That's almost impossible to say as many that seem inactive suddenly pop up again. There are a lot that only use the site here and there and many come and go. Really hard to put an accurate number to your question. Sorry.
It appears to be in the eye of the beholder. Somebody living by the Amazon or the Nile might consider the Potomac to be a creek.
According to the US government's educational site, the terms are interchangeable.