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Research

Barataria Barrier-Shoreline Feasibility Study


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cutting a vibracore
Jim Flocks (helped by Jack Kindinger, right, and Dave Bennett) is cutting a vibracore from the ebb-tide delta of Barataria Pass. The core is cut, capped, measured, and labeled for transport to the lab for analysis.
The USGS CMGP in St. Petersburg has entered into a new cooperative study with the University of New Orleans (UNO) and U.S. Army Corps of Engineers (USACE) to describe the geologic framework and sediment distribution within the south part of the Barataria Basin (Figure 1, below). The study has been fully funded by USACE with the primary goal of identifying sand resources for barrier-island restoration.

Jack Kindinger is the project leader assisted in the field and lab by Jim Flocks, Mike Stallings, Dana Wiese, Shawn Dadisman, Mark Hansen, Nancy Dewitt, B.J. Reynolds, Rich Young, Chuck Holmes, and Marci Marot.

Also participating through the USGS/Eckerd College co-op are Dave Bennett and Gregg Brooks. From UNO, Shea Penland, Mark Kulp, Phil McCarty, and numerous students are helping to collect and describe cores. Representing the USACE is Del Britch.

Figure 1—Lower Barataria Basin is located on the west side of the Mississippi River. The primary sand-survey area is up to 12 km offshore from Bell Pass to Sandy Point.

Map of Lower Barataria Basin

Located on the west side of the Mississippi River, the Barataria barrier shoreline is about 80 km long and extends from the Bell Pass to Sandy Point. The barrier shoreline provides some of the rarest habitats in Louisiana and the entire Gulf of Mexico and helps protect wetlands in the Barataria Basin from tidal inundation and storm-induced wave action. Equally important, the barrier shoreline helps protect communities and commercial and industrial infrastructure from hurricanes and storm surge. Unfortunately, the shoreline and the wetlands behind it are also some of the most rapidly eroding areas in Louisiana.

Examining a berm
Jim Flocks and Jack Kindinger examine a wave-cut beach berm along the Gulf shore of Grande Isle, La. The beach berm is a sandy veneer overlying a marsh platform that is also being eroded. Notice trees in the background that have recently been uprooted by high tides.
All of Louisiana's barrier shorelines have changed dramatically over the last 100 years. Retreat along the Barataria shoreline has ranged from 0.7 to 30 m per year (see photo at right). The average long-term (1880s to 1988) erosion rate there has been 5.5 m/yr. Thirty-year projections of shoreline loss indicate that high rates will continue at Cheniere Ronquille and Shell Island.

Landward of the barrier shoreline and throughout the basin, wetlands are disappearing rapidly. About 102,395 acres of marsh have been lost since 1932. Annual marsh loss in the project area is the highest in the state and the rate of loss has continued to increase. Because of proximity to the Gulf of Mexico, high subsidence rates and high loss rates, most wetlands that remain behind the barrier shoreline are expected to disappear within the next 20 years.

In early 1999, a Barataria Barrier-Island Restoration Project (BBIRP) was approved as a 'complex' project of the Louisiana Coastal Area, Ecosystem Restoration Feasibility Study. This study was intended to investigate the possibility of restoring the entire barrier-island chain from Grand Terre to Southwest Pass and look into the prospect of installing wave barriers in the interior bays to reduce shoreline erosion from waves regenerated behind the barrier islands. It was expected that the feasibility study would be submitted for funding under the Water Resources Development Act (WRDA).

After the BBIRP project was approved but before funding was granted for specific tasks to be undertaken, the USACE New Orleans District and Louisiana Department of Natural Resources agreed to assume a similar effort, the Coast 2050 Feasibility Study (CFS), under WRDA funding. Under the CFS, it is likely that some actual construction work could begin on the islands in 7 to 10 years.

Because the affected parishes and local citizens have made it clear that rapid restoration of the barrier-island chain is critical, and to avoid duplication of effort with the CFS project, the NMFS decided to scale back the BBIRP to 2 or 3 islands. The objective is to be ready to request funding for construction, using Coastal Wetlands Planning, Protection and Restoration Act dollars, in 2 to 3 years. The proposed BBIRP will restore from 8 to 16 km of barrier shoreline in Barataria from Grand Terre to Sandy Point using a combination of sand, alternative materials, and hard structures along the Gulf shore.

Phase I—Project Development

An inventory of existing data has been completed. Existing data were used to identify possible borrow areas prior to field efforts and to summarize information relative to the quantity and quality of sand available for use on the islands.

Phase II—Data

Collection, Processing, and Interpretation
Surveys of the potential borrow areas have begun. Information to be collected includes high-resolution seismic (subbottom profiler and chirp) and bathymetry data. In addition, cores will be taken and analyzed to verify seismic data and acquire sediment textural data.

Field operations began May 1st aboard the R/V G.K. GILBERT, with operations based out of Grande Isle, La. So far, we have recovered 64 vibracores in Barataria Bay and on the Barataria Pass ebb-tide delta and have acquired~300 line km of high-resolution seismic data from Bell Pass to Sandy Point to ~11 km offshore. The seismic data will be used to select additional coring sites. We have projected that 200-225 vibracores will be needed to characterize the area.

The interpreted data will provide sand-resource maps including isopach, percent sand, and texture maps for identifying the best borrow locations. Data (raw and preliminary interpretations) will be made accessible to the USACE New Orleans District as they become available.

Phase III—Products

Existing and newly acquired data will be integrated into final products. While data collection is in progress during Phase II, interim maps and data (raw and preliminary interpretations) will be made accessible to the USACE New Orleans District. Sand-resources maps will be constructed as needed by the USACE. The maps and data will be used to make final decisions on the usability, precise location, and quantity of sand in the borrow sites.


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