New Orleans is trying to ensure that Katrina's devastation never happens again

New Orleans after KatrinaMario TamaA woman jogs along a levee along the Mississippi River with the city skyline in the distance on May 16, 2015 in New Orleans, Louisiana.

Ten years ago, Hurricane Katrina devastated New Orleans and other parts of the Gulf Coast. It wasn’t the first storm to hit the Crescent City, but the failures of the city’s protection systems were so dramatic that engineers have revamped the way they prepare for natural disasters.

That’s essential, especially since New Orleans faces even greater risks in the future.

Most of the city is already below sea level, protected by an unreliable system of levees.

Flood risk will grow more severe as rising sea levels and sinking coastal land produce a local increase of at least four feet by the end of the century. And then there’s the inevitable increase in major storm surges caused by extreme weather events.

We’ve created a guide to the crises ahead and the city’s best hope for survival.

More than 50% of New Orleans is already below sea level. The only things keeping the city safe are levees and flood walls.

Note: The Mississippi appears so high because the banks on either side rise higher than anywhere else in the city, and the technology used to measure sea level doesn't function properly on water itself.

But sea levels are projected to rise by around 4.5 feet this century as global warming causes water to expand and land ice to melt.

National Climate Assessment via http://thelensnola.org/2013/02/21/new-research-louisiana-coast-faces-highest-rate-of-sea-level-rise-on-the-planet/

Sea levels are rising faster in Louisiana than almost anywhere else due to rapid sinking of marshy coastal land (orange shows land that disappeared between 1937 and 2000).

Louisiana Geological Survey via https://medium.com/matter/louisiana-loses-its-boot-b55b3bd52d1e

Here's a look at New Orleans elevations by the end of the century.

Mike Nudelman/Business Insider

It doesn't help that the land is sinking. The Louisiana coast has lost almost 2,000 square miles of land since the Mississippi's natural flow, which deposited sediment that replaced land carried away, was diverted in 1932 to protect communities from the river's seasonal floods. All the land in red is gone already, and the yellow patches are expected to disappear in the next 35 years.

US Geological Survey

Source: NOAA

Much of what has been lost is valuable marshland, which helps buffer storm impacts and absorb flooding. The marsh photographed here, part of Barataria Preserve, is likely to be gone in a few years.

Kevin Loria/Business Insider

Source: Matter

In some areas of coastal Louisiana, water is already rising between one and three to four centimeters a year -- the same rates predicted for the rest of the world by end of the 21st century.

Caitlyn Kennedy, NOAA Climate.gov

Source: Kolker

And then there's the steady increase in hurricane strength and frequency as water temperature increases.

Global annual power and frequency of tropical cyclones averaged in 10-y blocks for the period 1950 -- 2100, using historical simulations for the period 1950 -- 2005 and the modelled for the period 2006 -- 2100. For more info, see source link to paper.

Source: Proceedings of the National Academy of Sciences

America's Hurricane Alley is going to get a lot worse in the coming years.

Louisiana's average temperature is going up, according to NOAA, and the number of days over 65 degrees is expected to increase 43% by mid-century, according to a National Climate Assessment report released last year.

The OECD has estimated that climate change could put more than one million people and $200 billion at risk from damage to New Orleans and the surrounding area by the 2070s. It's one of the most vulnerable cities in the world, according to a recent study in Nature Climate Change.

There is a plan in place to try to protect the region by restoring valuable marshland and figuring out how to let the Mississippi's floods flow more naturally, along with building up levees and other protective structures -- but it's approximately a 50-year, $50 billion plan, and one where the funding for the entire thing is not there.

Chuck Wagner/Shutterstock

Source: Kolker, PRI

The plan itself has a variety of ways to both restore protective natural habitats and to bolster protection for human settlements.

Louisiana's 2012 Coastal Master Plan

New levees would be built up around New Orleans and swamps, marshes, and barrier islands could be restored with sediment from a more free Mississippi.

Louisiana's 2012 Coastal Master Plan

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