Danube delta coastline evolution (1856–2010)

Abstract

Danube Delta coastline evolution showed a significant variability in the past 150 years related to different driving forces which change the leading role between them depending on the temporal and spatial scales taken into consideration. At long time scales (centuries), coastline dynamics is mainly driven by the dramatic decrease of Danube sediment discharge after 1950. This is pointed out by the significantly higher shoreline migration rates and area changes between 1856 and 1961/1979 in comparison with the subsequent period, especially along the accumulative sectors. As a consequence, since mid-twentieth century, Chilia lobe started the transition from fluvial-dominated morphology to wave-influenced aspect and behaviour. At multi-decadal scale, shoreline dynamics is ultimately driven by climate variability, related to North Atlantic Oscillation (NAO), which controls the storminess variations along the Danube Delta coast. From this point of view, there is a marked difference between the 1961–1979 time interval, characterised by dominantly negative NAO phase, which determined active storminess, inducing high shoreline mobility, and the 1979–2006 period, which showed less dynamic coastlines (on both prograding and erosive sectors) as a result of the lower storminess imposed by the dominance of positive NAO phase. At inter-annual scale, waterline morphodynamics is influenced by storm regime and river floods.