A flooded neighborhood in East Orleans Parish, Sept. 2005. USACE photo by Hank Heusinkveld

Twenty years ago two powerful hurricanes, Katrina and Rita, struck the Gulf Coast within weeks of one another. Both storms caused widespread damage across portions of Louisiana and Mississippi. Combined, the storms led to more than 1,900 deaths and $143 billion in damages in the southeastern United States. In some areas Katrina’s storm surge extended ten miles inland. In New Orleans it overwhelmed many of the levees and floodwalls designed and constructed by the U.S. Army Corps of Engineers to protect the city from hurricanes. There were 50 breaches of the system. Eighty percent of New Orleans flooded, and the nation watched transfixed as thousands of survivors were rescued from rooftops by the Coast Guard and other first responders.

The Corps’ disaster response was unprecedented; during the relief and recovery efforts more than 6,000 personnel were deployed to the battered communities along the Gulf Coast. Working under the auspices of FEMA and the National Response Plan, the Corps mobilized thousands of contractors who removed approximately 100 million cubic yards of debris, installed 129,000 temporary roofs and 307 generators in Louisiana and Mississippi, rebuilt more than 220 miles of levees and floodwalls, and delivered 170 million pounds of ice, 23 million gallons of water, and more than eight million meals.                              

Operations in and around New Orleans posed special challenges. First, the Corps established a special task force to rid New Orleans of flood water. Task Force Unwatering removed 250 billion gallons of water from the city in 53 days. Engineers then launched a crash program to repair the city’s shattered hurricane protection system to be operational by the start of the 2006 storm season.

The Corps’ direct response to the disaster lasted more than two years, with levee construction continuing until 2011. The total budget for the Corps’ response exceeded $4.5 billion, making it one of the largest agency responses to any disaster to date. Numerous laws passed by Congress in the wake of Katrina resulted in a broad overhaul of both flood risk management and disaster relief missions.

Hurricane Katrina was one of the greatest disasters the Corps ever faced, and it led to both a systemic change in how the Corps evaluates risk and significant projects to reduce the risk of another flood. Even while recovery operations in New Orleans were under way, the Corps sought to understand why parts of the protection system failed, made urgent repairs in preparation for another hurricane season, and began planning a more robust system to reduce storm damage risk in the future.

Corps of Engineers personnel supervising the placement of a community health facility in Chalmette, La., Oct. 2005. Office of History		At a collection point outside of New Orleans, contractors process debris from Hurricane Katrina, Oct. 2005. Office of History

In September 2005, the Corps formed Task Force Guardian to assess and repair levees in southern Louisiana, with $638.5 million in repairs eventually identified. By June 2006, the task force had awarded 59 contracts worth $557 million to 26 contractors, executed a $47.1 million levee construction contract, repaired 195 miles of levees, removed 159 shipwrecks, repaired 4 closure structures, and partially installed 3 gates and 34 pumps.

The Secretary of Defense directed the Army to enlist the National Academy of Sciences to conduct a review of the levees and floodwalls that had failed during the storm. To support this engineering investigation, in late 2005 the Corps set up the Interagency Performance Evaluation Task Force (IPET) and commissioned what it called a Decision-Making Chronology to understand the design decisions that led to the failure. IPET comprised more than 150 scientists and engineers from the public and private sectors. It conducted a forensic analysis of the infrastructure failures and provided real-time input to those doing immediate repairs and long-term rebuilding of the system. Additionally, IPET worked with the Engineer Research and Development Center to develop computer models of Hurricane Katrina’s storm surge and the conditions future tropical cyclones might create in southern Louisiana.

In 2006 Congress authorized the Corps to design and construct a comprehensive Hurricane and Storm Damage Risk Reduction System (HSDRRS) for southeast Louisiana. With a budget of more than $14 billion, the HSDRRS became one of the largest civil works projects in USACE history. Over the next decade, the Corps improved 70 miles of the city’s risk reduction structures and strengthened the levees, floodwalls, gated structures, and pump stations that formed the 133-mile New Orleans perimeter system. Among the system’s technically advanced engineering solutions were the world’s largest surge barrier of its kind, the IHNC-Lake Borgne Surge Barrier, and the largest drainage pump station, the GIWW-West Closure Complex. The Corps designed the HSDRRS to protect against a level of storm surge that has a 1 percent chance of occurring in any given year.

During its post-Katrina investigations, the Corps became concerned that many of the weaknesses it saw in levees and floodwalls in Louisiana might exist elsewhere. In turn, Congress passed the National Levee Safety Act in 2007, which authorized the Corps to create a national levee database and perform inspections on 4,200 miles of federal levees in its purview. The Water Resources Reform Development Act of 2014 directed the Corps to create a National Levee Safety Program in consultation with FEMA.

The West Closure Complex on the Gulf Intracoastal Waterway south of New Orleans under construction to reduce flood risk associated with storm surge to communities on the west side of the Mississippi River, 2012. New Orleans District

After Katrina the Corps also began developing new approaches to levee safety governance, evaluation software, and improved technical competencies to better understand and evaluate risks. It identified twelve “Actions for Change” in categories such as using risk-informed decision making and better communicating risk to the public. Over the next decade Corps leadership instituted key organizational reforms and changes to its engineering and construction processes based on the Actions for Change. For example, Corps districts were required to consider their infrastructure as a system instead of as unrelated components. The Corps also directed that each critical design and construction decision, including those for the HSDRRS, was reviewed by an independent external panel and each project that could pose a significant threat to human life in the event of failure was given a safety assurance review to reduce that risk. Finally, the Corps established national centers for Risk Management, Flood Modeling and Mapping, Inland Navigation Design, and Dam and Levee Safety Modifications. As of 2018, the experts at these centers have collectively saved or avoided over $7 billion in expenditures while improving training and mentoring across the Corps.

In the aftermath of Hurricanes Katrina and Rita, the U.S. Army Corps of Engineers mounted one of the largest and most complex disaster responses in its history. The devastation in New Orleans exposed critical weaknesses in the city’s hurricane protection system and spurred a sweeping transformation in how the Corps manages flood risk. Through initiatives such as the Hurricane and Storm Damage Risk Reduction System and the establishment of national risk management centers, the Corps significantly enhanced its engineering standards, oversight processes, and risk communication practices. These reforms not only strengthened infrastructure in southern Louisiana but also reshaped national levee safety policy. Katrina ultimately became a turning point that redefined the Corps’ approach to resilience, preparedness, and public safety.

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August 2025. No. 170.