On the evolutionary patterns of the large river deltas. Examples from Danube delta and other deltaic systems

Large river deltas are the among the most dynamic and complex natural systems, with a  complicated evolution which explain the relative small number of deltas which formation has been fully understood (reconstructed). However, deltas evolution is governed by a series of laws and patterns starting from their formation to the present. The aim of this study is to define the specific growth models of the Danube Delta and to discuss them in association with the other deltas of the world which share similar patterns of evolution. Thus, 7 evolutionary patterns have been identified in the Danube Delta as follows: (i) starting the deltaic units formation (as a bayhead delta around 7500 BP) before the sea-level stabilization, (ii) the preference of delta development into the deeper sectors (of the Danube bay), (iii) the river mouths of the open-coast lobes get a policyclic evolution, (iv) open-coast lobes are asymmetric and share the same evolution, (v) deltaic lobes have large (multi-secular) periods of decay despite the short-time triggering events (i.e. avulsions, sediment reduction), (vi) neotectonic subsidence reshaped the southern delta, (vii) the land-use controls the sediments discharge and impose the rhythms of delta development. Although each delta has its own particularities, certain patterns that are found in the evolution of the Danube Delta have also been found in other deltas, apparently different from the morphological point of view. The specific cases of the large Asian deltas (e.g.: Changjiang, Mekong, Godavari, Krishna, Red River) and many other from around the world (Mississippi, Rhone, Po, Kuban, Rioni) are discussed in relation with different evolutionary patterns identified for Danube. A special attention is paid to the role of human influence (via deforestation, agricultural practices, river damming and channeling) on delta formation and evolution during different historical periods, from Neolithic to modern times.