Researchers prepare coast for the impact of storm surges driven by powerful hurricanes
Hurricanes or tropical cyclones are among the deadliest and most costly of natural disasters, and the rapid growth of population and property on US coasts makes them particularly vulnerable. Flooding driven by the wind, waves, and rain that comprise a major hurricane can erode coastlines and incapacitate underground infrastructure such as subways, highway tunnels and electricity. Although New York City has experienced a relatively mild recent hurricane history, major hurricanes have struck with devastating effect in previous centuries. Meanwhile, the potential for damaging storm surge in New York has multiplied with decades of growth and is exacerbated by the rise of sea level associated with climate change. Dr. Alan Blumberg and Dr. Philip Orton of the Center for Maritime Systems at Stevens Institute of Technology, in collaboration with Timothy Hall from the National Aeronautics and Space Administration (NASA), have received a NASA grant to assess the risks to New York City with an innovative and rigorous methodology.
Growth of US Coastal Populations
In 2003, approximately 153 million people (53 percent of the nation’s population) lived in the 673 U.S. coastal counties, an increase of 33 million people since 1980. That number is expected to rise to 165 million by 2015.
Climate Change and Extreme Weather Events
The Intergovernmental Panel on Climate Change reports that it is very likely (>90% likelihood) that mean sea level rise will contribute to upward trends in extreme coastal high water levels in the future. It is also likely that there has been a poleward shift in the main Northern and Southern Hemisphere extratropical storm tracks.
“Our coastal cities are not only home to millions of people, but they represent the maritime trade centers through which the vast majority of the consumer goods are transported,”says Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science. “This research helps us to quantify the hazards of extreme weather and climate events so that we can develop effective solutions to protect those areas.”
Nearly 5.3 million 20-foot container equivalent units transit through New York and New Jersey ports annually, and the Hudson River in the New York City area is one of the fastest, most complex, and most dynamic waterways in the world. Stevens and NASA researchers are therefore taking a meticulous approach to the question of hazard assessment, laying out the probability of flooding in the New York City area in a systematic manner that examines every contributing factor. This research effort combines NASA hurricane simulation expertise with Stevens modeling capabilities the New York waterways in order to comprehensively understand the risks associated with flooding under hurricane conditions.
Understanding the Impact of Storm Surge from a Direct Hurricane Strike
No hurricane has made a direct hit at New York City in over 100 years, but four are known to have hit in prior centuries. These extreme events have demonstrated the immense destructive power of storm surge. The last Category 2 hurricane occurred in 1821, raising a 13-foot storm surge in a single hour and flooding Manhattan below Canal Street. In 1893, a tropical cyclone struck Long Island, and the storm surge largely washed away Hog Island, which up until then was a playground of New York City political and business elite. It is believed to be the only recorded removal of an entire island by a hurricane.
“The washing away of Hog Island, Long Island is believed to be the only recorded removal of an entire island by a hurricane.”
According to Dr. Orton, “Even a powerful nor’easter can cause serious damage in NYC, and the most recent severe flooding incident occurred in December, 1992. Seawalls around the city are mostly only a few feet above normal high tide levels, so a relatively modest peak storm surge of 4.3 ft during that storm flooded into and shut down the subway system for several days.”
Taking this into account, the researchers are employing a unique research methodology that takes NASA statistical hurricane models, which include wind, atmospheric pressure, and rainfall, and combines them with a Stevens-based regional hydrodynamic modeling system to quantify flood probabilities due hurricane storm surge, rainfall, river flow, sea level rise, and atmospheric pressure on the Northeast’s most populous urban center in New York City.
“Do powerful hurricanes with potential for devastating storm surge strike New York City every 50, 100, or 500 years, and what kind of hazard is associated with a direct hit today?"
