Flood risk and tidal procedure updates at Ilfracombe

Challenge

To assess tidal flood risk in Ilfracombe on the north Devon Coast. Flood risk was identified at four known hotspots along the northern coastline of Ilfracombe; Wilder Mouth Beach, Cheyne Beach, and the inner and outer harbour.

Solution

We used the latest modelling methodologies to simulate a range of model scenarios and extreme events to map flood risk at Ilfracombe.

Following the flooding that arose over the Winter of 2013/2014, the Environment Agency updated the National Flood Risk Assessment (NaFRA), known as ‘State of the Nation’ (SoN). This included an improved multi-variate probability analysis of offshore wave, wind and water level data. This newly available dataset was transformed to the “foot” of Ilfracombe coastal defences using a detailed wave model together with a wave model emulator. Using 500 events which represented the wider multi-variate sample, the wave model was run and the results used to train wave model emulators. The emulators were then used to rapidly transform the offshore conditions for the complete 10,000-year multi-variate dataset. The resulting nearshore data was then used to calculate wave overtopping of the coastal defences.

A newly constructed TUFLOW flood inundation model was then used to map flood risk from a series of scenarios including defended, undefended, breach and breakwater failure scenarios.

Benefits

The results from these simulations were used to provide a greater understanding of the flood risk to Ilfracombe, to update flood map components and to update the flood warning tidal procedures.

Contact us

For more information: Ian Gaskell – Skipton Marine and Coastal Risk Management Team



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