10-Year Anniversary of Hurricane Katrina
By Climate Central
Ten years ago this week, Hurricane Katrina became one of the worst natural disasters in U.S. history. It caused the deaths of an estimated 1,200 people and more than $100 billion in damage as it barreled across Florida and then slammed into the Gulf Coast as a Category 3 hurricane (after peaking at Category 5 strength).
Katrina’s highest storm surge, some 27.8 feet, was recorded at Pass Christian, Miss. While in New Orleans, a surge from 5-10 feet piled up along the western shores of Lake Pontchartrain, straining the levee system until parts of it gave way, eventually inundating about 80 percent of the city in waters that reached up to 20 feet.
The storm was bookended by two major studies into the question of how climate change might impact hurricanes and helped to spur intensive study into that very question in subsequent years. Over the past decade, scientists have come to a general consensus that while globally there will be about as many — or perhaps even fewer — tropical cyclones as there are now, they will become more intense.
A 2013 study found that surge and flooding from Katrina was anywhere from 15-60 percent higher than it would have been under the climate and sea level conditions around 1900. This was primarily from local land subsidence, which accounted for about 1.8 feet of an estimated 2.4 feet of local sea level rise.
The researchers explain how the loss of protective wetlands and barrier islands contributed to the increased surge and flooding. Part of the reason these features are being lost is the lack of replenishing silt in the Mississippi Delta because of dams and other constructed features farther upriver.
The graphics below show the projected sea level rise for this region, as well as the effect climate change and sea level rise will have on the likelihood of extreme flooding events. What is considered an extreme flood today (about a 1-in-100 year flood or 1% annual chance flood) can be severely damaging and is only going to get higher in the future with sea level rise. (Note: Katrina was even worse than a 100-year storm.) All of these calculations were made from the NOAA National Climate Assessment (NCA) mid- to high-emissions scenario. Coastal cities and towns all along the Gulf and East Coasts will be increasingly vulnerable to hurricanes because of sea level rise, even without any changes to the storms themselves.