Current and Future Flood Risk in Greater New Orleans

David R. Johnson  (RAND Corporation) Jordan R. Fischbach  (RAND Corporation) Kenneth Kuhn  (RAND Corporation)

Published: Aug 26, 2015

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Neither flooding nor flood control are new issues for New Orleans. This report presents estimates of flood risk in New Orleans and quantifies the accomplishments of the post-Katrina efforts to improve coastal defenses. The authors find that significant risk reduction has been achieved, but that risk may increase in the future unless levees are maintained or further upgraded. They highlight the importance of an ongoing commitment to flood risk reduction investment in coastal Louisiana .

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Introduction

In 2005, Hurricanes Katrina and Rita, aided by levee failures, collectively damaged over 200,000 homes, killed over 1,400 Louisiana residents, and displaced more than a million others. These events marked flood risk as the primary climatic threat to the vibrant culture of New Orleans and the rest of the Gulf Coast. The average intensity of hurricanes is predicted to increase, which emphasizes how critical it is to be prepared for the next major storm.

Since 2007, over 160 miles of levees have been constructed, repaired, or upgraded in response to the crisis. The Greater New Orleans Hurricane and Storm Damage Risk Reduction System (HSDRRS) received $14.5 billion in federal and state investments to protect the metropolitan area: the US Army Corps of Engineers (USACE) has raised levee and floodwall elevations, built a massive new surge barrier, installed pumping stations, and constructed new canal closure structures. The Federal Emergency Management Agency (FEMA) has certified the upgraded HSDRRS as protecting New Orleans to at least the “100-year” level — meaning that there is less than a 1 percent chance of flooding occurring in a given year. The new system was baptized by Hurricane Isaac in August 2012 and suffered no significant overtopping or breaches. These risk reduction efforts have been guided by Louisiana’s Coastal Protection and Restoration Authority (CPRA), which is tasked to produce a long-term coastal master plan for flood risk reduction and coastal restoration.

Continue reading the full report [Download PDF]

Citations and sources can be found in the PDF copy of the report.

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