Cockermouth passive flood defense system

A key section of an Environment Agency (EA) and local authority partnership funded flood defence scheme has been completed in Cockermouth, Cumbria. The scheme encompassed a number of flood protection solutions to protect homes and businesses from flooding.

Passive flood defense in Cockermouth
Passive flood defense in Cockermouth

UK Flood Barriers (UKFB) were asked by the Environment Agency to provide a self-closing flood barrier (SCFB™) for a key section of the scheme along Rubby Banks Road, so that the amenity value of the river was not lost to local residents.

Cockermouth has been victim to some of the most severe flooding events in recent history. Most memorably in 2009 when the Rivers Derwent and Cocker both broke their banks after a record 314mm (12.3 inches) of rainwater fell in just 24 hours. Water levels subsequently rose 2.5 metres and river flow reached 10 m/s, resulting in total damages of £276.5 million, with £129m of this to businesses and the local economy.

The severity of these floods was unprecedented. Although estimated to be a one-in-450-year occurrence, the Environment Agency were looking for the most efficient, cost effective and sustainable solution to provide protection for a 'one-in-100-year event'.

No people – no power – zero operational costs

In operational use globally since 1998, the SCFB™ utilises the rising floodwaters to automatically raise the barrier -effectively using the problem to create the solution.

Rapid onset flooding usually causes the greatest damage. This is due to the lack of time to deploy the more traditional type of manually operated flood gates and 'demountable' systems, typically stored off site and requiring human intervention. The SCFB™ has the advantage of not requiring any intervention during a flood warning, which would otherwise put lives at risk.

As the SCFB™ has no operational costs, it has none of the high on-going expenditure associated with manually operated systems. When not in use the barrier is protected underground and its seals are sheltered from the elements.

The challenge

The area situated by the River Cocker is designated as a site of special scientific interest (SSSI). The Environment Agency and local residents were looking for not only a cost effective solution, but also one that would not adversely affect the unique landscape. Cockermouth holds much heritage value as a beautiful market town and it was vital to the scheme that this was maintained.

The SCFB™ provided a solution which would have little or no aesthetic impact on the surrounding environment. Installed beneath the ground the barrier only deploys when there is a threat of flooding. The river views so important to both residents and tourists would remain unaffected, whilst effective flood protection would be in place ready to deploy 24 hours a day.

The solution

The SCFB™ from the self-closing flood barrier range was installed by UK Flood Barriers, in conjunction with Volker Stevin for the Environment Agency.

Working in conjunction with the existing flood wall, the SCFB™ was tailor-made to meet the exacting requirements of the project. The barrier was implemented along 115 linear metres of the riverbank and designed to rise in one singular continuous motion. On deployment the SCFB™ rises to 1 metre, providing the required one-in-100-year protection above the existing wall.

Reducing risk

At the Environment Agency's request, a telemetry system has been fitted to the barrier to advise when it starts to deploy and when it has fully deployed. This system automatically sends texts or emails to managers when the SCFB™ activates. It can also be linked to warning beacons, audible warnings and even CCTV.

UKFB are providing the EA with a full 15 year maintenance contract to bring peace of mind that all costs are fixed for 15 years.

Following the second wettest year on record, the Government is now embracing passive innovations that will help protect communities.

The SCFB™ acts as a core element to the overall £4.4m flood defence scheme in Cockermouth, which will use a series of embankments, walls and gates to lessen the flood risk to 360 homes and 55 businesses. Once the scheme is completed it will reduce the risk of flooding to the town to a 1% chance in any one year.

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