When Hurricane Katrina struck New Orleans in 2005, it caused catastrophic damage to the city. Bernard Parish was completely flooded, with water levels reaching up to 14 feet. The City of New Orleans' drainage system had 24 pumping stations with a combined capacity of more than 50,000 cubic feet per second (cfs). City Park, located in the center of New Orleans, was twice the size of New York's Central Park.
In the aftermath of the storm, scientists and engineers from various institutions worked to analyze and evaluate the behavior of the system during Hurricane Katrina and to apply the findings obtained to repair and rebuild the storm surge protection system in and around New Orleans. Webster Rainy was rescued from his niece's rooftop in the Lower 9th Ward when floods swallowed his neighbors after Hurricane Katrina. To protect against future floods, wetlands around New Orleans were shrinking and open water was rapidly expanding throughout the city. Local governments ordered people to evacuate low-lying, exposed areas outside protective docks, including parts of New Orleans.
The city was also in the path of Hurricane Ida 16 years after the flood walls collapsed and the dikes were overwhelmed by a storm surge caused by hurricane Katrina. To protect against future storms, New Orleans' new and repaired flood walls and dikes inhibited the growth of wetlands, which provide a natural barrier against floods and storm surges. The IPET report compared the risk of flooding in New Orleans before Hurricane Katrina with the risk after the completion (in 2014) of the new Hurricane and Storm Damage Risk Reduction System (HSDRRS). The direct impact of a major storm in New Orleans could cause widespread deaths if the most vulnerable parts of the city aren't evacuated.
Fortunately, while Hurricane Katrina destroyed many buildings in New Orleans and cut off its entire energy supply, the worst potential damage was avoided. The water level rose up to 7 meters along the east side of New Orleans and up to 9 meters along the Mississippi coast.