Impact case study database

Informing beach management and flood risk assessment

Gravel beaches are widespread around the world and provide sustainable natural coastal defence for approximately 1/3^rd of the beach-fronted coast in the UK. In 2014, CPRG’s research directly led to the development of a numerical model, XBeach-G, that predicts the impact of storms on gravel beaches. XBeach-G is used widely nationally and internationally by coastal managers, engineers and consultants to safeguard the resilience of coastal communities and infrastructure (5.1).

In the UK, the EA has used XBeach-G to assess coastal vulnerability to sea-level rise and extreme storms along the south coast of England (5.2 and 5.3). As highlighted by EA’s senior coastal specialist, “development of XBeach-G has had a very positive impact on improving understanding within our coastal projects” (5.2). For example, at Chiswell beach, Dorset, the model “ influenced existing incident management procedures and understanding” by improving existing EA operational criteria for flood alerts and beach profiling strategy and helped to “programme future modelling improvements and upgrading of existing forecast systems within the EA” (5.3) . The EA now widely promotes the use of XBeach-G to assess coastal flood risk across the UK, and “ has actively encouraged external consultants to utilise the open-sourced XBeach-G model for additional work, e.g. Herrington Consulting used it for flood risk assessments at Medmerry and Climping” (5.2), a £28 million project which directly resulted in flood defences being moved inland, creating 183 hectare new intertidal habitat on the seaward side whilst also providing 1000 times flood protection than the previous system. At Dungeness Nuclear Power Station, XBeach-G was used to assess coastal flood risk, providing the managers of the power plant the information to make substantial cost efficiencies at this critical coastal infrastructure, where the results, “will ensure the defences are not over- or under-engineered to cope with a 0.5% annual probability event” (2016, Dungeness Report in 5.1). XBeach-G has been utilised globally to assess coastal vulnerability to extreme storm events, including in Croatia, the Netherlands, Spain, and the US. In New Zealand, XBeach-G was used in the Hawkes Bay Coastal Hazard Inundation Assessment, where the model directly “ forms the basis of inundation mapping” (5.1) used to safeguard coastal communities against flooding.

CPRG’s >10 years of beach monitoring data and coastal research has contributed to the management of several beaches in SW England. CPRG influenced coastal management at Slapton Sands beach (South Devon) by contributing a detailed examination of coastal processes to the Beach Management Plan. Subsequently the Beach Management Plan was used by the local council to seek EA funding for coastal defence works, including allowing them “to secure funding of £2m in 2018, to repair damage to the vital link road along the barrier” (5.4). Another coastal processes consultancy undertaken by CPRG was an Environmental Impact Assessment for Network Rail in 2019 that contributed to the design of major rail infrastructure works costed at £500m at Teignmouth Beach, by determining the likelihood of the beach fronting the rail line being lost as a result of the works (5.5). At Westward Ho! CPRG’s assessment of the gravel barrier dynamics has been deployed by the local council to produce revised plans for a proposed visitor centre at the site. It has provided Natural England with the evidence to “advance the understanding of this feature and what likely change will happen in future epochs” (5.6). CPRG consultancy work for the Scottish Environment Protection Agency (SEPA) helped them make a business case and undertake work to update coastal flood maps around the entirety of Scotland “to include flooding due to waves where our coastal maps previously only considered still water flooding, underestimating flood risk to many coastal communities” (5.7).

Safeguarding coastal communities through coastal flooding alerts

In 2017, CPRG co-created a coastal flooding early-warning-system, OWWL, with EA and Met Office. The system provides alerts for 213 locations in SW England and south Wales and for the first time provides the EA with accurate forecasts of wave runup and overtopping along these coasts, which are received daily by 25 EA and Natural Resources Wales flood response officers. The alerts have enhanced the EA’s capacity to respond to storm events in SW England, influencing decisions on how to “ prioritise where and when to deploy staff for reconnaissance and defence activities during storms”, such as where to place critical flood-defence infrastructure such as “ sandbagging, or deployment of temporary sea defences” (5.8). This specific understanding of where and when overtopping is happening was not previously available, and formerly the EA “ would have had a much wider response, a more reactionary response, or perhaps even not have responded at some of the key locations for wave overtopping” (5.8). Nick Ely, EA’s National Coastal Modelling and Forecasting Manager anticipates that this improvement in resource targeting “ will have saved the EA thousands of pounds during each of the six largest storms over the last two winters by being able to be more targeted in our working and reducing unnecessary trips and deployments”.

The SWEEP-OWWL model is directly used to inform EA’s flood warning team in the SW of England to help them consider potential flooding impacts of extreme wave and water level events on coastal communities. For example, when the remnants of Hurricane Epsilon (2020) reached the coast of Cornwall, the EA flood warning systems did not raise any flags as the predicted water levels were modest; however, the SWEEP-OWWL model, which also considers wave-driven runup, did flag up several potential flooding occurrence that subsequently took place e.g. Perranporth. As a result, the flood warning team in Cornwall used SWEEP-OWWL as “ an obvious complimentary layer of information to our forecasting system, with locally tailored wave overtopping forecasts available for specific defence”’(5.10).

CPRG has directly influenced coastal forecasting strategy at the EA, with data from OWWL feeding into a national-level strategic review of coastal forecasting in 2019. OWWL has provided EA with a regional pilot system which the EA consider “ an exemplar demonstration of the sort of coastal forecasting that could be achieved around the whole of the UK”(5.8)..

Influencing planning policy regarding future coastal change

CPRG has worked with Natural England (NE) and local coastal authorities in SW England to help develop Coastal Change Management Areas (CCMAs; 5.9), now required by the National Planning and Policy Framework (NPPF), to define locations likely to experience significant coastal change in the next 100 years – correctly and robustly identifying such regions is fundamental to sustainable coastal management. For example, A CCMA developed by CPRG in 2020 at Sidmouth, Dorset, has increased understanding within local planning authorities (LPAs) of the magnitude of coastal change happening, for the first time identifying that hundreds of houses there could be at risk of coastal erosion in the next 100 years. The CCMAs developed by CPRG (2020) are being directly used as evidence by LPAs in coastal planning applications to help decide where property and infrastructure can be built at the coast. Furthermore, the method developed provides a blueprint for national scale CCMA development, supporting the work of NE’s Lead Advisor for Planning Policy as it “has provided the confidence for us to have more informed CCMA conversations with our stakeholders across the south west as well as on a wider, national platform” (5.9).