Reconstructing changes in sediment input from the Danube into the Black Sea

Abstract

One of global changes affecting river-sea systems is a reduction in sediment flux. This is a direct consequence of human interventions in the river basin. The delta complexes, especially, record the most striking effects, such as coastal erosion and habitat degradation. This research assesses the change of sediment flux from the Danube Delta into the Black Sea, under the influence of dams and climate change. The effects are identified both on a long-term scale (one century) and on a short-term scale (seasonal variations). The results show how anthropic interventions at basin level – for example, the construction of dams and local interventions in the Danube Delta complex – change sedimentary rates across the delta complex, from the delta plain to the delta front area. The results also show modifications of the hydrological regime of the Danube, as a consequence of climate change. For the first time, the reduction in sediment deposition rates is quantified, of 46 % for the delta, 46-55 % for the delta front area and of 62 % for the prodelta. The local variations within the subaerial delta plain are controlled mainly by hydrological connectivity, while the variations within the subaqueous delta complex are controlled primarily by coastal jetties, proximity to river mouth and the character and evolution of the river plume. Seasonal variations of suspended sediment characteristics are largely controlled by the same factors, in addition to local phenomena (e.g. bottom resuspension) and the seasonality of water primary productivity. The results of this research can be used to improve management practices of the Danube Delta and its coastal zone, for land use and remediation practices. It can also contribute to future development of methodologies for monitoring environmental changes in a collective transboundary management system of the Danube catchment, which could be applied in other river basins around the world.