Three Arch Viaduct of former Merthyr, Tredegar and Abergavenny Railway is a Grade II listed building in the Brecon Beacons National Park local planning authority area, Wales. First listed on 27 July 2000. Viaduct.

Three Arch Viaduct of former Merthyr, Tredegar and Abergavenny Railway

WRENN ID
half-string-grain
Grade
II
Local Planning Authority
Brecon Beacons National Park
Constituency
Monmouthshire MP: Catherine Fookes (Lab)
Country
Wales
Date first listed
27 July 2000
Type
Viaduct
Address
Three Arch Viaduct of former Merthyr, Tredegar and Abergavenny Railway, Clydach, Llanelly, Monmouthshire
OS grid reference
SO 225 125
Coordinates
51.8059, -3.12469
Source
Cadw listing

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

Description

The Three Arch Viaduct is a structure from the former Merthyr, Tredegar and Abergavenny Railway. It spans a steep and narrow river gorge, with side abutments rising from the steep sides of the ravine. The viaduct is built of rock-faced limestone, featuring stone voussoirs that form the round arches. It has a rock-faced stringcourse and rock-faced copings on a low parapet.

Local climate

Three Arch Viaduct of former Merthyr, Tredegar and Abergavenny Railway sits in a wetter-than-average part of the UK, with an average of 1,040 mm of rain a year. This makes it wetter than 83% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 75% of listed buildings.

It experiences an average of 48 freeze-thaw cycles a year, more than 89% of listed buildings. Of these, 24 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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