The second post on this page includes some interesting information, with maps, of how the various names for small bodies of water vary across the United States. For example, “creek” is widespread, but “brook” is almost exclusive to New England. “Pond,” too, is more common in New England. “Fork” is far more common in West Virginian and eastern Kentucky, and there are only tiny pockets of people in Maryland, eastern Tennessee/western North Carolina, Mississippi, Louisiana, and Colorado/Montana that use “prong.”

Also interesting is the very clear dividing line between “branch” and “run.”

http://www.pfly.net/wp-images/gnis.branch-run.jpg