Editing IPCC:AR6/WGII/Chapter-13 (section)

==== 13.2.1.1 Risk of Coastal Flooding and Erosion ====

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Almost 50 million Europeans live within 10 m above mean sea level ( [[#Vousdoukas--2020|Vousdoukas et al., 2020]] ; McEvoy et al., 2021). Without further adaptation ( [[#13.2.2|Section 13.2.2]] ), flood risks along Europe’s low-lying coasts and estuaries will increase due to SLR compounded by storm surges, rainfall and river runoff ( ''high confidence'' ) ( [[#Mokrech--2015|Mokrech et al., 2015]] ; [[#Arns--2017|Arns et al., 2017]] ; [[#Sayol--2018|Sayol and Marcos, 2018]] ; [[#Vousdoukas--2018a|Vousdoukas et al., 2018a]] ; [[#Bevacqua--2019|Bevacqua et al., 2019]] ; [[#Couasnon--2020|Couasnon et al., 2020]] ). The population at risk of a 100-year flood event starts to rapidly increase beyond 2040 ( [[#Vousdoukas--2018a|Vousdoukas et al., 2018a]] ) reaching 10 million people under RCP8.5 by 2100, but it stays just below 10 million people under RCP2.6 by 2150 (Figure 13.5; [[#Haasnoot--2021b|Haasnoot et al., 2021b]] ) assuming present population and protection. The number of people at risk is projected to increase and risk to materialise earlier especially in response to increasing population under SSP5 ( [[#Vousdoukas--2018a|Vousdoukas et al., 2018a]] ; [[#Haasnoot--2021b|Haasnoot et al., 2021b]] ). Under high rates of SLR resulting from rapid ice sheet loss from Antarctica, risks may increase by a third by 2150 ( [[#Haasnoot--2021b|Haasnoot et al., 2021b]] ). Expected annual (direct) damages due to coastal flooding are projected to rise from 1.3 billion EUR today to 13–39 billion EUR by 2050 between 2°C and 2.5°C GWL and 93–960 billion EUR by 2100 between 2.5° and 4.4°C GWL, largely depending on socioeconomic developments (Cross-Chapter Box SLR in Chapter 3; [[#Vousdoukas--2018a|Vousdoukas et al., 2018a]] ) ( ''high confidence'' in the sign; ''low confidence'' in the numbers). UNESCO World Heritage sites in the coastal zone are at risk due to SLR, coastal erosion and flooding ( [[#13.8.1.3|Section 13.8.1.3]] ; Cross-Chapter Paper 4; [[#Marzeion--2014|Marzeion and Levermann, 2014]] ; [[#Reimann--2018b|Reimann et al., 2018b]] ) as are coastal landfills and other key infrastructures in Europe (AR6/SROCC; [[#Brand--2018|Brand et al., 2018]] ; [[#Beaven--2020|Beaven et al., 2020]] ).

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[[File:45f5737249250a5357d80d774e41fd9c IPCC_AR6_WGII_Figure_13_005.png]]

'''Figure 13.5 |''' '''Sea level rise (SLR) vulnerability and national planning in Europe:'''

'''(a)''' map of countries in Europe summarising the amount of SLR each country is planning for, at different time horizons (blue bars), and the present population (2020) at risk of a 100-year coastal flood event (orange bars) ( [[#Haasnoot--2021b|Haasnoot et al., 2021b]] ). The amounts of SLR and time horizons reflect national guidance or planning (local or project-based levels may differ) (McEvoy et al., 2021);

'''(b)''' projected population at risk to experience a 1-in-10-year coastal flood event under RCP2.6-SSP1 and RCP8.5-SSP5 assuming present protection and population levels, as well as population change according to, respectively, SSP1 and SSP5, based on Merkens (2016);

'''(c)''' projected population at risk to experience a 1-in-100-year coastal flood event under RCP2.6-SSP1 and RCP8.5-SSP5, assuming the present protection and population levels, as well as population change according to, respectively, SSP1 and SSP5, based on Merkens (2016) (based on [[#Haasnoot--2021b|Haasnoot et al., 2021b]] ).

Observations indicate that soft cliffs and beaches are most affected by erosion in Europe with, for example, 27–40% of Europe’s sandy coast eroding today, without climate change being identified as the main driver so far ( [[#Pranzini--2015|Pranzini et al., 2015]] ; [[#Luijendijk--2018|Luijendijk et al., 2018]] ; [[#Mentaschi--2018|Mentaschi et al., 2018]] ; [[#Oppenheimer--2019|Oppenheimer et al., 2019]] ). SLR will increase coastal erosion of sandy shorelines ( ''high confidence'' ) ( [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ), but there is ''low confidence'' in quantitative values assessment of erosion rates and amounts ( [[#Athanasiou--2019|Athanasiou et al., 2019]] ; [[#Le%20Cozannet--2019|Le Cozannet et al., 2019]] ; [[#Thieblemont--2019|Thieblemont et al., 2019]] ). Without nourishment or other natural or artificial barriers to erosion, sandy shorelines could retreat by about 100 m in Europe at 4°C GWL; limiting warming to 3°C GWL could reduce this value by one-third ( [[#Vousdoukas--2020|Vousdoukas et al., 2020]] ).

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