Thin Layer Marsh Restoration

by Damian Holynskyj | October 15, 2014

As part of our commitment to staying One Step Ahead…GreenVest has been actively developing new techniques and opportunities to restore lost salt marsh habitat that has been disappearing up and down the Eastern seaboard. These valuable marsh habitats have been eroding over the past hundred years as a result of sea level rise, lower accretion rates, and higher rates of anthropogenic erosion. In addition to losses of valuable ecological habitat, in many cases the loss of salt marshes near costal human populations, eliminates vital natural buffers and results in increased community vulnerability to coastal storm damage.

To address the issues of coastal community vulnerability and loss of ecological habitat, GreenVest and our project partners at the New Jersey Department of Environmental Protection, the US Army Corps of Engineers, the Nature Conservancy, GreenTrust Alliance and Princeton Hydro have been exploring “thin-layer marsh restoration” techniques in the New York/New Jersey area and were awarded a National Fish and Wildlife Foundation Grant (NFWF) to vet and apply this method of salt marsh restoration. Thin-layer marsh restoration is a promising technique that has been used successfully in Jamaica Bay by our GreenVest scientists and other areas of the country, including the Chesapeake Bay and the Gulf coasts. It involves the placement of beneficial reuse of dredged material to restore lost, eroding or subsiding salt marshes. It’s a means of restoration that has the potential for broad applications to both mitigation banks as well as restoration projects.

As sea levels continue to rise and storms become more frequent and intense, salt marshes that cannot keep pace with sea level rise will ultimately be lost along with the ecosystem services they provide. These salt marshes act as a vital storm buffer to coastal communities and the coastal economy. They act as barriers to help protect coastal communities and infrastructure from increased flooding and storm surges and provide habitat for economically and ecologically important fish and shellfish; nesting and foraging habitat for migratory and resident birds; and improve water quality through de-nitrification and sediment removal.

One way we can offset low accretion rates within existing salt marshes is to give these habitats a boost, by placing a thin layer of clean dredged material across the sinking marsh plain and raising the marsh plain elevation. This process, called Thin Layering, involves gathering dredged materials and pumping the sediment through a spray nozzle system in which a silty, slurry of sediment is sprayed across a low area of coastal marsh. Adding the sediment helps raise the marsh plain and as existing and new plants rise through the new sediment, their root systems help hold the new sediment in place and incorporate it into existing substrate. Thereby stabilizing acres of existing saltmarsh habitat that can be used by wading birds, shellfish, invertebrates, juvenile fish and other wildlife. This process helps to restore and maintain healthy chemical, physical and biological process and thus the ecosystem services these coastal marshes provide. This technique can also be used to restore historic areas of coastal marsh lost to erosion or other anthropogenic causes.

A key economic benefit of this technique is that it provides a valuable solution to the overwhelming shortage of dredged material placement sites. State, Federal, regional, municipal agencies as well as private entities and individuals routinely dredge navigational channels and harbors to maintain adequate channel depths and keep both recreational and commercial traffic moving on our waterways. This routine maintenance dredging is conducted as a result of influxes of sand and sediment that enters harbors seasonally under normal conditions; and dredging demands are greatly amplified during storm events such as Superstorm Sandy. New Jersey Agencies have estimated they will need to dredge over 5 million cubic yards of sediment as a result of Superstorm Sandy alone. Disposal costs for this dredged sediment is very costly, an issue that is magnified as there is a severe shortage of confined disposal facilities (CDFs) in the region. Linking this dredge material with Thin Layering creates dual benefits at a huge cost savings. It can help restore, on a large scale, disappearing salt marsh and habitat that would otherwise not have been restored due to high restoration costs and lack of adequate funding; and it will help facilitate much needed waterway dredging projects in New Jersey and elsewhere by sourcing proximate placement sites.

GreenVest brings a wealth of experience with thin-layer marsh restoration to this project as well as our own mitigation banks. Our scientists, Brett Berkley and Brian Cramer, worked on a large scale beneficial reuse project in consultation with the NY District of the Army Corps of Engineers to restore lost salt marsh islands in Jamaica Bay, NY. This restoration of the Marsh Islands, part of the National Park Service Gateway National Recreation Area in New York City, restored large sections of marsh that had completely eroded by restoring historic elevations and salt marsh vegetative composition. In addition, to helping manage the afore-mentioned NFWF grant thin-layer restoration projects, GreenVest has taken the successful experience gained in Jamaica Bay and is in the process of seeking out regional applications for these techniques, including on GreenVest’s coastal mitigation bank sites. We are actively seeking additional regional opportunities for the beneficial re-use of dredged material for salt marsh restoration with the DOD, Army Corps of Engineers, NJDEP Division of Fish and Wildlife plus our partners at GreenTrust Alliance. We anticipate pairing sites in need of restoration with regional dredging needs, which will include securing third party funding sources to implement restoration on a regional scale.

GreenVest is confident that thin-layer marsh restoration, using beneficial reuse of dredged material from routine maintenance and post-storm dredging activities, is a highly effective and economically feasible way to counter the loss of coastal salt marsh habitat, enhance/restore systemic functions and values, source much needed dredged material placement sites, and create coastal community resiliency. As a company, GreenVest is committed to pushing the scientific, economic, regulatory and political envelope to implement workable ecosystem restoration solutions with multiple benefits. We believe that in the next 3-5 years this method will see broad based application resulting in significant in-the-ground restoration up and down the Eastern coastline and beyond.

If you’d like to learn more about thin layer marsh restoration, your organization is in search of a placement site, has a suitable placement/restoration site or would like assistance with designing a thin layer marsh restoration project please contact Mr. Damian Holynskyj at