Wetland transport is often determined by a branching network of channels that cut through regions of vegetation. The channels provide most of the flow conveyance, but the vegetation provides most of the bioremediation and particle trapping. Thus, the exchange between the channel and vegetation is a crucial dynamic in determining the overall wetland function. This project uses laboratory experiments to study the transport between an open channel and adjacent vegetation. The figure shows a top view off our laboratory channel. The left side is filled with an array of circular cylinders, representing the vegetated bank. Dye is released in parallel filaments to reveal the structure of fluid motion near the canopy-water interface. The dye is fluoresced using a blue light. The filaments are distorted by coherent vortices generated at the interface. The vortices control lateral exchange. Detailed velocity profiles are measured using Laser Doppler Velocimetry (LDV). The models developed in the project will contribute to numerical representations of wetland circulation. The numerical tools will enable stakeholders to predict changes in wetland function that arise with proposed development and land-use changes.
Funded by the National Science Foundation.