Bioblocks for coastal sea defence
Business: RPC Contracts (Conwy)
Individual Assist: Louise Firth
SEACAMS contact: Jasmine Sharp
There are currently a number of coastal defence developments in North and mid-Wales. These developments utilise the standard types of coastal defence structure which usually consist of quarried boulders laid out in revetments or as concrete sea walls. Whilst the boulders are functional, and often designed to be aesthetically pleasing, they do not positively contribute to increasing biodiversity in the marine environment. The marine environment is often changed or damaged during the building phase of the development, and will be affected by the erection of defence structures.
As part of the THESEUS project (Innovative technologies for safer European coasts in a changing climate), Dr Louise Firth from Bangor University (now National University of Ireland, Galway) has designed an experimental block that could be incorporated into ongoing coastal engineering projects either as part of a wall design, or as part of a revetment structure. The purpose of the Bioblock is to provide additional suitable habitats within a sea wall or revetment structure to increase the biodiversity of the shoreline. The Bioblock is designed to contain rock-pool type environments, sheltered shelves and pockets which provide a stable habitat. RPC Contracts, a concrete manufacturer, were interested in investigating producing Dr Firth’s design for a prototype block.
RPC Contracts Ltd
RPC is a Conwy based manufacturer and installer of concrete products for the construction, civil engineering and environmental industries. RPC are providers of both ‘off the shelf’ systems, including precast concrete revetments used around Europe in both coastal embankments and inland waterways, and bespoke engineering solutions.
RPC Contracts Ltd and Dr Firth collaborated with SEACAMS to produce a mould and build a prototype Bioblock for deployment in an existing or new development.
The SEACAMS workshop constructed a prototype mould for a small number of castings of a concrete block for testing in a coastal embankment. Input for the block design was provided by Dr Firth, RPC Contracts and SEACAMS, based on the requirements for the habitat production, concrete constraints and constraints of mould build and casting. The mould was used to cast a prototype Bioblock at the RPC Contracts base in Conwy. Once cured, the block was shot blasted to expose a more suitable surface texture for sympathetic weathering. The Bioblock is a cuboid construction with dimensions 1.5 x 1.5 x 1 m and modifications on 5 sides. The block includes pools of variable depths on the upper surface, multiple depth holes on 2 opposing vertical surfaces and horizontal grooves on the remaining surfaces.
Colwyn Bay Development
The Colwyn Bay Waterfront Project is envisaged to bring together protective coastal defence works and environmental improvements to the promenade of Colwyn Bay. The on-site coastal protection work in Colwyn Bay began in January 2011, consisting of rock structures to protect the existing sea wall defence and additional walls to increase the level of protection. The development includes the addition of a rock groyne and rock revetment to the existing structure, installation of precast concrete wave walls to the seaward edge of the new, and redeveloped areas of the promenade. The rock groyne and revetment absorb the energy from the breaking waves to protect the sea walls. Conwy Council have kindly agreed to allow a trial and testing of the Bioblock in the Colwyn Bay Development.
The first Bioblock prototype was delivered to the VolkerStevin construction site in early February 2012 and placed in the Colwyn Bay Waterfront Project development on 14th February 2012. The block is located on the main groyne of the development in the intertidal zone. The block is expected to weather with the remainder of the revetment within a few weeks, and will be monitored for plant and animal colonisation. It is expected that rock-pool type habitats will form in the near-future. The Bioblock is now being monitored for plant and animal colonisation by Dr Firth and the SEACAMS team.
If successful, it is envisaged that this design could be used as a basis for building more blocks to be rolled out in future coastal defence developments and that the features of the design would become a gold standard for coastal defence development design in future.