Alluvial transport processes and the impact of Anthropogenic intervention on the Romanian littoral of the Danube Delta
Abstract Within the context of shoreline alteration, the impact of hydrotechnical works on coastal processes has been increasingly discussed in the literature. In this study, we analysed the Romanian deltaic littoral, which is situated between the mouths of the Chilia arm (North) and Midia Cape (South) of the Danube Delta, with a total length of 166 km. The present study examines the hydrotechnical works constructed at the mouth of the Sulina arm and the inlet of Portita. In 1858, the European Danube Commission (which was created in 1856 but whose projects were initiated previously to that date) built the first hydrotechnical works at the mouths of the Danube. The maritime sector between the two river mouths (the Sulina and the St. Gheorghe) is 33 km long and is impacted by maritime forces that run both parallel and perpendicular to the mouths of the river. The continuous advancement of dams, which currently reach lengths of 9 km, has altered the shore. As the dams advance towards the sea, the north–south current is forced to deviate from its original route. The northern current, which is at its maximum extent during the winter months, is eroding the areas located next to the Imputita brook (north) and the Sondei channel (south). These areas of the shore are also influenced by the southern current, which moves in a south–north direction and is at its maximum during the summer season when it pushes the northern current towards the “alluvial trap”. Therefore, the maximum erosion occurs next to the Imputita brook (north). In the “alluvial trap” located south of the advancing dams, the particle size of the sandy deposits is slightly different from that of deposits in the erosive sector of the Imputita-Sondei. The jetties curve south, which causes a slight decrease in the rate of the “Sulina bar” formation because the waves coming from offshore do not directly enter the channel mouth, and thus the deposition of alluvium is slowed. Lateral erosion is visibly increased between the two river mouths due to a decreasing alluvial budget. Intense erosive processes also affect the Razim-Sinoie coastal barrier, which closes the lagoon of the same name. The first major hydrotechnical alterations were erected in the 1970s (when channels connecting to the St. Gheorghe mouth were first dug, and contact with the sea was totally or partially interrupted), and the inlets and outlets of the lagoon complex are now human-controlled. The hydrotechnical works led to an alteration in the direction and force of the littoral currents as well as a decrease in the amount of alluvia, thus altering the sedimentary budget. Over 60% of the entire deltaic littoral is currently eroding and the other 40% is accumulating.