Abstract or Summary
Tidal marshes are an integral part of New Jersey’s estuaries. They form a charismatic green band that cleans water; provides critical habitat and food sources for fish, shellfish, and birds; and buffers coastal communities from storms, erosion, and flooding (Mitsch and Gosselink 2007, NJDEP 2007, Narayan et al. 2017). However, the continued existence of many tidal wetlands is threatened by sea-level rise. To maintain healthy salt marsh vegetation, marshes must accrete sediment and plant matter to gain elevation at a rate that keeps pace with sea-level rise and subsidence (Nyman et al. 2006, Mitsch and Gosselink 2007, Cahoon et al. 2009, Kirwan and Megonigal 2013). Some salt marshes are stressed and literally “drowning” because they cannot gain surface elevation at a rate that keeps pace with accelerating sea-level rise (Hartig et al. 2002, Ganju et al. 2017, Watson et al. 2017a).
A variety of factors decrease tidal wetland resilience to sea-level rise, including historic alterations, like ditching and diking, and ongoing stressors, such as severe storms, dredging, decreased sediment content of tidal waters, and edge erosion (Bertness et al. 2002, Hartig et al. 2002, Church and White 2011, Partnership for the Delaware Estuary 2012, Weston 2014, Watson et al. 2017b).
One possible solution to the problem is increasing the elevation of a salt marsh by placing sediment on it (e.g., dredged material; Daiber 1986, Ray 2007). An increase in marsh elevation reduces inundation by the tides, promoting the growth of vegetation. The vegetation in turn stabilizes the marsh soil and promotes further accretion and increased elevation via sediment trapping and root production. It forms a positive feedback loop that increases marsh resiliency (Wolanski et al. 2009).
New Jersey’s navigation channels and marinas must be dredged regularly to maintain safe passage for recreational and commercial vessels, which creates a ready supply of dredged material. There is great interest in leveraging existing dredging projects to restore and enhance salt marshes. This practice, the beneficial use of dredged material, combines the routine maintenance and post-storm dredging required to keep waterways navigable with projects to enhance, restore, and create salt marshes and other estuarine habitats.
One of the many impacts of Superstorm Sandy in 2012 was major shoal creation in the navigation channels along New Jersey’s coast. Traditionally, in coastal areas of the state, dredged material was placed in confined disposal facilities, effectively removing it from the coastal system. New Jersey lacks confined disposal facilities with the capacity to accept additional dredged material, and this has become a major problem for coastal communities, as well as for state and federal agencies that need to maintain navigable waterways. Following Hurricane Irene (2011) and Superstorm Sandy, the U.S. Army Corps of Engineers, Philadelphia District (USACE-OP), obtained emergency supplemental funding to clear critical shoals from the New Jersey Intracoastal Waterway (NJIWW), and the New Jersey Department of Transportation’s Office of Maritime Resources (NJDOT-OMR) planned to restore navigability by removing sediment from channels in Cumberland County.
In 2013, the New Jersey Department of Environmental Protection, Division of Fish and Wildlife (NJDEP DFW), partnered with the USACE-OP, the USACE Engineer Research and Development Center (USACE ERDC), NJDOT-OMR, The Nature Conservancy (TNC), and the Green Trust Alliance (GTA) to initiate three pilot projects. These projects intended to advance the concept that beneficial use of dredged material on stressed salt marshes to increase their elevation would increase the abundance of native salt marsh vegetation and would result in ecological uplift over their baseline condition, ultimately increasing their resiliency to sea-level rise. All parties acknowledged that this was an opportunity to explore a paradigm shift from thinking of dredged material as waste to thinking of it as a resource. The total cost of the pilot projects was $8 million. Approximately half of the funds were provided to NJDEP-DFW from the Hurricane Sandy Coastal Resiliency Competitive Grant Program (Grant #43095, administered by the National Fish and Wildlife Foundation; NFWF). The grant period was August 2014 through October 2017. The other half of the funds were provided by the USACE-OP and NJDOT-OMR.