Marsh Restoration

Marsh Dredging by Richard Weiner

Prime Hook National Wildlife Refuge is embarking on a large tidal marsh restoration project, one of the largest ever in the eastern U.S.  The project will restore a highly damaged tidal marsh/barrier beach ecosystem covering about 4,000 acres within the former freshwater impoundment system on the refuge. This coastal wetland restoration improves the ability of the refuge marshes to withstand future storms and sea level rise and improves habitat for migratory birds and other wildlife.  The restoration project is supported by funding from the Hurricane Sandy Disaster Relief Act.  See below for project updates.  (Photo by Richard Weiner)

December 7, 2020

The last couple growing seasons have resulted in continued recovery of the restored marsh in the restoration project area! During both 2018 and 2019, acres of marsh vegetation increased. There are no active restoration actions taking place in recent years, other than treating invasive Phragmites in priority areas. The area continues to recover and stabilize into a “new normal” as a tidal marsh, just as we had planned. Unfortunately, in-the-marsh monitoring in 2020 was limited, but remote sensing methods, such as using water monitoring equipment, satellite imagery, and drones, did take place. Results from this year are still being compiled.

However, one aspect of monitoring that did continue – with modifications for staff distancing and safety - was keeping tabs on the piping plovers and least terns that have flocked to the restored beach to breed. This year the beach was home to 16 pairs of piping plovers who fledged approximately 40 young. A colony of at least 70 least terns also nested, with even more documented nests and young than in past years. This site has become a regionally important nesting areas for both of these species of conservation concern.

Refuge staff and our monitoring partners expect to be back in action in 2021! In 2021 we will celebrate the 5-year milestone for this large and successful project.

September 9, 2018

  Prime Hook has rebounded ecologically; acres of mudflats are thriving with marsh grasses.  Nesting shorebirds, including piping plovers, as well as other wildlife and fish are returning to the refuge. Read more and watch the video from our local community newspaper below.

  Cape Gazette (Part 1) Ron MacArthur 

  Rebirth Occurring in Prime Hook Refuge Marshes 


September 30, 2017

 Refuge staff and partners spent the spring and summer of 2017 conducting continued monitoring of the restoration project.  Water levels, salinity, nutrients, and flow continued to be monitored in partnership with the Delaware National Estuarine Research Reserve and the University of Delaware.  This monitoring is ongoing year-round, and enables the refuge to track how the restored tidal hydrology in refuge wetlands translates into new patterns of water levels, sediment concentration, and salinity.  There are some small areas within the wetlands that need additional work, and the restoration project will benefit further from planned upgrades to culverts to be done by DelDOT.  But overall, the system is showing the expected positive response. 

It was an great year for the beach-nesting birds that have so quickly responded to the impressive new beach along the refuge shoreline.  Last year, the first ever piping plover nest was established on the refuge.  Piping plovers are a federally threatened species of considerable conservation interest to the refuge.  In 2017, there were 6 nests that successfully fledged a total of 12 young plovers!  In addition, there were nesting American oystercatchers and least terns.  The restored beach is open to visitors again, at least until the breeding season begins in 2018.

Refuge staff and interns carried out another season of vegetation surveys to monitor the wetland response.  These ground efforts are coupled with remote sensing analyses to track changes in the amount of open water and vegetated marsh, and the shifts in plant species composition.  Between 2015 and 2017, there was a reduction of 700 acres of open water and an increase of over 500 acres of vegetated marsh in the project area.  The amount of desirable salt marsh and brackish species such as Spartina alterniflora increased.  Planted areas of the back barrier marsh behind the restored dune are flourishing.  Thus far, recovery of the restored marsh is well on track.  


