The federal government spent $14.5 billion in New Orleans and it worked.

https://www.yahoo.com/news/new-orleans-improved-levees-hold-amid-idas-onslaught-but-the-changing-climate-will-continue-to-challenge-them-220854051.html

The newly rebuilt levees mostly held firm this week, despite facing the fifth strongest hurricane ever to hit the U.S. mainland as Hurricane Ida drew instant comparisons to Hurricane Katrina this week.

The federal government spent $14.5 billion on levees, pumps, seawalls, floodgates and drainage in New Orleans and its surrounding areas, the Associated Press reported, with most of that work complete.The levee system was reconstructed and completed about 15 years after Katrina, just in time for storms like Hurricane Laura, a deadly Category 4 from last year. “We had a record number of storms last year, and the system performed well.

 

There's some great write-ups online of what the Army Corps of Engineers did for the region that isn't really well known. Many people put their careers at risk to build a robust and effective system by going above and beyond the standard engineering practices.