*2.1. Study Area*

Fire Island is a barrier island along the southern coast of Long Island, New York, of which 7924 hectares are managed and protected by the National Park Service (NPS) (Figure 1). Salt marsh is the dominant land cover on the island comprising 26% of the protected area [37]. The bayside environment is polyhaline [38]. The island's geomorphology has been altered by urbanization, beach replenishment, and inlet stabilization [39]. More frequent medium intensity storms have been linked with salt marsh edge erosion [40]. Hurricane Sandy was a 1-in-500-year storm surge event that impacted the northeast Atlantic coastal region on 24 Oct 2012 [41]. In 2003, Quickbird-2 satellite images were used to map the study area with a focus on terrestrial and submerged aquatic vegetation [42]. Due to the limited bayside tidal exchange, Fire Island's salt marshes have a small tidal range of approximately 45.5 cm between MLLW and MHHW [43]. SLR is outpacing accretion on the salt marshes of Fire Island as determined by Surface Elevation Tables (SET) [5].

Recent estimates of salt marsh change using aerial imagery from 1974 to 2005/2008 found a 14.1% loss of salt marsh vegetation in a region including Fire Island [15]. The protected areas of FIIS include the William Floyd Estate on the mainland and large bayside islands of Sexton, West Fire and East Fire Island (Figure 1).

**Figure 1.** (**a**) A mosaic of Worldview-2 and Worldview 3 imagery of Fire Island and Sentinel-2 satellite image of the surrounding area (NIR, G, B displayed as R, G, B). (**b**) A post-Hurricane Sandy oblique aerial view acquired by U.S. Geological Survey (USGS) showing the bayside salt marshes surrounding the breach [44]. (**c**) A field photo of the Fire Island National Seashore (FIIS) salt marsh landscape.
