France

Coastal flood risk France

Vulnerabilities

Past and present

Until now, more than 40% of the 36,500 French communes have been affected by floods (both coastal and river), and flooding is responsible for 80% of the damage attributable to French natural disasters (12). It has been estimated that approximately 4.5 million people are at risk of flooding in France (13).

Future

France’s coasts and port cities could be affected by sea level rise (SLR) but to a lesser extent than many other countries across the globe. Adaptation (e.g. coastal defences) is important in mediating the impacts. Results show that by the 2080s under a high SLR scenario and without adaptation, the average annual number of people flooded in France could be around 463,000. This is greatly reduced with adaptation, to around 2,500. Under a low SLR scenario, 3,000 people could be flooded annually without adaptation and 1,800 could be flooded with adaptation (1). However, these results are based upon a limited number of studies and the impact of SLR for France requires further quantification (2).

Other studies also conclude that France is one of the countries where port cities are likely to be impacted least by SLR. They present other numbers, however: for example at present 13,000 people in port cities exposed to SLR in France, and 23,000 people with climate change in the 2070s (3).

According to the national adaptation strategy of France, an increase in sea level of 1 metre might significantly increase coastal hazards, especially for sandy coasts and soft rock cliffs. Low coasts will suffer erosion or permanent submersion and new zones will be subject to temporary submersions. 140,000 homes and 80,000 people (as against 15,000 homes today) and 10,000 businesses (employing 26,000 workers) are located in a zone affected by a risk of permanent submersion or erosion by 2100 in the Languedoc-Roussillon region. In the absence of a coastline management policy, the cost of damage linked to “permanent submersion” and erosion hazards is evaluated between EUR 15 and 35 billion for the Languedoc-Roussillon region alone (4).

Global sea level rise

Observations

For the latest results: see Europe Coastal floods

Projections

For the latest results: see Europe Coastal floods

Extreme water levels - Global trends

More recent studies provide additional evidence that trends in extreme coastal high water across the globe reflect the increases in mean sea level (8), suggesting that mean sea level rise rather than changes in storminess are largely contributing to this increase (although data are sparse in many regions and this lowers the confidence in this assessment). It is therefore considered likely that sea level rise has led to a change in extreme coastal high water levels. It is likely that there has been an anthropogenic influence on increasing extreme coastal high water levels via mean sea level contributions. While changes in storminess may contribute to changes in sea level extremes, the limited geographical coverage of studies to date and the uncertainties associated with storminess changes overall mean that a general assessment of the effects of storminess changes on storm surge is not possible at this time.

On the basis of studies of observed trends in extreme coastal high water levels it is very likely that mean sea level rise will contribute to upward trends in the future.

Relative sea level rise - Future trends along the Mediterranean coast

Locally, projected relative sea level rise at the northern Mediterranean coasts deviates substantially from the IPCC projections because of high rates of land subsidence or uplift. This is especially the case in Italy where projected relative sea level rise is much higher near Venice and the Po Delta because of high rates of land subsidence. High land uplift in the volcanic area near Naples of about 9.5 mm per year, on the higher hand, leads to very low values of projected relative sea level rise. Compared to the IPCC projections, projected relative sea level rise in 2100 is almost 1.1 m higher in the Po Delta and 0,8 m lower at the coast of Naples. Land uplift is an exception in the Mediterranean. Subsidence, on the other hand, occurs at several locations, and is also very high in the Thessaloniki plain in Greece and the Rhone delta in France (27).

Extreme waves - Future trends along the Western European and Mediterranean coast

Recent regional studies provide evidence for positive projected future trends in significant wave height and extreme waves along the western European coast (9) and for future declines in extreme wave height in the Mediterranean Sea (11). However, considerable variation in projections can arise from the different climate models and scenarios used to force wave models, which lowers the confidence in the projections (10).

The Atlantic coast of France, Spain and Portugal is exposed to very energetic waves generated along the North Atlantic (25), which constitute the dominant coastal hazard component (26).

Storm surges - Atlantic coast

Storm surge levels will probably be relatively stable or even decrease this century (23,24).

