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Manhattan Seawall faces a tidal challenge

NSF Award:

Secular Changes in Pacific Tides  (Portland State University)

NINETEENTH CENTURY US WEST COAST SEA LEVEL AND TIDAL PROPERTIES  (Portland State University)

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When Hurricane Sandy blew ashore, New York City's South Manhattan Seawall protected the island from the storm surge. After analyzing historical tide data, a team of NSF-funded researchers has found that the likelihood of water overtopping the seawall is now at least 20 times greater than it was 170 years ago.

Findings by David Jay, Stefan Talke and Edward Zaron of Portland State University suggest that the changes in storm tides are related to changes in climate, as well as effects from human activity such as modifying natural channels and limiting peak river flows. The research team applied their methods to New York Harbor to determine the likelihood of a Hurricane Sandy-like storm tide striking again.

They found that observed water levels from such 10-year storms have increased by approximately 0.72 (+/- 0.2) meters in the last 150 years (0.28 meters due to increased storm tides and 0.44 meters to relative sea-level rise).  Changes in channel geometry may be an important factor affecting the storm tides in New York City.  Deep, streamlined channels, like those commonly found in harbors, apply less friction on the water they carry than shallow channels.  As a result, water levels will likely be higher and reach inland destinations faster than they would if the channels were wider and shallower.

This work and similar findings in coastal cities around the U.S. could help municipalities plan for the impact of major storms that threaten these areas with storm tides that are higher than in past decades.

The research was publicized by the American Geological Union.

Images (1 of )

  • flood waters hit manhattan
  • maximum storm tides for the new york harbor area and trends in sea level rise
Hurricane Sandy flooding Avenue C at East 6th Street in Manhattan’s East Village.
David Shankbone/Wikimedia Commons
Annual maximum storm tide (AMST) for New York harbor (top) and the trend in major storm tides with a rise in sea level (bottom).
Stefan Talke, Portland State University

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