Grwyne Fawr

Last updated

The Grwyne Fawr is a river in the Brecon Beacons National Park in south Wales. A section of it forms the administrative border between Powys and Monmouthshire and also of the historic counties of Brecon and Monmouth. The river and its major tributary the Grwyne Fechan flow into the River Usk at Glangrwyney. [1]

Contents

The name probably originates from gweryn or gwerynau and mawr/fawr meaning 'large river at the wet place'. [2]

The southern part of the Grwyne Fechan valley in the Black Mountains Grwynefechan.JPG
The southern part of the Grwyne Fechan valley in the Black Mountains

The Gwryne Fawr rises at Blaen Grwyne Fawr on the southern slopes of Rhos Dirion in the Black Mountains and follows a southeastward course for several miles, its flow interrupted by the presence of Grwyne Fawr Reservoir, the only waterbody within this range of hills. Some way below the reservoir, Mynydd Du Forest clothes the sides of the valley. Though a public road penetrates the valley as far as the north end of the forest, the valley is very sparsely populated. It is only approaching the hamlet of Partrishow that the valley takes on a farmed appearance. The river now heads west along a valley whose alignment is guided by the presence of a geological line of weakness known as the Neath Disturbance.

Rhos Dirion in the Black Mountains Rhos dirion.JPG
Rhos Dirion in the Black Mountains

To the west, the Grwyne Fechan takes a parallel course to that of its larger neighbour. It rises on the southern slopes of Waun Fach and gathers a number of tributary streams from the broad ridge which separates it from the Grwyne Fawr. Though there are numerous conifer plantations, the valley has a more open aspect than that of the Grwyne Fawr.

The two rivers join near the village of Llanbedr and head south as the Grwyne Fawr through the hamlet of Llangenny to their confluence with the River Usk at Glangrwyney.

Geology

Both the Grwyne Fawr and the Grwyne Fechan drain the Old Red Sandstone hills of the Black Mountains. These are the Brownstones and Senni Formations which date from the Breconian stage of the Devonian period. The sandstones and mudstones of these formations can frequently be seen in the beds of the two rivers and sometimes exposed in the often steep valley sides. The lower reaches of the river run through an area blanketed with glacial till, a legacy of the last ice age. [3]

History

The valley of the Grwyne Fawr, then known as "Coed Grano", was the site of the murder in 1136 of the Norman Marcher lord Richard de Clare, 1st Earl of Hereford, by the Welsh under Iorwerth ab Owain and his brother Morgan, grandsons of Caradog ap Gruffydd. This resulted in a period of conflict between the Welsh and English in south Wales. [4]

The Grwyne Fawr Reservoir was built primarily between 1919 and 1928, although an earlier start had been made in 1912. [5]

Related Research Articles

Black Mountains, Wales Region of hills in Wales and England

The Black Mountains are a group of hills spread across parts of Powys and Monmouthshire in southeast Wales, and extending across the England–Wales border into Herefordshire. They are the easternmost of the four ranges of hills that comprise the Brecon Beacons National Park, and are frequently confused with the westernmost, which is known as the Black Mountain. The Black Mountains may be roughly defined as those hills contained within a triangle defined by the towns of Abergavenny in the southeast, Hay-on-Wye in the north and the village of Llangors in the west. Other gateway towns to the Black Mountains include Talgarth and Crickhowell. The range of hills is well known to walkers and ramblers for the ease of access and views from the many ridge trails, such as that on the Black Hill (Herefordshire) at the eastern edge of the massif.

Waun Fach Mountain in Wales

Waun Fach is, with a summit height of 811 metres (2,661 ft), the highest mountain in the Black Mountains in south-eastern Wales. It is one of the three Marilyns over 600 m that make up the range, the others being Black Mountain and Mynydd Troed. To the north Rhos Fawr and the Radnor Forest can be seen. It is the second highest mountain in Britain south of Snowdonia. It is situated at the head of the Grwyne Fechan valley, above and to the west of the Grwyne Fawr reservoir. It has an undistinguished rounded summit. The nearby tops on the ridge, Pen Trumau and Pen y Gadair Fawr, although lower, are very much more recognisable.

