River Honddu

The River Honddu rises in the Black Mountains within the Brecon Beacons National Park in southeast Wales. It flows for over twenty-four kilometres from Gospel Pass down the Vale of Ewyas into Monmouthshire. Near Llanvihangel Crucorney the river turns northeast to meet the River Monnow at the Wales–England border. Its only major tributary is the Nant Bwch, though many smaller streams feed the Honddu from the steep valley sides. The upper valley shows the deep U-shaped trench carved by glaciers long ago. A large terminal moraine west of Llanvihangel Crucorney once diverted the river from its original southerly course. The alignment of the Honddu and the Monnow follows an ancient geological weakness called the Neath Disturbance. Llanthony Priory stands in the valley and attracts many visitors to the National Park. At the lower end of the Vale of Ewyas, Cwmyoy’s church leans because the hillside beneath it has slowly moved. The whole hamlet rests on an old landslide that is not entirely stable.