Look at the first page in my original attachment 'BerrierMill2'. The headrace/sluice canal comes out of McLin Creek and goes around the base of a small hill. To me that says undershot.
https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Braine-le-Ch%C3%A2teau_JPG02.jpg/800px-Braine-le-Ch%C3%A2teau_JPG02.jpg
This is a mill in Belgium that seems to have the same type of foundation as Berrier Mill.
The attached pic is another mill with the same idea. There's a gate to open and close each side.
-Jennifer