Evolution of Chilia lobes of the Danube delta: Reorganization of deltaic processes under cultural pressures

The growth of Chilia deltaic lobes reflects a drastic reorganization of the Danube delta that accompanied its rapid expansion in the late Holocene. Using new cores collected at the apices of the two older Chilia lobes, together with historical maps and satellite photos, we find that a partial avulsion since ∼1500 years BP led to a gradual rejuvenation of the Chilia distributary. This process led to the successive infilling of a lake and a lagoon and subsequently to the construction of an open coast lobe at the Black Sea coast. The Chilia branch became the largest Danube distributary, reaching its maximum sediment load in the last 300 years as the southernmost St. George branch lost its previous dominance. Here, we propose that the intensive deforestation of Danube's lower watershed leading to this delta reorganization has historical cultural causes: an increase in sheep and timber demand associated to the Ottoman Empire expansion in Eastern Europe followed by the adoption of maize agriculture as a result of the Columbian Exchange. Rapid industrialization-driven damming during the Communist Era led to the current generalized sediment deficit for the Danube. Under these conditions, the modern Chilia lobe is rapidly remodeled by waves and may join the Sulina coast to impede navigation on the Sulina canal.