Journal Article by Stevens Researchers Reveals Storm Surge Forecasting Weaknesses

8/22/2012

As we approach the anniversary of last year’s landfall in New York City of Tropical Storm Irene, illuminating research on storm tides across the tri-state area by Philip Orton, Alan Blumberg, Julie Pullen and Nickitas Georgas of the Center for Maritime Systems (CMS) at Stevens has been published in the Journal of Geophysical Research.

The article, “Detailed Modeling of Recent Severe Storm Tides in Estuaries of the New York City Region,” provides a summary of water elevation measurements in waterways around New York City during Hurricane Irene, which brought strong winds, heavy rainfall and near record-breaking storm tides to New York, New Jersey and Connecticut. By conducting a series of in-depth modeling sensitivity experiments on eight tide stations, the researchers contrasted the accuracy of the CMS’ computer-based storm surge forecast model, the Stevens Storm Surge Warning System, with a simplified version of the model which emulates other commonly-used models.

“Our key finding is that our model is likely to be more accurate because it contains components not included in most real-time storm surge forecast models,” said Orton, a postdoctoral research associate at the CMS. A prior model-comparison study showed that the model is most accurate for nor’easter flooding, but no comparison has yet been made for tropical storms and hurricanes.

With their study, the researchers showed how simpler models will chronically underestimate water elevation, and therefore, flood risk. Specifically, most storm surge modeling studies and operational forecast systems do not take into account rainfall and freshwater river flow predictions, or water density variations, which can decrease turbulence and cause a storm surge to grow bigger.

“When these biases come into play, the result is flood maps that make people feel safer than they really are,” said Orton. “We found that ignoring these two inputs creates some bias near New York City, and even more bias as you go north along the Hudson.”

The CMS is currently engaged in a number of research projects to improve the accuracy of storm surge modeling and eliminate the bias the researchers identified in their study.

Through a two-year old project with the Consortium for Climate Risk in the Urban Northeast, CMS researchers are studying storm surge and sea level rise flooding risk and other coastal zone risks related to weather and climate.

A newly-funded project with the NASA Goddard Institute for Space Studies (NASA/GISS) will also work to quantify risk of coastal flooding in New York City from combined storm surge, sea level rise and rainfall.

Finally, a forthcoming study with the National Oceanic and Atmospheric Administration-Coastal and Ocean Climate Applications (NOAA-COCA) will reveal the adaptation methods of New York City and Boston to future coastal flooding threats, and another in partnership with the New York State Energy and Research Development Authority (NYSERDA) will develop a website that allows users to map flood zones along the Hudson River.

View animation of NYC-area water elevations caused by Irene last Aug. 28 at http://vimeo.com/48249903. For the full article from the Journal of Geophysical Research, click here. Learn more about the Center for Maritime Systems at www.stevens.edu/cms.