Cyngor Gwynedd flood prevention project reveals urban history

A £675,000 project that will protect dozens of homes and businesses in Caernarfon from flooding has revealed a piece of local history hidden beneath the town's busy streets. 

Most people may not be aware that the river Cadnant flows under their feet as they walk around the shops, cafés and pubs of Caernarfon. And in carrying out the work, Cyngor Gwynedd's engineers have been able to see the river's underground path which has been hidden for generations.   

“Although the Cadnant is a small river, it has influenced the development of the town of Caernarfon for centuries,” explained Emyr Gareth, Chief Engineer at Cyngor Gwynedd. “We have been working on a project that will protect 80 homes and 39 business properties from flooding which has been jointly funded by the Welsh Government and Cyngor Gwynedd.  

“We have installed a new screen that prevents rubbish and debris from entering the river Cadnant channel. Should the river channel become blocked under the town’s streets, it could cause flooding and major problems for the local community.” 

As part of the specialist engineering work, a drone was sent to follow the underground river course for 900 metres, revealing for the first time in generations what is going on beneath our feet. For many, until today, street names would be the only clue to what has been hidden but now the footage taken by the drone can be seen on the Council's website. 

Here is some of the history of the river Cadnant, as it winds its way towards the Menai Straits: 

• The river Cadnant disappears underground near the roundabout between Ffordd Llanberis, Ffordd Bethel and Tanrallt. This is where the new rubbish screen has been installed as part of the flood prevention project. 
• The river flows through a series of hidden culverts beneath the town. In Victorian times, the culvert was enlarged. 
• The Penllyn area (where the multi-storey car park stands today) is key. For about 800 years, there was a small lake here. This, of course, is the root of names such as Penllyn and Stryd y Llyn (Pool Street). The last section of this culvert was built in 1996-97. 
• The culvert consists of a number of unique pieces due to its age and the nature of its construction. 
• The lake emptied through bridge arches, turning a water mill further down its path. These features are reflected in street names such as Ffordd y Felin (Mill Lane) and Bont Bridd (Bridge Street). 
• The drone video shows the river dropping approximately 4 metres, under Bont Bridd near Canolfan Penllyn. 
• In 1868, the river Cadnant was channelled into a ditch at Victoria Dock by the Caernarfon Harbour Trust. To this day, the river flows out into the Menai Straits in the Dock area and when the tide allows, bubbles can be seen rising to the surface near the Records Office building.  

  Councillor June Jones, Cyngor Gwynedd's Cabinet Member for the Highways, Engineering and YGC Department, said: 

“Over the years, Caernarfon's infrastructure has been shaped by the river. Our priority today is of course to protect the town's homes and businesses from flooding and I'm delighted that we've been able to work with the Welsh Government and invest in this project for the benefit of the local community. 

“The video taken as part of the engineering work is extremely interesting and I'm sure people will be interested to learn about the river. Who would have thought that a contemporary project and the use of modern technology would have helped us to connect with the history of the town of Caernarfon.” 

Welsh Government Deputy First Minister with responsibility for Climate Change, Huw Irranca-Davies, said: “Our investment in this scheme, of nearly £590,000, will deliver long-term benefits to over 119 properties in the area – and is yet another example of our unwavering commitment to address the challenges we face from climate change.

“In recent years, we have invested more than £377 million to protect communities across Wales from increasingly unpredictable and extreme weather, with this year’s record funding rising to £85 million.”

Follow the link to watch the video: The hidden river beneath Caernarfon