The levees and other flood control measures along the lower Mississippi valley are the responsibility of the federal government because of a disaster long before Katrina:

If it keeps on rainin’, levee’s goin’ to break, (X2)
When The Levee Breaks I’ll have no place to stay.

Mean old levee taught me to weep and moan, (X2)
Got what it takes to make a mountain man leave his home,
Oh, well, oh, well, oh, well.

When the Levee Breaks, Bonham, Jones, Page, Plant, Memphis Minnie

Many of us have heard this Led Zeppelin song a thousand times without knowing what it’s about. Memphis Minnie is listed as one of the songwriters because she originally wrote the song, back in 1927, after the Great Mississippi Flood of 1927, which displaced 700,000 people permanently and probably got Herbert Hoover elected president.