River Thaw

The River Thaw flows for twenty kilometres entirely within the Vale of Glamorgan in south Wales. It rises in hills south of the M4 near Llanharry and runs south-east through Cowbridge before turning south to reach the Bristol Channel at Breaksea Point. The river once carried sea-going ships to villages along its banks, but silting has since narrowed its estuary. Archaeologists have found many sites beside the Thaw, and its valley still serves farms and anglers. The Kenson River, the Thaw’s largest tributary, joins near Rhoose after flowing just two miles from its start near Penmark. The Thaw supports healthy fish populations and once held large numbers of water voles, though some stretches now lack them. Unlike many Welsh rivers, it suffered little pollution except at its mouth where Aberthaw Power Station drew cooling water. The power station, opened in 1966, once generated 1 455 megawatts but has since closed and been demolished. Before the power station, the river’s estuary hosted a small port that closed by 1900 as the channel silted up. Remnants of salt-marshes and lagoons mark the former wider mouth east of the present outlet. Visitors can walk parts of the Thaw’s course, especially through Cowbridge and along the shingle beach at Breaksea Point. The river passes through farmland and near the dismantled railway at Flemingston, where an unnamed brook meets it. Nearby villages such as Aberthin and Llanblethian show signs of past floods, while the estuary at Breaksea Point offers views of the Bristol Channel. The route also passes archaeological sites and the quiet lanes of Penmark and Rhoose.