Honddu
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River Honddu Afon Honddu |
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 Honddu at Capel-y-ffin |
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| Data | ||
| location | Monmouthshire , Powys ( Wales ) | |
| River system | River Severn | |
| Drain over | River Monnow → River Wye → River Severn → Atlantic Ocean | |
| source | near the Gospel Pass 52 ° 1 ′ 9 ″ N , 3 ° 6 ′ 4 ″ W |
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| muzzle | in the River Monnow coordinates: 51 ° 54 ′ 17 " N , 2 ° 58 ′ 3" W 51 ° 54 ′ 17 " N , 2 ° 58 ′ 3" W
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| Communities | Capel-y-ffin , Cwymyoy | |
The River Honddu [ ˈhɔnðɨ ] ( Welsh Afon Honddu ) is a river in the Black Mountains within the Brecon Beacons National Park , in south-east Wales .
It rises in Powys near the Gospel Pass at the beginning of the Ewyas Valley, which it flows through to flow south to Llanvihangel Crucorney in Monmouthshire . It then changes direction to the northeast and flows into the River Monnow at the point of the border between Wales and England, where this river also suddenly changes direction. The only significant tributary of the Honddu is the Nant Bwch , although numerous smaller bodies of water flow into the Honddu from the steep walls of the Ewyas Valley.
Before the last ice age, the Honddu probably flowed further south after Llanvihangel Crucorney, but was then diverted by a large terminal moraine that stretches across the valley to the west of the village. The changes in direction of both the Honddu and the Monnow appear to be related to the Neath Disturbance , an ancient fault that runs through the valley north of Sugar Loaf in the Black Mountains, Wales, towards Hereford .
The upper river valley has the characteristic U-shape of a valley formed by a glacier. However, it is unclear where the ice that dug this deep rift through the eastern Black Mountains came from. The Honddu is not big enough to have created its own river valley. It has been suggested that glacier ice from the River Wye had entered the Ewyas Valley via the Gospel Pass; however, no marl boulder has yet been found in the valley that would support this thesis due to its origin in Mid Wales.
In the valley lies Llanthony Priory , a popular attraction for many visitors to the national park. At the bottom of the Ewyas Valley is Cwmyoy , famous for St Martin's Church , which is deformed by the slow movement of the slope on which it stands. The entire hamlet is built on an old landslide that is not completely inactive.
