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HYDRODYNAMIC ASSESSMENT OF VARIOUS TYPES OF BAFFLES IN A SEDIMENT RETENTION POND
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Transactions of the ASABE. Vol. 47(3): 741-749 . @2004
Authors: C. S. Thaxton, J. Calantoni, R. A. McLaughlin
Keywords: Baffles, Detention, Hydraulics, Hydrologic, Hydrology, Retention, Runoff, Sediment, Sedimentation
We assessed the relative improvement to the sediment trapping effectiveness of a permanent-pool sediment retention
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. The data was gathered at 25 grid points at two depths within the pond for three different fixed input flow
rates. The free flow maximum mean velocity in the pond, averaged over all input flow rates, was reduced by roughly 75% due
to the presence of baffles composed of jute germination biotextile backed by coir fiber. Baffles made from a standard tree-
protection fence, folded and tied together into three layers to reduce pore size, reduced the free flow maximum mean velocity
by 65%, while baffles made of standard silt fabric fence reduced the free flow maximum mean velocity by 55%. A similar trend
in the reduction of the signal-to-noise ratio along the length of the pond confirmed that the jute/coir baffles most effectively
reduced the concentration of turbulent density fronts over that of the tree-protection fence or silt fence baffles, or free flow.
In addition, analysis of the transverse velocity variance and vertical velocity gradients for each experiment further demonstrated
that the jute/coir baffles most effectively diffused inflow momentum along the width and depth of the pond. The results
of our analysis were used to calculate a sediment trapping efficiency based on Stokes settling. The minimum grain size captured
would range from 30 to 42 microns with jute/coir baffles, compared to 68 to 86 microns for free flow.
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