Contaminated sediments can cause serious water quality problems. Fundamental understanding of bottom velocity and sediment profiles under current dominated flows and wave-current interactions is critical. In the past both laboratory methods and in-situ methods have been used to provide information of critical bed shear stress and sediment erosion rate. Although the in-situ methods can directly measure sediment resuspension rate under natural flow conditions, capability of characterization of bottom sediment profiles remains an issue. Therefore, laboratory methods are still cost-effective for determining sediment resuspension. The objective of the stduy is to determine characteristics of 1 ft bottom sediment profiles for the purpose of numerical model calibration and simulation. An innovative and well controlled laboratory open channel tilting flume with an automatic piston-image system, digital particle image velocimetry (DPIV), and optical backscatter sensors are used to obtain the critical shear stress and erosion rate for sediment bed cores.
Most in-situ methods utilize flow past through a straight, annular or radial flume to measure erosion rates. Questions regarding the ability of these methods to correctly represent natural flow conditions remain. We are developing an in-situ Bottom Erosion and Deposition System (BEDS), which consists of an acoustic doppler velocimetry (ADV) to measure 3-dimensional bottom turbulence at one point; two pulse to pulse, coherent, acoustic Doppler current profilers (ADCPs) to measure the mean and turbulent velocity bottom profiles; five optical back scattering sensors (OBS) and a laser in-situ scattering and transmissometry (LISST-ST) and a three-frequency, acoustic backscatter system (ABS) to measure settling velocity, concentration profiles of fine and coarse sediments, and an automated stereo-imaging system (ASIS) to measure bottom sediment evolution. In collaborating with NOAA - Great Lakes Environmental Research Laboratory, BEDS has been deployed in St. Joseph and Muskegon in Lake Michigan. Preliminary results show that waves play an important role in resuspension sediments. BEDS was deployed in the Sheboygan river and estuary , indicating that sediment is likely to be eroded to the depth where exiting contaminants, i.e. PCB, are located. Our ultimate goal is to understand the coastal and riverine processes responsible for the resuspension, transport, and deposition of contaminated sediment, the cycling of pollutants, and biological productivity in the Great Lakes or inland lakes.
In recent years, we have been developing a combined geophysical technique, based upon acoustic-wave based sub-bottom profiler (SBP) and electromagnetic-wave based ground penetrating radar (GPR), to map bathymetry and sediment sublayers. In areas with high silt and clay contents, the SBP is able to image the sediment sublayers, whereas in the areas with sand cover and vegetation, the GPR provides sediment stratigraphic information. In addition we use Shelby tubes and hydraulic jetting to collect ground-truth information so that we can accurately to map sublayer thicknesses based upon a mixture-based equation. The technique allows us to effectively map three-dimensional contaminated subbottom sediments, which is valuable to any remediation plan process.
Sponsor : NOAA, University of Wisconsin Sea Grant InstituteNOAA, Cooperative Institute for Limnology and Ecosystems Research
USEPA
US Army Corps of Engineers
Wisconsin Department of Natural Resources
Wisconsin Alumni Research Foundation
W.F. Baird & Associates Ltd.
Status : Active
Student Investigators: Josh Anderson, (M.S.-Ph.D.), Kevin Lin (Ph.D.), Khurran Sattar Khan (Ph.D.), Laura Seabury (M.S.) and openings
Graduated: Cheegwan Lee (Ph.D.)
Collabarator: Professor Qian Liao at Unviersity of Wisconsin-Milwaukee
Publications:
- Anderson, J.D., and Wu, C.H., The role of high frequency
fluctuatons on bed shear stress in the lower Sheboygan River, Lake
Michigan, to be submitted, 2009.
- Lee, C., Wu, C.H., and Hoopes, J.A., Laio, Q. Particle
entrainment
in open channel
flow using sequential PIV and a back-lighted particle imaging
technique, to be
submitted,
2009.
- Lin, Y.T., Schuettpelz, C., Wu, C.H., and Fratta, D., A.,
combined acoustic and electromagnetic wave-based technique for
bathymetry and subbottom profiling in shallow waters. Journal of
Applied Geophysics, 68, 203-219, 2009.
- Lee, C., Wu, C.H., and Hoopes, J.A., Simultaneous
particle size
and
concentration measurements by a back-lighted particle imaging system,
Flow
Measurement and Instrumentation, 20, 189-199, 2009.
- Ng, C.O. and Wu, C.H., Dispersion of suspended particles in
a wave boundary layer over a viscoelastic bed. International J.
of Engineering Science 46, 50-65 2008.
- Lee, C., Wu, C.H. and J.A. Hoopes. Automated sediment erosion testing system using digital imaging, J. Hydraulic Engineering, ASCE, 130, 8, 771-781, 2004.
<>Lake Michigan Muskegon deployment
Waves-Sediment-Acoustic
strength
