Effects of the Addition of Multi-Slip Docks On Reservoir Flushing and Water Quality: Hydrodynamic Modeling; Aquatic Impact;
Regulatory Limits

John E. Edinger
Consultant in Environmental Hydrology, 63 Crestline Rd., Wayne, PA 19087. E-mail:
jeedgr@aol.com (Corresponding Author)

James L. Martin
Professor, Department of Civil and Environmental Engineering, Mississippi State University, P.O. Box 9546, Mississippi State, MS 39762. E-mail: jmartin@cee.msstate.edu


Abstract: Numerous multi-slip docking facilities are planned for placement along the shoreline of Tims Ford Reservoir located on the Elk River in south central Tennessee, USA. These multi-slip docking facilities will occupy different kinds of shoreline configurations including coves, mouths of small tributaries, and other regions of limited flushing. Placement of the multi-slip docking facilities will limit the amount of local flushing that will take place in the vicinity of the multi-slip docking structures. Very few of the multi-slip docking facilities have been built to date, therefore comparative simulations of flushing need to be performed for conditions without and with the proposed multi-slip docking structures. This report describes the results of comparative simulations using computational hydrodynamic and transport models. The analysis shows that there will be reduced flushing in over 92% of the proposed multi-slip docking locations. The reduction in flushing will worsen water quality conditions. The analysis and results of flushing estimates are compared to flushing guidelines used by some US State regulatory agencies and international guidelines used by ANZECC (2000).

The comparative analysis of flushing allows evaluation of the changes in water quality including coliforms, dissolved oxygen, algal densities and sedimentation that will take place along the shoreline and in the vicinity of the multi-slip docking facilities. The magnitude of the probable changes due to construction of the multi-slip docking facilities for coliforms, dissolved oxygen and algal densities is greater than the seasonal changes in these water quality constituents as observed over the years in Tims Ford Reservoir. In addition, flushing and the changes in algal densities could be compared to the ANZECC (2000, Sec. 8.1.9.1) algal growth guideline. The change in water quality will not be limited to the multi-slip docking areas alone. Many of the local changes that will take place at the individual multi-slip docking facilities will affect water quality throughout 67% of the area of the reservoir. In particular the increased algal densities will generate seed for spores and cysts that will spread throughout the reservoir by attachment to sediment and decaying algae. The increase in benthic spores and cysts will increase the likelihood of the occurrence of algal blooms in the years following construction of the multi-slip docking facilities.
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Keywords: Water resources, marinas, mathematical models, sitting regulations, aquatic impacts,
environmental studies.
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