By Chad R. Wagner
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 03-4336
Louisville, Kentucky 2004
PDF Version (10.1 MB PDF)
Errata Sheet (Feb.
15, 2005)
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The Olmsted two-dimensional hydrodynamic and sediment-transport model was developed in cooperation with the U.S. Army Corps of Engineers, Louisville District. The model was used to estimate the effects that the phased-construction sequence and operation of the Olmsted Locks and Dam had on sediment-transport patterns in the 11.9-mile study reach (Ohio River miles 962.6 to 974.5), particularly over an area of endangered orange-footed pearly mussel (Plethobasus cooperianus) beds beginning approximately 2 miles downstream of the dam construction. A Resource Management Associates–2 (RMA-2) two-dimensional hydrodynamic model for the reach was calibrated to a middle-flow hydraulic survey (350,000 cubic feet per second) and verified with data collected during low- and high-flow hydraulic surveys (72,500 and 770,000 cubic feet per second, respectively). The calibration and validation process included matching water-surface elevations at the construction site and velocity profiles at 15 cross sections throughout the study reach.
The sediment-transport aspect of the project was simulated with the Waterways Experiment Station's Sed2D model for a 6-year planned-construction period (construction-phase modeling) and a subsequent 3-year operational period (operational-phase modeling). The sediment-transport results from the construction and operational models both were compared to results of concurrent baseline simulations to determine the changes in erosional and depositional patterns induced by the dam construction and operation throughout the study reach and more importantly over the area of the endangered mussel beds.
Simulation of the phased-in-the-wet Olmsted Locks and Dam construction and subsequent operation period resulted in a maximum additional deposition of approximately 2 feet over a localized region of the mussel beds when compared to the bed change simulated with baseline conditions (river conditions that included only the completed locks section). Most areas on the mussel beds experienced less than 0.5 feet of cumulative bed change between the baseline and construction phases during the nine annual hydrographs. The bed change over the 9 year Olmsted Locks and Dam simulation reveals a continuous downstream progression and deepening of the main channel and deposition along the right bank with limited lateral migration toward the more densely populated mussel-bed areas. The sensitivity of the mussels to sediment deposition is difficult to quantify; therefore, the effect of simulated deposition on the welfare of the mussels is uncertain. The model also will provide the U.S. Army Corps of Engineers a tool to predict the locations of high deposition in navigable sections, which can save engineers time and resources when monitoring the need for dredging operations.
Abstract
Introduction
Background
Purpose and scope
Study area
Construction-phase model
Modeling approach
Hydrograph development
Construction phases
Operational-phase model
Modeling approach
Hydrograph development
Hydrodynamic-model development
RMA-2 hydrodynamic model description
Field data collection and interpretation
Water-surface elevations
Velocity and discharge
Bathymetry
Computational-mesh configuration
Boundary conditions
Discussion of calibration and validation results
Sediment-transport model development
Sed2D sediment-transport model description
Model input parameters
Bed material
Selection of representative grain size
Time step
Particle-fall velocity
Concentration of sediment inflow
Calibration of sediment-transport model
Model results
Construction-phase model—hydrodynamics
Construction-phase model—sediment transport
Operational-phase model—hydrodynamics
Operational-phase model—sediment transport
Model comparison between Sed2D and previous TABS-1 simulation
Model development
Comparison of model results
Summary and conclusions
References cited
Appendix A: High-flow comparisons of baseline and phase-3 construction
cross-sectional velocity profiles
in the Olmsted Locks and Dam study reach
Appendix B: Low-flow comparisons of baseline and phase-3 construction
cross-sectional velocity profiles
in the Olmsted Locks and Dam study reach
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