Storm surge barriers: the New England experience
Back in 1938, long before satellites, radar, the hurricane hunters, and the modern weather forecasting system, the great New England hurricane of 1938 roared northwards into Long Island, New York at 60 mph, pushing a storm surge more than 15 feet high to the coast. Hundreds of Americans died in this greatest Northeast U.S. hurricane on record, the strongest hurricane to hit the Northeast since the 1800s. A destructive storm surge of 13 feet (4 meters) barreled though Long Island Sound into Stamford, Connecticut, inundating the downtown region and causing heavy damage ($6 million in 1938 dollars.) Sixteen years later, a storm surge from Hurricane Carol of 1954 inundated the city again, causing $3.4 million in damage. In response to these twin storm surge disasters, work was begun in 1965 on a 17-foot high, $14 million (1965 dollars) hurricane barrier. Completed in 1969, the barrier across Stamford Harbor is high enough to protect the city from a storm surge of 14.8 feet above mean sea level. Had the barrier been in place during Hurricane Carol, the Army Corps of Engineers estimates damage to Stamford could have been reduced by 85%.
Figure 1. Bedford Street looking south towards Broad Street in Stamford, Connecticut, after the Great New England Hurricane of 1938. Image credit: stamfordhistory.org.
Figure 2. The storm surge from Category 2 Hurricane Carol in 1954 batters the Edgewood Yacht Club near Providence, Rhode Island. Image credit: NOAA Photo Library.
The Providence storm surge barrier
Stamford isn't the only New England city that suffered destructive storm surges from the 1938 and 1954 hurricanes. The 1938 hurricane brought a storm surge that covered the commercial district of Providence, Rhode Island with 8 feet (2.5 m) of water, causing $16.3 million in damage. On August 31, 1954, Hurricane Carol produced a storm surge of up to 14.4 feet (4.4 m) in Narragansett Bay, surpassing that of the New England Hurricane of 1938. The resulting storm surge flooded downtown Providence with 12 feet (3.7 m) of water. Some entire coastal communities were nearly destroyed, and damage was estimated at $25.1 million. In response to the devastation wrought by these storms, a $15 million hurricane barrier 25 feet (7.6 m) high was built across the 1000-foot (300 m) entrance to Providence Harbor between 1961 - 1966.
Figure 3. A ship passes through the Providence, Rhode Island storm surge barrier. Image credit: Douglas Hill, EngScD, P.E., Stony Brook University.
The New Bedford storm surge barrier
New Bedford, Massachusetts lies near the end of a narrow bay, and narrow bays and river estuaries can act as funnels that focus storm surges to extreme heights if the hurricane's direction of motion is aligned so that the surge propagates up the bottleneck. In fact, the shape of the coast near New Bedford makes it the most vulnerable portion of the U.S. coast for a hurricane storm surge. The highest theoretical storm surge produced by NOAA's SLOSH model for the U.S. is 38.5 feet above mean sea level, for a Category 4 hurricane hitting New Bedford. Destructive storm surges hit New Bedford during the 1938 hurricane and 1954's Hurricane Carol, the latter storm causing $8.3 million in flood damages. A hurricane barrier 23 feet (7 m) high and 4900 feet (1500 m) long across New Bedford Harbor was completed in 1966 at a cost of $19 million (1966 dollars.) The barrier separates the New Bedford Harbor from Buzzard's Bay, and successfully kept out the 8 foot (2.5 m) storm surge from Hurricane Bob in 1991, and a 6.5 foot (2 m) surge from the January 1997 Nor'easter.
Figure 4.The 4,900 foot-long New Bedford, Massachusetts storm surge barrier as seen using Google Earth. The city of New Bedford lies to the north (top) of this image.
Figure 5.The four regions of the U.S. theoretically prone to storm surges in excess of 33 feet at the coast. These Maximum of the Maximum Envelope Of Waters (MOM) SLOSH model plots are for a maximum strength hurricane hitting at high tide. A theoretical peak storm surge of 33 - 34 feet (pink colors) is predicted by the SLOSH model for New York City near the JFK Airport (upper left), for the Big Bend region of the Florida Gulf Coast (lower right), and for the Intracoastal Waterway north of Myrtle Beach, South Carolina (lower left). The highest theoretical surge occurs at New Bedford, Massachusetts (upper right): 38.5 feet for a Category 4 hurricane.
More storm surge barriers needed
Storm surge barriers in Stamford, New Bedford, and Providence have already proved their worth and prevented damages more than the cost of their construction. For example, the Stamford barrier kept out the storm surge from the December 1992 Nor'easter, which neighboring New York City suffered storm surge flooding of it subway system and roads that caused hundreds of millions in damage. Similar barriers in the Netherlands and England's Thames River have also proved their worth, and multi-billion dollar storm surge barriers are nearing completion in St. Petersburg, Russia and the Venice Lagoon in Italy. Many more such barriers will be needed world-wide in the coming decades, because of sea level rise.
Sea level rose an average of 7 inches (18 cm) during the 20th century. The 2007 report of the U.N.'s Intergovernmental Panel on Climate Change (IPCC) predicted global sea level rise of 0.6 - 1.9 feet (18 - 59 cm) by 2100--excluding the contribution from melting of the Greenland and Antarctic ice sheets. Several studies published since that report predict much higher levels of sea level increase will occur if one includes the melting from Greenland and Antarctica, For example, a 2008 paper published by Pfeffer et al. in Science concluded that the "most likely" range of sea level rise by 2100 is 2.6 - 6.6 feet (80 - 200 cm.) If these higher sea level rise estimates prove correct, storm surge damage could easily double of triple, particularly if climate change makes the strongest storms stronger. A Report to Congress by FEMA (1991) estimated that existing development on the U.S. coast would experience a 36 - 58% increase in annual damages for a 1-foot rise in sea level, and a 102 - 200% increase for a 3-foot rise. Much of this additional damage would result from storm surges riding on top of heightened sea levels. As I'll report on in future blog posts in this series, even if the sea level does not rise this century, there are three locations along the U.S. coast that should immediately begin planning to install hurricane storm surge barriers: New York City, Galveston/Houston, and Tampa Bay.