Articles | Volume 15, issue 6
Nat. Hazards Earth Syst. Sci., 15, 1215–1229, 2015

Special issue: Monitoring and modelling to guide coastal adaptation to extreme...

Nat. Hazards Earth Syst. Sci., 15, 1215–1229, 2015

Research article 15 Jun 2015

Research article | 15 Jun 2015

Estimating the long-term historic evolution of exposure to flooding of coastal populations

A. J. Stevens1, D. Clarke1,3, R. J. Nicholls1,3, and M. P. Wadey2 A. J. Stevens et al.
  • 1Faculty of Engineering and Environment, University of Southampton, University Road, Highfield, Southampton, SO17 1BJ, UK
  • 2Ocean and Earth Science, National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
  • 3Tyndall Centre for Climate Change Research, Norwich, UK

Abstract. Coastal managers face the task of assessing and managing flood risk. This requires knowledge of the area of land, the number of people, properties and other infrastructure potentially affected by floods. Such analyses are usually static; i.e. they only consider a snapshot of the current situation. This misses the opportunity to learn about the role of key drivers of historical changes in flood risk, such as development and population rise in the coastal flood plain, as well as sea-level rise.

In this paper, we develop and apply a method to analyse the temporal evolution of residential population exposure to coastal flooding. It uses readily available data in a GIS environment. We examine how population and sea-level change have modified exposure over two centuries in two neighbouring coastal sites: Portsea and Hayling Islands on the UK south coast. The analysis shows that flood exposure changes as a result of increases in population, changes in coastal population density and sea level rise. The results indicate that to date, population change is the dominant driver of the increase in exposure to flooding in the study sites, but climate change may outweigh this in the future. A full analysis of changing flood risk is not possible as data on historic defences and wider vulnerability are not available. Hence, the historic evolution of flood exposure is as close as we can get to a historic evolution of flood risk.

The method is applicable anywhere that suitable floodplain geometry, sea level and population data sets are available and could be widely applied, and will help inform coastal managers of the time evolution in coastal flood drivers.

Short summary
Using census data, historic maps and hydrodynamic modelling, this paper presents a methodology for assessing how the exposure of people to flooding has changed over the last 200 years at the local level in the UK. The method is applied to two case studies at Portsea and Hayling Islands in the UK's Solent region. The analysis shows that for the case studies, population rise has, to date, had a much greater influence on exposure than sea level rise.
Final-revised paper