“It was a stink hole,” says Al Rizzo, the refuge manager of Prime Hook National Wildlife Refuge in Delaware Bay. Humans had messed with hydrology in an ill-conceived project aimed to convert salt marsh into a large open freshwater impoundment system to attract migrating waterfowl among others. Lines of dunes and tidal gates were constructed to barricade the inflow of salt water. However, severe storms, including Hurricane Sandy, tore open gaps in dune lines, inundating the re-engineered system with salt water, killing fresh-water marsh grass, and turning a healthy riparian forest into a wasteland of dead trees.
In order to reverse the damage of this unnatural disaster, government agencies and conservation groups used the Hurricane Sandy Disaster Relief Fund to embark on a $38 million attempt to restore 4000 acres of damaged wetland. Engineering with nature is how Rizzo and Bart Wilson, restoration project manager, describe their approach, in which they are taking cues from nature to create a more resilient ecosystem. The objective is to allow the system to adjust itself and to work based on normal coastal dynamics.
Relying on existing data, extensive hydrodynamic modeling was applied to find out what actually works. The refuge was found to have no elevation problem but rather a plumbing challenge. Work started with closing up the breaches by reconstructing the beach and dunes. The restored dunes are now 10ft high, allowing for overwash to dissipate storm and wave power. Sediments produced were cast onto the banks creating sand flats that are being colonized naturally by native grass. A neural network of channels was opened on historic waterways to let the tide flow back in and out. The result is a healthy tidal marsh with meandering channels, lush salt-tolerant grasses and mudflats that attract rich diversity of fish and birdlife. The Prime Hook is becoming a model for wetland restoration globally.
Diaz, Sandra, et al., 2019, Summary for policymakers of the global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, 29 May 2019, https://ipbes.net/global-assessment-report-biodiversity-ecosystem-services.