Soft Cliffs Retreat Under the Shadow of Three Ports on the Southern Romanian Coast

Abstract

The soft rocky coast between Cape Midia and Vama Veche was investigated based on cartographic documents. Shoreline evolution was computed for the past century focusing on two different periods: in cvasi–natural regime/low anthropic pressure (before 1960; 1910–1960) and under strong human influence (after 1980). Two decades of transition (1960–1980) were characterized by the construction of new defence structures, new resorts, and other industrial facilities that transformed completely the coast. Lithological formations (limestone, clay, and loess) cause the unstable nature of these cliffs. The highest erosion values occur on Mangalia beach and 2 Mai coast, with more than 4 m/year. In cvasi–natural regime, progradation represents 62.5 % and the retreat area only 37.5 % of the entire coast. The balance was tilted quickly in just two decades (1960–1980), when the erosion sectors affected 50.8 % of the coastline. Coast responded to these anthropogenic pressures by a pulsating behavior, with higher amplitude of oscillations after 1980 and with a spread of erosion processes that affect now 67.3 % of the coast. Construction of the three ports, Midia, Constanța, and Mangalia, imposed a new scenario by changing the distribution/settling of sediments coming from the Danube and generating a positive feedback. Intense retreating rhythms correspond to the negative phase of the NAO from 1961 to 1972. In the next decades, a period with a positive NAO index, the magnitude of erosive processes on the deltaic coast was smaller. In the case of cliff coast, this process has not reflected in shoreline dynamic and erosion rates became higher, as a direct effect to anthropogenic impact. After a strong intervention, the ability to withstand disturbances induced by human influence should be considered in a larger context, which cannot exclude the upstream Danube valley, the most important source of sediment, not only for the deltaic coast, but also for the cliff one. Accelerated anthropogenic pressure on the environment, involving dams on rivers and extending coastal structures, will generate negative effects in the future, in a difficult context imposed by the climate change.