First Advisor

Shu-Guang Li

Term of Graduation

Spring 1997

Date of Publication

1997

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Department

Civil Engineering

Language

English

Subjects

Sediment transport -- Oregon -- Portland -- Mathematical models, Contaminated sediments -- Oregon -- Portland, Columbia River Slough (Portland, Or.)

DOI

10.15760/etd.8154

Physical Description

1 online resource (xiii, 194 pages)

Abstract

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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Persistent Identifier

https://archives.pdx.edu/ds/psu/39580

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