Thursday, November 8, 2012

Hurricane Sandy and the NY Barrier Island Estuaries

Old Inlet near Pelican Island is where Fire Island was cut in half by the storm

The storm surge, waves and wind of Hurricane Sandy brought destruction to the ocean front communities of New Jersey and New York. As a child I spent many a weekend visiting Neponsit driving from Ditmas Avenue in Brooklyn a straight shot down Flatbush Avenue to the causeway. Neponsit, the western most part of the Rockaways, is part of Queens borough- though still part of the same barrier island (sandbar) that contains Breezy Point. For residents that think I invaded their strictly private beach, I had cousins that lived in Neponsit a couple of houses from the ocean. Crossing over to the sand bar always seemed like entering another world with the beautiful homes and white beaches, but after Hurricane Donna and the winter storm the following year, I understood both the magic of the Ocean and its power and danger.

Neponsit is part of the New York estuary. Estuaries occur in quiet, partly enclosed coastal regions where rivers meet the sea. Estuaries are the mixing zone where the fresh water and sediments from rivers meets the seawater and tidal forces.  The ecological balance within the estuary can be very complex, affected by the volume and rate of fresh water flow from the river, the type and quantity of sediments in the river, the topography of the coastline, the tidal range, and the strength and direction of prevailing wind and waves. With all the variations possible there are actually only four major types of estuaries in the world: Drowned River Valleys; Tectonic Estuaries; Sand Bar or Barrier Island Estuaries; and Fjords. New York harbor, New Jersey and Long Island are barrier Island estuaries.

Barrier islands in the United States occur along the east coast and the Gulf. Barrier islands were created by the waves depositing sand along the eastern coast and Gulf when sea level began to rise 18,000 years ago. As sea level continues to rise, year after year for hundreds of centuries the seaward side of the barrier island has been eroded away by waves and wind. Sea level continues to rise (reportedly at an accelerated pace) and waves continue to erode away the seaward side of the barrier islands while winds carry sand and silt to be deposited on the landward side in the marshes and harbors. This is a continual process that left to nature would find the barrier islands moving landward each year allowing storms to dissipate their energy across them while protecting the mainland. These islands along the shore have not been for the most part left to nature. We have developed them, and to maintain them we are locked in the endless programs of dredging and beach restoration to maintain the white sand beaches that are tourist attractions.

In nature, barrier islands provide protection for the mainland against flooding. However when we build beach front property on the barrier islands it is only protected by the fragile sand dunes. Erosion of beaches and dunes that serve as the defense for these coastal communities against storm surge and flooding, increase the risk of destruction of coastal property, infrastructure, and public safety during storms. The recent storm surge from Hurricane Sandy at 13 feet above normal tides dwarfed the 6 foot surge of Hurricane Donna in 1960. Many of the sandy beaches along the Atlantic Coast have become increasingly vulnerable to storm damage due to erosion of the beaches during past storms, despite the constant beach restoration projects. Hurricanes Sandy, Irene (2011) and Ida (2009), as well as large northeaster storms in 2007 and 2005 appear to be winning the battle of the beaches.

Elevated water levels and waves during tropical storms can lead to dramatic coastal change through erosion of beaches and dunes. Wave dominated estuaries often have a sand bar or sand spit across the mouth of the estuary. This sand bar breaks the force of the waves and physically protects the estuarine lagoon from wind and waves. That is their purpose in nature, but when you build multi-million dollar homes and high rises with roads that serve as passageways for waters of the tidal surge on the sand bar and use the tributaries for disposal of human and chemical waste, the resilience of the estuary is destroyed.

Like all estuaries, barrier islands are an incredibly complex ecosystem that we are only beginning to understand. Estuaries are productive ecosystems and habitats determined by geology, salinity and climate. In the United States the ecology of estuaries has been severely damaged by man because most of our large coastal cities are built where rivers meet the oceans on estuaries. Over half of the population of the country lives within cities and suburbs build within or adjacent to these estuaries. Diverting fresh water from tributaries for irrigation and drinking water supplies changes flow, quantity of fresh water entering the estuary, and impacts the balance within the ecology. Excess nutrients and sediment from sewage treatment plants, farm fields and animal pastures, urban and suburban run off from roads and landscaping can cause eutrophication. As the ecosystem of estuaries declines, species die out, coastlines experience excessive erosion by wind, tidal action and ice. The day will come when we no longer have the resources to continue to rebuild on the Barrier Islands- for now just add it to the tab.

Neponsit Before Hurricane Sandy USGS

Neponsit After Hurricane Sandy USGS

No comments:

Post a Comment