Hurricane Katrina impacted the US Gulf Coast on August 29, 2005. This week an article entitled Ten Years After Katrina: What Have We Learned? was published in the journal EOS. They recapped the destruction caused by Hurricane Katrina as well as provide some suggestions on how to better prepare for another inevitable hurricane.
One reason Hurricane Katrina was so devastating was due to the general topography of the New Orleans area. The city is essentially a bowl that is below sea level. About 1000 of the 1800 deaths that resulted from Hurricane Katrina took place in New Orleans. The city is subsiding at a rate of 5-6 mm per year and in some areas as much as 2 cm per year. We can calculate relative sea-level rise by taking into account how fast the ocean level is rising in conjunction with how fast the land is subsiding. The New Orleans area has some of the largest relative sea-level rise rates in the United States.
The city was built on the Mississippi River delta. Over time the sediments that make up the delta are compacted down. In addition, because the Mississippi River is dammed up, it no longer floods the area. Flooding is important because it adds a layer of sediment, which helps alleviate the subsidence. Some areas in New Orleans are as much as 3 m below mean sea level.
The levees that protect New Orleans from flooding and storm surge failed during Hurricane Katrina. This, in conjunction with the failure of pumping stations as well, resulted in the flooding of St. Bernard Parish, damaging or destroying 80% of the houses.
The article concludes with four recommendations: scientists need to do a better job of communicating climate change risks to the public, more sea-level rise modeling is needed, a need for better safety features for coastal flooding, and rezoning residential zones inpotentially hazardous areas prone to coastal flooding.