Perhaps i'm misguided in my observations, but it seems to me that throughout America's history, rivers see very little development along their banks. Going through many downtowns buildings seem to face away from rivers (I believe this has to do with how rivers near urban areas were filled with trash and sewage and thus smelled and looked displeasing), but also through rural areas, very few farms seem to back up right to rivers, homes aren't built along rivers, yards don't lend views to rivers. If you follow a river on something like google earth, they are always accompanied by trees lining their banks, and untouched by development. So why is this? Is their an act to conserve the banks of rivers, or are rivers really considered such an unsightly thing in America?
Rivers in America tend to flood, especially in the spring (when the snow melts), but also when a hurricane or tropical storm dumps vast amounts of rain into a rivershed.
It is not a good idea to build infrastructure where it will be wiped away by floods.
Of course, over time, and with a lot of dam building and levee building by the US Army Engineers, many rivers flood less (or the floods are more controlled) than they once were.
Still, the rivers can, even now, escape their controls and create dangerous floods. This has happened several times in various parts of America in recent years.