The dune breaches are filled, the beach restoration is nearly done, and the dredging of 22 miles of coastal channels is on track for completion this summer.
At Prime Hook National Wildlife Refuge on the southern Delaware shore near Milton, a $38 million project to stop the waters of the Delaware Bay flooding important wildlife habitat while building it up against future sea-level rise is well on its way.
The project, among the biggest and most ambitious of its kind in the country, aims to return the 10,000-acre refuge to its original purpose of harboring migrating birds, while preventing coastal flooding that has bedeviled nearby homeowners and farmers since 2008.
Initially, the restoration is a response to a line of four breaches that opened in the dunes during a series of storms, notably Hurricane Sandy, in the last eight years. The breakdown in the refuge’s only defense against the waters of the Bay turned its freshwater coastal impoundments saline and continually flooded its ecologically important salt marsh, killing vegetation and reducing the marsh’s biodiversity.
The longer-term goal is to create conditions that allow the salt marsh and the dunes to repair themselves and to become resilient to the higher ocean levels that are forecast in coming years.
“As we close the breaches, put all these channels in, water levels are going to drop, and that will allow native vegetation to recolonize all these mud flats,” said the restoration project manager, Bart Wilson, an official with the U.S. Fish & Wildlife Service. “We are engineering with nature, not against it or in spite of it.”
By combining enhanced coastal defenses with a rebuilt marsh, the project may become a template for efforts to defend Delaware’s other coastal wetlands, which are expected to be virtually wiped out by rising seas by the end of the 21st century, according to official projections.
Both tracks of the Prime Hook project began last fall and are ahead of schedule, although the marsh-restoration component has paused for now because of the winter cold, said Wilson.
Although the work is not yet complete, Wilson and his colleagues got an early indication that they were on the right track when the rebuilt dunes survived Winter Storm Jonas in late January.
“A testament to the design and the team was that Jonas came in, which was bigger than the storm of ‘62, bigger than Sandy, and our marsh project and the beach project both held up great,” Wilson told Delaware Public Media after a presentation on the project at a wetlands conference held by Delaware’s Department of Natural Resources and Environmental Control.
He said the rebuilt beach and dunes survived the storm because of the width and low angles of their construction. “Jonas has helped to show us that our beach design is the right thing, building it wide with low angles,” he said. “We all suspected that was going to be the best way, and it helps to prove that.”
When work on the marsh restoration resumes, there will be three dredgers digging silt from the floor of the coastal impoundments that lie in between the dunes and the rest of the refuge. The excavation is designed to restore the flow of tidal currents in the impoundments from Slaughter Canal in the north and Broadkill River in the south so that water can once again flow out of the refuge and drain the marsh at low tide.
The tidal flows will be aided by the construction of a 70-foot bridge in place of a stretch of the road that links the barrier-island community of Prime Hook Beach with the mainland. The new bridge, whose construction by the Delaware Department of Transportation is due to begin on Feb. 15, will allow engineers to remove a part of the road that is prone to flooding, and which frequently prevents Prime Hook Beach residents from entering or leaving the community during storms and high tides.
Richard Huffman, a year-round resident at Prime Hook Beach, welcomed the restoration project, saying that water levels in the impoundment to the north of Prime Hook Road have dropped since the breaches closed, and that the longstanding flooding of Prime Hook Road seemed to be “under control at last”.
But he said Jonas “wreaked havoc” with the community’s shoreline by opening some smaller breaches, and he hopes those will now be closed as part of the restoration project.
“We hope that Fish and Wildlife will not compromise its current restoration plans by not addressing this new problem,” Huffman said in a statement.
He said the community’s beach does not qualify for state assistance because it is classified as a private beach. Consequently, there is a continuing effort to gather easements from the 109 bayfront property owners, to enable the beach to qualify for public assistance.
Wilson of FWS confirmed that the restoration project is being extended to reach the north end of Prime Hook Beach.
Within the refuge, dredgers will soon resume spraying a thin layer of mud and silt from the channels onto mudflats that will become salt marsh if the project succeeds. Officials will be watching closely in the spring of 2017 for the first signs that marsh vegetation is coming back.
By recreating the marsh, refuge managers hope they will attract wildlife such as crabs and fish which in turn will attract the birds for which the refuge was originally built in the 1960s.
Restoration of the salt marsh is designed to jump-start a natural process in which vegetation re-establishes itself in areas where it has not been able to grow because of the flooding. Over time, the marsh will build up with sand driven in by storms, and will itself become a dune as the existing dunes are worn away by rising ocean waters.
At the same time, a new marsh would start to form inland of the current one, as another example of the inward movement of coastal features that is expected to result from sea-level rise.
“The dune is going to keep wanting to move landward and the salt marsh is going to move landward,” Wilson said.
The project’s lead designer, Jeffrey Tabar, predicted the restoration will be used to guide other projects in Delaware and beyond.
“It’s a phenomenal template of how this approach can be taken in other locations,” said Tabar, a senior coastal engineer with Stantec, an engineering firm. “This challenge, largely due to climate change, is being faced all over the coastline, whether it’s habitat restoration or flood-proofing for cities.”
Tabar, who has also worked on restoration in Louisiana, said the multi-faceted approach of the Prime Hook project, which takes into account the different sources of flooding, can be applied to other locations that might be affected by flooding from rivers, coastlines or marshes.
“The fundamentals of the approach in terms of climate change, resiliency, long-term projections – those things can all be incorporated” in other projects, he said.
In Delaware, the restoration may become a model for nearby state-run preserves at Little Creek and Port Mahon that have similar challenges to those at Prime Hook, said DNREC Secretary David Small.
He said the project is more likely to be replicated for habitat preservation than for urban coastal defense but could become a model in Delaware’s wider efforts to plan for rising seas along its low-lying coast.
“I think it does provide a model to think about resiliency in the short term but the question is for how long and at what cost,” Small said. “Nobody has good answers to those questions but at some point in the future government agencies and the public and elected officials are going to be having that conversation.”
Meanwhile, the beach restoration, which is expected to be complete by the end of February, will continue to operate around the clock as it has since it began last October. The operation uses a dredger which takes sand and gravel from the bottom of the Bay and deposits it on the beach where five bulldozers have filled the breaches and will complete their work in building up the dunes.
When they are done, the beach portion of the project will have moved 1.25 million cubic yards of sand and gravel out of the bay and on to the beach. In the impoundments, the dredging is expected to move about 600,000 cubic yards of mud and silt. By comparison, Rehoboth and Dewey Beaches received 1.67 million cubic yards of sand when they were replenished in 2005.
A little further south at Broadkill Beach, the U.S. Army Corps of Engineers has built up dunes in a separate project, where local residents have put up post-Jonas signs saying “New Dune Tested. It Passed” and “We Love Our Dune, Thank You”.
That’s consistent with the early indications that the Prime Hook project itself is working, and is doing so on a much bigger scale than most other coastal restoration projects.
“We are looking to have thousands of acres restored,” Wilson said. “That’s huge.”