Dutch style solution to be deployed on Somerset coast

Working on behalf of the Environment Agency, Team Van Oord will shortly commence work on an innovative scheme to provide improved protection from flooding to households, infrastructure and agricultural land adjacent to the West Somerset coast.

The village of Stolford and surrounding area – located on the Bristol Channel, just east of Hinkley Point – is currently protected from flooding by a shingle ridge that needs regular recharging (see pic above). This is viewed as unsustainable (in various respects) over the longer term, so a new approach will transfer the primary flood defence function to an existing earth bank further inland (see pic below).

However, the existing bank needs to be improved so that it can withstand 1:100 per year water levels and waves: it should remain intact under those storm conditions, and even then any wave ‘overtopping’ has to be of an acceptable level.

The £850k scheme at Stolford will see block revetments, as developed in the Netherlands, deployed instead of the conventional rock revetment approach.

Jaap Flikweert, Leading Professional Resilience with Team Van Oord partner Royal HaskoningDHV, said:

“The project team reviewed the initial standard rock revetment design and agreed there was a need to look at alternative solutions.

“We added ‘Dutch style’ block revetments to the shortlist, and developed outline designs of all options to meet the technical requirements.

“We compared these options on costs and environmental impacts and opportunities, and identified the Hillblock product as the preferred solution.”

The proposed solution was taken through the regular permitting processes and agreed by the Environment Agency, with funding then secured.

The project team then worked to overcome the practical challenges associated with delivering an innovative solution.

Jaap Flikweert continued:

“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 product development to optimise solutions.

“However, all of this knowledge and experience is difficult to access outside the Netherlands, due to the specific conditions there and the language barrier.

“This creates potential obstacles throughout the process including: translating design spread sheets and guidance; production facilities which are currently only available in the Netherlands; and variations in liability and insurance arrangements between the UK and the Netherlands.

“In addition, the project team has to be happy with any new product and installation method – and the client and ultimate asset manager need to be comfortable with the proposed solution.

“These challenges have been overcome at Stolford, which means the process will be much smoother when applied to future schemes.”

The project has also 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.

Jaap Flikweert concluded:

“The design confirmed block revetments as a more cost-effective option than a traditional rock revetment, even when the blocks are produced in, and transported from, the Netherlands – even if we had not secured the Partners for Water funding.

“This means there is a good chance that block revetments can be a competitive option for many other coastal defence projects in the UK and worldwide.”

The implementation of the Stolford scheme, including transport to site and placement of the blocks, will commence in early November and should be complete before the end of 2018.

Footnote:
Team Van Oord is a Joint Venture partnership between Van Oord, Kier, Mackley and Royal HaskoningDHV who between them have a combined turnover in excess of £5bn.

Team Van Oord has previously worked in this part of Somerset when delivering the award winning Cannington Flood Defence Scheme which was officially opened by the chair of the Environment Agency, Emma Boyd-Howard, in October 2017.