Extreme sea levels and coastal flooding

Assessment versions

Published (reviewed and quality assured)

• 23 Feb 2021, 03:58 PM
  - Extreme sea levels and coastal flooding

Rationale

Justification for indicator selection

Sea level rise can have significant impacts on settlements, infrastructure, people and natural systems. In Europe, the potential impacts of sea level rise include flooding, coastal erosion and the submergence of flat regions along continental coastlines and on islands. Low-lying coastlines with high population densities and small tidal ranges are most vulnerable to sea level rise and coastal flooding, particularly where adaptation is hindered by a lack of economic resources or other constraints. Currently, around 200 million people live in the coastal zone in Europe.

Damage associated with sea level rise is mostly caused by extreme events, such as storm surges. Of most concern is the coincidence of a storm surge with high tidal levels, leading to extreme sea levels. In Europe, the most intense surge events typically occur during the winter months. Furthermore, the concurrence of high sea levels and heavy precipitation resulting in large run-off volumes may cause compound flooding in low-lying coastal areas.

Scientific references

• Acevedo, A., et al., 2018, Climate datasets and related coastal exposure databases,  ECLISEA Deliverable 1.A accessed 4 January 2021.
• Bevacqua, E., et al., 2019, ‘Higher probability of compound flooding from precipitation and storm surge in Europe under anthropogenic climate change’ Science Advances 5(9, eaaw5531) (DOI: 10.1126/sciadv.aaw5531)
• EEA, 2020, ‘Global and European sea level rise’ EEA indicator accessed 4 January 2021.
• Idier, D., et al., 2017, ‘Sea-level rise impacts on the tides of the European Shelf’ Continental Shelf Research 137, pp. 56-71 (DOI: 10.1016/j.csr.2017.01.007).
• Kirezci, E., et al., 2020, ‘Projections of global-scale extreme sea levels and resulting episodic coastal flooding over the 21st Century’ Scientific Reports 10(1, 11629) (DOI: 10.1038/s41598-020-67736-6).
• Marcos, M. and Woodworth, P. L., 2017, ‘Spatiotemporal changes in extreme sea levels along the coasts of the North Atlantic and the Gulf of Mexico: extreme sea level changes’ Journal of Geophysical Research: Oceans 122(9), pp. 7031-7048 (DOI: 10.1002/2017JC013065).
• Oppenheimer, M., et al., 2019, ‘Chapter 4: Sea level rise and implications for low lying islands, coasts and communities’ in: Pörtner, H.-O. et al. (eds), IPCC special report on the ocean and cryosphere in a changing climate, Cambridge University Press, Cambridge, UK
• Pickering, M. D., et al., 2017, ‘The impact of future sea-level rise on the global tides’ Continental Shelf Research 142, pp. 50-68 (DOI: 10.1016/j.csr.2017.02.004).
• Vousdoukas, M. I., et al., 2016, ‘Projections of extreme storm surge levels along Europe’ Climate Dynamics 47(9), pp. 3171-3190 (DOI: 10.1007/s00382-016-3019-5).
• Vousdoukas, M. I., et al., 2017, ‘Extreme sea levels on the rise along Europe’s coasts’ Earth’s Future5(3), pp. 304-323 (DOI: 10.1002/2016EF000505).
• Vousdoukas, M. I., et al., 2018, ‘Global probabilistic projections of extreme sea levels show intensification of coastal flood hazard’ Nature Communications9(1), p. 2360 (DOI: 10.1038/s41467-018-04692-w).
• Weisse, R., et al., 2014, ‘Changing extreme sea levels along European coasts’ Coastal Engineering 87, pp. 4-14 (DOI: 10.1016/j.coastaleng.2013.10.017).
• Woodworth, P. L., et al., 2016a, GESLA (Global Extreme Sea Level Analysis) high frequency sea level dataset Version 2, British Oceanographic Data Centre (BODC) accessed 5 January 2021.
• Woodworth, P. L., et al., 2016b, ‘Towards a global higher-frequency sea level dataset’ Geoscience Data Journal 3(2), pp. 50-59 (DOI: 10.1002/gdj3.42).

Indicator definition

This indicator reports changes in the frequency of historically 1-in-100-year floods along the European coastline. Such floods are caused by extreme sea levels, particularly during storm surges.

Units

• Frequency amplification factor of historical 1–in–100 year extreme sea level event
• Return period (years)

Policy context and targets

Context description

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Targets

No targets have been specified

Related policy documents

No related policy documents have been specified

Methodology

Methodology for indicator calculation

Changes in the frequency of coastal flooding are calculated by comparing the observed distributions of extreme high sea levels at European tide gauges, based on the GESLA-2 data set (Woodworth et al., 2016a, 2016b), with projected distributions under various climate change scenarios. These model projections consider changes in local mean sea levels as well as changes in the storm, wave and tidal characteristics expected to occur as a result of climate change.

Uncertainty in future projections of extreme sea level for Europe remains high and is ultimately linked to the uncertainty around future changes in mid-latitude storminess. Scientific understanding is advancing quickly in this area, as climate model representations of northern hemisphere storm track behaviour are showing improvements associated with, for instance, greater ocean and atmosphere resolution. However, the most recent global climate models have typically not yet been downscaled to suitably fine scales and used in studies of future storm surges.

Methodology for gap filling

Not applicable

Methodology references

No methodology references available.

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• Extreme sea levels on the rise along Europe’s coasts (Dataset URL is not available)
• IPCC SROCC data on sea level rise

Data sources in latest figures

Uncertainties

Methodology uncertainty

Not applicable

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty

No uncertainty has been specified