Flooding from the sea represents a major threat to the UK; this was demonstrated most recently during the winter of 2013/14, when widespread flooding and damage occurred around much of the coastline. Whilst major advances have helped us to better assess flood risk from our rivers, the complex nature of the coastal environment has proved to be more challenging. At the Flood and Coast Conference in February, the Environment Agency’s Tim Hunt will unveil the major leap forward in the science and understanding of coastal flood risk that the Environment Agency and HR Wallingford have developed over the past two years.
Tim explains: “We engaged HR Wallingford to develop the science and use it to improve our coastal flood risk data around the English coastline. This has been a huge effort over the last two years to produce a robust nearshore Monte Carlo dataset of all possible event combinations at the nearshore which can then be applied to coastal defences.
We have sourced data from the Met Office (Wave Watch III hindcast), Environment Agency (Coastal Flood Boundaries, surfzone bathymetry, tide gauge data, defence data), SeaZone (TruDepth offshore bathymetry), Cefas and Channel Coast Observatory (wave buoy data) to use in the analysis.
Twenty four SWAN 2D wave transformation models have been developed around England to transfer multivariate joint probability analysis from offshore through to nearshore before being further transformed to the defences. In constructing these models we were able to utilise wave buoy data to help us calibrate and sense check the results. This modelling gives us data at every 1 km interval around the coastline each with upwards of 400,000 possible event combinations for further analysis.
The demand for robust coastal flood information is only set to increase. National scale assessments are likely to be part of this as government demands the country wide story for present day and future risks. This will be a difficult balancing act not least because of the complexities and uncertainties already described and the need for sound engineering judgement and evidenced decisions that are needed at each location.”