Introduction
The Black Sea basin is a unique and very complex environment in the World Ocean as a result of its evolution, location and history. This is the reason why in the last years there is an increasing scientific interest in deciphering the processes and mechanisms governing this area. Besides the well-known environmental problems of the basin related to pollution, eutrophication, overfishing and loss of biodiversity, erosion (as a result of storminess, sea level rise and human interventions) is affecting many coasts around the Black Sea.
Beaches are vital coastal ecosystems and ecological habitats. They are the first line of defence against sea flooding of indispensable back-barrier coastal habitats and very valuable economic assets and infrastructure. At the same time, beaches are vulnerable to erosion and inundation. Two main erosion types contribute to the total risk: long-term, irreversible landward migration and/or drowning of the beaches due to mean SLR or negative coastal sedimentary budgets and short-term erosion, caused by storm surges and waves, which even if they do not result in permanent shoreline retreats, can nevertheless be destructive. The projected SLR and potential increases in the destructiveness of extreme events, as well as intensifying coastal development, threaten to exacerbate the already significant erosion, with severe impacts on coastal populations, infrastructure, assets and ecosystem services.
Actual Situation in Black Sea Basin
Results showed circa 19% (800 km) of the Black Sea coasts are undergoing serious erosion, affecting mostly the coastlines of Romania (37%), Ukraine (29%) and Georgia (26%). The most sensitive sectors to erosion are superposed on the areas with relatively high storm waves and incidence angles: the deltaic coastlines of the main deltas (Danube, Kizilirmak, Yesilirmak, Sakarya, Rioni, Enguri, Kodori, Chorokhi) of the Black Sea, the low-lying areas along the lagoons, limans, coastal barriers and spits from Kalamitsky, Odessa and Karkinitsky Bays (Dniester, Tendrovskaya and Dzharlygachskiy areas), Chornomorske – Yevpatoriya area (in Crimea), Taman – Anapa (in Russia) and Karasu – Karaburun (in Turkey) and the rocky areas Gelendzhik – Tuapse (in Russia), Sevastopol – Cape Meganom (in Crimea) and Inebolu – Eregli (in Turkey). These highly sensitive sectors cover extensive areas along the coastlines of Russia (57%), Georgia (46%), Turkey (44%), Romania (43%) and Ukraine (35%).
Actual Situation among Romania’s coastline
Romania has the coastline of 245 km along the northwestern shore of the Black Sea together with Bulgaria, Turkey, Georgia, Russia, and Ukraine in the counterclockwise direction. Similar as any coast in the world, the Romanian coast has been suffering from the problem of beach erosion. The Government of Romania requested the Government of Japan to extend technical assistance for a study to formulate the coastal protection plan for the Southern Romanian Black Sea shore and to make a feasibility study on priority project(s). On behalf of the Japanese Government, the Japan International Cooperation Agency (JICA) undertook the study, which began in March 2005 and will be completed in early 2007. The present paper is based on the interim report of the study submitted to the Government of Romania in February 2006. The Romanian coastline in divided into the northern and southern units. The northern unit is the deltaic coast of the Danube, which is the second largest river in Europe. The sediment transport load of the Danube became less than one half in recent several decades owing to construction of many dams in her mainstream and tributaries (Bondar and Panin, 2000). Extension of two entrance jetties by 8 km at the Sulina Channel near the border with Ukraine, which is opened to the international fairway through the Central Europe, has aggravated the beach erosion severely. Some sections of the northern unit indicate the shoreline recession with the rate of 10 m/year with the maximum of 19 m/year. The southern unit of the Romanian Black Sea Coast, which is the area under study, is also experiencing severe beach erosion. Figure 1 shows the location map of the study area, which extends from Midia to Vama Veche next to the border with Bulgaria over some 80 km. Midia, Constan a, and Mangalia are the port areas, while Mamaia, Eforie, Constine ti and Vama Veche are the famous resort beaches.
Present state of beach erosion
The shoreline position change has been investigated by two methods: one with comparison of topographic maps and satellite images and another with regression analysis of the beach profile data, which have been surveyed by the National Institute for Marine Research and Development over years. Figure 2 is an example of the regression analysis of the shoreline distance from the bench mark M-14 at Mamaia Beach. Mamaia Beach was around 100 m wide in the 1960s, but severe erosion began in the late 1970s, when the north breakwater of Midia Port, which is located at the northern end of the 11 km long beach, began to be extended to the water of 10 m deep. The terrigenous sand from the Danube has been transported southwestward along the northern unit of the Romanian Black Sea Coast over tens of millenniums. The transported sand contributed to elongation of sand spits at a number of embayments and finally to their closure with barrier beaches. The barrier beach of Mamaia seems to have landlocked the embayment of Siutghiol around the second century. Being alarmed by disappearance of beaches of Mamaia, the Romanian Government built six detached breakwaters and took a beach fill operation in 1988 to 1990. The decrease of the shoreline distance before 1986 in Figure 2 indicates the beach erosion caused by the extension of the Midia breakwater, a jump of the distance between 1986 and 1991 is the result of beach fill operation, and a straight line fitted to the data between 1989 and 2005 indicates the shoreline regression rate of 2.25 m/year.