December 16, 2016

The Prime Hook NWR tidal marsh restoration project has been the largest of its kind ever on the east coast, and therefore has and will continue to gain a lot of attention by others who work on restoration science and coastal ecology.  This week, members of the refuge staff and key partners from DNREC attended the 2016 joint summit of Restore America’s Estuaries and The Coastal Society, held in New Orleans.  The theme of the conference was “Our Coasts, Our Future, Our Choice” and it was the largest national gathering of the coastal restoration and management community in 2016.  Prime Hook NWR was the topic of an entire dedicated session, which included individual presentations on the history of our wetland management challenges, the planning and permitting of the restoration project, the many partnerships that were key to success, and the abiotic and biological monitoring conducted thus far.  Scientists and wetland managers around the country will continue to learn from the work we have done, and that we will continue to do through ongoing monitoring.  Although the impressive and complex construction of the restoration project is complete, the story of our wetlands’ recovery is only just beginning!  Stay tuned for future updates and photos in the upcoming months.    



September 12, 2016 

The construction work on the refuge’s large tidal marsh restoration project is essentially complete! The past 15 months have been a whirlwind of restoration activities along the refuge shoreline and within the marsh interior:

  •  A dune, beach, and back-barrier beach platform has been restored along nearly 8,000 feet of shoreline, including closure of four large breaches, using more than 1 million cubic yards of dredged from the Delaware Bay.
  •  The restored dune is 9 feet high with a 100- to 600-foot-wide back barrier platform extending into the marsh.
  •  American beach grass was planted and 10,000 feet of fencing have been installed to stabilize the dune and back barrier.
  •  Tidal marsh and dune grasses (Panicum and Spartina species) were planted in portions of the back barrier platform, to promote a return to vegetated salt marsh.
  •  More than 25 miles of tidal channels have been dredged out in the marsh interior to restore flow of tidal water throughout the wetland complex; The channel network was designed in large part based on historic tidal channels present prior to conversion of the wetlands to freshwater impoundments.
  •  Several man-made water-control structures were removed to improve tidal connection with the existing salt marshes to the north and south of the refuge.
  •  Restoration has reduced water levels in much of the marsh interior, especially in Unit III. Tidal wetland grasses and other vegetation have already begun to recolonize many of the exposed mud flat areas, although full recovery will take some time.
  •  Wild millet seed was scattered from the air over 1,000 acres in the Unit 3 impoundment, in order to give revegetation in that area a boost.
  •  Asphalt pieces of what was left the easternmost 1,800-foot section of Fowler Beach Road were removed; The refuge hopes to eventually construct a walkway to the beach.
  •  Most of the restored wetlands will revert back to a saltwater marsh with some areas of fresher or brackish wetlands.

The biological response to the restoration was immediate and impressive! Spring brought the horseshoe crabs to the brand new beach to spawn, in larger numbers than anticipated. The first documented piping plover nest was found on the restored shoreline, along with nesting by other birds of interest such as American oystercatchers and least terns. Many areas of the restored wetland were covered with new vegetation this year, where just last year there was shallow open water. Monitoring of the biological response will continue over upcoming years. The refuge works closely with partners at the Delaware Department of Natural Resources and Environmental Control (DNREC) and the University of Delaware to monitor vegetation, birds, fish, and physical factors such as water quality and marsh elevation.

PLEASE NOTE that Fowler Beach Road remains closed to all traffic, including foot traffic, due to restoration activities. There are some final touch-up steps needed on the remaining road and parking areas before the beach can be re-opened for limited public access, hopefully by the end of September. The refuge will keep visitors updated on their Facebook page and this website.



May 17, 2016

The refuge’s large tidal marsh restoration project is entering its final stages this spring.  The Shoreline Recovery portion of the project, which involved restoring the dune, beach, and back barrier platform along more than a mile of shoreline near Fowler Beach, was completed in late March.  American beach grass was planted along the restored dune, and it is thriving. Planting is underway now in portions of the back barrier platform. So far nearly 200,000 Spartina patens plugs have been planted, with more than 50,000 to go. Next month 140,000 Spartina alterniflora plants will be planted as well.  Aerial seeding of barnyard grass in Unit III will be conducted, in order to give revegetation in that area a boost. In addition, 150 shrubs have been planted in areas that were damaged during the major nor’easter storm in late January.

