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Coastal flood risk Lithuania

The Lithuanian coast

Lithuania has an about 92 kilometer long coastline of the Baltic Sea. It is a complex area including terrestrial and marine features: sandy beaches, dunes, fens, inshore waters and an underwater slope, a few moraine cliffs (1).

The area of the Curonian Lagoon is about 1584 km2. The Lagoon is a semi-enclosed almost fresh water body, which is separated from the sea by a narrow sandy spit (minimum width is about 400 m). In some extreme cases during stormy weather, the Curonian Spit is flooded and the water flows over it into the Lagoon near Zelenogradsk (Russian territory). This event was last observed in 1983 (2). Only the narrow Klaipėda Strait in the northern part of the Lagoon connects it with the Baltic Sea.

River discharge has a strong influence on water level in the Lagoon. The Nemunas River flowing into the Baltic Sea through the Curonian Lagoon is the third largest river runoff to the Baltic Sea. Its annual discharge is on average 22 km3. About 26% of the Curonian Lagoon area belongs to the Lithuanian Republic, the other part to the Russian Federation. The length of the Lithuanian part of the Lagoon coastline is about 150 km (1).

Sea level rise in Lithuania in the future

In the Baltic region, sea level rise with respect to the land (relative sea level rise) is the combination of absolute sea level rise and land uplift since the most recent glacial period.

The rate of land uplift of Fennoscandia increases from south to north. In the southeastern Baltic Sea the calculated sea level rise is about 1.7 mm/yr, while it reverses to -9.4 mm/yr in the northwestern Gulf of Bothnia (thus the land rises 9.4 mm/yr with respect to the sea) (1).

It was found that a global mean sea level rise of 50 cm from 1990 to 2080 would lead to a sea level rise of 33-46 cm in Danish waters (6). It can be expected that by the year 2100 many regions currently experiencing relative sea level fall will instead have a rising relative sea level (6).

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.

Short-term water level fluctuations on the Baltic Sea

The North Atlantic Oscillation (NAO) is the main source of interannual climate variability in the North Atlantic region.The NAO is essentially a measure of the atmospheric pressure difference between the Icelandic Low and the Azores High.A large pressure gradient between a well-developed Icelandic Low and a strong Azores High (termed a positive NAO) results in a strong westerly air flow on a more northerly track over the eastern North Atlantic and Europe. Thiswind forces  water through the Danish Straits into the Baltic Sea and also forces an east-west directed slope on the water surface within the Baltic Sea (7).

The variability of the sea level in the Baltic Sea and the Curonian Lagoon correlates with the NOA index (8). Strong westerly winds cause high sea levels near the Lithuanian coast. Since the middle of the 20th century stormy weather conditions seem to have increased and extreme values of sea level have been more frequent (1).

Rate of sea level rise not corrected for land movement in the Lithuanian region has been 1.3 ± 0.2 mm/yr during 1898-2002. Sea level rise, however, has increased to 3 mm/yr since the 1970s (1).

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 (9). The results show:

  1. 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.
  2. 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.
  3. 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 - 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 (10). 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 (10).

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 (10).

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 (10).

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 Lithuania.

  1. Dailidiené et al. (2006)
  2. Fenger et al. (2001), in: Dailidiené et al. (2006)
  3. Johansson et al. (2004)
  4. Johansson et al. (2001, 2004); Ekman (2003), in: Dailidiené et al. (2006)
  5. Bindoff et al. (2007), in: IPCC (2012)
  6. Church and White (2011), in: IPCC (2012)
  7. Velicogna (2009); Rignot et al. (2011); Sørensen et al. (2011), all in: IPCC (2012)
  8. Marcos et al. (2009); Haigh et al. (2010); Menendez and Woodworth (2010), all in: IPCC (2012)
  9. Bosello et al. (2012)
  10. Hinkel et al. (2010)
  11. Cazenave et al. (2014)
  12. IPCC (2014)
  13. Watson et al. (2015)
  14. Yi et al. (2015)
  15. Church et al. (2013), in: Watson et al. (2015)
  16. Shepherd et al. (2012), in: Watson et al. (2015)
  17. Church et al. (2013), in: Watson et al. (2015)
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