The shoreline position change rate analyzed for 34 bench mark data is shown in Figure 3. A large recession rate at MM-7 is due to the local erosion at the northern boundary zone of a series of detached breakwaters. At the southern area of Mamaia Beach, an average erosion rate of –2 m/year is registered. Along Mamaia Beach, the northward sediment transport is predominant, but no clear shoreline advance is observed at its north end; there is a possibility of offshore loss of sediment there. In the south of Constan a Port, low sea cliffs occupy the majority of the coastline. Constantinescu (2005) revealed the mean cliff erosion rate of 0.5 to 0.7 m/year on average through comparison of topographic maps in 1924 and the satellite Ikonos images taken in 2002. A shoreline advance at EF-1 at Eforie Nord is the result of tombolo formation by construction of a marina after 1986. A conspicuous shoreline recession of –2.5 m/year at EF-6 seems to be caused by reflected waves from a collapsed seawall located south of EF-7. The shoreline recession of about –1.5 m/year at a beach of SN-1 and -2 would have been compensation of suppressed beach erosion at both the north and south of the beach by shore protection facilities built there in the 1970s. At the bench mark VV-1 ofVama Veche, the shoreline recession rate of 0.7 m/year corresponds to cliff erosion that has been taken over millenniums.
Conclusion
The study on beach erosion and coastal protection planning along the Southern Romanian Black Sea shore has successfully been carried out, thanks to the invaluable database of geophysical observation data accumulated over years at the National Institute for Marine Research and Development, the National Institute of Marine Geology and Geo-ecology, and other institutions. The study is an example of highlighting the necessity of long-range field measurements in the coastal area. The one-line theory has again proved to be an effective model to simulate the shoreline change over the coast of several tens of kilometer long and the period of scores of years, when field measurement records of beach topography over many years are available for providing the good data for model calibration.
Sources:
https://www.sciencedirect.com/science/article/abs/pii/S0964569119303199
Foto: Bogdan Bola/ Facebook
Author: Muntoiu Alexandru – ECOM Team Romania
2 Comments
Schema de protecţie costieră a litoralului Mării Negre
Proiectul cuprinde o gamă variată de lucrări de inginerie pe o porţiune de 7,3 km de plajă din cinci locuri: Mamaia Sud, Tomis Nord, Tomis Centru, Tomis Sud şi Eforie Nord. Această investiţie de-a lungul litoralului Mării Negre va contribui la atenuarea efectelor eroziunii costiere, într-o manieră care va fi benefică atât pentru turişti, cât şi pentru localnici. De asemenea, măsurile vor spori suplimentar gradul de atracţie comercială şi turistică a regiunii.
Schema include construirea unor noi diguri de larg şi repararea celor deja existente, restaurarea şi prelungirea epiurilor şi construirea de diguri de anrocamente şi epiuri îngropate. (Epiurile sunt bariere cu rolul de a prinde nisipul şi de a-l reţine pe plajă.) În plus, se construieşte un promontoriu artificial, demolându-se anumite structuri existente. Finanţarea acoperă şi asistenţa tehnică pentru gestionarea proiectului, publicitatea, echipamentele şi monitorizarea lucrărilor, alături de refacerea plajelor.
De această schemă vor beneficia cei 278 000 de localnici şi cei 32 000 de turişti care vizitează această zonă anual. În plus, aproximativ 120 de întreprinderi locale vor fi scutite de griji, datorită nivelurilor îmbunătăţite de protecţie costieră asigurată de proiect. Este de aşteptat ca proiectul să genereze 250 de locuri de muncă.
Asistenţă tehnică
Printre lucrările specifice din fiecare dintre cele cinci locuri se numără:
Mamaia Sud – reabilitarea digurilor paralele cu malul mării şi construirea a şase epiuri geosintetice şi a unui epiu de anrocamente;
Tomis Nord – reabilitarea şi prelungirea digurilor existente, reabilitarea epiurilor existente, precum şi construirea unui dig scufundat paralel cu malul mării şi a trei epiuri geosintetice îngropate;
Tomis Centru – reabilitarea şi prelungirea epiurilor existente, precum şi construirea unui dig de larg scufundat paralel cu malul mării şi a două epiuri geosintetice îngropate;
Tomis Sud – reabilitarea şi prelungirea epiurilor existente, precum şi construirea a două diguri de larg scufundate paralele cu malul mării şi a unui epiu geosintetic îngropat;
Eforie Nord – reabilitarea şi prelungirea epiurilor existente, demolarea a patru epiuri existente şi construirea a trei diguri de larg scufundate paralele cu malul mării.
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