Geology and history of Waterfall Country in the Brecon Beacons National Park

This landscapes of this part of the Brecon Beacons National Park have been shaped by natural forces and human industry.

Carved over millennia: the geology of Waterfall Country

Waterfall Country is part of the Fforest Fawr Geopark, the most geologically significant part of the Brecon Beacons National Park. Here, over millennia, natural processes have created an area of raw natural beauty.

Each one of the growing international family of European and UNESCO Geoparks is an area with an important and often extraordinary geological heritage. Geoparks are not just about rocks, however, they are also about people. Fascinating human stories emerge from their unique landscapes. Geoparks celebrate local legends and culture, archaeology and our wider relationship with the land. They are also first class outdoor classrooms and places for scientific study.

During successive ice ages in the last couple of million years the Vale of Neath has been gouged out by glacial ice so that its floor is hundreds of metres lower than it would have been prior to the ice ages. This has resulted in the various tributary rivers of the Neath (including the Mellte, Hepste and Nedd-Fechan) being rejuvenated - cutting down into their beds to form the deep gorges characteristic of Waterfall Country.

Down-cutting has been most marked where the bedrock is mudstone whilst sandstone beds offer more resistance and are responsible for the falls and rapids. Where much older faults have brought the two rock types into conjunction, down-cutting by rivers in the mudstone has normally left a projecting lip of sandstone which in the most extreme cases is tens of metres high.

With continued fracturing of the underlying exposed mudstones and their removal, the stresses on the protruding sandstone cap-rock above leads to its collapse. Severe weather conditions – high flow rates and severe frosts – accelerate the process.

The waterfalls migrate slowly upstream at a rate which can be determined by the distance between the current location of each individual fall and the fault which often lies some metres downstream of it. Sgwd-yr-Eira provides a good example of this process, one which continues to this day, as evidenced by the problems experienced with loose rock in 2008.

Quarries, mines and gunpowder: the history of Waterfall Country

There are around 130 known historic sites within Waterfall Country, including the hillfort at Craig-y-Ddinas, the industrial structures of the Glyn-Neath Gunpowder Works near Pontneddfechan, and Sarn Helen, an ancient Roman road running between Coelbren and Brecon Gaer forts, that skirts the north-western edge of the region.

The National Museum of Wales holds artefacts from the area dating back to the Neolithic age. A magnificent bronze axe-head has been recovered from a field in Pontneddfechan.

The Normans annexed Forest Fawr making it a jealously guarded preserve for hunting deer. In medieval times some local men were recruited by the military, trained at Tretower Court and fought at the Battle of Agincourt.

The southern fringe of the Park is geologically varied and a range of industrial mining and quarrying activities were developed here. These included silica mining, millstone quarrying and limestone burning in kilns built in areas of enclosed limestone to produce lime for local agricultural use.

Corn mills and the Glyn-Neath Gunpowder Works ran on river power. The Gunpowder Works is thought to have been unique in Wales. The site was chosen for its enclosed and isolated location.

It’s thought that many more former sites of industry still await discovery in the region. Some of these may be major sites, comparable in size to the large quarrying complex on Moel Penderyn, which includes quarries, inclines and tramways.