River Mellte

The River Mellte rises where the Afon Llia and Afon Dringarth join in the hills of south Wales. It flows south through Ystradfellte village to Pontneddfechan, where it meets the Nedd Fechan to become the River Neath. The name comes from the Welsh word for lightning, describing how quickly the river swells after heavy rain. Half a kilometre of the river disappears underground at Porth yr Ogof through Carboniferous Limestone. It returns to daylight at Pwll Glas after passing through a maze of cave passages. The river’s underground section has fifteen known entrances and can flood completely in extreme conditions. Adventure groups use parts of the cave, though some routes are dangerous and have caused fatalities over the years. Downstream, within Waterfall Country, the Mellte drops over several falls including Sgwd Clun-gwyn, Sgwd Isaf Clun-gwyn and Sgwd y Pannwr. The deep, wooded valleys shelter rare bryophyte plants, protecting the area as a site of special scientific interest and a special area of conservation. Walkers follow public and concessionary paths along the river to reach the waterfalls. The Brecon Beacons National Park Authority has worked with partners to repair path erosion caused by heavy use. Remains of two weirs and waterwheels mark the former gunpowder works at Pontneddfechan, where production ended in 1931. The valley also offers caving, canyoning, gorge walking and white water kayaking, with local companies providing guided days out on grade 4/5 rapids.