Only if the sentence actually refers to the tribe. Since the sentence involves a word that could rever to a small stream OR a tribe of native americans, it is ambiguous.
Give that you just mentioned Creek from Oklahoma, and the quote is from a hillbilly speech, which tended to come from the Appalachian mountains, the matter is further ambiguous.
Unless the Creek were far reaching (or moved), it would imply they existed in the West, and thus wouldn't be a part of hillbilly concerns in the East. Therefore increasing the likelyhood the hillbillies were concerned about water rising, not native americans.
I'm sure some expert on Native American history can chime in with "...actually, they lived in lands taken over by hillbillies..." But until such evidence comes up, we need not assume and enforce captilization rules on a topic that is all wet.