River Usk River Usk The River Usk (; ) rises on the northern slopes of the Black Mountain ("y Mynydd Du"), Wales, in the westernmost part of the Brecon Beacons National Park. Initially forming the boundary between Carmarthenshire and Powys, it flows north into Usk Reservoir, then east by Sennybridge to Brecon before turning southeast to flow by Talybont-on-Usk, Crickhowell and Abergavenny after which it takes a more southerly course. Beyond the eponymous town of Usk it passes the Roman legionary fortress of Caerleon to flow through the heart of the city of Newport and into the Severn estuary at Uskmouth beyond
River Gwaun River Gwaun The River Gwaun (Welsh: "Afon Gwaun", ""Gwaun"" meaning 'marsh, moor') is a river in Pembrokeshire, West Wales, which flows west to the sea at Fishguard (Welsh: "Abergwaun" - 'mouth of the Gwaun'). The Gwaun rises in the Pembrokeshire Coast National Park on the northern slopes of "Foel Eryr" in the Preseli Hills, to the east of Pontfaen hamlet. The river is a slowly meandering stream passing through marshy, wet woodland with alder trees, water meadows and flood plains. Its river valley is deep and secluded through the Gwaun Valley, past the hamlets of Cwm Gwaun and Llanychaer to