Dyke Marsh, restoration, Corps of Engineers, U.S. Army, Baltimore, Washington, District of Columbia, D.C., Fairfax, national harbor, wetlands, marsh wrens, freshwater, George Washington Memorial parkway, project, National Park Service, NPS, USACE, erosion, Virginia, Maryland
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Dyke Marsh Wildlife Preserve Restoration

 

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The Baltimore District and the National Park Service (NPS), George Washington Memorial Parkway, are working on a project to protect and restore freshwater tidal marsh within the Dyke Marsh Wildlife Preserve in Fairfax County, Virginia, which is just across the Potomac River from the National Harbor. This is an NPS-funded project that the Corps is authorized to design and construct. NPS is providing funding to the Corps through the Hurricane Sandy Mitigation Program. 

U.S. Geological Survey (USGS) estimates that the southern marsh has existed for approximately 2,200 years, and the northern marsh has existed for 500 years.

Dyke Marsh is viewed as a national treasure that holds extensive value not only for plants and animals, but for its recreational, educational and cultural purposes. It is one of the best studied wetlands in the U.S. and is the largest remaining freshwater, tidal wetlands in the Washington metropolitan area. It is home to six state-listed species of special concern (two bird species and four plants species) and has the only known nesting population of marsh wrens in the Upper Potomac River tidal zone. 

It is critical to act now to protect and restore Dyke Marsh.

From 1940 to 1972, approximately 270 acres of marsh were dredged by a corporation for the valuable sand and gravel beds that laid in a thick layer 16 to 40 feet below Dyke Marsh. In the 1950s, the promontory south of Hog Island Gut was removed due to dredging. 

Dyke Marsh is now exposed to storm waves, susceptible to erosion, and unable to sustain itself.


In 2009, NPS partnered with USGS to investigate the state of Dyke Marsh. USGS found that the post-mined marsh is rapidly shrinking as a result of erosion caused primarily by storm waves driven northward up the Potomac River. Erosion in the marsh averages between 6 and 8 feet per year. USGS found that without intervention, this unique ecosystem would be entirely lost by 2035. 

In 2013, Congress recognized Dyke Marsh as an invaluable resource to the District of Columbia region and allocated $24.9 million to restore the site. In 2014, an Environmental Impact Statement and preliminary plans were released by NPS for public comment. In August 2015, NPS and the Corps signed an interagency agreement to start the project. The Record of Decision for the project was signed in June 2016. 

This project is critical to the ecology of the Potomac through the protection and restoration of valuable, historic tidal wetlands and habitat. 

With the available project funding, work includes an approximately 1,500-foot breakwater and approximately 5.45 acres of restoration of freshwater tidal marsh using clean sandy material. Marsh plants will be established on the marsh restoration site.

This design has been set up to allow for expandability. Remaining construction work that cannot be completed could be identified as future phases of the project to be constructed as more NPS funding becomes available.

The breakwater will help protect the existing and restored marsh from erosion and will help re-establish the marsh’s ability to regenerate naturally within the preserve’s historic footprint through the collection of sediment.

This project will provide a storm buffer for the historic and scenic George Washington Memorial Parkway, a natural filter to clean the Potomac River, and habitat for a variety of plants and wildlife.

Construction is anticipated to start in early 2018 and end in 2019 or 2020. Once construction is completed, NPS will continue to monitor the site to ensure no invasive/non-native plant species become established in the restored marsh and that restoration efforts are on track, as it takes time for habitat to develop and self-sustain. 

 

Project Manager

Ray Tracy, P.E., 410-962-6114,

Raymond.M.Tracy@usace.army.mil

Dyke Marsh Project FAQs

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Climate change was incorporated into the design by adding one foot of height to the breakwater. Given the current data on water rise, the extra foot should be sufficient over the next several decades. More information is available at http://www.corpsclimate.us/ccaceslcurves.cfm regarding Sea Level Rise.

Construction of the breakwater and restoration of the (up to) 5 acres of marsh will not have significant impacts on boating and fishing. There will still be able plenty of areas to fish and boat in and around Dyke Marsh. In addition, the breakwater will not impede boating in the existing navigation channel. National Park Service will mark the waterward end of the breakwater with lights and signs to caution boaters.  

Construction is anticipated to begin in early 2018 and wrap up in 2019 or 2020. National Park Service will monitor the site following construction completion. 

