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Hydrodynamic Assessment of Various Types of Baffles in a Sediment Detention Pond

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 557-557 in Total Maximum Daily Load (TMDL) Environmental Regulations–II Proceedings of the 8- 12 November 2003 Conference (Albuquerque, New Mexico USA), Publication Date 8 November 2003.  .(doi:10.13031/2013.15614)
Authors:   Christopher S. Thaxton, Joseph Calantoni, Richard A. McLaughlin

We assess the relative improvement to the sediment trapping effectiveness of a permanent-pool sediment detention pond due to the installation of baffles composed of different materials commonly used on construction sites. A suite of experiments was performed at the Sediment and Erosion Control Research and Education Facility (SECREF) at North Carolina State University in which an acoustic Doppler velocimeter was used to record steady-state flow velocity and signal-to-noise ratio data at 50 grid points within the pond at three different fixed input flow rates. The maximum mean flow velocity in the pond, averaged over all input flow rates, is reduced to roughly 25% of the free flow maximum mean flow velocity by the presence of a jute germination geotextile backed by coir fiber. A standard tree protection fence, folded and tied together into three layers for stability, reduces the free flow maximum mean velocity by 35%, while a standard silt fence reduces the free flow maximum mean velocity by 45%. Signal-tonoise ratio degradation along the length of the pond confirms that the installed jute/coir and tree baffles most effectively reduce the concentration of turbulent density fronts responsible for Doppler backscatter over that of silt baffles or free flow. In addition, analysis of the transverse velocity variance and vertical velocity gradients for each experiment further demonstrates that the jute/coir and tree baffles most effectively diffuse inflow momentum. The results of our analysis are used to project a theoretical sediment trapping efficiency based on Stoke's settling.

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