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Using Dredge Spoil to Stabilize Deteriorating Marshes
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Project Title: Sediment recycling:marsh renourishment through dredge material disposal
Research Locations: North Carolina
Last Update: 2-01-02
The stability of coastal salt marshes is highly dependent on the natural accumulation of sediments. As coastal populations have increased in recent years, coastal management practices such as inlet stabilization, post-storm bulldozing and beach front development have interrupted the natural supply of sediments to back barrier marshes, resulting in deterioration of marsh systems. This project examines the feasibility of introducing sediments, specifically dredged material, to stabilize deteriorating marshes. This project will also help establish management guidelines for this new marsh restoration technique.
Approach
The right amount of sediment can help stabilize a deteriorating marsh, but too much sediment can be lethal to the vegetation. The focus of this project is on determining that critical threshold.
Experimental Design
Researchers established five plots in two different areas of the marsh: one with deteriorating vegetation, the other with healthy vegetation. In each plot, sediment was added at three levels of thickness and a portion of the plot was left unchanged as a control. For all plots, researchers measured changes to the plant, algae and benthic faunal communities.
Results
Preliminary results indicate that:
- adding sediment to the deteriorating marsh sites increased vascular and microalgal biomass
- adding sediment to the healthy sites did not impact the marsh
- the level of sediment addition did not have a significant effect. This result is encouraging for those looking to find beneficial uses for dredged sediment.
Broad Scale Test Needed
Dealing with permitting issues was definitely a concern for this project. In fact, the North Carolina Coastal Area Management Act regulations set maximum size limits on the plot sizes. Therefore, researchers were unable to use high-pressure sediment sprayers as was planned, because the sprayers cover too large an area. In the future, researchers hope to collaborate with the U.S. Army Corps of Engineers so that this technique can be tested on a broader scale.
Winter vs. Summer
For this project, sediment additions occurred during spring and summer when plant biomass was high. As a result, plants suffered an initial impact. Though not possible for this project, adding the sediment during winter, when there is little above ground biomass, may renourish the marsh without the initial negative impacts.
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Project Coordinator
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Lynn Leonard Univ. of North Carolina, Wilmington Center for Marine Science (910) 962-2338 lynnl@pop.uncwil.edu |
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Start -End Date:
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09/01/1999 - 09/01/2001
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NERR Reserve(s):
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North Carolina
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| For more information: |
Dolores Jalbert Leonard Phone: (603) 862-3685 Email: dolores.leonard@unh.edu |