Author Mark Twain grew up in Hannibal, Missouri, on the banks of the Mississippi River, and he wrote often about its savage nature. He watched people's efforts to dam it and channel it and control it with wry disdain. Twain did not think anyone who tried to shove the Mississippi around would succeed. He thought the river would always get its way. About the Mississippi, Twain wrote: "Four years at West Point and plenty of books and schooling will learn a man a great deal, I reckon. But it won't learn him the river."

One of the ways humans have tried to control flooding on the Mississippi and on other rivers worldwide is by building dams. Ruins of dams, built thousands of years ago to control the Nile, still exist in Egypt. The Chinese have been building dams since before...