Geomorphology, sedimentology and recent evolution of the anthropogenically modified Simeto River delta system (eastern Sicily, Italy)
The purpose of this paper is to present a complete stratigraphic framework for the modern Simeto River delta (eastern Sicily, Italy) by the description of its geomorphology and sedimentology, which allow an analysis of its recent evolution. The Simeto River delta represents an asymmetric wave-influenced delta which developed during the Holocene by prograding into the Catania Gulf. This delta represents a good example of a Mediterranean-type system, characterized by a micro-tidal regime and moderate wave energy; the peculiar distribution of sedimentary facies both in the subaerial and in the subaqueous sectors is interpreted as the response of the system to the intimate interaction of geological and, in recent times, anthropogenic coastal activity. The integration of a large amount of historical data allows the definition of prograding and retrograding pattern within the delta and the cyclical shifting of the river mouth over the last two centuries. A hypothetical model is proposed to explain this phenomenon, and it is suggested that this may be a characteristic of several Mediterranean-type deltas. Progradation of the delta ended during the early-middle XIX Century after which it began to retreat. The retreat of the coastline accelerated after the 1950s when owing to the construction of embankments on the delta plain and, since 1970s, increasing diversion of water resources in the upper part of the Simeto River drainage basin, the sediment input of the river to the Ionian Sea sharply decreased. This caused a dramatic change of the deltaic morphology and significant coastal land loss. The morphological and sedimentary features of the Simeto River fully reflect the processes of its adaptation to the persistence of coastal human activity within an active geological setting.