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3. Hydraulics Laboratory - (8/1/1972 - 9/1996)
4. Publication
5. Technical Report

Title:	Mayport-Mill Cove Model Study. Report 2, Mayport Naval Basin Study : hydraulic model investigation
Authors:	United States. Army. Corps of Engineers. Jacksonville District Brogdon, Noble J.
Keywords:	Fixed-bed models Mayport Naval Basin Flushing Salinity Hydraulic models Shoaling Sediment transport Sedimentation Deposition Mayport-Mill Cove Estuary Estuaries Inlets Jacksonville (Fla.)
Publisher:	Hydraulics Laboratory (U.S.) Engineer Research and Development Center (U.S.)
Series/Report no.:	Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL-79-12 rept.2.
Description:	Technical Report Abstract: A fixed-bed model of Mayport-Mill Cove, constructed to scales of 1:500 horizontally and 1:50 vertically, reproduced a portion of the Atlantic Ocean adjacent to the entrance and the St. Johns River upstream to Hibernia Point. The purpose of the model study was twofold: (a) to investigate the effects of proposed improvement plans for the Mayport Naval Basin area on existing shoaling rates, hydraulics, salinities, and flushing; and (b) to investigate the effects of proposed improvement plans in the Mill Cove area on flushing, hydraulics, salinities, and channel shoaling. The model study was conducted in three phases: phase 1 involved the model verification tests, phase 2 involved the Mayport Naval Basin study, and phase 3 involved the Mill Cove study. Phase 2 is reported herein; phases 1 and 3 are reported in Reports 1 and 3 of this series The model verification tests described in Report 1 indicated that the model hydraulic and salinity regimes were in satisfactory agreement with those of the prototype for comparable conditions. Model verification also included a comprehensive shoaling verification of shoaling rates and patterns in the navigation channel and Mayport Naval Basin. During the shoaling verification, model operation procedures were developed by trial and error to achieve satisfactory reproduction of observed prototype shoaling distribution patterns within the various reaches of the navigation channel and in Mayport Basin. This report contains the results of tests conducted for phase 2 of the study. Based on model shoaling test results conducted for 11 proposed plans, four plans were selected on their merit to reduce shoaling within the basin for further, more extensive testing. Plans 1, 3, 4B, and 5B were tested extensively. Model test results showed that none of the four plans would cause any major change in and along the navigation channel with respect to existing current velocities, salinities, channel shoaling, or dye flushing; however, each plan did result in considerable changes within the basin. Plans 1 and 3 resulted in better navigation conditions in the basin in the vicinity of the carrier berths as maximum current velocities in this area were generally less than those of base conditions. Plans 4B and 5B resulted in increased maximum flood current velocities in the carrier berthing area that could create berthing problems for the carriers and other vessels. Flow predominance calculations showed that plan 1 resulted in increasing the net flow in the ebb direction throughout the basin by about 2.7 percent, while plan 3 resulted in decreasing the net flow in the ebb direction by about 2.7 percent. Plans 4B and 5B changed the base condition net ebb flow into a significantly strong net flood. Maximum effects to base condition flow predominance for each plan were similar in that greatest effects were observed at mid-depth and bottom elevations. Average salinity concentrations in navigation channel, exit channel, and basin were generally slightly lower than the base for each of the four plans investigated. There was no indication that one plan resulted in more or less change than another, as a very large percentage of the data was within limits of accuracy of repeating identical model tests, particularly within the basin. Results of dye tests do not indicate any significant improvement of flushing for plans 1 and 3. Results for plans 4B and 5B indicate a significant improvement in overall flushing within the basin near the bottom. Lesser reductions were observed at shallower depths with essentially no change near surface. Plans involving no secondary openings, gated or otherwise, were more effectlve in reducing shoaling in the Mayport Naval Basin. Plan 1 was the most effective as model tests showed a reduction in the present rate of approximately 47 percent. Plan 2 showed a reduction in shoaling rates of about 46.6 percent, and plan 3 resulted in reducing the shoaling rate by about 39.5 percent. Plans involving ungated openings (plans 4, 4A, 4C, 5, 5A and 5C) each resulted in an increase of shoaling in the basin. Plans involving gated openings (4B and 5B) effected a reduced shoaling rate in the basin but were not as efficient as plans which did not include an opening. Surface current pattern photographs showed no adverse effects resulting from any of the four plans investigated extensively. NOTE: This file is large. Allow your browser several minutes to download the file.
Rights:	Approved for public release; distribution is unlimited.
URI:	http://hdl.handle.net/11681/13618
Appears in Collections:	Technical Report