Momentum and Scalar Exchange Between Channels and Vegetated Banks

尼泊尔湿地系统通常由穿过植被茂密地区的分叉河道网络组成。虽然河道提供了大部分的水流输送，但植被覆盖的地区提供了大部分的生物修复和颗粒捕获。因此，河道和植被带之间的交换可以控制整个湿地的功能，特别是在水质和泥沙捕获方面。河道和水系植物繁茂的河岸之间也存在着类似的关系。实验室实验将被用来量化河道和等深或更小深度的新兴植被带(堤岸)之间的动量和质量交换，并开发一个模型，根据典型的植被和水流参数预测这种交换。在水槽模型中，将通过跟踪从海峡和植被带内不同位置释放的染料羽流的演变来观察交换。模型植被的设计将采用与真实植被几何和动态相似的方法。初步的流动可视化研究将用于评估主要机制，定义不同几何形状的行为范围，并改进实验系统。随后的详细研究将同时测量浓度和速度，以直接量化动量和质量的湍流通量。这项研究将借鉴现有的泛滥平原模型，包括植被对水力粗糙度和泛滥平原地貌的影响。本项目完成后，未来的研究阶段将把新的河道和植被带交换模型与现有的河道流和植被流模型相结合，构建一个能够预测湿地循环和迁移的综合湿地模型。该模型将为湿地系统的管理提供重要的工具，使利益相关者能够预测随着拟议的开发和土地利用的变化而产生的湿地功能的变化。

0125056NepfWetland systems often consist of a branching network of channels cutting through regions of dense vegetation. While the channels provide most of the flow conveyance, the vegetated regions provide most of the bioremediation and particle trapping. Thus, exchange between the channel and vegetated zone may control the overall wetland function, in particular with regard to water quality and sediment trapping. A similar relationship exists between the channel and vegetated bank of a river system. Laboratory experiments will be used to quantify the exchange of momentum and mass between a channel and a zone of emergent vegetation of equal or lesser depth (a bank), and to develop a model that predicts this exchange from representative vegetation and flow parameters. In the flume model, the exchange will be observed by tracking the evolution of dye plumes released from different locations within the channel and vegetated zone. The model vegetation will be designed using geometric and dynamic similarity to real vegetation. A preliminary flow visualization study will be used to assess major mechanisms, to define ranges of behavior across different geometry, and to refine the experimental system. Subsequent detailed studies will simultaneously measure concentration and velocity to directly quantify turbulent fluxes of momentum and mass. The study will draw from existing models for floodplains, including the effects of vegetation on hydraulic roughness and floodplain geomorphology. After the completion of this project, future phases of this research will integrate the new model for exchange between channels and vegetated zones with existing models for channel flow and vegetated flow to construct a comprehensive wetland model capable of predicting wetland circulation and transport. This model will provide an important tool for managing wetland systems by enabling stake holders to predict the changes in wetland function that will arise with proposed development and land-use changes.