Panning around I did spot one, but those hills in the middle look ideal for a nice flowing river don't they! Some of the terrain is a bit "sharp" in height. Was also worried if it was too tall it'd end up being flat, and I don't use the SpintiresMod to increase the height limits and whatever else it does.
I'd wish I'd tried this sooner, I found that video of yours and thought OK I'll try again, how hard can it be etc..
Wonder what the Grand Canyon would be like..
Edit: Saved the height map in 4K resolution, looks a lot better IMO