Status: this discussion paper is a preprint. It has been under review for the journal Natural Hazards and Earth System Sciences (NHESS). The manuscript was not accepted for further review after discussion.
Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis
Athanasios T. Vafeidis,Mark Schuerch,Claudia Wolff,Tom Spencer,Jan L. Merkens,Jochen Hinkel,Daniel Lincke,Sally Brown,and Robert J. Nicholls
Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK
Abstract. This study explores the uncertainty introduced in global assessments of coastal flood exposure and risk by not accounting for water level attenuation due to land–surface characteristics. We implement a range of plausible water level attenuation values in the flood module of the Dynamic Interactive Vulnerability Assessment (DIVA) modelling framework and assess the sensitivity of flood exposure and flood risk indicators to differences in attenuation rates. Results show a reduction of up to 47 % in area exposure and even larger reductions in population exposure and expected flood damages. Despite the use of a spatially constant rate for water attenuation the reductions vary by country, reflecting the differences in the physical characteristics of the floodplain as well as in the spatial distribution of people and assets in coastal regions. We find that uncertainties related to the omission of this factor in global assessments of flood risk are of similar magnitude to the uncertainties related to the amount of SLR expected over the 21st century. Despite using simplified assumptions, as the process of water level attenuation depends on numerous factors and their complex interactions, our results strongly suggest that future impact modelling needs to focus on an improved representation of the temporal and spatial variation of water levels across floodplains by incorporating the effects of relevant processes.
How to cite. Vafeidis, A. T., Schuerch, M., Wolff, C., Spencer, T., Merkens, J. L., Hinkel, J., Lincke, D., Brown, S., and Nicholls, R. J.: Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis, Nat. Hazards Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/nhess-2017-199, 2017.
Received: 02 Jun 2017 – Discussion started: 07 Sep 2017
Global assessments of coastal flooding are based on the assumption that water propagation follows a bathtub pattern across the floodplain. Using a global model we find that this assumption can lead to overestimation of impacts, with an uncertainty range that can be of equal magnitude to uncertainties related to future sea-level rise. Our results highlight the importance of improving the representation of the spatial/temporal variation of water levels across floodplains of different landcover.
Global assessments of coastal flooding are based on the assumption that water propagation...