Grwyne Fawr
Encyclopedia
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.
The name probably originates from gweryn or gwerynau and mawr/fawr meaning 'large river at the wet place'.
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
.
To the west, the Grwyne Fechan takes a parallel course to that of it 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.
hills of the Black Mountains. These are the Brownstones and Senni Formations which date from the Breconian stage of the Devonian
period. The sandstone
s and mudstone
s 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.
Marcher lord Richard de Clare, 1st Earl of Hertford
, 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
.
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
in the Brecon Beacons National Park in south Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. A section of it forms the administrative border between Powys
Powys
Powys is a local-government county and preserved county in Wales.-Geography:Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire , and a small part of Denbighshire — an area of 5,179 km², making it the largest county in Wales by land area.It is...
and Monmouthshire
Monmouthshire
Monmouthshire is a county in south east Wales. The name derives from the historic county of Monmouthshire which covered a much larger area. The largest town is Abergavenny. There are many castles in Monmouthshire .-Historic county:...
and also of the historic counties of Brecon
Brecknockshire
Brecknockshire , also known as the County of Brecknock, Breconshire, or the County of Brecon is one of thirteen historic counties of Wales, and a former administrative county.-Geography:...
and Monmouth
Monmouthshire (historic)
Monmouthshire , also known as the County of Monmouth , is one of thirteen ancient counties of Wales and a former administrative county....
. The river and its major tributary the Grwyne Fechan flow into the River Usk
River Usk
The River Usk rises on the northern slopes of the Black Mountain of mid-Wales, in the easternmost part of the Brecon Beacons National Park. Initially it flows north into Usk Reservoir, then east by Sennybridge to Brecon before turning southeast to flow by Talybont-on-Usk, Crickhowell and...
at Glangrwyney.
The name probably originates from gweryn or gwerynau and mawr/fawr meaning 'large river at the wet place'.
Rhos Dirion
Rhos Dirion is a top of Waun Fach in the Black Mountains in south-eastern Wales. It is the highest point on the Rhos Dirion - Chwarel y Fan ridge....
in the Black Mountains
Black Mountains, Wales
The Black Mountains are a group of hills spread across parts of Powys and Monmouthshire in southeast Wales, and extending across the national border into Herefordshire, England. They are the easternmost of the four ranges of hills that comprise the Brecon Beacons National Park, and are frequently...
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
Partrishow
Partrishow, also known as Patricio or Patrishow, is a small village in the Black Mountains of South Wales, within the Brecon Beacons National Park.-Location:...
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
Neath Disturbance
The Neath Disturbance is a geological structure which stretches across south Wales from Swansea Bay northeastwards as far as Hereford in western England. It comprises a series of both faults and associated folds which were active during the mountain-building period known as the Variscan orogeny...
.
To the west, the Grwyne Fechan takes a parallel course to that of it larger neighbour. It rises on the southern slopes of Waun Fach
Waun Fach
Waun Fach is the highest mountain in the Black Mountains in south-eastern Wales. It is one of the three Marilyns over 600m 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 situated at the head of the Grwyne...
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
Llanbedr, Crickhowell
Llanbedr is a hamlet northeast of Crickhowell in the county of Powys in south Wales. It lies above the river known as the Grwyne Fechan just above its confluence with the Grwyne Fawr in the southern reaches of the Black Mountains range. The hamlet lies within the shadow of Table Mountain, an...
and head south as the Grwyne Fawr through the hamlet of Llangenny
Llangenny
Llangenny is a small hamlet in the Brecon Beacons National Park in southern Powys, Wales.Llangenny has approximately 100 inhabitants and is a village in the Vale of Grwyney, the lower reaches of the Grwyne Fawr, which comprises Llangenny, Glangrwyney and Llanbedr.The two main features of Llangenny...
to their confluence with the River Usk
River Usk
The River Usk rises on the northern slopes of the Black Mountain of mid-Wales, in the easternmost part of the Brecon Beacons National Park. Initially it flows north into Usk Reservoir, then east by Sennybridge to Brecon before turning southeast to flow by Talybont-on-Usk, Crickhowell and...
at Glangrwyney.
Geology
Both the Grwyne Fawr and the Grwyne Fechan drain the Old Red SandstoneOld Red Sandstone
The Old Red Sandstone is a British rock formation of considerable importance to early paleontology. For convenience the short version of the term, 'ORS' is often used in literature on the subject.-Sedimentology:...
hills of the Black Mountains. These are the Brownstones and Senni Formations which date from the Breconian stage of the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
period. The sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s and mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s 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.
History
The valley of the Grwyne Fawr, then known as "Coed Grano", was the site of the murder in 1136 of the NormanNormans
The Normans were the people who gave their name to Normandy, a region in northern France. They were descended from Norse Viking conquerors of the territory and the native population of Frankish and Gallo-Roman stock...
Marcher lord Richard de Clare, 1st Earl of Hertford
Richard de Clare, 1st Earl of Hertford
Richard fitz Gilbert de Clare was a Norman nobleman, the son of Gilbert Fitz Richard de Clare and Adeliza de Claremont. He founded the priory of St, Mary Magdalene, Tonbridge.-Welsh revolt:Richard held the Lordship of Ceredigion in Wales...
, by the Welsh under Iorwerth ab Owain and his brother Morgan, grandsons of Caradog ap Gruffydd
Caradog ap Gruffydd
Caradog ap Gruffydd was a Prince of Gwent in south-east Wales who made repeated attempts to gain power over all of southern Wales by seizing the Kingdom of Deheubarth.- Lineage :...
. This resulted in a period of conflict between the Welsh and English in south Wales
South Wales
South Wales is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of...
.