TheNant Llech is a minor river inPowys,Wales and which lies wholly within theBrecon Beacons National Park. The name means 'slab stream', presumably in reference to the sandstones across which it runs. Its headwater streams, the Nant Llech Pellaf and the Nant Llech Isaf join forces at Blaen Llech and then continue westwards as the Nant Llech for 3 km / 2 mi to a confluence with theRiver Tawe just east of the village ofAbercraf.[1]
The most famous feature of the river isHenrhyd Falls (Sgwd Henrhyd or Rhaeadr Henrhyd inWelsh), a 27m/90 ft high fall where the river plunges over the edge of a band of hard sandstone known as the 'Farewell Rock' into a deep plunge pool. The river continues below in a steep wooded gorge cut into mudstones and sandstones of theCarboniferous ageCoal Measures.[2] The falls are owned and managed by theNational Trust which provides a free car park off the minor road betweenCoelbren and Pen-y-cae for visitors wanting to explore the area.
A public footpath runs the length of the valley though part runs across a landslip area which has been active in recent years. The river gorge is asite of special scientific interest.[3] SirWilliam Edmond Logan, first director of theGeological Survey of Canada discovered some fossil trees near the base of the falls. These are now on display outsideSwansea Museum.
51°48′05″N3°41′32″W / 51.8014°N 3.6921°W /51.8014; -3.6921