Portland State University. Department of Civil Engineering
Term of Graduation
Date of Publication
Master of Science in Civil Engineering (MSCE)
Sediment transport -- Oregon -- Portland -- Mathematical models, Contaminated sediments -- Oregon -- Portland, Columbia River Slough (Portland, Or.)
1 online resource (xiii, 194 pages)
Recent screening-level risk assessment of Slough sediments initiated by the City of Portland identified five contaminated areas in the Slough as posing the greatest potentially significant risks to human health. These five areas were recommended for accelerated remedial action.
But one question remains, does the sediment contamination at these hot spots change over time in response to the changing Slough hydrodynamics? Specifically, will the contamination move or spread even before remedial action is taken? Will they still be there by the time when potential remedial action is taken? Will any new hot spots be created in response to nonuniform transient flow conditions?
In responding to these concerns, an integrated mathematical modeling system simulating sediment and contaminated sediment transport in the Lower Slough system was developed. The Lower Slough modeling system consists of a coupled hydrodynamic model, a sediment transport model, a bed morphology model and a contaminant transport model.
The Lower Slough hydrodynamic model was calibrated using water level and flow data obtained over a two-month dry period in 1990 and verified using a two-month wet period in 1991. The sediment transport model was calibrated to the suspended sediment data over a synthetic-year period in 1994-1995.
The model predicts that the tidal effect is important in the lower half of the Lower Slough, downstream of the North Portland Road. Tidal flushing has minimal impact on the North Slough and tributaries. Tidal flushing has much more impact on sediment transport in a dry season than in a wet season in the Lower Slough. The dominant mode of sediment transport in the Lower Slough is resuspension. Bedload transport is generally small in the Lower Slough. The model predicts that the concentration of sediment attached contaminants at upstream of I-5 changes very little over the 5 year simulation time span and near St. Johns Landfill and the downstream of North Portland Road seem to change significantly.
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Chen, Min, "Simulating Migration of Contaminated Sediments in the Lower Columbia Slough System" (1997). Dissertations and Theses. Paper 6294.