Habitat Restoration Through Application of Dredged Material for Sediment Enrichment

The New Jersey Department of Environmental Protection (NJDEP) received a grant for this project from the National Fish and Wildlife Foundation. Grantees were required to complete projects that increase resilience to natural infrastructure, in turn increasing the resiliency of coastal communities in the face of future storms like Hurricane Sandy. This project site required the design to maintain navigation channels and assist in the adaption of tidal marshes to sea level rise and subsidence. The project was completed to investigate and assess the use of dredged material disposal placement, and the effectiveness of this method in maintaining marshes at an elevation that supports native marsh vegetation to reinforce the subsoils, and protect the local community. This project entailed the following at two different sites along the Delaware Bay.

The work completed at the Fortescue site involved the dredging of Fortescue Creek and the restoration and enhancement of interior high and low marsh, coastal dune, and beach habitats. Biological benchmarks representative of each targeted habitat type were identified and evaluated to determine the upper and lower elevational tolerances for target communities and plant species. To achieve the habitat enhancement, approximately 33,300 cubic yards of dredged material was borrowed from the navigation channel by the New Jersey Department of Transportation. The dredged material was beneficially used to restore a degraded salt marsh, restore an eroded dune, and replenish Fortescue Beach. The eroded dune was replaced with a dune designed to meet target flood elevations and protect the marsh behind it against future damage. The dune was constructed using sand dredged from the channel and material was contained using Filtrexx material to prevent sedimentation entering the waterways.

This site consists of a tidal marsh complex located within a back-bay estuary proximal to Stone Harbor and Avalon, New Jersey. The placement of dredged material onto eight distinct areas (totaling 51.2 acres) aims to enhance the marsh to achieve the primary goal of restoring the function of this tidal marsh complex. The two activities included the application of dredged material to the impaired marsh plain. First, a layer of dredged material for sediment enrichment was placed over targeted areas of existing salt marsh to increase marsh elevations; the second activity involved concentrated placement of material to fill expanding pools by elevating the substrate to the same elevation as the adjacent marsh. Thus, the goal of these restoration activities is to arrest the subsidence-based marsh loss at the project site by filling isolated pockets of open water and increasing marsh platform elevation. In addition, the beneficial reuse of dredged material facilitates routine and post-storm dredging and improves the navigability of the Waters of the United States.