Coastal flood risk Estonia
The Estonian coast
Estonia has a long (3,800 km) coastline due to numerous peninsulas, bays and islands (over 1,500). It has large untouched bogs (ca 15% of territory), a large number of lakes (ca 1,450) and rivers, and a very flat relief (almost two thirds of the territory lies less than 50 m above sea level). The highest point is Suur Munamägi, 317 m above sea level). It has limestone cliffs all along the Nordic coastline of the mainland and largest islands (1).
Owing to its flat and low-lying coastal zone, which is experiencing isostatic and tectonic uplift, the development of the coast should be stable, although activation of coastal processes has been observed in Estonia for the last 20-30 years. Researchers relate the extensive erosion and alteration of depositional coasts, such as sandy beaches, to the recent increased storminess in the eastern Baltic Sea (2).
Due to a long coastline and extensive low-lying coastal areas, global climate change through sea-level rise will strongly affect the territory of Estonia. A number of valuable natural ecosystems will be in danger. These include both marine and terrestrial systems containing rare plant communities and suitable breeding places for birds. Most sandy beaches high in recreational value will disappear. However, isostatic land uplift and the location of coastal settlements at a distance from the present coastline reduce the rate of risk (3).
In Estonia, the most vulnerable areas to storm surges are the shallow and narrow bays of Pärnu, Matsalu and Haapsalu, which are exposed to the strongest storm winds in the Baltic Sea region (4).
Sea level rise in Estonia
Global sea level rise has been 1-2 mm/yr during the 20th century. The postglacial land uplift rate varies in the coastal areas of Estonia between 0,5 and 3,5 mm/yr (5). Thus, while in Finland clear decreasing sea level trends are still evident (6), the present-day global sea level rise is roughly compensated by uplift in Estonia (4).
Maximum relative sea level rise by 2100 is estimated to vary from 0.9 m in southwest Estonia to 0.7 m on the northwestern coast due to different velocities of land uplift in the studied areas (3).
Global sea level rise
In their fourth assessment report the IPCC reported that there was high confidence that the rate of observed sea level rise increased from the 19th to the 20th century (13). They also reported that the global mean sea level rose at an average rate of 1.7 (1.2 to 2.2) mm yr-1 over the 20th century, 1.8 (1.3 to 2.3) mm yr-1 over 1961 to 2003, and at a rate of 3.1 (2.4 to 3.8) mm yr-1 over 1993 to 2003.
According to satellite altimetry-based data anthropogenic global warming has resulted in global mean sea-level rise of 3.3 ± 0.4 mm/year over the period 1994-2011 (19). According to a recent study, however, this previous estimate of global mean sea level rise is too high and global sea level rise over the period 1993 to mid-2014 has been between +2.6 ± 0.4 mm/year and +2.9 ± 0.4 mm/year (21). According to this same study sea-level rise is accelerating; this acceleration is in reasonable agreement with an accelerating contribution from the Greenland and West Antarctic ice sheets over this period (23,24), and the Intergovernmental Panel on Climate Change projections (23,25) of acceleration in sea-level rise during the early decades of the twenty-first century of about +0.07 mm/year. Sea-level rise varies from year to year, however, due to short-term natural climate variability (especially the effect of El Niño–Southern Oscillation) (19,22): the global mean sea level was reported to have dropped 5 mm due to the 2010/2011 La Niña and have recovered in 1 year (22).
Updated satellite data to 2010 show that satellite-measured sea levels continue to rise at a rate close to that of the upper range of the IPCC projections (14). Whether the faster rate of increase during the latter period reflects decadal variability or an increase in the longer-term trend is not clear. However, there is evidence that the contribution to sea level due to mass loss from Greenland and Antarctica is accelerating (15).
For 2081-2100 compared to 1986-2005, projected global mean sea level rises (metres) are in the range (20):
- 0.29-0.55 (for scenario RCP2.6)
- 0.36-0.63 (for scenario RCP4.5)
- 0.37-0.64 (for scenario RCP6.0) and
- 0.48-0.82 (for scenario RCP8.5)
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 (16), 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
Combining total land uplift and change in sea level records, a summarized sea level rise during the period 1924-2003 between 7,5 and 15,3 cm was obtained. According to the estimates of the global mean sea level rise, about 7-8 cm could be explained by that global component. Up to 6 cm should be explained regionally or locally. Mean sea level in Estonia has a significant positive correlation with storminess and atmospheric circulation indices (7). If the frequency and intensity of westerly storms continue to increase, we may anticipate a further rise in sea level of up to ten cm along the windward locations of the heavily serrated Estonian coast (4).
