Yes, the streams are the tiny steep valleys. The map website (before it went down) would let you control depth and width of them. I probably could have done a better job of matching them up with the borders... maybe next time

I'm assuming the streams are the small valleys on the map, but I've been using them as track bed so I don't mind if you keep them in or remove them from map data from now on. the only thing I'd like is if theres some next to the border to shift the border just past them so that way the valley/stream is still inside the borders

I may be a bit of an outlier but I like playing with the hydro plants available on the workshop. The two that I use the least are little tiny hydro dams that only fit on the smallest of streams.