The Berthin Brook is a minor right bank tributary of the

River Usk The River Usk (; cy, Afon Wysg) 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 fl ...

Monmouthshire Monmouthshire ( cy, Sir Fynwy) is a county in the south-east of Wales. The name derives from the historic county of the same name; the modern county covers the eastern three-fifths of the historic county. The largest town is Abergavenny, with ...

, in south

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

. Flowing north from

New Inn New Inn - ( cy, Y Dafarn Newydd) - is a village and community directly south east of Pontypool, within the County Borough of Torfaen in Wales, within the historic boundaries of Monmouthshire. It had a population of 5,986 at the 2011 Census. L ...

initially, it turns east at Little Mill to flow along a former

glacial meltwater channel A meltwater channel (or sometimes a glacial meltwater channel) is a channel cut into ice, bedrock or unconsolidated deposits by the flow of water derived from the melting of a glacier or ice-sheet. The channel may form on the surface of, within, ...

past the former Royal Ordnance Factory site (now BAE Systems) at

Glascoed } Glascoed is a village in Monmouthshire, south east Wales. It is east of Pontypool and west of Usk. Glascoed is mostly associated with the Royal Ordnance Factory nearby at ROF Glascoed. Llandegveth Reservoir A reservoir (; from French ...

and by Rhadyr to join the major river 1 km north of the town of

Usk Usk ( cy, Brynbuga) is a town and community in Monmouthshire, Wales, northeast of Newport. It is located on the River Usk, which is spanned by an arched stone bridge at the western entrance to the town. Usk Castle, above the town, overlooks th ...

. At the height of the last ice age (the Devensian), the Usk valley glacier reached as far down the Usk valley as Little Mill and sediment-laden meltwater created a valley sandur over which the post-glacial Berthin Brook now flows.

References

{{DEFAULTSORT:Berthin Brook Rivers of Monmouthshire