Coastal flood risk Turkey
The Turkish coast
The Turkish coastline is 8,333 km long and is bordered by four different seas: the Mediterranean Sea, the Black Sea, the Aegean Sea, and the Marmara Sea, which is connected to the Black Sea by the Bosphorus Strait and to the Aegean Sea by the Dardanelles Strait (3).
The estimated population according to the 2005 census is approximately 72.5 million. The urban population is growing rapidly; from 14% of the total population in 1950, to 70% in 2000 and urbanisation, often in coastal locations, is expected to continue. This increase in urban population is due to intensive migration from eastern and south-eastern Turkey to the large coastal cities such as Istanbul, Izmir, Adana, Antalya, and Alanya. Hence, the population exposed to sea level rise is also increasing (3).
By 2015, Istanbul is forecast to have a population of more than 12 million, making it one of the world’s major coastal cities. 25 coastal cities and towns that had populations over 100,000 in 2000. Almost half (11) are located in the narrow coastal belt along the Black Sea and these contain about 22% of the total national population (3).
The Turkish coast consists of three main types: (i) erosional rocky and softer cliff coastlines (5752 km or 69%), (ii) accretional sandy coasts (1546 km or 19%), (iii) accretional, partly swampy, deltaic coasts (1035 km or 12%) (5). Turkey has well-developed coastal dunes, especially along the western Black Sea coast and in the deltas of the Aegean and Mediterranean Seas. These natural barriers to storms provide some defence against the consequences of accelerated sea-level rise (ASLR), at least in the short term. Elsewhere, beach rock has developed along numerous low soil cliffs, notably on the Aegean and Mediterranean coasts and the Black Sea coasts of Istanbul province.
The deltaic regions are threatened most by sea level rise, especially the agricultural areas on the Cukurova, Bafra, Carsamba, and Meric plains (3).
Sandy beaches are found along 845 km (10%) of the Turkish coast (KAYA, SEKER, and MUSAOGLU, 2001). Although some of these sandy coasts are national parks, one-third are being degraded by rapid tourist development. Although the coastal zone contains the most fertile agricultural land of the country, agriculture has generally declined in the face of urbanization, industrialisation, and increasing tourism. Over the last two decades, coastal tourism and yachting have experienced rapid growth, mostly along the Aegean and Mediterranean coastlines (6). Tourist areas were built first on the narrow beach strip but are now expanding landward on to agricultural areas—trends that are expected to continue. Nonetheless, agriculture in coastal areas will remain an important activity that is vulnerable to SLR (3).
Sea level rise in Turkey in the past
Much of the Turkish coast appears to experience sea-level changes within the generally accepted range of sea-level rise (1-2 mm/yr). The areas in which the rate of the sea-level rise has been less than 1-2 mm/yr (e.g. Samsun to Antalya) are assumed to have undergone tectonic uplift, whereas several of the larger river deltas have experienced sea-level rises substantially greater than the global rise. These areas are assumed to have undergone subsidence (1).
No systematic research has been conducted for the study of long-lasting trends in sea-level changes in Turkey. Sea-level measurements have been recorded in Turkey since 1974 whereas the most reliable series start in 1986 in Antalya of the Mediterranean Sea, Bodrum of the Aegean Sea, Erdek of the Marmara Sea and Samsun of the Black Sea coasts (2). No significant acceleration in the rate of sea level rise has been detected during the 20th century (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 (10). 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 (16). 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 (18). 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 (20,21), and the Intergovernmental Panel on Climate Change projections (20,22) 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) (16,19): 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 (19).
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 (11). 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 (12).
For 2081-2100 compared to 1986-2005, projected global mean sea level rises (metres) are in the range (17):
- 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 (13), 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.
Extreme waves - Future trends along the Mediterranean coast
Recent regional studies provide evidence for projected future declines in extreme wave height in the Mediterranean Sea (14). 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 (15).
A number of national scale studies suggest that Turkey could experience appreciable coastal impacts from sea level rise (8). One study estimates that the population in Turkey exposed to SLR is around 428,000 along the Mediterranean coast, 208,000 along the Aegean coast, 842,000 in the Marmara region and 201,000 along the Black Sea coast (9).
