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Open-File Report 2011-1022

Shoreline Surveys of Oil-Impacted Marsh in Southern Louisiana, July to August 2010

By Raymond F. Kokaly,1 David Heckman,2 JoAnn Holloway,1 Sarai Piazza,2 Brady Couvillion,2 Gregory D. Steyer,2 Christopher Mills,1 and Todd M. Hoefen1

1USGS, Crustal Geophysics and Geochemistry Science Center, Denver, CO 80225
2USGS, National Wetlands Research Center, Coastal Restoration Field Station, Baton Rouge, LA 70802
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This report describes shoreline surveys conducted in the marshes of Louisiana in areas impacted by oil spilled from the Deepwater Horizon offshore oil drilling platform in the Gulf of Mexico. Three field expeditions were conducted on July 7-10, August 12-14, and August 24-26, 2010, in central Barataria Bay and the Bird’s Foot area at the terminus of the Mississippi River delta. This preliminary report includes locations of survey points, a photographic record of each site, field observations of vegetation cover and descriptions of oil coverage in the water and on plants, including measurements of the distance of oil penetration from the shoreline. Oiling in Barataria Bay marshes ranged from lightly oiled sections of stems of the predominant species Spartina alterniflora and Juncus roemerianus to wide zones of oil-damaged canopies and broken stems penetrating as far as 19 m into the marsh. For the 34 survey points in Barataria Bay where dimensions of oil damaged zones were measured, the depth of the oil-damaged zone extended, on average, 6.7 m into the marsh, with a standard deviation of 4.5 m. The median depth of penetration was 5.5 m. The extent to which the oil-damaged zone stretched along the shore varied with location but often extended more than 100 m parallel to the shoreline. Oil was observed on the marsh sediment at some sites in Barataria Bay. This oiled sediment was observed both above and a few centimeters below the water surface depending on the level of the tide. Phragmites australis was the dominant vegetation in oil-impacted zones in the Bird’s Foot area of the Mississippi River delta. Oiling of the leaves and portions of the thick stems of P. australis was observed during field surveys. In contrast to the marshes of Barataria Bay, fewer areas of oil-damaged canopy were documented in the Bird’s Foot area. In both areas, oil was observed to be persistent on the marsh plants from the earliest (July 7) to the latest (August 24) surveys. At sites repeatedly visited in Barataria Bay over this time period, oiled plant stems and leaves, laid over by the weight of the oil, broke and were removed from the vegetation canopy, likely due to tidal action. In these areas, a zone of 2-5 cm high plant stubble remained at the edge of the marsh. Signs of both further degradation and recovery were observed and varied with site. Oil damage to the marsh at some sites resulted in complete reduction of live vegetation cover and erosion of exposed sediments, while other damaged zones had signs of regrowth of vegetation in up to 10 percent of the areal coverage.

First posted March 2, 2011

For additional information contact:

USGS Crustal Geophysics and Geochemistry Science Center
Box 25046, Mail Stop 964
Denver, CO 80225

http://crustal.usgs.gov/

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Suggested citation:

Kokaly, R.F., Heckman, David, Holloway, JoAnn, Piazza, Sarai, Couvillion, Brady, Steyer, G.D., Mills, Christopher, and Hoefen, T.M., 2011, Shoreline surveys of oil-impacted marsh in southern Louisiana, July to August 2010: U.S. Geological Survey Open-File Report 2011–1022, 124 p.



Contents

Abstract

Introduction

Shoreline Survey Methods

Shoreline Observations and Measurements

July 7-10, 2010

Field Photos July 7-10, 2010

August 12-14, 2010

Field Photos August 12-14, 2010

August 24-26, 2010

Field Photos August 24-26, 2010

Discussion

Next Steps

Acknowledgments

References Cited

Appendix A

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