Particle capture by aquatic vegetation modeled in flume experiments: the effects of particle size, stem density, biofilm, and flow velocity

Wednesday, 17 December 2014
Rachel Kerwin1, Kristen Fauria1,2, Daniel Nover1,3 and Geoffrey Schladow1,4, (1)University of California Davis, Davis, CA, United States, (2)University of California Berkeley, Berkeley, CA, United States, (3)USAID West Africa, Accra, Ghana, (4)UC Davis Tahoe Environ.Res. Cent., Davis, CA, United States
Vegetated floodplains and wetlands can trap and remove particles from suspension thereby affecting water quality, land accretion, and wetland functioning. However, the rate of particle removal by vegetation remains poorly characterized, especially for fine particles. In this study, we monitored particle concentration and size distribution (1.25 – 250 µm diameter suspended road dust) in a laboratory flume as flow velocity, plant stem density, initial particle concentration, and the presence of biofilm on vegetation were varied. We characterized change in particle concentration through time by calculating decay constants, termed capture rates. Based on our experiments, we found that suspended particle concentration decayed more rapidly in the presence, rather than in the absence, of vegetation. Additionally, particle capture rates increased with stem density, particle size, and the presence of biofilm, while decreasing with flow velocity. These results demonstrate that low flow velocities and the presence of biofilm optimize particle capture by vegetation. Our results are relevant to floodplain and wetland restoration efforts.