Cwm Clydach Dam (partly in Blaenhonddan community) is a Grade II listed building in the Neath Port Talbot local planning authority area, Wales. First listed on 26 November 2003. Dam.

Cwm Clydach Dam (partly in Blaenhonddan community)

WRENN ID
waning-panel-gilt
Grade
II
Local Planning Authority
Neath Port Talbot
Constituency
Neath and Swansea East MP: Carolyn Harris (Lab)
Country
Wales
Date first listed
26 November 2003
Type
Dam
Address
Cwm Clydach Dam (partly in Blaenhonddan community), Neath Abbey, Dyffryn Clydach
OS grid reference
SS 739 987
Coordinates
51.67347, -3.82497
Source
Cadw listing

Also on this page: flood risk · radon risk · weather exposure · detailed attributes ↓

Description

Cwm Clydach Dam is a notable structure featuring a high wall made of Pennant sandstone, which has a battered lower face. At the western end, the dam includes buttresses positioned between twin outlets that lead from vertical cast-iron tubes, one of which is equipped with cast-iron paddle gearing on the north side. Above these outlets, there are four overflow outlets, each supported by cast-iron stop-plank supports. The dam also serves as a minor roadway, which is bordered on the eastern side by rubble stone walls, 20th-century railings, additional 20th-century rubble stone walls, and concreted walls at the western end. The reservoir behind the dam is heavily silted, nearly reaching road level.

Local climate

Cwm Clydach Dam (partly in Blaenhonddan community) sits in one of the wettest parts of the UK, with an average of 1,380 mm of rain a year. This makes it wetter than 97% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 96% of listed buildings.

It experiences an average of 28 freeze-thaw cycles a year, fewer than 69% of listed buildings. Of these, 12 follow at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.3°C per decade since 1991.

Averages for 1991–2020; temperature trend 1991–2025. Figures describe the wider area (a grid cell of roughly 10 km), not the individual site. Contains modified Copernicus Climate Change Service information 2026.

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Nearby listed buildings

  1. Cwm Clydach Dam (partly in Dyffryn Clydach community) Grade II 5 m
  2. Former forge and rolling mill at Neath Abbey Ironworks Grade II 720 m
  3. Forge tramroad bridge at Neath Abbey Ironworks (partly in Dyffryn Clydach community) Grade II 814 m
  4. Forge tramroad bridge at Neath Abbey Ironworks (partly in Blaenhonddan community) Grade II 820 m
  5. Neath Abbey Railway Viaduct (partly in Dyffryn Clydach community) Grade II 929 m
  6. Neath Abbey Railway Viaduct (partly in Blaenhonddan community) Grade II 936 m
  7. Former icehouse to Dyffryn House Grade II 982 m
  8. No. 1 Blast Furnace at former Neath Abbey Ironworks Grade II* 987 m
  9. The Grange, former stables and coach house to Dyffryn House Grade II 1.0 km
  10. No. 2 Blast Furnace at former Neath Abbey Ironworks Grade II* 1.0 km