The Marsh Resiliency portion of the project involves dredging more than 20 miles of historic tidal channels within Units II and III, which began last summer.  The dredging in Unit III was completed in early April, and dredging in Unit II is now well underway.  Final stages of the restoration project will include removal of water control structures and the easternmost 1/3 of a mile of Fowler Beach Road, to facilitate improved tidal connection with adjacent salt marshes.  Check out a collection of photos and several videos on Facebook showing the restoration work in action!

 Meanwhile, Delaware’s Department of Transportation (DelDOT) is constructing a new bridge on Prime Hook Rd. which will span one of the largest conveyance channels dredged as part of the restoration project.  While the bridge is an independent project managed by the state, the refuge restoration project staff and engineers worked closely with DelDOT to ensure the two projects would complement each other to meet mutually beneficial objectives for both agencies.  The bridge is expected to be completed in early July. 

Monitoring of vegetation, wildlife, and physical conditions has been conducted throughout the pre-restoration stages and will continue this summer, next year, and beyond.  The refuge is working closely with partners at the Delaware Department of Natural Resources and Environmental Control (DNREC) Coastal Program, Wetland Assessment, and Wildlife Conservation & Research sections, with the Delaware National Estuarine Research Reserve (DNERR), with several researchers at the University of Delaware, and with USFWS Maryland Fisheries Resources Office fishery biologists.  Not only will the refuge be able to monitor the success of the restoration project over time, but there will be many valuable lessons for the science of marsh restoration and ecology that will benefit projects elsewhere.

PLEASE NOTE that Fowler Beach Road remains closed to all traffic, including foot traffic, due to restoration activities. It is anticipated to be re-opened in September, and the refuge will keep visitors updated on their Facebook page and this website.  



February 1, 2016

Prime Hook National Wildlife Refuge’s Recovery and Resiliency Project, that has been on-going since October 2015, experienced minimal impacts from winter storm Jonas, which hit the area the weekend of January 23-24, 2016. Work crews conducting the beach and dune portion of the project were forced to seek safe harbor prior to filling the last remaining breach. However, all completed portions of the project held-up exceptionally well considering the magnitude of the storm. Beach construction contractors resumed work the following week.

In the marsh interior, the channel dredging portion of the project within Unit III of the refuge was temporarily ceased due to the presence of ice and will resume in near future.  DelDOT has begun initial work on construction of a bridge on Prime Hook Rd. that will cross one of the large conveyance channels associated with the restoration project.


October 30, 2015

The Shoreline Recovery phase of the Tidal Marsh Restoration Project got underway on October 21, 2015. Sand is being dredged and pumped continuously from an off-shore borrow area onto the shoreline in the Fowler Beach area. Because of the ongoing work, the eastern portion of Fowler Beach Road will remain closed to all traffic, including foot traffic, to maintain safe and efficient operations. Photos of the work will be shared periodically on this website, and on the Refuge’s Facebook Page. Check it out, if you haven’t already!

During this week of the 3rd anniversary of Hurricane Sandy’s landfall in the northeast, Prime Hook NWR’s restoration project was featured by the U.S. Fish & Wildlife Service and by the Department of the Interior as an important recovery story. (Read the short article HERE).

September 4, 2015

Tidal marsh restoration work is well underway at Prime Hook NWR! The first phase of the project began in mid-June, when the first dredging vessel from Dredge America began recreating historic tidal channels within the former freshwater impoundment complex, starting in the southeast corner of Unit III. Since then, two more vessels have arrived. The three dredges – the Aline, the Volunteer, and the Victory – have been operating 10 hours a day, 6 days a week. So far, the dredges have created over 8100 linear feet, or more than 1.5 miles, of tidal channels, recently making their way into the interior of Unit III. Over the upcoming weeks, work will continue northward toward Unit II. In early October, the second phase of the restoration will begin, with dredges starting work at an offshore borrow area about 1.5 miles from the refuge, pumping sand onto the shoreline in northern Unit II to close the breaches and create a back-barrier marsh platform. This restoration of habitat and natural tidal water circulation will enable salt marsh vegetation to return and flourish, improving the resilience of refuge wetlands against future storms and sea level rise, and providing valuable habitat for birds and other wildlife.

