Plants were modeled using 1/2" PVC pipe, set vertically into an array 24" X 36" (61 X 91.5 cm). This was designed to simulate relatively rigid, approximately cylindrical emergent plants such as cattails. I built a support structure for the pipes using plywood, and supporting the pipes above the water, and at the bottom. 

The Experimental Setup

    The length of the pipes was sufficient to prevent the waves from reaching the upper piece of plywood. Two capacitance wave gauges, one located before the assembly and one after, recorded incident and transmitted wave heights.

    I generated waves at three frequencies (1,2, and 3 Hz) and varying heights (the 3 Hz waves were recorded at only one height, as the wave generator was unable to create larger ones due to oscillation in the flume). I also varied the density of the stems, using 81, 60, 40, and 20 stems (corresponding to 144, 107, 71 and 36 stems/m²). 

    I predicted greater attenuation at high stem densities, for the simple reason that the waves would have to interact with more stems, and should, presumably, lose more energy. I also expected more attenuation at larger wave heights and frequencies, since both of these conditions lead to higher horizontal velocities. Since drag increases with the square of the velocity, this should have a significant effect on the total attenuation.