Dyke Marsh is viewed as a national treasure that holds extensive value not only for plants and animals, but for its recreational, educational and cultural purposes. It is estimated that the southern marsh has existed for 2,200 years, and the northern marsh has existed for 500 years. Dyke Marsh is one of the largest remaining freshwater tidal wetlands in the Washington metropolitan area.

Dyke Marsh provides a storm buffer for the George Washington Memorial Parkway, a natural filter for the Potomac River, and habitat for a variety of plants and wildlife, including six state-listed species of special concern (two bird species and four plant species).

It is critical to act now to protect and restore Dyke Marsh. Approximately 270 acres of marshland were damaged from the 1940s to the 1970s through the dredging of sand and gravel. In 2009, National Park Service partnered with U.S. Geological Survey to investigate the state of Dyke Marsh. USGS found that the post-mined marsh is rapidly shrinking as a result of erosion caused primarily by storm waves driven northward up the Potomac River. Erosion in the marsh averages between 6 and 8 feet per year. USGS found that without intervention, this unique ecosystem would be entirely lost by 2035. 

There will be temporary impacts to water quality due to the short-term disturbance/turbidity in the water from the construction efforts. Construction will be conducted to minimize these impacts as much as possible, such as careful placement of marine mattresses. After the project has been completed, it will assist in nutrient reduction in the Potomac River and positively impact long-term water quality in the area.

This is a National Park Service, George Washington Memorial Parkway, project that the U.S. Army Corps of Engineers is authorized to design and construct through the Interagency and International Support program. NPS is providing funding to the Corps through the Hurricane Sandy Mitigation Program. Construction costs are approximately $19.26 million.

This is a National Park Service project that the U.S. Army Corps of Engineers is authorized to design and construct using NPS funding. The intent of this project is to protect and restore valuable, historic tidal freshwater wetlands and habitat.

With the available funding, the project includes an approximately 1,500-foot breakwater and approximately 5.45 acres of restoration of freshwater tidal marsh using clean sandy material. Marsh plants will be established on the marsh restoration site.

This design has been set up to allow for expandability. Remaining construction work that cannot be completed as part of this effort could be identified as future phases of the project to be constructed as more NPS funding becomes available.

The breakwater will help protect the existing and restored marsh from erosion and will help restore the marsh’s ability to regenerate naturally within the preserve’s historic footprint through the collection of sediment.

This vital project will provide a storm buffer for the historic and scenic George Washington Memorial Parkway, a natural filter to clean the Potomac River, and habitat for a variety of plants and wildlife.

Once construction is completed, NPS will continue to monitor the site to ensure no invasive/non-native plant species become established in the restored marsh and that restoration efforts are on track, as it takes time for habitat to develop and self-sustain.


The cost to construct the recommended project outlined within the Environmental Impact Statement (EIS) far exceeds National Park Service's available funding. The U.S. Army Corps of Engineers worked with NPS to design a project based on the recommended project that still meets intended objectives and fits within the existing budget.

This design has been set up to allow for expandability. Remaining construction work that cannot be completed as part of this effort could be identified as future phases of the project to be constructed as more NPS funding becomes available.

The breakwater is the most critical aspect of the project and will help protect the existing and restored marsh from erosion and will help reestablish the marsh’s ability to regenerate naturally within the preserve’s historic footprint through the collection of sediment.

The ecological benefits of preserving and restoring Dyke Marsh outweigh the impacts to the submerged aquatic vegetation (SAV) at the site.

While an analysis shows that construction will result in permanent and temporary impacts to the existing SAV within and adjacent to the footprint of the proposed project, the SAV consists primarily of Hydrilla verticillata, which is an invasive (non-native) species and a federally-listed noxious weed that has been shown to displace native submerged plants. There are numerous NPS policies and federal executive orders and laws that direct federal agencies to remove or protect against exotic and invasive species, hydrilla being one of them.  

Dyke Marsh is viewed as a national treasure that holds extensive value not only for plants and animals, but for its recreational, educational and cultural purposes. Dyke Marsh is one of the best studied wetlands in the U.S., and is one of the largest cattail marshes in the national park system. Dyke Marsh provides a storm buffer for the George Washington Memorial Parkway, a natural filter for the Potomac River, and habitat for a variety of plants and wildlife including six state-listed species of special concern (two bird species and four plant species). Native plants will be established at the marsh restoration site.