River Neath

River Neath is a river in south Wales running south west from the point at which its headwaters arising in the Brecon Beacons National Park converge to its mouth at Baglan Bay below Briton Ferry on the east side of Swansea Bay.

Afon Hepste River in the United Kingdom

The Afon Hepste is a river in Powys, Wales, though partly forming the county's border with Rhondda Cynon Taf. It runs wholly within the Brecon Beacons National Park.

Beacons Way

The Beacons Way is a waymarked long distance footpath in the Brecon Beacons National Park, Wales. It is a linear route which runs for 99 miles (159 km) east to west through the National Park, and passes many of the most important landmarks and mountain peaks in the mountain range. It also includes a few of the towns in the park as well as popular attractions such as Carreg Cennen Castle near Llandeilo at the western end of the path.

Fan Fawr

Fan Fawr is a mountain in the Fforest Fawr section of the Brecon Beacons National Park, in Powys, Wales and over 734 m (2,408 ft) high.

Pen Cerrig-calch

Pen Cerrig-calch is a subsidiary summit of Waun Fach in the Black Mountains in the Brecon Beacons National Park in southern Powys, Wales. Its summit, at a height of 701 m (2,300 ft), is marked by a trig point. The peak sits high above the River Usk valley as it narrows above the small town of Crickhowell.The views from here are wide-ranging and extend as far as the Beacons themselves to the west. A ridge runs off to the northwest and the shoulder of Pen Gloch-y-pibwr then turns north to the secondary top of Pen Allt-mawr whose peak at 719m is also crowned by a trig point.

The Nedd Fechan is a river almost wholly within the county of Powys, Wales, currently administered as part of the unitary authority of Powys. It rises on the eastern slopes of Fan Gyhirych in the Fforest Fawr section of the Brecon Beacons National Park and flows south for 7 miles (12 km) to join with the Afon Mellte at Pontneddfechan, their combined waters continuing as the River Neath to the sea near Swansea. The only significant tributary of the Nedd Fechan is the Afon Pyrddin which joins it at Pwll Du ar Byrddin. Downstream of this confluence it forms the boundary between Powys to its east and Neath Port Talbot to its west.

Fan Nedd

Fan Nedd is a mountain in the Fforest Fawr area of the Brecon Beacons National Park in Wales. In common with the rest of the Fforest Fawr uplands it is within the county of Powys.

Mynydd Llangynidr is a mountain in the Brecon Beacons National Park largely in the county of Powys, south Wales. Its southern slopes extend into the northernmost parts of the county borough of Blaenau Gwent. It is named from the village of Llangynidr which sits in the valley of the River Usk to the north of it. It is essentially an undulating plateau rising in the west to a height of 557m at Garn Fawr at OS grid ref SO 123151. A secondary high point is achieved at a point marked by a trig point at SO 147159. To the north the hill overlooks the valleys of Dyffryn Crawnon and Cwm Claisfer, themselves tributary valleys of the Usk. The shallow upper valley of the Ebbw River reaches into the plateau in the southeast whilst the upper reaches of the Sirhowy Valley and its tributary the Nant Trefil define its western margins. A further tributary, the Nant Milgatw, reaches in from the south whilst the sharp edge of Rassau Industrial Estate also defines a part of its southern margin. Passing east across the B4560, the hill merges with Mynydd Llangatwg which has a similar character.

Allt yr Esgair

Allt yr Esgair is a hill in the Brecon Beacons National Park in Powys, Wales. It is commonly referred to locally as simply 'The Allt'. The Welsh name signifies 'wooded slope of the ridge'. It takes the form of a northwest-southeast aligned ridge which rises to a height of 393m and which overlooks the valley of the River Usk to the west and south. To the northeast are panoramic views across Llangorse Lake to the Black Mountains There is a viewfinder on the summit erected as a monument to Eirene Lloyd White, Baroness White of Rhymney. It is a Marilyn with a prominence of 199 metres.

River Sawdde

The Afon Sawdde is a river in the county of Carmarthenshire, Wales. For most of its course it flows through the Brecon Beacons National Park and Fforest Fawr Geopark.

