Why Is Louisiana Under Water?

On August 11th, 2016 a torrential rain pour began dumping more than 7 trillion gallons of water on Louisiana. Less than fifteen deaths were reported, but more than 20,000 people were rescued from their homes and 40,000 homes were damaged. The rains flooded busy highways and submerged thousands of vehicles, and Louisiana declared a state of emergency on August 12th. Twenty parishes were named federal disaster areas because so few homeowners were insured – in St. Helens Parish less than 1% of homeowners had flood insurance. Most of these homes were apparently not in high risk areas.

How can homes covered in 30 inches of water be at “low risk” for flooding?

In short, climate change is making it harder for us to predict the weather and—even aside from the fact that humans cause climate change—we are making matters worse with our environmental policies. Floods continually devastate Louisiana: in 2001 Tropical Storm Allison touched down in Texas and pushed eastward into LA wreaking $6 billion in damages, in 2005 Hurricane Katrina flooded 80% of New Orleans and killed 1,836 people, in 2006 the Western Gulf Coast Flood damaged homes that had not recovered from the year before, in 2011 the Mississippi River flooded and forced the state to open 330 floodgates to protect New Orleans (which is actually 14 feet below sea level) levees from collapsing, and in 2015 the Red River of the South flooded to its highest levels in 70 years. Here are a few reasons why:

1. Climate change is causing more extreme weather events. Warm air can absorb more moisture in the atmosphere than cold air, meaning that the volume of rain will be greater when the water precipitates from the sky. To put that in perspective: last year Texas and Louisiana experienced six 500-year rainfalls—storms so extreme that they are predicted to only occur once every 500 years.

2. Much of Louisiana is below sea level because of flood abatement methods. Without human interference, rivers follow a path of least resistance and carve out the land, dragging with them sediment they have eroded away. The rivers deposit the sediment when they reach the sea and build “deltas” on the coast over time. Levees and canals are man-made structures that funnel water at high speeds and volumes into the routes engineers determine, preventing the natural build-up of deltas and sweeping sediment out to sea. Louisiana’s coast is constantly eroded by natural processes, but we have stopped the rivers from replenishing the land.

3. Urbanization itself increases the size and frequency of floods. Natural landscapes absorb water into the ground and slow run-off. By contrast, streets become rivers and streams during floods because cement is so impermeable. Urban obstructions like buildings and bridges also trap water aboveground, reducing drainage time for floods. More natural areas within cities would allow water to drain more quickly and provide places to replenish ground water so floods are less severe.

4. Oil and gas drilling depresses the land. The petroleum deposits fill up space underground, but we are constantly removing that volume from beneath our feet. At peak production in 2009 we extracted almost 1.8 million barrels from the Gulf every day and, like a balloon losing helium would sink from the sky, Louisiana is sinking into the sea. Combined with the effects of canals and levees (including the 100,000 miles of canals created for oil and gas production), the Louisiana delta is decimated at the rate of a football field every 48 minutes.

Flooding will not prove to be a diminishing problem for Louisiana. The land is sinking due to petroleum development and delta erosion, extreme weather events are increasing the occurrence of floods, and urbanization itself prevents the natural drainage of water. The southeastern part of Louisiana is only 3 feet above sea level on average and absolute sea level in the Gulf is expected to rise 4.3 feet by 2100.

There are no simple solutions to this issue, and any fix would require vast sums of money. Increased vegetation cover and permeable concretes are can help reduce the severity of floods, and government will probably continue to invest in flood barriers to wall off the ocean from underground cities. However, a drastic reduction in fossil fuel use is the only solution to slow the rate at which our climate is changing. #KeepItInTheGround

by Michaela Stith