It flows in a generally south-eastern direction through the town of Cowbridge, then turns southward and reaches the Bristol Channel at Breaksea Point, south of Aberthaw.

Unlike many rivers in south Wales, the Thaw was never subject to much pollution, except at its mouth which was diverted to feed the Aberthaw Power Station.

Its major tributary, the Kenson River, is polluted in its lower reaches due to agricultural run-off and effluents leaking from nearby quarries.

[clarification needed] The river is also a popular site for various kinds of recreation, accessible for much of its course, much of which is used for agriculture.

The river picks up many tributaries along its course, making its watershed the largest in the Vale of Glamorgan.

It has a total length of 2 miles and is formed at the confluence of two other rivers, the Waycock and the Nant Llancarfan.

It starts near the small village of Llantrithyd near the A48 and flows southwest for nearly 3 miles, through the hamlet of Treguff (this name is a corruption of Tre-gof).

Proposals for a nuclear power station on the site were rejected due to close proximity to Cardiff.

For centuries, an active, albeit small, port stood at the river's mouth, and provided docking facilities.

[2] The Thaw was used to cool the power station, which led to a small amount of thermal pollution in the river's mouth.

The river's original mouth was actually slightly further east of here; many lagoons, small pools and salt-marshes are left over from its once large estuary.