Cooperator: University of Wisconsin—Milwaukee
Project Chief: Stephen M. Westenbroek/Peter E. Hughes
Location: Brown County
Project Number: 9KO34
Period of Project: July 2003–October 2004
Problem
PCB concentrations in the bottom sediment deposits of the Lower Fox River have high concentrations of PCBs. Depending on the hydrodynamic conditions present at these deposits, the choices for remediation can include dredging and removal from the river, capping the sediments in place, or burial by natural sediment transport. The design of a capping system requires information about the stability of the bed sediments and the shear stress produced by high flow in the river. Measurement of velocity at the streambed interface is extremely difficult but recent advancements in the design of acoustic Doppler velocity profilers is making it possible to measure the velocity profile at a fine enough resolution to be able to provide accurate estimates of velocity at this streambed interface.
Objective
The objective is to provide data for evaluation of river bed shear stresses arising from low frequency hydrologic events (that is, high flood flows) or seiche-induced currents. To accomplish this objective, this proposal includes the collection of velocity data at multiple cross sections and at different flow conditions in the Lower Fox River. Depending on wind and flow conditions during data acquisition, these data may also provide a basis for evaluation of wave and current action during reversals of flow nto the Lower Fox River from Green Bay and/or during related flow oscillations. These data will provide an additional measure for calibrating models used to predict such bed shear stresses.
Approach
Velocity data will be collected at multiple cross sections in Operating Unit 4 (OU-4) during a range of flow conditions in the Lower Fox River. Depending on wind and flow conditions during data acquisition, these data may also provide a basis for evaluation of wave and current action during reversals of flow into the Lower Fox River from Green Bay and/or during related flow oscillations. These data will provide an additional measure for calibrating models used to predict such bed shear stresses. Hydrodynamic data will be measured using an acoustic Doppler velocity profiler (ADCP). A complete discharge measurement will be made at the cross section locations and three vertical profiles will be made along each cross section to determine the bottom shear velocity. Data will be post-processed and provided to Sea Engineering, San Diego, for use in calibrating a hydrodynamic model for OU-4.
Progress (July 2003–June 2004)
Velocity measurements were completed for four events on the Lower Fox River. Flows for these measurements were: June 2003 greater than 4,000 cfs, November 2003 greater than
8,000 cfs, March 2004 greater than 10,000 cfs, and May 2004 greater than14,000 cfs. Measurement data have been compiled and forwarded to Sea Engineering for use in calibrating the hydrodynamic model for OU-4.
Plans (July 2004–September 2004)
A report will be written describing the utilization of ADCP technology for measuring shear velocity in a riverine environment. The hydrodynamic model being calibrated by Sea Engineering will be reviewed.
Reports
Pending.
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