East Rhyl Coastal Flood Defence Scheme
One of the largest coastal defence schemes in Wales, supported by expertise from across JBA, and underpinned by innovations in design development to improve adaptability and long-term resilience.
The deterioration of existing coastal flood defences in East Rhyl led to them being overtopped in 2013, causing significant damage and disruption to residential and commercial properties. The improved coastal defence scheme aims to provide protection to more than 470 of these properties over the next 100 years.
- Client Denbighshire County Council,
- Location Rhyl, North Wales
Innovative coastal defence design to provide long-term resilience and adaptability to the future challenges of climate change
Forming part of the Welsh Government's Coastal Risk Management Programme, the East Rhyl Flood Defence Scheme aims to prevent coastal flood events and improve the standard of protection to 472 properties in the area, whilst also taking into account the future impacts of climate change.
By undertaking the detailed design, numerical and physical modelling, environmental consenting and business case development of the £30m scheme, we were able to propose a series of defence improvements. Key to these improvements was providing a resilient response to the effects of climate change and also including inbuilt adaptability allowing defences to be extended or modified in the future.
Through the appraisal and concept design phases we were able to identify that the performance standards of the existing defences had been exceeded and that the best way of addressing this would be the construction of a rock armour revetment and new sea wall, designed to absorb wave energy during storm events.
These designs also included the creation of rock revetments, access for pedestrians and vehicles, flood storage areas, surface water drainage and drainage outlets, as well as a new raised promenade - making this one of the largest coastal defence schemes in Wales. By making use of our coastal modelling expertise we were also able to demonstrate the effectiveness of theses designs through the creation of a 3D model and adoption of Multi Variate Approach to derive design conditions.
We were able to make significant savings in physical modelling costs by working with the Queensland Government Hydraulics Laboratory, supervised by our colleagues at JBPacific.
Design development - an industry leading approach
The East Rhyl Coastal Defence Scheme was designed using the Multi Variate Approach (MVA) to the definition of the ‘design storm event’. This approach is a method of analysing data that takes into account multiple variables and in this instance involved processing the data to identify independent storm events, calculating the dependence between variables, and extending the analysis to 10,000 years’ worth of synthetic data. As a result, this process creates over 1,500,000 storm events which can then be used to better understand the relationship between different variables and how they affect each other. By making use of this innovative approach alongside EurOtop2 overtopping calculations we were able to consider thousands of defence configurations, providing a solution that was truly optimised for both cost and carbon.
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