English

Abstract

River deltas are extremely important to the Mediterranean region’s geography and resources, and have been for many millennia. They offer fertile soils for agriculture, freshwater resources and rich biodiversity. The nature and growth of the Mediterranean’s river deltas reflect the cumulative interplay of several natural factors and the increasingly overarching influence of human activities. These factors include inherited coastal geology and coastal morphology, sea-level oscillations, a potentially complex and variable relationship between climate change, landscape degradation and fluvial sediment supply, and the oceanographic regime. The human influence has acted directly and indirectly on fluvial sediment supply and via engineered interventions on rivers and the coast. The patterns of river delta growth and delta morphodynamics in the Mediterranean, thus, reflect adaptations to pulsed sediment supply, river discharge variations, the microtidal, fetch-limited context, and human interventions. The marked progradation dynamic that prevailed during the Roman period, influenced by human activities, and during the Little Ice Age, contrasts markedly with the situation of common destabilisation over the last two centuries, particularly well documented for the last 50 years. This period has been characterised by reduced sediment flux due to catchment reforestation, retention within reservoirs, and fluvial regulation and dredging, resulting in the erosion of deltas and adjacent barrier-lagoon and beach-dune systems. In addition to catchment destabilisation, the human presence on Mediterranean deltas is also a challenge in terms of maintaining their integrity. Many of the societal problems associated with deltaic erosion and flooding are, unfortunately, often compounded by high population densities and by the economic attractiveness of these areas for urbanisation, agriculture, transport, industry and recreational purposes. Human impacts in Mediterranean river catchments and human presence and activities within the regions’ deltas have thus been driving significant changes in deltaic and adjacent systems, and today human engineering largely controls the growth and evolution of many of the Mediterranean’s most important deltas (e.g. the Nile, the Rhone, the Ebro, the Po). It has been argued that Mediterranean river deltas may be capable of coping with sealevel rise (SLR) through three self-reinforcing mechanisms as the SLR rates increase,