的和淹没的树冠中的流动和输送，即纵向范围远大于树冠高度或宽度。这些项目使用了刚性的树冠模型，这是新兴植被的合理替代品，但不太适合沉水植物，因为它们往往是灵活的。连续、坚硬的天篷是必要的第一步，因为它很容易通过数学模型来表示，从而允许进行稳健的模型测试。我们现在已经准备好建立第一个简单的模型，并探索自然界中存在的树冠形态的范围。这项工作将分两部分进行。其中一个项目将开发单向流动和波浪下的柔性树冠模型。第二个将开发有限长度和宽度的水下和紧急树冠的模型，现有的二维模型不适用于这些几何图形。第二个项目将再次使用硬质天篷，以方便测试新的数学模型。这两个部分具有很强的智力协同效应。从事这两个项目的学生将举行小组会议，共享共同的实验室空间，新想法将在项目之间快速传递，每个项目将受益于不同形态的持续比较和对比。植被水动力学的联合活动也将吸引更多的访问学者，为这项工作带来新的想法和视角。其次，有限顶棚工程构思采用刚性模型。当同时工作时，柔性天篷项目将提供如何使刚性模型适应柔性天篷的洞察力，并将提供一个柔性天篷来测试这些洞察力。这样，有限冠层的研究将在将新的有限冠层模型扩展到柔性形态方面取得更大的进展。第三，植被消波的研究将大大扩展，因为实验室将提供柔性和刚性树冠模型。由于湖泊和海洋海岸都有淹没的柔性树冠和坚硬的突起树冠，因此确定这两个区域的波浪衰减特性是很重要的。这项工作将通过在圣安东尼瀑布实验室的野外规模的室外StreamLab中进行真实植被实验，向实地测试迈出重要的一步。明尼苏达州)。生态学家、地质学家和水动力学家将同时使用室外StreamLab，促进跨学科联系。

Predicting the Impact of Vegetation on Velocity Heterogeneity and TransportHeidi NepfAquatic vegetation impacts water and habitat quality in several ways. Aquatic plants remove nutrients and produce oxygen. They create regions of diminished bed stress that promote the retention of particles and influence morphological evolution. Both submerged and emergent canopies are known to damp waves and reduce coastal and bank erosion. Finally, by introducing spatial heterogeneity to the velocity field, vegetation increases habitat diversity, and thus species diversity. Because of its many benefits, some researchers now advocate wide spread replanting and ecologically based management of channel and coastal vegetation.Under previous grants (EAR0309188, EAR0125056), the PI has described flow and transport in long, emergent and submerged canopies, i.e. with longitudinal extent much larger than canopy height or width. These projects used rigid canopy models, which are a reasonable surrogate for emergent vegetation, but are less appropriate for submerged plants, which tend to be flexible. The continuous, rigid canopy was a necessary first step, as it is easily represented through mathematical models, allowing robust model testing. We are now ready to build on those first simple models and explore the range of canopy morphology present in nature. This work will proceed in two parts. One project will develop models for flexible canopies under both unidirectional flow and waves. The second will develop models for submerged and emergent canopies of finite length and width, geometries for which the existing two-dimensional models do not apply. The second project will again use rigid canopies to facilitate the testing of new mathematical models. The two parts have strong intellectual synergy. The students working on the two will hold group meetings and share common lab space, new ideas will be quickly transferred between projects, and each project will benefit from ongoing comparison and contrasting of different morphologies. The combined activity in vegetation hydrodynamics will also attract more visiting scholars, bringing new ideas and perspectives to the work. Second, the finite-canopy project was conceived to use rigid models. When working simultaneously, the flexible canopy project will provide insight into how one adapts rigid models to flexible canopies and will also provide a flexible canopy for testing these insights. In this way, the finite-canopy study will progress much further in extending new finite-canopy models to flexible morphologies. Third, the study of wave-damping by vegetation will be greatly expanded, because both flexible and rigid canopy models will be available in the lab. Because both lake and ocean coasts have zones of submerged flexible canopies as well as rigid emergent canopies, it is important to characterize wave damping in both zones. The work will take an important step toward field testing through experiments with real vegetation in the field-scale Outdoor StreamLab at the Saint Anthony Falls Laboratory (Univ. of Minnesota). Ecologists, geologists, and hydrodynamicists will be using the Outdoor StreamLab simultaneously, facilitating inter-disciplinary connections.