Things have n't been worse since the Mississippi flood in 1927 after which engineers built a system of levees and reservoirs that protect some four million people today .
The Mississippi flood in 1927 is the most destructive in U.S. history .
Things have n't been worse since the Mississippi flood in 1927 , the most destructive in U.S. history , after which engineers built a system of levees and reservoirs that protect some four million people today .