An Experiment in Wetland Habitat Restoration
A Failure to Learn
Our work on Thompson’s marsh covers only a tiny patch of the Delaware Bay marsh. One might say our one-acre restoration is too small to have any significant impact, so why do it? Big projects are certainly more important. And ultimately we will need many of them to realize Governor Murphy’s recently
But big projects can fail big and waste taxpayer dollars. The Delaware Bay has seen a number of these failed expensive projects, like the shoreline restoration of Sea Breeze where $6 million in state-funded cinder blocks lie
Working With Nature
These resiliency failures occurred for many reasons, but an important one was failing to take advantage of natural defenses to augment protection. Why defeat the Bay with concrete and
Perhaps this is the most the failure because the experience provided no clues on how to carry out the next project. Each new project becomes a gamble or worse useless in the face of an ever-growing threat. Instead, the failed projects speak for themselves, apocalyptic-like reminders of our inability to protect the wildlife and people of Delaware Bay.
Start Small and Learn
So our project provides more than a one-acre fix for abandoned salt hay farms. It also helps us understand the most cost-effective way of conducting larger more expensive projects and create innovations that can improve ecological condition Better to start small and learn.
First the problem. Over 10,000 acres of Delaware Bay marsh remains damaged after a wholesale abandonment of at least a century and a half of restricting tidal flow with earthen dikes. The dikes blocked sediment-rich tidal waters to allow salt hay or spartina patens to grow and cut for hay. Each cutting removed vital biomass. Without new sediment or biomass, marsh elevations fell about 2 feet but in some areas as much as 5 feet. Without the dikes, the sea scoured the newly exposed and sparsely vegetated wetlands leaving bare mud as shown in the photos of my previous blog.
Thompson Marsh could have turned into a big mud flat like Cox Meadow endangering the people in the town of Heislerville NJ. Instead, the state allowed PSEG to avoid the cost of a new cooling tower by managing wetlands. They hoped the addition of productive marsh would offset the loss of fish killed by increased use of cooling seawater. One can see the work in the following series of photos.
The PSEG engineers dredged a new watershed of small creeks allowing a slower draining and flooding of the marsh. It worked. The wetland began recovering slowly over time. New inflow of sediment and the sparse growth of Spartina alterniflora or marsh cord grass built new biomass. The papers of the restoration team spoke of recovery.
Unfortunately, sea level rise dashed those hopes. It matched the elevation gained by a renewed marsh. The higher volume of water and more frequent storms scoured mud and sand in the mouth of the creeks. It also eroded creek banks thus increased tidal flow. There is spartina growing over much of the restored area but at a much lower density and slower growing than cordgrass at the proper elevation.
A New Start on Thompsons Marsh
For Thompsons and many of the once farmed tidal wetlands on Delaware Bay, the only hope is to start rebuilding elevation with new mud.
Our wetlands restoration is an experiment with two goals. First how best to manage an old hay farm back to a stable, productive marsh? The second how to do at a practical cost?
For example our dikes. In the old days and the PSEG work, workers made new dikes by digging into the marsh. This damaged marsh and created new ditches for water to scour away sediment. We use Coir logs, or 10 feet long 24-inch diameter jute bags of coconut fiber, to form our dikes. They are cheaper than digging and will gradually degrade into the marsh. Most important we avoid damaging the fragile wetland. Managers have used Coir logs elsewhere to confine mud but not in Delaware Bay with its 7-foot tide swing. If successful we will have a low cost and an environmentally friendly solution that can be scaled up to larger areas, one of our top goals.
Restoration Is Experimental
In a way all restoration is experimental. Even when done successfully conditions matter enough to make every job different. Restoring a wetland on the gulf coast where tides rise no higher than 2 feet, is far different than Delaware Bay, where the
This is why we must conduct this experiment in marsh restoration.