Eigiau Valley Gravel Road – Eigiau Dam Ruins loop from Tal-y-Cafn
Eigiau Valley Gravel Road – Eigiau Dam Ruins loop from Tal-y-Cafn
5
riders
Eigiau Valley Gravel Road – Eigiau Dam Ruins loop from Tal-y-Cafn
03:03
36.7km
760m
Mountain biking
Moderate mountain bike ride. Good fitness required. Suitable for all skill levels. The starting point of the route is accessible with public transport.
Last updated: May 21, 2026
Tips
Your route passes through protected areas
Please check local regulations for:
Waypoints
Start point
Train Station
Get Directions
494 m
Coed Siambr Groes
Forest
10.8 km
Eigiau Valley Gravel Road
Highlight (Segment) • Trail
Tip by
12.4 km
Eigiau Dam Ruins
Highlight • Structure
On 2 November 1925 the failure of two dams caused a flood that swamped the village of Dolgarrog, killing 16 people. The disaster was started by the failure of the Eigiau Dam, a gravity dam owned by the Aluminium Corporation. The water released from the reservoir flooded downstream,[10] and overtopped the Coedty Dam, an embankment dam. This dam also subsequently failed, releasing the huge volume of water that flooded Dolgarrog.[11] Many more villagers could have been killed had they not been in the local theatre watching a film that night.
The disaster at Dolgarrog led the British parliament to pass the Reservoirs (Safety Provisions) Act in 1930, which introduced laws on the safety of reservoirs. This has since been updated, and the current one is the Reservoirs Act, 1975.
Tip by
12.4 km
Eigiau to Coedty Bridleway
Highlight (Segment) • Trail
Tip by
18.2 km
Coed Dolgarrog
Nature Reserve
19.5 km
View of Snowdonia
Highlight • Viewpoint
Tip by
22.0 km
Brwynog
Ruins
23.9 km
Navni's Rock
Viewpoint
24.6 km
View of Llanrwst and Llyn Geirionydd
Highlight • Viewpoint
30.8 km
Dolgarrog Dam Disaster Memorial
Highlight • Monument
Dolgarrog, Wales
The worst flood disaster in Welsh history might have been a lot worse if it had not happened on movie night.
LLYN EIGIAU, A LAKE AT the edge of the Carneddau mountains in Snowdonia, Wales, was the origin of the worst dam disaster in Welsh history. The devastating flood of 1925 is commemorated by a plaque placed on the massive boulders that came to rest after destroying much of the village of Dolgarrog.
In 1911, a dam three-quarters of a mile long and 35 feet high was built across part of the eastern side of the lake to supply water for the hydroelectric power station in the village and power the aluminum works next to the station. A new tramway was constructed to bring materials for the dam from Dolgarrog.
It is reported that the original contractor withdrew from the project, unhappy that corners were being cut in the construction of the dam. And indeed, his misgivings were realized. In November, 1925, after 26 inches of rain fell in just five days, the Eigiau dam failed. The water flowed down to Coedty Reservoir, which rapidly caused its earth bank dam to burst as well and release billions of gallons of water.
The torrent of water, estimated at over 70 billion gallons, flowed down into the village of Dolgarrog, creating massive damage and leading to the loss of 16 lives. The death toll could have been worse, but it was fortunate that the breach occurred on the night when the local community hall was used as a cinema. The hall was on slightly higher ground, and many of the town residents were safe inside.
The force of water carried some massive boulders (some as heavy as 200 tonnes) down to into the village, which was destroyed by the flood. Gwilym Wyn Roberts, whose mother survived the flood, told the BBC that “Cows were seen hanging from the trees and the aluminum works were submerged under 5 feet of mud.”
These boulders are now marked with a memorial plaque, and the village has been rebuilt away from the devastated area. The remains of the dam are easily accessible on foot from a parking lot about half a mile away from the breached dam wall.
A close look at the remains of the Eigiau dam today reveals that the foundations were insufficient, and close observation reveals large lumps of unmixed concrete. The dam material that can be seen through existing holes tends to break away easily and is clearly badly graded. After the disaster, an additional breach was created in the dam to ensure that water could not build up to dangerous levels. A Parliamentary investigation led to more stringent rules on British dam construction, as part of the Reservoirs (Safety Provisions) Act in 1930.
Today the lake covers an area of about 120 acres (about half the impounded area when the dam was in use) and is only about 32 foot deep. This memorial commemorates the victims of the dam disaster in Dolgarrog on the dark and stormy night of 2 November 1925.
Tip by
36.7 km
End point
Train Station
Way Types & Surfaces
Way Types
21.7 km
14.0 km
846 m
101 m
Surfaces
14.1 km
11.1 km
10.9 km
353 m
207 m
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Elevation
Highest point (430 m)
Lowest point (0 m)
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Weather
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Sunday 5 July
24°C
16°C
0 %
Additional weather tips
Max wind speed: 18.0 km/h
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Our route recommendations are based on thousands of hikes, rides, and runs completed by other people on komoot.
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