Gaer (Black Mountains)

Gaer is the name of a hill in the Black Mountains of the Brecon Beacons National Park in Monmouthshire, south Wales. It lies at the southern end of the long ridge between the valley of the Grwyne Fawr and the Vale of Ewyas one mile to the north of Bryn Arw and 3 miles northeast of Sugarloaf. Its summit at 427m above sea level sits within an Iron Age hillfort known as Twyn y Gaer.

River Honddu (Powys) River in Powys, Wales

The River Honddu is a river in the county of Powys, mid Wales. Early recorded versions of the name are of the form Hothenei and hodni which are believed to contain the Welsh adjective 'hawdd', meaning 'pleasant' or 'easy', together with a suffix -ni. Later forms such as Honddey and Honthy have undergone metathesis whereby -ddn- became -ndd-.

Afon Ysgir

The Afon Ysgir is a river which rises on the southern slopes of Mynydd Epynt in Powys, Wales. The tributaries known as Ysgir Fawr and Ysgir Fechan flow past the hamlets of Pont Rhyd-y-berry and Merthyr Cynog to combine at Pont-faen and continue past the village of Battle to join the River Usk at Aberyscir.

Crug Mawr

Crug Mawr is a hill in the Black Mountains in the Brecon Beacons National Park in southern Powys, Wales. Its summit at a height of 550 m (1,805 ft) is marked by a trig point. The peak sits high above the valleys of the Grwyne Fawr and Grwyne Fechan to the north of the more well-known Sugar Loaf. The views from here across the Black Mountains are wide-ranging and also extend eastwards across Monmouthshire. Four ridges run off to the northwest, east, southeast and southwest, the last ending in the subsidiary summit of Blaen-yr-henbant.

Pontsticill

Pontsticill is a village within the county borough of Merthyr Tydfil in South Wales. It lies within the valley of the Taf Fechan on the southern edge of the Brecon Beacons National Park. The village lies within the community of Vaynor in an area that was, until the local government re-organisation of 1974, within the historic county of Brecknockshire.

Pen-y-crug

Pen-y-crug is a hill in the Brecon Beacons National Park in the county of Powys, south Wales. It is commonly referred to locally as simply 'The Crug'. The Welsh name signifies 'top of the mound'. It slopes are moderately gently on three sides; only to the west do they steepen somewhat. Its flat trig point adorned summit at 331m overlooks the valley of the River Usk to the south. To the southeast are panoramic views over Brecon whilst eastwards are the Black Mountains and south the Brecon Beacons.

Vale of Grwyney Human settlement in Wales

The Vale of Grwyney is a community in Powys, Wales. It follows most of the border between Powys and Monmouthshire. It takes its name from the river Grwyney which flows through it into the River Usk. The river Grwyney has two sources, called the Grwyne Fechan and the Grywne Fawr, which both rise in the Black Mountains and converge into one river near Llanbedr before meeting the Usk.

Glangrwyney or Glangrwyne is a village 2 miles (3.2 km) southeast of Crickhowell in Powys, Wales. The village is where the Grwyne Fawr has its confluence with the River Usk, southeast of the Sugar Loaf and at the junction of the road from Gilwern with the A40 trunk road. Glangrwyney is in the Vale of Grwyney Community for administrative purposes. The village is built upon the sands and gravels of a dissected alluvial fan which extends into the floodplain of the Usk, together with till derived from the former Usk Valley glacier.

References

  1. Ordnance Survey Explorer map OL13 'Brecon Beacons National Park: eastern area'
  2. Owen, H.W. & Morgan, R. 2007 'Dictionary of the Place-names of Wales' Gomer Press, Ceredigion
  3. British Geological Survey 1:50,000 map sheets 214 'Talgarth' & 232 'Abergavenny' and accompanying memoir/sheet explanation
  4. "Brecon Beacons Park Society". Archived from the original on 29 September 2008. Retrieved 24 February 2009.
  5. "GRWYNE FAWR RESERVOIR (INDUSTRIAL SITE)". COFLEIN. Retrieved 10 May 2016.

Coordinates: 51°50′N3°06′W / 51.833°N 3.100°W / 51.833; -3.100