Extreme sea levels are a major threat for coastal communities and they are expected to become more severe in a warming climate either due to rising mean sea levels or due to potential changes in storminess. This is particularly true for densely populated and microtidal environments that are particularly sensitive to sea-level changes, such as the German Baltic Sea coast. Despite this, the needed adaptation responses are poorly understood in this region due to a number of limitations. Adaptation risk management requires local statistical information on both heights and duration of extreme sea-level events, as well as on the upper tail of the uncertainty of future projections (high-end scenarios), both of which are currently not available for the German Baltic Sea coast. Another limitation is that both hydrodynamic and stylized methods for coastal flood impact assessments generally ignore the wider range of adaptation measures such as ecosystem-based protection options, accommodation options and retreat options, which are, however, essential for long-term strategic responses to sea-level rise. Finally, long-term adaptation decision making requires the application of robust decision-making methods, which are difficult to combine with the computationally expensive hydrodynamic models. Instead, stylized flood models are required, which, however are often not very accurate due to a lack of calibration.

The proposed project addresses these limitations and presents an integrated assessment of coastal flood risk and adaptation responses for the German Baltic Sea undertaken through a close collaboration of three work packages (WP) rooted in the fields of coastal engineering, coastal geography and economic decision analysis. The first WP develops local scale bivariate probabilistic information on both extreme sea-levels and their duration by combining historical observations with numerical modelling for the application of multi-variate extreme value statistics. This will be complemented with the generation of return water levels under high-end sea-level rise scenarios. The second WP develops improved methods for the socio-economic assessment of coastal flood impacts by combining hydrodynamic inundation modelling with protection, accommodation and retreat adaptation options. These methods are applied to assess current and future coastal flood risk for selected locations at the German Baltic Sea coast under a range of adaptation measures. The third WP develops a stylized model of coastal flooding that includes a wide range of adaptation options and is sufficiently fast that it can be run within a range of suitable robust decision-making methods, which will also be implemented in this WP. The stylized model will be calibrated through the hydrodynamic inundation modelling carried out in WP2 and then applied to develop coastal adaptation pathways for whole German Baltic Sea coast.

Publications of the SEASCApe Baltic project:

Hinkel, J., J.A. Church, J.M. Gregory, E. Lambert, G. Le Cozannet, J. Lowe, K.L. McInnes, R.J. Nicholls, T. van der Pol, and R. van de Wal (2019), Meeting User Needs for Sea Level RIse Information: A Decision Analysis Perspective, Earth's Future, 7, 320-337, doi:10.1029/2018EF001071.

Hinkel, J., J.C.J.H. Aerts, S. Brown, J.A. Jiménez, D. Lincke, R.J. Nicholls, P. Scussolini, A. Sanchez-Arcilla, A. Vafeidis, and K.A. Addo (2018), The ability of societies to adapt to twenty-first century sea-level rise, Nature Climate Change, 8, 570-578, doi:10.1038/s41558-018-0176-z.

Merkens, J., and A.T. Vafeidis (2018), Using Information of Settlement Patterns to Improve the Spatial Distribution of Population in Coastal Impact Assessments, Sustainability, 10(9), 3170, doi:10.3390/su10093170.

Van der Pol, T., and J. Hinkel (2019), Uncertainty Representations of Mean Sea-Level Change: A Telephone Game?, Climatic Change, 152 (3-4), 393-411, doi:10.1007/s10584-018-2359-z.