I just ran into this video on stream building. Best I've seen for this natural style of pond. It shows many aspects that you may have read about but is really clear in this video. Like running the stream before finishing the edge and how the edge is done. Rock size and placement, excellent. I'm not a huge fan of Aquascape type ponds, but these guys are very good at this look. This video is geared more toward Aquascape contractors I think, but still good tips for people planning a stream.