Why is the rock revetment needed?
The existing coastal defences, which opened in 2017, have not performed as the designers expected. In a localised area, movement and damage to the revetment structure has occurred.
To address this, large rocks will be added to the existing revetment. This will add weight to stabilise the structure and protect it from further damage.
The rock revetment will also absorb wave energy more effectively than the existing smooth concrete slope, providing better flood protection. In 2018 (after the existing defences were designed and built), updated climate change projections for the UK were published indicating that future sea levels will rise more than previously predicted.
Though the existing sea wall height does not need to rise, action is needed to address the growing flood risk. Rising sea levels and larger waves could breach the existing defences without additional measures.
Why are the groynes needed?
A healthy beach is the first line of defence against coastal flooding and erosion. Although Blackpool's beach levels naturally fluctuate throughout the year, there is a long-term trend of erosion and beach lowering.
The underlying clay on Anchorsholme beach has at times become exposed. When this erodes the beach is lost permanently. Intervention is needed to stabilise the beach and maintain its protective function.
Rock groynes will trap sand and raise beach levels. This will help absorb some wave energy and reduce the size of the waves that reach the revetment during storms, lowering the risk of flooding.
A higher and more stable beach will also enhance public use and the addition of rocks will create habitats, boosting biodiversity.
Rock groynes have been effective along the coast at Rossall to the north. There are also plans to implement them in the southern areas of Blackpool.
Diagram of the rock revetment
Rossall Coastal Defence Scheme
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