John A. Roebling Memorial Park Tidal Wetland Restoration

Mercer County’s John A. Roebling Memorial Park offers residents in the surrounding area a freshwater marsh with river fishing, kayaking, hiking, and wildlife-watching. The park contains the northernmost freshwater tidal marsh on the Delaware River, Abbott Marshland. Tidal marshes, like the 3,000-acre Abbott Marshlands, contain valuable habitat for many rare species like River Otter, American Eel, Bald Eagle, and many species of wading birds. Unfortunately, the Abbott Marshland has experienced a significant amount of loss and degradation, partially due to the introduction of the invasive Phragmites australis (Phragmites).

For the Mercer County Park Commission (MCPC), Princeton Hydro put together a plan to reduce and control the Phragmites to increase biodiversity, improve water quality, broaden recreational opportunities, and enhance the visitor experience at the park. This stewardship project replaced the Phragmites with native species with a goal to reduce its ability to recolonize the marsh. Once the restoration was completed, these areas gave way to native flora, enhanced tidal function, and incredible viewscapes. Princeton Hydro also conducted a Floristic Quality Assessment to identify invasive areas and an Evaluation of Planned Wetlands to identify key wetland functions/values to be enhanced/restored, as well as performed hydrologic monitoring to understand tidal stage elevations.

Phase 1 of the restoration process included multiple herbicide applications in Spring and Fall to eradicate the Phragmites. We led the permit application process, which included securing a Flood Hazard Area (FHA) General Permit #4, Freshwater Wetlands (FWW) General Permit #16, and Coastal (CZM) General Permit #24. Our field operations crew applied the herbicide Imazapyr using our amphibious Marsh Master vehicle and airboat as well as on foot with a backpack sprayer. Following herbicide treatment, the Marsh Master was be equipped with a steel lawn roller with a welded angle iron to roll over and crush/snap the common reed stalks. The stalks would be rolled in opposite directions to break and mulch the stalks and expose the native seedbank. One year later, we documented a dozen “volunteer” native species growing in the marsh. During the project, Princeton Hydro worked alongside MCPC to keep the public informed and engaged through public meetings and outreach. MCPC launched the “Capture the Change” initiative to help document the visual changes seen in the park as the restoration progresses by sharing photos on social media using #BagthePhrag.