Although coastal cities cover less than 5% of the total surface area of Turkey, over 30 million people live in coastal areas. More than 60% of the GNP in Turkey is produced in the coastal strip along the northern shoreline of the Marmara Sea (4). When the Common Methodology of the IPCC CZMS (1992) is applied to both Turkey and Istanbul province, assuming a scenario of 1 m sea level rise, Turkey lies in the class of low risk countries, but Istanbul has high risk values (2). The preliminary assessment of vulnerability analysis yields about 6% of its GNP for capital loss, and about 10% of its GNP for protection and adaptation costs of the country (1).
When planning and building coastal infrastructure, sea level and other environmental conditions are unfortunately assumed to be constant. This is despite current evidence that suggests sea levels around Turkey are already rising. Soft engineering and beach nourishment have not been practiced to date, although it is increasingly being used in many other European countries (7).
The only easy and safe transportation route between the eastern and western ends of the of Turkish Black Sea coast is along roads built near the shoreline. These routes will definitely be affected in the long term by erosion because of sea level rise and, in the shorter term, by increasing storm and surge damage. Fishing in the eastern Black Sea could also be adversely affected. Rising sea levels and increases in storm surges will also have an effect on agriculture and tourism along the Aegean and Mediterranean shorelines (e.g., cotton production in Cukurova) (3).
Only eight out of the 485 dams were built before 1960, and 89% of dams hold sediment, reducing sediment flux to the coast. Although it has not been investigated, the effect of this reduction of sediment supply is expected to have adverse long-term effects, which will exacerbate the effects of sea level rise (erosion) (3).
One of the key potential effects of sea level rise on Istanbul is saltwater intrusion. Two big lagoons (Büyücekmece and Kücükcekmece) and the Halic estuary that separates old town from the business district in Istanbul are vulnerable to salinisation. So is the freshwater supply of Istanbul: Terkos Lake, located near the coastline of the Black Sea. ‘‘Flagship’’ cultural and historical sites along the Bosphorus in Istanbul are definitely threatened by the projected rise in sea level, such as the 200 year old Dolmabahce Palace and Mosque, the Ortaköy Mosque, the Beylerbeyi Palace, and the Kücüksu Kiosk. The vulnerability of Turkey to sea level rise appears to be intermediate between northern and southern Mediterranean states: less vulnerable than Egypt and the Nile delta, but more vulnerable than France and Spain (3).
To establish a crude estimate of potential adaptation costs to protect the people and capital values, the costs of protecting all the coastal cities with a population of more than 50,000 people was estimated. Assuming a standard sea wall at a unit cost of US$5000/m, with the state planning office of Turkey approximation of the length of coastal frontages in each town/city (totally 240 km or 2.9% of Turkey’s coast), the resulting cost is US$20 billion. Note that these costs exclude the cost of beach nourishment at tourist facilities, protecting agricultural areas (including modified water management), cliff protection, and issues such as port and harbour upgrade (3).
Even though Turkish coastlines are characterised as exhibiting low to medium vulnerability, the size of the potential economic loss due to sea level rise and storm surges, and the response costs are significant in relation to the existing size of the Turkish economy (3).
However, none of the governmental agencies are yet dealing with the issues and problems that will accompany future sea level rise or, more broadly, long-term coastal management. When asked about the problem, they generally minimise its significance. Even coastal engineers, who would seem more predisposed to incorporate technical information, are still designing coastal infrastructure without any allowance for future changes. In the Turkish law for coastal protection, sea level is treated as an ‘‘unchanging’’ boundary between the land and sea (3).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Turkey.
- Güven, C. (2007)
- Karaca (2001), in:Güven, C. (2007)
- Karaca and Nicholls (2008)
- DPT (2001), in: Güven, C. (2007)
- EROL (1990, 1991), in: Karaca and Nicholls (2008)
- Kaya, Seker and Musaoglu (2001), in:Karaca and Nicholls (2008)
- Hanson et al. (2002), in:Karaca and Nicholls (2008)
- Demirkesen et al. (2008); Kuleli (2010); Kuleli et al. (2009), all in: MET Office (2011)
- Kuleli et al. (2009), in: MET Office (2011)
- 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)
- Lionello et al. (2008), in: IPCC (2012)
- IPCC (2012)
- 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)