ROAD CLOSURE:  Please note that the eastern 1-mile of Fowler Beach Rd. will be temporarily closed to ALL traffic, including foot traffic, beginning on Wednesday, September 9, 2015.  The closure is due to the staging and movement of equipment necessary for the next phase of restoration.



June 12, 2015

Work to restore refuge tidal marshes is expected to start this month, a $38 million project to provide a more resilient coast against future storms and improve habitat for migratory birds and other wildlife. The first phase of the project will involve dredging approximately 30 miles of historic tidal channels throughout Unit III and then Unit II, to allow the marsh to drain and improve tidal circulation.  This fall, the next phase of project will begin, pumping 1.1 million cubic yards of sand along 7,000 feet of shoreline in northern Unit II.  Learn More


February 23, 2015

 The U.S. Fish and Wildlife Service is seeking public input on an Environmental Assessment, as it evaluates the restoration of a 4,000-acre tidal marsh at Prime Hook National Wildlife Refuge along the Delaware Bay. The project is supported by federal funding from the Hurricane Sandy Disaster Relief Act.  Learn More 

June 12, 2014

In recent months, we have reached major milestones on the marsh restoration project timeline:

  •  We entered into an agreement with the Army Corps of Engineers to design the project based on the engineering studies completed by Atkins Global, described below.
  •  We have identified a large borrow area to secure sand to complete Phase I of the project.
  •  We have made significant progress in developing monitoring protocols with the state and other partners.
  •  And, we are negotiating a conservation easement with a private landowner on a 10-acre parcel that lies in the center of the project area.
Despite these significant accomplishments, it will be impossible for us to complete the design, permitting and contracting necessary to begin Phase I this fall. Our project timeline was ambitious for a project of this magnitude and complexity.
While we continue to make progress, the scientific sampling and analyses that are necessary to evaluate the borrow site and secure permits for the project will take several months longer than we anticipated in our original timeline. The delay will make our construction project window too narrow to complete the dune work before March 2015, when beach restrictions to protect nesting birds take effect.
Our best alternative is to begin Phase I of the marsh restoration in fall 2015, and complete the work by March 2016. We are on track to start Phase II of the project, the restoration of the marsh behind the dunes, immediately upon completion of the construction of the breach closures. 


February 6, 2014

Understanding how fresh and salt water circulate within the existing refuge impoundments, and how water flow and salinity would change in various marsh restoration scenarios, is a fundamental consideration as we move forward with the Army Corps of Engineers to design the project. The engineering firm, Atkins Global, has completed a model that evaluates existing hydrological conditions in the impoundments as well as two additional alternatives – maintaining one open breach or filling all breaches. Click here to read the full hydrological report.

The model shows that maintaining an open breach to the bay would result in the same high water levels and salinity that occur in the impoundments today as a result of multiple breaches. Atkins found that several restoration benefits would result if all breaches were closed, including:

  • Adding a main channel connecting Slaughter Canal to the Broadkill River and removing water control structures will enhance water exchange between the refuge and Delaware Bay as opposed to not having a main conveyance channel.
  • The increased water exchange and flow provided by this channel would help lower the water level within the refuge by reducing the amount of water “stacked” within the refuge units.
  • The improved water exchange would increase the average and maximum salinity levels within Unit II and the east side of Unit III.
  • Adding secondary finger channels to the main channel would successfully distribute saline water to a larger area of the refuge than the main channels would alone.
  • Closing the breaches would reduce storm surge levels within the refuge by about 1.6 feet in the event of a storm similar in magnitude to Hurricane Sandy.

In their evaluation, the engineers at Atkins evaluated the potential for water levels with the breaches closed and also considered the implications of how the different scenarios would impact flooding of area communities and roads.

The hydrological modeling complements an engineering report completed last summer by Atkins Global evaluating the repair of dune breaches at Prime Hook as the first phase of the marsh restoration project (see June 25, 2013 update below).


