Hi samjcorbin,

The stream is sourced from OS OpenData StreetView, and the fences are drawn out from Cadastral Parcels where there are land ownership boundaries. There is usually a fence on land boundaries, regardless of the existance of a hedge, as hedges are usually to the side of fences or the fences are within the hedge. Therefore they should be drawn as two separate ways next to each other.
You can see the sources/backgrounds used for changesets in the imagery_used tag. If you wish you can change the stream tag to a ditch, but there is not much difference between the two tags and it does eventaully become a stream in the lower parts nearer the sea.

conifermapper