NEW ORLEANS – Today, in advance of the 10th anniversary of Katrina, The Data Center released the tenth in a series of reports on changes post-Katrina. This report is contributed by David Johnson, Jordan Fischbach, and Kenneth Kuhn of the RAND Corporation.
The report finds, according to new flood risk models, New Orleans’ current hurricane protection system protects against flooding from a 100-year storm – that is, a storm that has a 1 percent chance of occurring in any given year. However, a 500-year storm (Katrina was a 400-year storm) would lead to significant levee overtopping and extensive flooding in low-lying parts of the metro. The current system is built for current environmental conditions.
Models for environmental conditions in 2065 show that during a 100-year storm, significant portions of New Orleans East, Lakeview, Gentilly, St. Bernard Parish, and Jefferson Parish would flood due to overtopping, the report finds. And a 500-year storm in 2065 would be catastrophic, inundating the city, even with just rainwater and levee overtopping and no breaches.
Since 2007, the Greater New Orleans Hurricane and Storm Damage Risk Reduction System (HSDRRS) received $14.5 billion in federal and state investments to protect the New Orleans metropolitan area. With this investment, the U.S. Army Corps of Engineers has raised levee and floodwall elevations, built a massive new surge barrier, installed pumping stations and constructed new canal closure structures. FEMA has certified the upgraded system as protecting New Orleans to at least the “100-year” level, signifying that there is less than a 1 percent chance of storm surge-based flooding in any given year.
This report is the first to quantify the accomplishments of the post-Katrina efforts to improve coastal defenses. The report concludes that significant risk reduction, meeting a 100-year standard, has indeed been achieved, but that risk may increase in the future unless levees are maintained or further upgraded. Moreover, the report notes that the current standard is likely worth upgrading in the near-term, given that a 500-year storm would inundate much of the metro and cause enormous economic damages.
Expected annual damage could increase by an order of magnitude over the next fifty years if no further action is taken, the report finds. These conclusions underscore the importance of an ongoing commitment to investments in flood risk reduction, as exemplified by the state’s Comprehensive Master Plan for a Sustainable Coast.
