Overlooking the Bristol Channel, Stolford has a history of coastal erosion and is prone to flooding. In 1981 high tides overtopped sea defences and flooded 660 hectares of land including 24 properties. Livestock also died. In 1990 a high tide and storms caused further flooding.
There are already coastal defences between Stolford and Hinkley comprising of rock armour and an embankment wall. These defences adjoin a shingle ridge that was prone to serious erosion. Rising sea levels and more extreme weather conditions have made the ridge and embankment increasingly vulnerable to erosion and increased the risk of a breach. Conventional rock armour, also known as rock revement, would have been too costly and visually intrusive. In addition, the transportation of rock armour would have caused excessive disturbance from heavy lorries travelling in narrow lanes to a remote coastal location.
It was decided the best solution was a Dutch system known as Hillblock, a type of block revetment, that uses a series of specially-shaped concrete blocks positioned on the seaward side of an embankment. Storm waves flow over the structure and enter a network of cavities between the blocks that absorb wave energy.Shaped like champagne corks, the blocks are made from high density concrete and held in place by steel piles and concrete kerbs. Although extremely heavy, each block is designed to move slightly, keeping the structure in place through friction.
The Hillblock system, that has been used extensively in Dutch coastal defences, has been optimised over recent years to maximise stability and minimise wave run-up. This means the height of revetments can be reduced compared to conventional systems, hence reducing the quantity of construction material, costs and eCO2.
The Stolford scheme will provide a higher standard of flood protection to 20 properties, the village access road and approximately 70 hectares of agricultural land. It is an example of international co-operation and shared learning in the development of new coastal defence solutions.
"The use of an innovative and proven Dutch system at Stolford has enabled us to deliver an economic alternative to rock armour at this remote location on the Somerset coastline. It’s a great example of partnership working made possible thanks to a contribution from the Dutch government through the ‘Partners for Water Scheme" said Nol Vincent, Environment Agency project manager.
Jaap Flikweert, Leading Professional Flood Resilience with Royal HaskoningDHV, part of Team Van Oord, said: block revetments are the default solution for protecting Dutch sea defences against storms as extreme as 1:10,000 per year. A €1bn improvement programme over the last 20 years has driven a lot of innovation: sharper design rules, better blocks, streamlined placement methods. We are opening up all this innovation to the UK, and Stolford is the first scheme to profit.
The Dutch government contributed £100,000 under the Partners for Water Scheme which supports the use of Dutch water management innovations worldwide with the aim of improving global resilience while supporting Dutch businesses.