sorry ga pond rookie, but i'm finding it really difficult to visualize from yer description, perhaps you could try a field sketch or some (compressed) pictures of area and post them.
it sounds like you want to build on the flood plain of creek? i have a dammed creek style pond and wish i had the situation to only divert creek water and control the water budget of my pond. if you have the opportunity to construct a pond with controlled input and output, i would think that the best of all possible situations.