Economic impacts of sea level rise for Europe

The direct and indirect costs of sea level rise for Europe have been modelled for a range of sea level rise scenarios for the 2020s and 2080s (14). The results show:

First, sea-level rise has negative economic effects but these effects are not particularly dramatic. In absolute terms, optimal coastal defence can be extremely costly. However, on an annual basis, and compared to national GDP, these costs are quite small. On a relative basis, the highest value is represented by the 0.2% of GDP in Estonia in 2085.
Second, the impact of sea-level rise is not confined to the coastal zone and sea-level rise indeed affects landlocked countries as well. Because of international trade, countries that have relatively small direct impacts of sea-level rise, and even landlocked countries such as Austria, gain in competitiveness.
Third, adaptation is crucial to keep the negative impacts of sea-level rise at an acceptable level. This may well imply that some European countries will need to adopt a coastal zone management policy that is more integrated and more forward looking than is currently the case.

Adaptation strategies

According to the national adaptation strategy of France, adequate adaptation strategies are (4):

take into account climate change in planning and development documents;
development of detection and warning systems;
analysis of the effects of strategic withdrawal/natural operation restoration/coastline maintenance-type measures

Adaptation strategies - The costs of adaptation

Both the risk of sea-level rise and the costs of adaptation to sea-level rise in the European Union have been estimated for 2100 compared with 2000 (15). Model calculations have been made based on the IPCC SRES A2 and B1 scenarios. In these projections both flooding due to sea-level rise near the coast and the backwater effect of sea level rise on the rivers have been included. Salinity intrusion into coastal aquifers has not been included, only salt water intrusion into the rivers. Changes in storm frequency and intensity have not been considered; the present storm surge characteristics are simply displaced upwards with the rising sea level following 20th century observations. The assessment is based on national estimates of GDP.

The projections show that without adaptation (no further raising of the dikes and no beach nourishments), the number of people affected annually by coastal flooding would be 20 (B1 scenario) to 70 (A2 scenario) times higher in 2100 than in 2000. This is about 0.05 - 0.13% of the population of the 27 EU countries in 2010 (15).

Without adaptation, damage costs would increase roughly by a factor of 5 during the century under both scenarios, up to US$ 17×10⁹ in 2100. Total damage costs would amount to roughly 0.04% of GDP of the 27 EU countries in 2100 under both scenarios. Damage costs relative to national GDP would be highest in the Netherlands (0.3% in 2100 under A2). For all other countries relative damage costs do not exceed 0.1% of GDP under both scenarios (15).

Adaptation (raising dikes and beach nourishments in response to sea level rise) would strongly reduce the number of people flooded by factors of 110 to 288 and total damage costs by factors of 7 to 9. In 2100 adaptation costs are projected to be US$ 3.5×10⁹ under A2 and 2.6×10⁹ under B1. Relative to GDP, annual adaptation costs constitute 0.005 % of GDP under B1 and 0.009% under A2 in 2100. Adaptation costs relative to GDP are highest for Estonia (0.16% under A2) and Ireland (0.05% under A2). These results suggest that adaptation measures to sea-level rise are beneficial and affordable, and will be widely applied throughout the European Union (15).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for France.

Richards and Nicholls (2009), in: UK Met Office (2011)
UK Met Office (2011)
Hanson et al. (2010), in: UK Met Office (2011)
ONERC (2007/2009)
Bindoff et al. (2007), in: IPCC (2012)
Church and White (2011), in: IPCC (2012)
Velicogna (2009); Rignot et al. (2011); Sørensen et al. (2011), all in: IPCC (2012)
Marcos et al. (2009); Haigh et al. (2010); Menendez and Woodworth (2010), all in: IPCC (2012)
Debernard and Roed (2008); Grabemann and Weisse (2008), both in: IPCC (2012)
IPCC (2012)
Lionello et al. (2008), in: IPCC (2012)
Pottier et al. (2005), in Lumbroso et al. (2011)
Enjolras et al. (2008), in Lumbroso et al. (2011)
Bosello et al. (2012)
Hinkel et al. (2010)
Cazenave et al. (2014)
IPCC (2014)
Watson et al. (2015)
Yi et al. (2015)
Church et al. (2013), in: Watson et al. (2015)
Shepherd et al. (2012), in: Watson et al. (2015)
Church et al. (2013), in: Watson et al. (2015)
Vousdoukas et al. (2016)
Marcos et al. (2012), in: Vousdoukas et al. (2016)
Pérez et al. (2014), in: Vousdoukas et al. (2016)
Almeida et al. (2012); Ciavola et al. (2011), both in: Vousdoukas et al. (2016)
Vecchio et al. (2024)