Case study
When restoring saltwater became a marsh reality
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Video
A Marsh Reality
Project details
Project name:
Prime Hook Restoration
Client name:
U.S. Fish and Wildlife Service
Location:
Delaware
Christina Warner
Vice President, Environment and Consents
Andy Clevenger 
Principal - VP, Global Technical Lead for Water and Wastewater 
Key stats
Damaged marshland:
4,000 acres
Amount of sand used:
1.1 million cubic feet
Sand fence constructed:
10,000 feet

Back to nature – combatting climate change with coastal restoration

The 10,000-acre Prime Hook National Wildlife Refuge located along the marshes of Delaware Bay was impounded and managed as a freshwater system beginning in the 1980s. During a series of severe storms culminating with Hurricane Sandy in 2012, the dunes along the beach were breached, causing salt water to flow through the area, leading to beach erosion and flooding. Vital substrate was lost and freshwater vegetation died. Nature, as it often does, began restoring the habitat to its natural state and there was a small resurgence of tidal marsh plants. The U.S. Fish and Wildlife Service sought to rebuild the refuge in a way that strengthened the local ecology for wildlife and people alike.

Restoration and rebirth

Opening water control structures and restoring historical tidal channels, Wood spent a year helping Mother Nature restore her natural defenses to create a more resilient coastline. Now, after months of restoration work, newly restored habitats are attracting migratory birds that have returned after decades; freshly-dug and restored channels attract new types of fish, and horseshoe crabs are coming back in record numbers. Plus, the restored saltwater marsh is once again home to native species of plants and grasses. The approach taken to bring about this renaissance is set to be a bellwether for efforts to protect our coastlines in the face of rising sea-levels and climate change.

How?

Wood supported the U.S. Fish and Wildlife Service to restore 4000 acres of damaged marshland at one of the largest and most complex coastal restorations in the eastern US. The $17 million project leveraged multidisciplinary services to replace the inundated refuge with a sustainable, resilient ecosystem. Our onsite project team worked to restore the damaged marshland to create tidal channels through draft hydraulic dredging, planting and invasive species management. We used historical tidal channel patterns and modified the existing water control structures to allow for the free flow of water. We installed around one million native marsh grasses and removed invasive plants. More native plants will grow naturally as the system recovers over the next several years.

The first phase began by digging channels in strategic patterns to allow water to flow through the marsh. Over the course of a year, dredging took place 20 hours a day, six days a week to create tidal inundation allowing the salt water to move through the channels with the tide. The resulting mudflats created the optimal habitat for native marsh grass to grow, improving the area’s resiliency to storms.

A second, more intensive phase, conducted by the U.S. Army Corp of Engineers, saw 1.1 million cubic feet of Delaware Bay sand used to rebuild 7,000 feet of beachfront and 10,000 feet of sand fence constructed in three rows far wider than standard practice in coastal reconstruction. Wood further supported these resiliency efforts with the planting of 20 acres of saltwater-resistant Spartina to protect the reserve. The fundamental theory behind this approach was observations that wider and more heavily vegetated dunes were able to repair themselves more quickly than narrower, less vegetated areas. So far, this tactic has been successful at increasing the resiliency of coastal dunes to the elements and could shape the standard approach to this type of reconstruction in the future.

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