Hydro-Brake® Flood flow controls protect 200 homes and critical infrastructure in Cannington, Somerset.

Situation

Situated between the Quantock and Mendip hills, the village of Cannington sits beside the River Parrett in the Somerset Levels. 

As a low-lying coastal plain and wetland, the Somerset Levels are criss-crossed by rivers and brooks, which make the area particularly prone to flooding, and as climate change makes extreme weather events more intense and more frequent, the risk is increasing.

Problem

Cannington’s position in the Somerset Levels makes it particularly vulnerable to flood water—indeed, local archaeological evidence suggests that inhabitants were undertaking flood prevention projects as far back as the Roman occupation. 

A brook was built in 1984 to help alleviate flood flows, but in 2012 more than 40 homes were flooded on two separate occasions, so it became clear that the existing solution had become outdated. 

To mitigate future flood risks a £4.5M project was set up involving a range of local stakeholders including the Environment Agency, EDF Energy, Cannington Parish Council and Somerset Rivers Authority. 

With around 200 homes, the local A39 road and the nearby Hinkley Point power station—both critical infrastructure—at risk from disruption and damage, the team needed to identify an effective, efficient flood mitigation system.

Solution

The project required the construction of a flood alleviation channel to divert flood water away from Cannington, but this channel alone was insufficient—it needed something to control the flow in order to hold back flood waters and release them at a safe, manageable rate. 

The project team identified the Hydro-Brake® Flood precision flow control as the flood alleviation system that would best meet site requirements, as its precision hydraulic curve and flow control capacity enabled engineers to precisely design a high-volume flood mitigation solution. 

The team solved the challenge by using a network of culverts situated beneath the roadway, containing a series of three Hydro-Brake® Flood units. 

The Hydro-Brake® Flood units provide large-scale, watershed-level flood mitigation, and are capable of managing flows as high as 11,500 l/s and storing flood water in a designated flood storage area of up to 5,750 ha.

Outcome

Since installation the Hydro-Brake® Flood systems have successfully protected the village and the A39 road from flooding, having effectively diverted potentially damaging flood waters on ten separate occasions in just the six months following installation. 

Data provided by a Hydro-Logic® Flexi Logger smart monitoring system installed at the site similarly indicates that Hydro-Brake® Flood flow controls are operating continuously, allowing low flows to pass as normal while holding back water during periods of heavy rainfall. 

Councillor Anne Fraser, Sedgemoor District Council’s portfolio holder for economic growth said: 

I am delighted that this work has been completed. Not only will it save residents’ homes from potential future flooding but enable road users in the area to benefit from the scheme.

Quote courtesy of gov.uk.