What is storm surge? The potential impact of Irma
Nearly 6 million people have been ordered to evacuate Florida as Hurricane Irma approaches the state, nearly every corner of which is expected to feel the storm’s impact. The storm is set to bring driving rains, towering storm surges and lingering flooding in low-lying areas.
And in South Florida, those low-lying areas are abundant. The tip of the state was made habitable by water control, making the swampland sturdy enough to build on. As resorts and retirement communities sprung up on the dried out land, millions have flocked to Florida for its warm weather nearly year round.
But as a map from NASA shows, humans won’t be able to control water levels in Florida forever. Only a few feet of sea level rise could put the southern part of the state completely under water.
In the above image, the map on the left shows the elevation of Florida, with yellow being the highest and green being the lowest. (Even the highest elevation in the Sunshine state only maxes out at 197 feet above sea level.) The map on the left shows what will be left of Florida under 5 meters (about 15 feet) of water: Light blue indicates areas that are only 10 meters above sea level, while the darker blue is areas 5 meters above sea level.
Miami, the Florida Keys and the Everglades would be completely under water.
NASA collected the 3D measurements of Earth during a space shuttle topography mission. According to the agency’s latest data, sea levels have risen 3 inches since 1992, with a more drastic rise of 9 inches seen in some parts of the globe. As sea levels continue to go up, that variation could continue.
Hurricanes have given people pause about building in South Florida before, but only briefly: A Category 4 storm (hurricanes didn’t get names until 1953) killed 400 people in 1926 and just two years later another Category 4 killed 2,500 people. In response to that catastrophic flooding, the Army Corps of Engineers built the 85-mile long Herbert Hoover Dike. After more storms, Congress approved $208 million in 1948 for the Central and South Florida Flood Control Project, which built 16 major pumping stations and 1,700 miles of canals and levees.
But even if Irma devastates South Florida, people aren’t likely to move away. More recently, Hurricane Andrew ripped Miami to shreds in 1992, and while building codes were strengthened, people rebuilt homes and businesses in the exact spots where they’d stood before the storm.
So how long before Miami could be under water as ice melt accelerates around the globe?
“Given what we know now about how the ocean expands as it warms and how ice sheets and glaciers are adding water to the seas, it’s pretty certain we are locked into at least 3 feet of sea level rise, and probably more,” said Steve Nerem of the University of Colorado, Boulder, and lead of the Sea Level Change Team, a NASA collaboration. “But we don't know whether it will happen within a century or somewhat longer.”