River Clydach, Brecknockshire
The River Clydach is a short, steep and fast-flowing river in Brecknockshire. It lies within the Brecon Beacons National Park. It is around six miles in length.
The river rises on the southern slopes of Llangattock Mountain (51°48’44"N, 3°11’38"W) then heads south-east through Clydach Dingle past Brynmawr. It then enters the spectacular Clydach Gorge, dropping about 1,000 ft to Gilwern and its confluence with the River Usk (51°49’58"N, 3°6’3"W).[1]
"Clydach" is a common name for watercourses in south Wales and is thought to derive from an old Welsh-language word for "swift" or possibly "stoney", both of which would apply in this case.[2]