The long term evolution of flood risk in a coastal area due to (a) Sea level rise and (b) Population rise is assessed. Historic maps and population data are used to estimate the spatial distribution of the coastal population through time, and extrapolated sea levels are used as a boundary condition in a hydrodynamic flood model to estimate the historic flood exten

Clarke, D.

Stevens, A.

Wadey, Matthew P.

English

Southampton (e-Prints Soton)

Geophysical Research AbstractsVol. 16, EGU2014-13348, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Estimating the Evolution of Flood Risk to Coastal PopulationsAndrew Stevens (1), Derek Clarke (1), and Matthew Wadey (2)(1) Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom(andy.stevens@soton.ac.uk), (2) Faculty of Engineering and the Environment, University of Southampton, Southampton,United Kingdom (d.clarke@soton.ac.uk), (3) Ocean and Earth Science, National Oceanography Centre, University ofSouthampton, Southampton, United Kingdom (m.p.wadey@soton.ac.uk)The long term evolution of ﬂood risk in a coastal area due to (a) Sea level rise and (b) Population rise is assessed.Historic maps and population data are used to estimate the spatial distribution of the coastal population throughtime, and extrapolated sea levels are used as a boundary condition in a hydrodynamic ﬂood model to estimatethe historic ﬂood extent. The population exposed to ﬂooding is then estimated for each time step. Uncertainty isaddressed by comparing results for different population spreading techniques and rates of sea level change. Theevolution of ﬂood risk over a period of over 200 years (1801 to 2011) is assessed.This work identiﬁes a fundamental gap in (1) the assessment of exposure of coastal populations to ﬂood-ing, and (2) the assessment of how this exposure can develop over time. This has implications for the currentassessment of coastal ﬂood events, and also for future planning decisions.The technique developed is applied to a case study of Portsmouth on the UK’s south coast. Flood risk inthe case study area is seen to have increased dramatically over the last 200 years, mostly as a result of populationrise. Climatic changes have also increased exposure, with signiﬁcantly less population exposed to coastal ﬂoodingwhen changes in sea level are accounted for. This result shows that for long term (100+ year) studies even modestchanges in sea level can have signiﬁcant impacts on the extent of the coastal ﬂoodplain.

Estimating the evolution of flood risk to coastal populations

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