Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi River delta

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Although hurricanes can damage or destroy coastal wetlands, they may play a beneficial role in reinvigorating marshes by delivering sediments that raise soil elevations and stimulate organic matter production. Hurricane Katrina altered elevation dynamics of two subsiding brackish marshes in the Mississippi River deltaic plain by adding 3 to 8 cm of sediment to the soil surface in August 2005. Soil elevations at both sites subsequently declined due to continued subsidence, but net elevation gain was still positive at both Pearl River (+1.7 cm) and Big Branch (+0.7 cm) marshes two years after the hurricane. At Big Branch where storm sediments had higher organic matter and water contents, post-storm elevation loss was more rapid due to initial compaction of the storm layer in combination with root-zone collapse. In contrast, elevation loss was slower at Pearl River where the storm deposit (high sand content) did not compact and the root zone did not collapse. Vegetation at both sites fully recovered within one year, and accumulation of root matter at Big Branch increased 10-fold from 2005 to 2006, suggesting that the hurricane stimulated belowground productivity. Results of this study imply that hurricane sediment may benefit subsiding marshes by slowing elevation loss. However, long-term effects of hurricane sediment on elevation dynamics will depend not only on the amount of sediment deposited, but on sediment texture and resistance to compaction as well as on changes in organic matter accumulation in the years following the hurricane.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi River delta
Series title Wetlands
DOI 10.1672/08-32.1
Volume 29
Issue 1
Year Published 2009
Language English
Publisher The Society of Wetland Scientists
Contributing office(s) National Wetlands Research Center
Description 14 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Wetlands
First page 2
Last page 15
Country United States
State Louisiana
Other Geospatial Mississippi River Delta
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