The source of the river is found at a place named God's Bridge where Chapel Beck disappears underground and the Doe begins.

The first named tributary is Light Water Spring which feeds northwest into the river near a disused quarry.

Near Twisleton Dale House, the river can be crossed by some stepping stones at a fording point as well as some 700 yards (640 m) later near the disused granite quarry.

[3] The main rock of the river valley is turbidite sandstone with some siltstone which are prevalent in the waterfalls and plunge pools.

These lay on a bed of Precambrian sedimentary rock which show evidence of its oceanic origins in the ripple and folding marks on exposed surfaces.