The Challenge:

To provide improved protection from flooding to households, infrastructure and agricultural land and deliver this within tight cost constraints was a very real challenge the team from Kier as part of Team Van Oord and their Dutch based designers RHDHV, faced at Stolford beach in Somerset.

Existing flood protection for the village of Stolford, located within the Severn Estuary Ramsar, SPA and Special Area of Conservation (SAC), was a shingle ridge on the beach that needed regular recharging. This was viewed as unsustainable by the Environment Agency over the longer term, so an innovative new approach was agreed to transfer the primary flood defence function to an existing earth bank further inland. The existing bank required building up to withstand 1 in a 100-year water levels.

The Solution:

Given the cost constraints at Stolford, various options were assessed. Traditional flood protection methods e.g. Rock revetment and wave recurve walls proved too costly both financially and environmentally, meaning a new design was required. Using their extensive knowledge, Kier and RHDHV identified an innovative Dutch block flood protection system called Hillblock as the most cost-effective option that used less CO2.

The project received some funding from the Dutch Government’s ‘Partners for Water’ programme, which supports the use of Dutch water management innovations worldwide, with the aim of improving global resilience while supporting Dutch businesses.

This was the first time Hillblock had been used in the UK. The Hillblock system produces significantly greater wave abatement and up to 50% less wave run-up than existing bank and shore protection. The use of the Hillblock meant that revetments required less heightening.

The development of the Hillblock represents a new standard in coastal protection providing stronger revetments at lower cost.

The Impact:

Hillblock’s shape and mass make it more stable, better for the environment and easier to install. Due to the nature of Hillblock it required less lorries on the roads to deliver it to the Stolford site. It could be installed quickly at a rate of up to 250m2 per day using a special grabber to install 20 blocks at a time. This was significant when compared to other options of delivering large volumes of rock in many large truck loads via small villages and narrow roads to the beach to achieve a similar effect. This reduced the disruption to residents in the area along with reducing environmental impact.

Due to its design the hollow spaces of the blocks provide living space for flora and fauna, both above and below water. This will allow for habitats to develop over the coming years by the waterline adding to the area’s many features of outstanding natural beauty.

" Block revetments are the default solution in the Netherlands for protecting sea banks against waves. Hundreds of millions of Euros have been spent on levee improvements since 1998, and millions more on research and development to optimise solutions. However, all this knowledge and experience is difficult to access outside the Netherlands, due to the specific conditions there and the language barrier. "
Jaap Flikweert Leading Professional Resilience with Team Van Oord

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