Spatial analysis and simulation of extreme coastal flooding scenarios for national-scale emergency planning

Spatial analysis and simulation of extreme coastal flooding scenarios for national-scale emergency planning.
Wyncoll, D.and Haigh, I. and Gouldby, B.P. and Hames, D. and Laeger, S. and Hawkes, P.J. and Hammond, A.
In: FLOODrisk 2016, 18-20 October 2016, Lyon, France. (2016)

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Abstract:Coastal flood risk analysis is often undertaken at local scales and hence does not consider the likelihood of simultaneous flooding at multiple locations over a larger area. The flooding within the UK over the Winter of 2013/2014 was notable both for its long duration, lasting over 2 months, and its spatial extent, affecting many different areas of England and Wales. It is thus apparent that to plan and prepare for these types of extreme events it is necessary to consider the likelihood of flood events arising at different locations simultaneously (i.e. to consider the spatial dependence of extreme flood events). Methods for evaluating the joint probability of extreme waves and water levels at a specific location are well-established. To date, however, these methods have generally comprised technical limitations that have restricted their application to single site analysis. More sophisticated statistical methods have been developed, see Heffernan and Tawn (2004) for example. These more flexible methods enable extension of coastal joint probability analysis to cover wider spatial extents. The UK has a long history of coastal flooding and these events are driven by large scale low pressure weather systems. Haigh et al. (2015) have developed a comprehensive database of historical coastal flood events in the UK over the last century. The database contains information on the weather systems that caused the events, the associated extreme sea levels at different locations and the extent of flooding. This paper describes the application of the Heffernan and Tawn (2004) multivariate extreme value methodology to extreme sea levels and wave conditions around the coast of England and Wales. The output of the analysis comprises a synthetic set of extreme but plausible events that explicitly captures the dependence between sea conditions at different spatial locations. The output from the statistical model has been verified through comparison with events contained within the historical database. This process shows that synthetically generated events from the statistical model are realistic in terms of the dominant spatial characteristics of the past events. It is envisaged these types of synthetic events can be used to aid the planning and preparedness for national scale emergencies and risk assessments. The Winter 2013/2014 flooding comprised flooding from both coastal and fluvial sources and a companion paper, Lamb et al. (2016), describes how the coastal analysis described above can be combined with inland fluvial analysis to simulate extreme flood events from multiple sources.
Item Type:Conference or Workshop Item (Paper)
Uncontrolled Keywords:Multivariate extremes; coastal flooding; spatial dependence
Subjects:Coasts > Coastal erosion and flooding
ID Code:1297
Deposited On:17 May 2016 15:11
Last Modified:18 Jan 2017 13:14

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