Shoreline position and coastal topographical change monitoring at Gateway National Recreation Area: 2017–2022 and 2007–2022 trend report

Abstract

This trend report summarizes the results of shoreline position and coastal topography monitoring conducted at Gateway National Recreation Area (GATE) in 2007 through 2022. The data collection and report were completed by Rutgers University for the National Park Service, Northeast Coastal and Barrier Network, Inventory and Monitoring Program. Gateway National Recreation Area (GATE) is made up of three units: Sandy Hook Unit, Jamaica Bay Unit (Breezy Point, Plumb Beach), and Staten Island Unit (Great Kills, Miller Field, Fort Wadsworth). Shoreline position change results include a spatial depiction and statistical analysis of annual changes and 5-year changes in shoreline position as well as a longer-term trend analysis incorporating the full shoreline analysis of 2007 through 2022, all following the model presented in Psuty et al. (2022a). Coastal topography datasets include profiles of survey data collected annually, annual change metrics, net change metrics, as well as an alongshore depiction of net change, following the model presented in Psuty et al. (2012). This 2007–2022 trend report is the third GATE trend report to incorporate both shoreline position and coastal topographical change data. Due to the variable exposure to incident waves influencing inputs of sediment to the alongshore transport system in the various units from updrift sources, there was no common direction of shoreline displacement or profile change throughout the GATE park units. Engineering structures along the beach and adjacent to inlets altered the shoreline position and coastal topography responses in much of GATE. Generally, the largest vectors of shoreline position change and changes in coastal topography were produced by natural impacts such as storms and by anthropogenic impacts such as dredging or beach nourishment at an updrift location. All of the park units in GATE displayed the impacts of an absence of a source of sediment to counter the erosional impacts of the coastal storms. All of the units had a net inland displacement of shoreline position over the survey period, with some short term recovery associated with local pulses of sediment transfer. Sites with ocean exposure were more heavily eroded (Sandy Hook Oceanside, Breezy Point Oceanside, and Great Kills Oceanside), than sheltered sites (Sandy Hook Bayside, Breezy Point Bayside, Great Kills Bayside, Plumb Beach, Miller Field, Fort Wadsworth). A comparison of the shoreline position and profile data from this survey period with those from the previous trend reports highlights the impacts of Hurricane Sandy and the variety of recovery episodes throughout GATE (Psuty et al. 2018). The trend lines for the sites are often divided into pre-Hurricane Sandy (2012) and post- Hurricane Sandy because of the magnitude of the changes to the shoreline position (1D) and coastal topography (2D) metrics. There was considerable resilience in the system to re-establish the dune-beach system, although not in its original location. The continuing negative sediment budget and the increasing rate of relative sea-level rise will result in episodic inland migration of the dune-beach system and will necessitate a concomitant review of the allocation of space for visitor use and recreation.