As researchers continue to study the effects of climate change, one main focus continues to be the relationship between coastal flooding and global warming. Louisiana flooding during 2016 was called “a historic, unprecedented flooding event” by governor John Bel Edwards. California flooding in 2017 saw the Russian River rising three feet above flood stage, with dams and floodgates being opened for the first time in years. Roads closed, homes were lost and mudslide conditions occurred.
But is coastal flooding a consequence of global warming?
Studies have indicated that New York City, Miami, Charleston, St. Petersburg, Atlantic City and many other Florida communities have thousands of people at risk of coastal flooding. A rise in sea levels (even a minute rise) multiplies this risk, and the consensus is that rising sea levels are directly tied in to global warming. Research indicates that sea levels are rising at about 4 mm per year, with melting ice caps and warming, expanding oceans. It’s expected that lower latitudes will be the first to feel the impact, from the tropics to Africa, Southeast Asia and South America, followed by Europe’s Atlantic coast and the west coast of the United States.
Louisiana Flooding
In August of 2016, a low pressure system over southern Louisiana resulted in torrential rains, at rates of up to 2 to 3 inches per hour. The system remained almost stationary, with some areas receiving between two and three feet of rain. It’s estimated that this storm brought almost three times as much rain to Louisiana as Hurricane Katrina did. Its 7.1 trillion gallons of rainwater was enough to fill Lake Ponchartrain about four times.
A Louisiana flood map from this event shows major flooding well north of Baton Rouge, with more than ten rivers above flood stage. Almost 150,000 homes were damaged or destroyed in the floods, with thousands of Louisianans forced to seek shelter. Almost 30 percent of the school-aged population of the state was put out of school – over a quarter of a million children – due to the direct damage to schools and teachers’ homes.
The Scientific Community Weighs In
A recent study from researchers at Princeton and Rutgers warn that flood models currently in use aren’t a good reflection of the types of floods that American cities are likely to face in coming decades, as sea levels and global temperatures go unchecked.
Michael Oppenheimer is a Princeton professor who has studied sea level rise for two decades and co-authored the study:
Oppenheimer’s team took a dated study from the Intergovernmental Panel on Climate Change, added their own numbers on sea level rise and combined them with recent data from every tide gauge around the United States. From this, they calculated risks for various locations. They concluded that major coastal flooding, formerly called a “100 year flood,” would swamp coastal cities about 40 times more frequently by the year 2050. By the end of this year, major floods could hit New York City yearly, and could roll through Seattle almost weekly.
The outlook for low-lying areas like Charleston, S.C. and South Florida looks even worse:
“These areas have terrain that’s gently sloped,” Oppenheimer said. “South Florida is really in trouble. Not only are they having a lot of nuisance flooding, but they sit on limestone, which makes it extremely difficult to build coastal defenses. These places really have to get on the ball and decide what they have to protect.”
Economic Impacts
In 2017, natural disasters such as extreme rainfall, coastal flooding and a devastating round of wildfires cost the United States $306 billion in damages, a record that surpasses the previous highest amount by almost $90 billion. The year 2017 was warmer than average across every state in the lower 48 and Alaska, as well as being the third-hottest year on record.
Hurricane Irma, Hurricane Harvey and Hurricane Maria brought coastal flooding and widespread devastation to Florida, Texas, Puerto Rico and the Virgin Islands. Hailstorms tore through Colorado, Minnesota, the Upper Midwest and the Great Plains, with tornadoes in the Midwest and South and freezing rain along the eastern seaboard. Flooding and wildfires ravaged California and the western states, and in the end Congress had to approve more than $130 billion in disaster aid.
It may be premature to assume that a warming climate played a role in these disasters, studies do point to changing weather patterns making California more susceptible to wildfires. Two studies indicate that climate change made Hurricane Harvey’s rainfall more intense as well. While the debate over climate change may still rage on, the destruction from natural disasters is absolutely real.