Dam-Break Wave Fronts in Vegetated Wetlands

As wetlands are increasingly used worldwide for environmental benefits, wetland hydraulics and vegetation resistance parameters have become extensively studied subjects. Vegetation resistance parameters are valuable not just for the design and operation of treatment wetlands, but also for continuous monitoring of the health of the vegetation. A method is introduced in this paper to calculate basic vegetation resistance parameters using the shape of the wave front, and particularly the relatively steep gradient, observed during sudden discharges into wetlands. Vegetation resistance, its variation over the depth, and the level of turbulence dictate the shape of the wave front. Field experiments were carried out in storm water treatment areas (STAs) in south Florida managed by the South Florida Water Management District (SFWMD) to collect data on the movement and the shape of the wave front. Results of the experiment include water surface profiles of the steep wave fronts observed during the movement of the front. Mass balance conditions at the leading edge of the wave front were used to develop approximate values of vegetation resistance in terms of hydraulic conductivity or transmissivity. The results show that the transmissivities obtained using the method agree with the transmissivities obtained using generated water waves.