October 31, 2013

 The U.S. Fish and Wildlife Service will invest $39.8 million in Hurricane Sandy Disaster Relief appropriations at Prime Hook National Wildlife Refuge. The Service received $20 million of that funding in May to repair beach and dune breaches at the refuge following the storm. On October 24, we received an additional $19.8 million to build upon the dune repairs by restoring a robust marsh environment at Prime Hook that will better withstand the tests of time, future storms and a changing environment.  Click here for more information about Hurricane Sandy funding.

In October, we received the peer-reviewed information from Atkins-Global, and a decision has been made on how we will proceed with the design of the dune and breach repair project. We have determined that the best course of action is to completely fill the breach and create a dune crest of approximately six feet above mean sea level.

In the coming months, we will work with the Army Corps of Engineers on a design for the dune repair and full marsh restoration. While the ACOE is doing that work, the Service will fulfill the requirements of environmental review for the project under the National Environmental Policy Act.

The $19.8 million in additional Sandy funding will allow us to proceed with marsh restoration behind the repaired dune line after that work is completed. It will entail building up the marshes' elevation, removing water control structures, and creating channels in the marsh to manage how water flows. After that foundational work has been done, marsh grasses will be planted to make the system more stable and sustainable.

Here is our current timeline of next steps:

 Fall/Winter 2013-2014

  • ACOE begins work on dune repair design, possibly with subcontractor
  • FWS and ACOE applies for State permits to secure sediment source
  • FWS develops scope of work and requests bids for marsh restoration designs
  • FWS develops monitoring protocols with State and NGO partners
  • FWS establishes agreement with Delaware DNREC to conduct a sediment transport analysis in order to develop an adaptive management strategy for the marsh restoration
  • FWS initiates environmental assessment required under NEPA to do the dune repairs and full marsh restoration project

 Spring/Summer 2014

  • FWS awards contract for marsh design
  • ACOE issues request for proposals from contractors to complete dune repairs, and secures necessary state permits for the dune repair and marsh project

 Fall 2014

  • Work begins on dune repairs and initial marsh platform behind dune line

 Fall 2014 to Spring 2015

  • FWS initiates monitoring protocols. These data will inform how the system is working and if additional sediment will be needed to restore the marsh plant community.
  • Plant grasses (Spartina alterniflora) in marsh

 Summer/Fall 2015

  • Begin conveyance channel construction in marsh
  • Continue to monitor sediment transport and vegetation

June 25, 2013

 We are moving ahead with important steps in planning the marsh restoration project in Units I, II and possibly III at Prime Hook National Wildlife Refuge. Earlier this year we contracted with Atkins Global to complete an engineering study for the Phase I of the project. That full study is available  here to read or download (pdf)

The study includes environmental survey results, project overviews, conceptual designs, and potential sites to secure material to build up the dunes and beaches at Prime Hook to complete the initial phase of marsh restoration. It offers a suite of alternatives ranging from partially to fully closing the breaches, and with varying dune and berm widths. These alternatives to complete Phase I would require between 275,000 and 725,000 cubic yards of sand with estimated costs ranging from $3.5 to $11.5 million.

The next step in planning is to apply the engineering data to hydrological modeling this summer. The models will provide us with a sound scientific understanding of how water flows into and out of the marshes, and this information will serve as the foundation for our plan to restore the marshes.

Our goal remains to begin marsh restoration during 2014. The U.S. Fish and Wildlife Service received funding under the Disaster Relief Appropriations Act of 2013, which provided emergency supplemental funding to agencies for repairs and coastal recovery projects following Hurricane Sandy.

March 18, 2013

 The U.S. Fish and Wildlife Service earlier this year contracted with an engineering firm, Atkins Global, to obtain information on repairing the dune breaches at Prime Hook as a first phase in a refuge marsh restoration project. The restoration project is the Service’s preferred management action in a comprehensive conservation plan for Prime Hook National Wildlife Refuge that is expected to be approved in the coming weeks.

Atkins Global has calculated that it would take between 500,000 and 800,000 cubic yards of material to complete the first phase of the restoration project.

