STONE HARBOR – The Scotch Bonnet Marsh Enhancement Project now underway is an attempt to build up low-lying marsh areas that are quite literally drowning. For many areas of New Jersey marshland, sea level rise has transformed marsh areas into mud flats and open water.
The Scotch Bonnet Island project is part of the ongoing efforts undertaken by the Seven Mile Island Innovation Laboratory, a partnership of the Philadelphia District of the Army Corps of Engineers, the state, the Wetlands Institute and the Army Corps’ Engineer Research and Development Center.
According to the Army Corps, the Innovation Lab has already restored 85 acres of marsh area and has protected two island complexes from future degradation. The projects, which make use of dredge materials, also result in deeper channels and improved navigation on waterways.
Restoring shrinking bird and wildlife habitat, buttressing the marshes for their vital role in mitigating flooding, and keeping sediment from dredging within the sediment system are just some of the other project benefits.
Monica Chasten, a project manager for the Army Corps, says the projects have paved the way for a better understanding of beneficial use of sediment. “We used to just throw the dredge sediment away,” Chasten said. After superstorm Sandy, “we changed the way we use it.”
Wetlands Institute Executive Director Lenore Tedesco points to the 50-year history of the Wetlands Institute in the marshes off Seven Mile Island, a history that brings with it decades of data to benefit the projects. The institute itself also serves as a field station for the collaboration.
Scotch Bonnet Island is an 86-acre marsh island that now lies at or below what is termed “stable low marsh elevation.” The area has seen the formation of unvegetated mud flats. Wetlands Institute scientists have documented dramatic marsh loss and expanding tidal channels.
Modeling suggests that without intervention only 34 acres will remain as vegetated marsh by 2050, the Army Corps website says.
This movement of dredge material to fortify and elevate marsh areas has many challenges that are better informed with each experiment and success. The efforts involve preplacement monitoring, material placement methodologies and post-placement monitoring.
According to the Army Corps, mixed fine sand and muddy sediment is hydraulically pumped onto the marsh platform to build elevation. Biodegradable logs are used to direct flow into lower-lying areas and to prevent sediment from migrating away from target areas. Tidal flooding is then allowed to naturally distribute the sediment across portions of the marsh.
The Scotch Bonnet project initially was building elevation quicker than anticipated, and adjustments were made. The actual placement of sediment on the island is nearing its end, perhaps even within a week or two. Monitoring and data collection efforts will continue.
The project at Scotch Bonnet Island, which is visible from the road, is just one of five beneficial-use projects within the area of the Innovation Lab. The partnerships that resulted in the creation of the Innovation Lab date to the spring of 2019. Each project now builds on the success and knowledge gained at several other beneficial-use projects in the state’s coastal areas.
Contact the reporter, Vince Conti, at vconti@cmcherald.com.
