Thanks Mitcorb, you're correct, my issue is more to do with how to show the water rather than the terrain through which it runs. As it is a 'brook' and not a 'stream', the water trickles unevenly over rocks etc and drops into pools in some places along the way and I'm not sure how I should attempt to show it.
PS: The waterfall you mentioned sounds interesting, I'll try to look for it.