3D river of money

Hi,

I would like to create a waterfall of dollar bills way off in the distance and have the dollars cascade down the rocks creating a river at the bottom that flows toward the camera and off-screen at the bottom of the frame. This seems like a pretty simple thing to do, but I'm fairly new to AE and can't find what I'm looking for in tutorials. I've looked for two days. Can anyone offer suggestions?

Thank you

Ty