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

Abstract

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.

Preface: Monitoring and modelling to guide coastal adaptation to extreme storm events in a changing climate

“…Rising sea level needs to be considered in assessments of extreme events , while changes in coastal land use and infrastructure need consideration in assessment of the impact of events (Fakhruddin et al, 2015;Stevens et al, 2015;Sekovski et al, 2015). In support of proactive long-term adaptive management, guidance on suitable frameworks to apply when considering climate change is also required (Armstrong et al, 2015).…”

“…Coastal urbanization (Stevens et al, 2015;Sekovski et al, 2015) and modern life style, such as commuting to work, are placing people in a hazard zone, even if temporarily. The infrastructure that supports these coastal communities is also at risk (Fakhruddin et al, 2015).…”

“…Analysis of the temporal variability in floodplain population and infrastructure vulnerability is therefore required to inform adaptive management. Transferable methods can be used to assess changes in risk in response to residential population growth relative to sea-level rise (Stevens et al, 2015), and to assess the change in hazard for chosen storm levels in response to different types of urban growth (Sekovski et al, 2015). It is suggested that population growth is a greater contributor to increased flood risk than sea-level rise (Stevens et al, 2015) and that a "compact" growth type increases the flood hazard over other modes of urbanization (Sekovski et al, 2015).…”

“…More recently, the need for data assimilation into coastal impact models is being addressed in order to improve the capability of early warning systems (Van Dongeren et al, 2013;Sembiring et al, 2015). An example of how research can guide management decisions is in the improved understanding of a systems response to intervention through the development of transferable tools that incorporate leading scientific developments to reduce the uncertainty in alternative solutions and designs for sustainable long-term defence schemes (e.g.…”

Assessment and comparison of extreme sea levels and waves during the 2013/14 storm season in two UK coastal regions

“…Storm surges and flooding are a threat to low-lying coastal zones, with risks increasing due to sea-level rise (Haigh et al, 2010;Menéndez and Woodworth, 2010;Wahl et al, 2011) and floodplain development (Hanson et al, 2011;Stevens et al, 2014Stevens et al, , 2015. Northwest Europe, in which the case studies described in this paper are located, has historically suffered terrible losses from coastal flooding (Lamb, 1991;Gönnert et al, 2001).…”