The statistical hurricane model to be used was constructed in New York, NY, at NASA GISS, and has been utilized successfully as part of a NASA-Aspen Reinsurance collaboration. It will be used to calculate annual landfall probabilities of hurricanes regionally on the US Northeast as a function of key variables that determine hazard: intensity, size, propagation speed, impact angle, and tidal phase. The researchers are not just looking at a few sample storms, but they are also assessing the statistics of all recorded hurricanes in the Atlantic with the aid of Dr. Hall’s hurricane forecasting expertise. They are examining more broadly tens of thousands of years of statistical “synthetic” storms and analyzing their impact in order to address two pressing questions: do powerful hurricanes with potential for devastating storm surge strike New York City every 50, 100, or 1000 years, and what kind of hazards are associated with a direct hit today?
Climatic causes of sea level rise
(a) changes in ice mass—melting and ice sheets
(b) changes in ocean volume—thermal expansion.
Thermal expansion was the dominant source of sea level rise for the last 40 years; ice melting has now likely become the main source and is expected to accelerate through this century.
As the rate of sea level rise increases due to climate change, the destructive power of even weaker, more frequent storms will increase. If sea level rises by 1 meter, an intense winter storm that currently occurs every 10 years or so will acquire the impact typical of those rare storms with 3-meter storm surge.
Renowned Harbor Observing and Prediction System Based at Stevens
In order to run simulations of the “synthetic” storms and understand the ocean’s response to storm forces, the researchers are using a prominent mathematical model of the equations that govern how water moves, which was developed and refined at Stevens and now used around the world. The model is used in the New York Harbor Observing and Prediction System(NYHOPS), which is based at Stevens and forecasts storm surges, water currents, water temperature, water levels, and waves throughout the region's waterways including New York Harbor, Newark Bay, Long Island Coast, Long Island Sound, and New Jersey Coast. NYHOPS combines real-time and historic data with an advanced understanding of ocean physics to make predictions about how tides and other cyclical ocean behaviors influence the potential impact of storms.
NYHOPS’ modeling system consists of a three-dimensional circulation model and a wave model. It is based on the Estuarine Coastal and Ocean Model (ECOMSED), a derivative of the Princeton Ocean Model developed by Blumberg and Mellor (1987). It simulates a wide variety of marine phenomena, including circulation and mixing processes in rivers, estuaries, shelf and slope, lakes, semi-enclosed seas as well as open and global oceans. The ECOMSED/POM combination has been adapted by over 3,000 research groups around the world, and over 600 papers employing the modeling engine have been published. The NYHOPS operational forecast system (OFS) adheres to NOAA National Ocean Service standards and guidelines for OFS use and reliability [Georgas and Blumberg, 2010; Georgas and Blumberg, 2010], and now meets the NOS standard of keeping root-mean-square forecast errors below 0.5 ft 90% of the time. The operational version of sECOM has been providing highly accurate storm surge predictions as part of the NY Harbor Observation and Prediction System (NYHOPS), with mean water level errors of 0.33 ft since 20071.
Climate Change Research at Stevens
Stevens hurricane modeling and storm surge prediction is part of a larger initiative in climate change research to understand how the coasts of the United States will change in terms of flooding and damage from storms, and to plan for adaptive or preventative action. “There is often speculation in the media that building structures such as islands and land bridges will help to protect the city from storms, and this research will help to quantify the results of such undertakings and help us determine if such efforts are beneficial and advisable,” says Dr. Blumberg.
Dr. Blumberg and Dr. Orton, in collaboration with the Center for Climate Systems Research at Columbia University, have also won a grant to build maps of coastal flooding probabilities and vulnerabilities for Boston and New York. In addition, they are collaborating with the Center for International Earth Science Information Network (CIESIN) and the Water Center of the Earth Institute at Columbia University, with funding from the New York State Energy Research Development Authority (NYSERDA), to develop on on-line flood risk assessment tool for communities along the Lower Hudson River.
In 2011, Dr. Blumberg was invited to join UNESCO's Intergovernmental Oceanographic Commission (IOC) on collaborative research addressing urban coastal ecosystems.
Learn more about maritime research at Stevens by visiting the Center for Maritime Systems or reading the Maritime Systemsissue of Nexus, the School of Science and Engineering Research Magazine. Start your own maritime journey at Stevens by visiting the Department of Civil, Environmental and Ocean Engineering, or visit Undergraduate Admissions or Graduate Admissions to apply.