title: Sea-level rise induced amplification of coastal protection design heights.
abstract: Coastal protection design heights typically consider the superimposed effects of tides, surges, waves, and relative sea-level rise (SLR), neglecting non-linear feedbacks between these forcing factors. Here, we use hydrodynamic modelling and multivariate statistics to show that shallow coastal areas are extremely sensitive to changing non-linear interactions between individual components caused by SLR. As sea-level increases, the depth-limitation of waves relaxes, resulting in waves with larger periods, greater amplitudes, and higher run-up; moreover, depth and frictional changes affect tide, surge, and wave characteristics, altering the relative importance of other risk factors. Consequently, sea-level driven changes in wave characteristics, and to a lesser extent, tides, amplify the resulting design heights by an average of 48-56%, relative to design changes caused by SLR alone. Since many of the world's most vulnerable coastlines are impacted by depth-limited waves, our results suggest that the overall influence of SLR may be greatly underestimated in many regions.
authors.affiliation: Research Institute for Water and Environment, University of Siegen, Paul-Bonatz-Str. 9-11, 57076, Siegen, Germany.
authors.forename: Arne
authors.initials: A
authors.lastname: Arns
authors.affiliation: Research Institute for Water and Environment, University of Siegen, Paul-Bonatz-Str. 9-11, 57076, Siegen, Germany.
authors.forename: Sönke
authors.initials: S
authors.lastname: Dangendorf
authors.affiliation: Research Institute for Water and Environment, University of Siegen, Paul-Bonatz-Str. 9-11, 57076, Siegen, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Jensen
authors.affiliation: Civil and Environmental Engineering Department, Portland State University, 1930 SW Fourth Avenue, Portland, OR, 97201, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Talke
authors.affiliation: Research Institute for Water and Environment, University of Siegen, Paul-Bonatz-Str. 9-11, 57076, Siegen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Bender
authors.affiliation: School of Civil, Environmental and Mining Engineering &The UWA Oceans Institute, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia.
authors.forename: Charitha
authors.initials: C
authors.lastname: Pattiaratchi