The River Honddu ( cy, Afon Honddu) (pronounced ''hon-thee'') is a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

in the Black Mountains within the

Brecon Beacons National Park The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain (range), Black Mountain ...

, southeast

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 ...

. Early recorded versions of the name are of the form ''Hothenei'' and ''hodni'' which are believed to contain the adjective 'hawdd' meaning for example, pleasant or easy. Later forms such as ''Honddye'' have undergone metathesis whereby -ddn- became -ndd-. It rises within the county of

Powys Powys (; ) is a Local government in Wales#Principal areas, county and Preserved counties of Wales, preserved county in Wales. It is named after the Kingdom of Powys which was a Welsh succession of states, successor state, petty kingdom and princi ...

near the

Gospel Pass The Gospel Pass (Welsh: ''Bwlch yr Efengyl'') is the highest road pass in Wales. It is at the head of the Vale of Ewyas in the Black Mountains of southeast Wales. Starting from Hay-on-Wye the narrow mountain road climbs steeply to a height of ...

at the head of the

Vale of Ewyas The Vale of Ewyas ( cy, Dyffryn Ewias) is the steep-sided and secluded valley of the River Honddu, in the Black Mountains of Wales and within the Brecon Beacons National Park. As well as its outstanding beauty, it is known for the ruins of Lla ...

down which it flows, passing southwards into

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 ...

Llanvihangel Crucorney Llanvihangel Crucorney ( cy, Llanfihangel Crucornau) is a small village in the community (parish) of Crucorney, Monmouthshire, Wales. It is located north of Abergavenny and south-west of Hereford, England on the A465 road. Setting Llanvihan ...

before turning northeastwards to join the

River Monnow The River Monnow ( cy, Afon Mynwy) marks the England–Wales border for much of its length. After flowing through southwest Herefordshire, England, and eastern Monmouthshire, Wales, its confluence with the River Wye is approximately south of ...

at the point on the Wales-England border where that river too makes a sudden change of direction. The only significant

tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage ...

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 A terminal moraine, also called end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge ...

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 The Neath Disturbance is a geological structure which stretches across south Wales from Swansea Bay northeastwards as far as Hereford in western England. It consists of a series of both faults and associated folds which were active during the mo ...

, an ancient geological weakness, which runs through the valley to the north of the

Sugarloaf A sugarloaf was the usual form in which refined sugar was produced and sold until the late 19th century, when granulated and cube sugars were introduced. A tall cone with a rounded top was the end product of a process in which dark molasses, a ri ...

and on towards

Hereford Hereford () is a cathedral city, civil parish and the county town of Herefordshire, England. It lies on the River Wye, approximately east of the border with Wales, south-west of Worcester and north-west of Gloucester. With a population ...

. 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 image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

containing clasts of rock from mid Wales has yet been found within the valley to support that proposal.British Geological Survey 1:50,000 map sheet 214 'Talgarth' & accompanying sheet explanation Llantony Abbey, Monmouthshire

Within the valley is

Llanthony Priory Llanthony Priory ( cy, Priordy Llanddewi Nant Hodni) 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 Monmou ...

, a popular attraction for the many visitors to the National Park. Towards the lower end of the Vale of Ewyas is

Cwmyoy Cwmyoy is an extensive rural parish in Monmouthshire, Wales ( cy, Cwm Iou for the valley and parish, cy, Cwm-iou for the village). The standard Welsh name is ''Cwm Iau'' or ''Cwm-iau''. In the Gwentian dialect of Welsh that was spoken here until ...

with its celebrated church, distorted by the movement of the hillside on which it stands; the entire hamlet has been built on an ancient, and not entirely dormant,

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...

References

External links

{{authority control Honddu Honddu Honddu Honddu