As part of the same study, Atkins Global created a hydrological model that will help evaluate specific marsh restoration actions. Once the CCP is approved, we plan to move ahead with design and further engineering studies for the marsh restoration.

We will continue to work with Delaware Department of Natural Resources and Environmental Control and the U.S. Army Corps of Engineers to identify sources of material for all phases of marsh restoration. The Service received emergency supplemental funding to repair the dune breach as part of marsh restoration, which widened significantly during Hurricane Sandy.

Winter storms continue to cause extensive flooding at Prime Hook. By restoring Unit II to a healthy and resilient salt marsh, we would create an environment that is more resilient to the influence of coastal storms. We do not expect that the project would eliminate all future flooding of Prime Hook Beach community or its access roads. DNREC has contracted with Atkins Global and another engineering firm to identify short-term solutions for community protection and flood mitigation.

December 28, 2012

 Now that the comprehensive conservation plan (CCP) is done, what happens next for marsh restoration?

Our next step is to complete a breach engineering study that will tell us how many cubic yards of material is needed to fill the breach as part of the broader marsh restoration. We need this new information after Hurricane Sandy, since the storm deepened and widened the breach, from about 300 feet to 1500 feet wide.

The same breach engineering study will also develop hydrological models and a design for the breach repair that contributes to marsh restoration.

Once we know how much material is needed for the breach repair and where to place it, we will have a better estimate of how much this breach repair will cost.

Finally, we will need to secure the needed sand and sediment for the breach repair, and the funding to pay for the work.

We do know that we do not have enough sand onsite to repair the breach. The state exhausted the sand supply in October, 2011 when it tried to repair the breach. We will likely have to bring sand from offshore, and that will require a substantial dredging effort.

 When will the breach engineering study be complete?

We are finalizing negotiations with Atkins Global, an engineering firm, now. We expect to have a final estimate of the cubic yards of material needed to close the breach by March.

 When will you start the marsh restoration project identified in the CCP?

In addition to the breach engineering study and hydrological models, Atkins Global is providing a variety of management options for a marsh restoration plan for the refuge. All of these efforts work together toward restoration called for in the CCP.

We expect the more detailed restoration plan to be complete in 2013. That plan will tell us how much sand and sediment is needed for marsh restoration. We can also then develop a cost estimate for the broader restoration project.

Once the marsh restoration plan is complete, we will need to secure a source of sediment and the needed funding for marsh restoration.

 Will you repair the breach independently of marsh restoration?

The breach repair is an important first step toward the broader marsh restoration outlined in the CCP. Ideally, we would secure enough material and funding in order to repair the breach and complete marsh restoration at the same time.

However, we recognize that we may not be able to secure all of the resources needed for both of these important steps to happen simultaneously. Because breach repair will help us to restore the marsh, we intend to proceed with the breach repair once funding and a source of sand are identified, and complete marsh restoration as resources become available.

 Are there any short-term solutions to address flooding at the Prime Hook Beach community? When can they be implemented?

The Service intends to restore Unit II to a healthy and resilient marsh that can handle more intense and frequent coastal storms. Marsh restoration will not eliminate all future flooding of Prime Hook Road during extreme high tides and storm events, since floodwaters enter the road through locations other than the breaches.

However, the Delaware Department of Natural Resources and Environmental Control (DNREC) is negotiating a contract with Atkins Global, as well as another engineering firm, to identify short-term solutions for community protection and to minimize flooding to individual homes at Prime Hook Beach. The Service looks forward to the results of those studies, and will partner with the state to implement feasible short-term solutions.

 Was funding for Prime Hook NWR included in the Hurricane Sandy emergency supplemental bill?

Yes, $20 million for Prime Hook NWR was included in the Administration's request for emergency supplemental funding for Hurricane Sandy. This is currently the Service's best estimate for the cost to repair the breach that was widened by Hurricane Sandy. The Hurricane Sandy supplemental bill is being considered by Congress. For updates regarding the Hurricane Sandy supplemental bill, please click here.