River Honddu
Encyclopedia
The River Honddu is a river
in the Black Mountains
within the Brecon Beacons National Park, southeast Wales
.
It rises within the county of Powys
near the Gospel Pass
at the head of the Vale of Ewyas
down which it flows, passing southwards into Monmouthshire
to Llanvihangel Crucorney before turning northeastwards to join the River Monnow
at the point on the Wales-England border where that river too makes a sudden change of direction. The only significant tributary
to join the Honddu is the Nant Bwch though numerous smaller streams flow down the steep sides of the Vale of Ewyas to add to the river's flow.
It is likely that the Honddu continued on a southerly course beyond Llanvihangel Crucorney prior to the last ice age but has since been diverted by the presence of a large terminal moraine
which stretches impressively across the valley to the west of the village. The southwest to northeast alignment of both the Honddu and the Monnow appear to be related to the course of the Neath Disturbance
, an ancient geological weakness, which runs through the valley to the north of the Sugarloaf and on towards Hereford
.
The upper valley of the Honddu has the characteristic U-shape of a glacially scoured valley though it is not clear where the ice originated that cut this deep trench through the eastern Black Mountains. The modern Honddu is thus something of a misfit river
. It has been speculated that glacial ice from the Wye
valley glacier invaded the Vale of Ewyas over the Gospel Pass, though no evidence of any glacial till containing clasts of rock from mid Wales has yet been found within the valley to support that proposal.
Within the valley is Llanthony Priory
, a popular attraction for the many visitors to the National Park. Towards the lower end of the Vale of Ewyas is Cwmyoy
with its celebrated church, distorted by the movement of the hillside on which its stands; the entire hamlet has been built on an ancient, and not entirely dormant, landslide
.
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 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...
within the Brecon Beacons National Park, southeast 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...
.
It rises within the county of 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...
near the Gospel Pass
Gospel Pass
The Gospel Pass is a high road pass at the head of the Vale of Ewyas in the Black Mountains of southeast Wales. The narrow mountain road climbs steeply from Hay-on-Wye to a height of 538m above sea level, squeezing between the mountains of Twmpa to the west and Hay Bluff to the east, before...
at the head of the Vale of Ewyas
Vale of Ewyas
The Vale of Ewyas is the steeply-sided and secluded valley of the Afon Honddu, in the Black Mountains of south Wales and within the Brecon Beacons National Park. As well as its outstanding beauty, it is known for the ruins of Llanthony Priory, and for several noteworthy churches such as those at...
down which it flows, passing southwards into 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:...
to Llanvihangel Crucorney before turning northeastwards to join the River Monnow
River Monnow
The River Monnow flows through south-west Herefordshire, England and eastern Monmouthshire, Wales.- Border River :For much of its short length it marks the border between England and Wales before it joins the River Wye at Monmouth. The Wye is also half English from Monmouth until it meets the...
at the point on the Wales-England border where that river too makes a sudden change of direction. The only significant tributary
Tributary
A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...
to join the Honddu is the Nant Bwch though numerous smaller streams flow down the steep sides of the Vale of Ewyas to add to the river's flow.
It is likely that the Honddu continued on a southerly course beyond Llanvihangel Crucorney prior to the last ice age but has since been diverted by the presence of a large terminal moraine
Terminal moraine
A terminal moraine, also called end moraine, is a moraine that forms at the end of the glacier called the snout.Terminal moraines mark the maximum advance of the glacier. An end moraine is at the present boundary of the glacier....
which stretches impressively across the valley to the west of the village. The southwest to northeast alignment of both the Honddu and the Monnow appear to be related to the course of 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...
, an ancient geological weakness, which runs through the valley to the north of the Sugarloaf and on towards Hereford
Hereford
Hereford is a cathedral city, civil parish and county town of Herefordshire, England. It lies on the River Wye, approximately east of the border with Wales, southwest of Worcester, and northwest of Gloucester...
.
The upper valley of the Honddu has the characteristic U-shape of a glacially scoured valley though it is not clear where the ice originated that cut this deep trench through the eastern Black Mountains. The modern Honddu is thus something of a misfit river
Misfit stream
A misfit stream is a stream that is far too small to have eroded the valley which the stream occupies. The shape of the valley may also be inconsistent with a typical valley that has been eroded by water. Generally it is reasonable to expect a valley to be in proportion with the stream that...
. It has been speculated that glacial ice from the Wye
River Wye
The River Wye is the fifth-longest river in the UK and for parts of its length forms part of the border between England and Wales. It is important for nature conservation and recreation.-Description:...
valley glacier invaded the Vale of Ewyas over the Gospel Pass, though no evidence of any glacial till containing clasts of rock from mid Wales has yet been found within the valley to support that proposal.
Within the valley is Llanthony Priory
Llanthony Priory
Llanthony Priory is a partly ruined former Augustinian priory in the secluded Vale of Ewyas, a steep sided once glaciated valley within the Black Mountains area of the Brecon Beacons National Park in Monmouthshire, south east Wales. It lies seven miles north of Abergavenny on an old road to Hay...
, a popular attraction for the many visitors to the National Park. Towards the lower end of the Vale of Ewyas is Cwmyoy
Cwmyoy
Cwmyoy is an extensive rural parish in Monmouthshire, Wales. Alternate spellings include Cwm Iau, the name translating from the Welsh as "valley of the yoke"...
with its celebrated church, distorted by the movement of the hillside on which its stands; the entire hamlet has been built on an ancient, and not entirely dormant, landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
.