Impacts of climate change on coastal flooding
Bill Donovan, Kevin Horsburgh, Tom Ball and Guy Westbrook
Donovan, B., Horsburgh, K., Ball, T. and Westbrook, G. (2013) Impacts of climate change on coastal flooding, MCCIP Science Review 2013, 211-218, doi:10.14465/2013.arc22.211-218
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As we reported in 2010/11, extreme coastal water levels and hence the increasing likelihood of coastal flooding in the future are likely to be dominated by climate driven changes to the mean sea level, rather than waves or storm surges. There is a great deal of uncertainty surrounding the magnitude of changes in mean sea level and wind waves (thus extreme events), but not the direction of change for mean sea level. This will increase the likelihood of coastal flooding. Without adaptation this will lead to significant losses to economic, social and environmental assets by the end of this century and beyond. Since sea-level rise is committed to continue beyond 2100, even with immediate stabilisation of greenhouse gas emissions, then policy and adaptation measures require a strategy over a much longer period.
The number of residential properties at significant risk of coastal flooding now is 115,300. This could rise to between 345,000 and 470,000 depending on climate change with no change to population size and location, by the 2080s. Considering population growth too, the number of residential properties at significant risk could be up to 910,000 by the 2080s.
Over the past century, natural variations in storm frequency and magnitude over 10-20 year cycles have been an important climatic factor driving coastal flood risk. In addition the roughly 14 cm rise in mean sea level during the 20th century has significantly increased (as much as doubled) the risk of flooding since 1901 at many locations around the UK coastline.
Development in the floodplain has continued over the last ten years. While the majority (87%) of all new development in England occurs outside the floodplain, the rate of development in the floodplain between 2001 and 2011 was higher (12%) than outside the floodplain (7%). Since 2008, there has been a decline in this rate,
The decline in the rate has been more rapid in the coastal floodplain than in that of rivers, although it still remains above the national average (0.8% per year versus 0.6% per year); and
There has been a noticeable decrease in the rate of development behind eroding coastlines, which is now well below the national average.