Afon Marlais, Pembrokeshire


The Afon Marlais is a right-bank tributary of the River Tâf in Pembrokeshire, West Wales. It flows through the Vale of Lampeter to join the Tâf just west of Whitland. Its length is approximately. The name derives from the Welsh 'marw glais' and signifies a 'stagnant stream'.

Course

An indication of the source of the river comes from Ordnance Survey maps which show, a short distance east of Redstone Cross, a place called Blaenmarlais in the community of Narberth at. In its first kilometre, the Marlais, flowing in a roughly easterly direction, then southeasterly, is joined by an unnamed left bank tributary before running under the A478 at Pant-y-gorphwys, then another left bank tributary and two right bank tributaries before turning east, then northeast meandering along Lampeter Vale where it is joined by numerous further tributaries, to pass under the A40 again at Pont Fadog. Approximately 500m further, it joins the Tâf at. For all of its length after Pant-y-gorphwys, the river marks the boundary between the communities of Lampeter Velfrey and Llanddewi Velfrey in Pembrokeshire. Ordnance Survey names one of the tributaries as Afon Cwm at.

Geology

In the catchment area limestones of Llandeilo age are common.
Gold grains have been found in the river, the angular nature of some suggesting a local source.

Bridges

Pant-y-Gorphwys and its bridge, and Pont Fadog, are Royal Commission recorded historic place names.

Buildings

A mill labelled as White Mill is shown on a 1907 map and current Ordnance Survey maps at.