The town of Clonmel, Ireland, suffered from continued flooding by the River Suir. Records show that the quays in the town flooded on average six out of every 10 years, having a severe impact on the town’s population, commerce and infrastructure. A steering group was formed to oversee the process of developing and implementing a flood relief plan that was economically viable and environmentally acceptable.
To manage the flood risk, hard-engineered defenses were provided to contain the floodwater within the river channel. The channel would require walls 2.8 m high. In order to mitigate the negative effects on the town and its residents of such high walls, it was decided to design for a removable wall on top of a permanent wall of standard 1.2 m along the river quays. This effectively meant that the river would be above street level during flood events, and installing non-return valves on the outfalls would form a key component of the design. The valves would prevent floodwaters from pushing upstream through road gullies, manhole covers, and back inlet gulley traps.
River outfalls can be notoriously problematic, being prone to accumulation of debris, silt and exposure to fast flowing waters. In this plan, it was important to ensure there would be no blockages during normal function and, conversely, reliable and total exclusion of water ingress during flood conditions.
With the assistance of MeasurIT Technologies, a UK and Ireland valve distributor, Tideflex® Check Valves were selected by the design team as the drainage valves for these conditions and six large rubber duckbill Tideflex® Check Valves were chosen for the outfalls.
Tideflex® Check Valves were chosen for another reason too. Because the river would flood while flowing under high volume and velocity, any valves exposed to the flow would need to be able to handle a large sideways force. With access to years of research and development by Tideflex® Technologies and other independent bodies, the design team saw that Tideflex Check Valves were up to the challenge. This was especially important as the valves needed to be mounted directly on the quay walls, sticking out into the river.
During a flood event in February 2014, the new system was put to the test. While this was not an extreme event, a manhole cover was lifted off by the force of floodwater rushing upstream from an unsealed outfall, resulting in a dramatic water “fountain” that caused significant damage to the road. Investigation discovered a previously unknown outfall buried in silt in the river. It had no functioning valve to prevent backflow. Once again, a Tideflex Check Valve was installed to prevent a repeat incident.
Over the 2015-2016 winter, Ireland was battered by severe storms and many areas experienced high river levels and severe flooding. Thankfully, the flood defenses of Clonmel performed admirably and it was business as usual for much of the time, even though at one point the water level rose higher than the old quay walls.
Red Valve Company and Tideflex® Technologies are exhibiting at WEFTEC.16, Booth 2639. For more information, visit www.redvalve.com.