Consistent with the observed tendencies for an increase in atmospheric westerly winds, the hydrodynamic model simulations indentified a mean sea level rise in some windward bays of the Gulf of Riga of between 5-6 cm under a simulated mean wind speed increase of just 1-2 cm/s (4). The rise is bigger (up to 9-11 cm) in more stormy winter months, while in the summer the sea level rise is unlikely (7,8). These results hold for 1-3 m/s changes in wind speed, considered realistic for the Baltic Sea, though not expected unconditionally in the future (8). According to overviews in the scientific literature (9) some of the climate models predict the following increase in the mean westerly wind flow by the 2080s: in the winter up to 2,3 m/s, in spring up to 2,8 m/s, in autumn up to 1,9, in the summer up to 1 m/s.
An additional sea level rise component of the Baltic Sea is expected because the water inflow in the Danish Straits is sensitive to the same wind change scenarios. Intensified westerlies and storminess will cause an additional mean volume surplus in the Baltic Sea, and a change in sea level inclination, which is due to the fjord-like shape of the Baltic Sea. Simulations show that an up to 3–4 cm sea level rise component would occur in the central Baltic in the case of a 30% increase in wind speed (10).
Considering both the regional (Baltic) and the local sea level change components, a total average sea level rise of 8–10 cm could occur e.g. at Pärnu as a result of a change in the wind regime component, the magnitude of which is quite realistic and has been forecast by many authors (8).
Vulnerabilities – The storm Gudrun
In Pärnu (Estonia) the storm resulted in the highest storm surge ever recorded. It was the worst natural disasters for Estonia in terms of property damage due to storm wind and flooding. The maximum coastline recession reached about 1 km in Pärnu, flooding densely populated urban areas (11).
Erosion of the western coast of Harilaid is revealed by the position of the lighthouse that was originally erected at the centre of the cape (about 100 m from the shoreline) and which currently stands in the sea and is tilted about 10⁰. The gravel-pebble beach ridges that were formed during Gudrun near the Küdema spit – positioned as they are so far inland from the mean shoreline and located at such higher elevations due to storm’s high sea levels – are likely to remain there unchanged for a long time (4).
Gudrun exposed the lack of adaptation towards weather borne hazards that already today pose a threat to the countries bordering the Baltic Sea. Climate change is expected to enhance extreme weather events that are thus likely to occur at a shorter interval in the future (11).
Vulnerabilities – Coastal flood risk
The main hazards and economic losses in Estonia will result from the rise of sea level which will cause flooding in coastal areas, the erosion of sandy beaches and the destruction of harbor constructions. Also a number of valuable natural ecosystems will be in danger. These include both marine and terrestrial systems containing rare plant communities and suitable breeding places for birds (1).
Flooding and storms (especially during winter season) are already a major threat in the Baltic Sea Region. The impact of storms is enhanced when extreme weather events follow each other in a time span shorter than the recovery time of the given ecosystem. Furthermore, the severity of storms is increasing with prolonged ice free periods due to the mild winter climate. Storm winds and the changes in the atmosphere pressure cause sea level fluctuations on the coast. The impact of the sea level rise is considered to be the most influential factor for flood damage. When several unfavourable conditions (wind speed and direction, general water level and long waves in the Baltic Sea) coincide, a short-time sea level rise of 1–2 meters may occur and several places may be inundated. The areas that are most influenced by this are the coastal zones of shallow bays in Western Estonia with natural landscapes and dispersed settlements (1).
A 1m global sea-level rise would jeopardise the survival of several natural areas but would not cause widespread relocation of the population owing to the general sparsity of settlements and low population density in the coastal zone. About 3% of the country would be inundated or temporarily damaged, requiring relocation of about 40,000 inhabitants (12).
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 (17). 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 - 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 (18). 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 (18).
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 (18).
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 (18).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Estonia.
- Ministry of the Environment of Estonia (2009)
- Orviku et al. (2003)
- Kont et al. (2003)
- Kont et al. (2007)
- Vallner et al. (1988), in: Kont et al. (2007)
- Johansson et al. (2004)
- Suursaar et al. (2006a)
- Suursaar and Kullas (2006)
- Jylhä et al. (2004); Räisänen et al. (2003), in: Suursaar et al. (2006a)
- Meier et al. (2004), in: Suursaar and Kullas (2006)
- Suursaar et al. (2006b)
- Kont et al. (2008)
- 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)
- 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)