The rivers Usk The Usk The River Usk (Afon Wysg in Welsh) rises on the northern slopes of the Black Mountain (y Mynydd Du) at the western edge of Brecon Beacons National Park. Its headwaters drain into the Usk reservoir, from where the river flows in an easterly direction to begin with. The river passes to the north of the Brecon Beacons before starting to take a more southerly bearing through Abergavenny and the town of Usk itself, joining the Bristol Channel at Newport. The Usk is host an array of wildlife and is both a Site of Special Scientific Interest (SSSI) and Special Area of Conservation (SAC) for most of its length. Catchment map.