Mapping Vegetation-Resistance Parameters in Wetlands Using Generated Waves

摘要

Constructed wetlands, referred to as stormwater treatment areas (STAs), are important components of the water management infrastructure in south Florida. These systems have complex internal flow patterns due to uneven growth of vegetation, short-circuiting flows, and variable microtopographic features. Artificially generated water waves were used in an experiment to determine the combined effects of these influences on overall flow rates and water distribution in the treatment areas. Wave speeds and wave decay characteristics measured at points in a triangulated network were used to calculate resistance to flow, which depends on energy gradient and depth. The results were used to produce two-dimensional maps of hydraulic transmissivities, stem-drag resistance coefficients, and parameters of power law equations describing resistance. The results also included bulk parameters or single parameters defined for the entire wetland. They show that the patterns of many resistance parameters plotted in two-dimensions (2D) are similar to the general patterns of the distribution of vegetation in areal maps. Moreover, they indicate that power law equations can represent not just the vegetation resistance but also the effects of topography, resistance due to blockages, and the effects of short-circuiting and turbulent behaviors. The dimensionless parameters provided can be used to determine if the governing equation is primarily hyperbolic or parabolic, and to what extent the flow behaves like porous-media flow with diffusive wave behavior or short-circuiting stream flow with kinematic wave behavior. (C) 2017 American Society of Civil Engineers.