United States Department of Transportation
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Sediment management alternatives for the Port of Bienville.
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2010-02-01
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[PDF-2.49 MB]
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Alternative Title:Port sedimentation solutions - Gulf Coast : sedimentation management alternatives for the port of Bienville.
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Edition:Final report
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Abstract:The objective of this report is to present economical, environmentally friendly, and effective alternatives to maintenance
dredging for the Port of Bienville and its access channels. The Port of Bienville is located in Hancock County, directly off the
Pearl River in the southeastern corner of Mississippi. Access to the Port from the Gulf of Mexico is provided by a channel that
passes through Lake Borgne to the Rigolets, then through Little Lake to the Pearl River. When ports such as Bienville
experience sediment deposition that will ultimately lead to unacceptable loss of water depth, solutions to maintain navigability
include the traditional method of dredging or one of many other alternatives that can be complete - eliminating sediment
deposition - or partial - reducing sediment deposition so as to reduce dredging need. Solutions tend to be unique to each
port, for a successful design depends on port layout, waterway configuration, flow conditions, and sediment type and supply;
however, all solutions can be placed in three categories methods that keep sediment out of the port, methods that keep
sediment that enters the port moving (and prevents net deposition), and methods that remove sediment after it has deposited in
the port. The loss of all Port records during Hurricane Katrina required that other estimates of sedimentation volume, location
and processes be made. In July 2008 the University of Southern Mississippi Hydrographic Science Program did a navigation
chart comparison between their chart completed in July 2008 and NOAA’s navigation chart from 1995, producing a map of
depth changes along the Pearl River. Field observations, a numerical hydrodynamic model, and standard sediment analyses were
used to estimate sediment deposition in the Port as averaging 10,000 tons per year. Two alternatives are suggested – a sediment
trap to capture sediment and prolong the periods between dredging and agitation to prevent sediment from consolidating on the
bed. Neither will be cost effective at present sedimentation rates. An alternative that would reduce access dredging requirements
and provide easier, faster access is relocation of the navigation channel from Little Lake to the lower Pearl River directly to
Lake Borgne. A proposed design for that relocation is provided. It will require some new work dredging and relocation of a
railroad bridge, but will provide safer, easier access and reduced channel dredging.
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