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Title: Grays Harbor Estuary, Washington. Report 5, Maintenance studies of 35-ft-deep (MSL) navigation channel : hydraulic model investigation
Authors: United States. Army. Corps of Engineers. Seattle District.
Brogdon, Noble J.
Keywords: Channel improvements
Hydraulic models
Dredged material
Navigation channels
Grays Harbor Estuary
Sediment transport
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; H-72-2 rept.5.
Description: Technical Report
Abstract: The existing, comprehensive fixed-bed model of the Grays Harbor estuary was used to determine the effectiveness of three proposed dredged material areas in the estuary entrance in retaining material deposited from a hopper dredge; the effects of three proposed Sand Island Shoal Channel realignment plans (including one plan with a confined disposal area) on channel shoaling, current velocities, and salinities; the effects of eight proposed confined dredged material disposal islands on channel shoaling; and the effects of six channel improvement plans (training dike, groin fields, and turning/settling basin) on channel shoaling, current velocities, surface directions, salinities, and dye dispersion. Prior to conducting channel shoaling tests, a comprehensive shoaling verification of the navigation channel was completed. During the shoaling verification, model operation procedures were developed by trial and error to achieve satisfactory reproduction of observed prototype shoaling distribution patterns within various reaches of the navigation channel. Model test results showed that hopper dredge disposal areas 1 and 3 (northernmost and southernmost areas tested, respectively) were the most effective in retaining dredged material deposited within the prescribed boundaries, while area 2 was the least effective in retaining material. There was no significant return of sediment to the navigation channel for any of the three areas tested. Based on model test results, none of the three proposed Sand Island Shoal Channel realignment plans would cause any major changes in existing current velocities or salinities. Either plan 1 (southernmost alignment) or 1A (plan 1 with a confined disposal area) would reduce the present shoaling rate (existing Sand Island Shoal Channel) by about 70 percent, whereas plan 2 would increase the shoaling rate by about 10 percent. Channel shoaling tests conducted with proposed dredged material disposal islands installed showed that islands 2 (at the upstream end of Crossover Channel) and 8A (at the upstream end of the existing Sand Island Shoal Channel) would result in increased shoaling rates or create adverse navigation conditions. The remaining six islands tested (1, 3 , 4, 5, 6, and 7 at various locations from the upstream end of Crossover Channel to Hoquiam) resulted in essentially unchanged shoaling rates or reductions of no more than about 10 percent. Channel improvement plan 1A (training dike) resulted in reducing channel shoaling in Crossover Channel reach and Moon Island reach slightly more than 10 percent. A 35-ft-deep turning basin located at Cow Point (plan 4) did not adversely affect the channel shoaling rate; deepened to 45ft (plan 4A), the basin was an effective sediment trap. A significant amount of materi al deposited in that part of the basin located outside the navigation channel limits which would otherwise have deposited in the navigation channel. The overall shoaling rate, however, was unchanged. Plans 2, 3, and 5 consisted of 5, 13, and 20 groins, respectively. For each plan, shoaling was significantly reduced in the channel opposite each groin. Plan 5 was the most effective in reducing the shoaling rate in each channel reach from the upstream end of Crossover Channel to about South Aberdeen. This plan reduced shoaling in the Moon Island reach by about 36 percent, in the Hoquiam reach by about 20 percent, and in the Cow Point, Aberdeen, and South Aberdeen reaches by about 11 percent. Plan 3 was the only channel improvement plan subjected to tests to determine effects on current velocities, salinities, and dye dispersion. Average salinities were affected very little downstream from the downstream end of South Channel. Upstream from this area, groin plan 3 caused an increase in vertical mixing as surface salinities were increased and bottom salinities were decreased. The extent of upstream salinity intr usion was reduced slightly (about a mile) as a result of the plan 3 groin system. No adverse effects were evident from surface-current pattern direction photographs taken for any of the 35-ft-deep (msl) channel improvement plans. NOTE: This file is large. Allow your browser several minutes to download the file.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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