SELA did not make New Orleans flooding worse, study finds

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The New Orleans Sewerage and Water Board and the city of New Orleans today announced the findings of a third-party study into whether the Southeastern Louisiana (SELA) flood control improvements somehow made flooding worse in some parts of the city during a July 10 downpour. The study concluded that it did not.

The city hired Ardurra Group, an engineering firm out of North Carolina to do the study. Using digital modeling based on rainfall totals measured around the city, they concluded the SELA improvements could not have possibly caused flooding that occurred in the CBD and Mid-City.

The city's announcement highlighted some of Ardurra's findings:

  • The model used accurately simulated the July 10 rain event – the result of more than eight inches of rain falling in three hours in some areas.
  • The rainfall on July 10 in some blocks reached a volume and intensity of a storm that had less than a .01 percent chance of happening in any given year.
  • The SELA canals installed under Uptown streets held and conveyed the expected amount of stormwater as designed.
  • SELA did not contribute to flooding in other areas. The drainage system downstream from the SELA canals had been expanded in the 1980s and 1990s to manage a 10-year storm event in similar fashion to SELA’s design.
  • Uptown SELA improvements do not drain Mid-City or downtown, where separate canal networks convey water to different pump stations.

"Therefore, it is impossible for SELA improvements to have in impact on flooding in Mid-City and downtown," the city said. 

"We take the safety, wellbeing, and trust of our residents very seriously, and we understand that the flooding has taken a toll on our people," said Mayor LaToya Cantrell. "It was important to have Ardurra conduct this study to ensure that the SELA project is doing what it supposed to do."

"This report is an example of our commitment to being transparent about how our system works," said Ghassan Korban, Executive Director of the Sewerage and Water Board. "As a public utility, it is our responsibility to hear the concerns of those we serve. That is why Mayor Cantrell and I called for this thorough, third-party analysis. I hope these findings help inform the public of the impact of the SELA improvements while shedding light on how our system handles these more intense rainstorms."