Developments in large-scale coastal flood hazard mapping

Abstract

Abstract. Coastal flooding related to marine extreme events has severe socioeconomic impacts, and even though the latter are projected to increase under the changing climate, there is a clear deficit of information and predictive capacity related to coastal flood mapping. The present contribution reports on efforts towards a new methodology for mapping coastal flood hazard at European scale, combining (i) the contribution of waves to the total water level; (ii) improved inundation modeling; and (iii) an open, physics-based framework which can be constantly upgraded, whenever new and more accurate data become available. Four inundation approaches of gradually increasing complexity and computational costs were evaluated in terms of their applicability to large-scale coastal flooding mapping: static inundation (SM); a semidynamic method, considering the water volume discharge over the dykes (VD); the flood intensity index approach (Iw); and the model LISFLOOD-FP (LFP). A validation test performed against observed flood extents during the Xynthia storm event showed that SM and VD can lead to an overestimation of flood extents by 232 and 209 %, while Iw and LFP showed satisfactory predictive skill. Application at panEuropean scale for the present-day 100-year event confirmed that static approaches can overestimate flood extents by 56 % compared to LFP; however, Iw can deliver results of reasonable accuracy in cases when reduced computational costs are a priority. Moreover, omitting the wave contribution in the extreme total water level (TWL) can result in a ∼ 60 % underestimation of the flooded area. The present findings have implications for impact assessment studies, since combination of the estimated inundation maps with population exposure maps revealed differences in the estimated number of people affected within the 20-70 % range.

Understanding epistemic uncertainty in large-scale coastal flood risk assessment for present and future climates

“…Dynamic inundation simulations have been shown to be more reliable (Ramirez et al, 2016). However, Vousdoukas et al (2016) have shown that VI can be a good surrogate when computational efficiency is the priority, as also demonstrated by Breilh et al (2013). In flatter terrains, VI tends to be outperformed by hydraulic models, or other empirical approaches, such as the flood index method (Dottori et al, 2016a).…”

Global changes of extreme coastal wave energy fluxes triggered by intensified teleconnection patterns

“…Extreme waves transfer large amounts of energy to the coast, applying huge stress to coastal installations and protection structures [Oumeraci, 1994;Van der Meer et al, 2016], accelerating sediment transport processes and coastal erosion [Masselink and Puleo, 2006;Vousdoukas et al, 2012b;Archetti et al, 2016;Masselink et al, 2016;Monioudi, 2016;Postacchini et al, 2017], and driving dune breaching [Matias et al, 2008;Roelvink et al, 2009] and inundation [Bertin et al, 2012;Vousdoukas et al, 2016b]. By modulating interactions between oceans and the atmosphere waves play an important role in the climate system [Hemer et al, 2012] and are likely to be affected by global warming.…”

Costs of sea dikes – regressions and uncertainty estimates

“…In order to estimate costs and benefits of adaptation to sealevel rise (Fankhauser, 1995;Jonkman et al, 2004;Dawson et al, 2009Dawson et al, , 2011Klijn et al, 2012;Boettle et al, 2013a;Eijgenraam et al, 2014;Jongmann et al, 2014;Kind, 2014;Kreibich et al, 2014;Boettle et al, 2016), various categories are required -in particular (i) the change of frequency and magnitude of coastal floods (Eijgenraam et al, 2014;Dawson and Hall, 2006;Vousdoukas et al, 2016), (ii) the expected (direct, monetary) damage without adaptation (Bouwer, 2013;Prahl et al, 2016), (iii) the residual (direct, monetary) damage with adaptation (Kreibich et al, Published by Copernicus Publications on behalf of the European Geosciences Union. 766 S. Lenk et al: Costs of sea dikes 2014), and (iv) the construction costs of the adaptation measure (Jonkman et al, 2013;Aerts et al, 2013).…”