Sunday, August 3, 2008

Timing is everything: How vulnerable to flooding is New York City?

American Meteorological Society press release: A report just released in the most recent issue of the Bulletin of the American Meteorological Society offers hope that a new high resolution storm surge modeling system developed by scientists at Stony Brook University will better be able to predict flood levels and when flooding will occur in the New York metropolitan area, information crucial to emergency managers when planning for impending storms. The report also warns that flooding is dependent not just upon the intensity of the tropical storm, hurricane, or nor’easter, but also on the local phase of the tide at the time of the storm.

In a project funded by New York Sea Grant, Brian Colle, Associate Professor in the School of Marine and Atmospheric Science (SoMAS) at Stony Brook University, and colleagues tested the utility of coupling a state of the art atmospheric model with an ocean model from the Stony Brook Storm Surge (SBSS) system in order to predict storm surges for the NYC metropolitan region. Colle and colleagues tested their combined model against Tropical Storm Floyd and a nor’easter from 11-12 December 1992, and found the model predicted peak water levels comparable (within 10 percent) to those measured during the storms at several water level gauges around the region.

“Ultimately, the goal is to provide emergency managers with a range of possibilities as to what may happen as the result of a storm, and this approach shows great promise,” says Dr. Colle. The modelers also performed simulations to assess the impact of parameters such as local tide level and wind intensity on flooding severity. Model simulations showed that if Tropical Storm Floyd had arrived in NYC a week earlier, coinciding with a spring (fortnightly) high tide, water levels would likely have been high enough for minor flooding to occur. Another simulation, which used wind levels of a Category 1 hurricane timed to arrive at spring high tide, predicted water levels likely to have caused significant flooding.

…“We’re playing Russian roulette in some sense with these storms coming up the coast,” says Colle. “If we have a high tide or spring high tide when we have one of these events, then we’re in trouble.”

…“The vulnerability of the area speaks for itself as we’ve already had cases of flooding,” says Colle. “When coupled with sea level rise, it’s not going to take much of a storm to cause flooding as we go into the coming decades, so we are working to provide better forecasting of these events in the future.”

Sunset over New York City in "Flug und Wolken" (Flight and Clouds), Manfred Curry, Verlag F. Bruckmann, München (that's Munich to you, dude). Image from United States Coast and Geodetic Survey, Wikimedia Commons

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