Ever-Changing Fire Island

All barrier islands are ever changing, as they are constantly shaped and reshaped by the complex interaction of wind, waves, sediment, and currents. Mother Nature creates, destroys, and recreates a dynamic landscape of beaches, dunes, and spits.

The Otis Pike Fire Island High Dune Wilderness on the east end of Fire Island National Seashore is an example of time and nature’s styling. There’s beauty in the changing landscape even as what was vanishes or transforms.

From ocean to bay in Fire Island’s wilderness the terrain transitions from a wide, gently sloping sandy beach, through undulating back dune habitat, to the bay’s shore edged in sand and salt marsh.  Along with the readily apparent changes, there are signs within the wilderness landscape of nature’s handiwork, such as gaps in the primary dune exposing its history of influential weather events.

Overwashes are imprints on the landscape left behind when powerful waves penetrate the dunes. Though an interruption in

the island’s first line of defense, this natural process helps sustain the elevation of the barrier island’s interior and bay side in the face of sea level rise by carrying sediment towards the bay.

Breaches and inlets have come and gone, opening with powerful storms and closing gradually as sand is moved along the coast by waves and currents. This has certainly happened with breaks in the chain of barrier islands spanning Long Island’s south shore. Aerial images reveal clues of historic breaches and inlets on the eastern portion of Fire Island — lobes of its salt marsh contain sand deposited in the bay as overwash and/or by the incoming tide at a breach or inlet.

Superstorm Sandy’s high water levels and large waves brought dramatic changes to Fire Island’s wilderness in October 2012.

This history-making storm scoured sand from the dunes and beach face, leaving behind a lower, wider beach. The force of moving water pushed sand over the top of dunes and across the width of the island in overwashes; the storm also opened a breach through the wilderness from ocean to bay.

While action was taken to remedy some of Sandy’s wrath, some remnants from the storm (including a breach) were allowed to recover naturally because federal wilderness areas are managed to preserve natural conditions. However, nature has no mandate — the hard lines of the post-storm landscape were softened with each tidal cycle, waves gradually returned sand that was carried offshore, and American beach grass and other native barrier island plants emerged to trap sand and rebuild beach and dunes.

The natural forces that govern the shape and position of the barrier island also influence the seafloor. Seagrass and shellfish beds dot wide swathes of sand beneath the surface of the Great South Bay; gradual modifications of mud flats, sand plains, and channels is punctuated by rapid alterations during hurricanes and nor’easters.

The shifting shoals north of the wilderness breach have proven dangerous for many who attempted to navigate them. Great South Bay boaters quickly learn to sail cautiously near breaks in the barrier island — where once a deep channel meandered through the bay, a shallow sand shelf may now exist. The breach provides a direct connection between ocean and bay, a conduit for swift-moving tides and sediment. It is also a reminder that this is a landscape in flux, a cordon of sand bounded and shaped by moving water. Someday the breach will be gone and both nature and boaters will find another way.

Elizabeth Rogers contributed to this story.