ENVIRONMENTAL AND GEOLOGIC INDUCED RISK: A CASE STUDY IN ALCAMO MARINA (TRAPANI, SICILY)

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Abstract

Human activities often interfere with the natural evolution of the environment, even more so when any rule or criterion of respect for the environment or urban planning is followed. This, in addition to perturb the natural system, determines conditions for geological and environmental risks, particularly when acting on vulnerable areas, poorly suited for urbanization. In the present study, risk conditions for the site of Alcamo Marina, in the territory of the town of Alcamo (TP), are analyzed, which are determined due both to the geomorphologic setting of the territory and to a large number of human interventions. carried out under an irrational approach since the 70s, in this stretch of coast of Sicily.The geologic and structural setting of the area is controlled by the tectonic superimposition of carbonate and clastic-terrigenous units, set up during the Miocene; in discordance on the deformed Mesozoic-Tertiary formations, calcareous-terrigenous dating to the Lower Pliocene have deposited. The sequences are covered by the sandstones of the Emiliano – Siciliano, that are truncated by large upper planation surfaces (quaternary marine terraces) and, along the coastline, are linked trough very steep slopes to beach deposits.The analysis of historical maps and illustrations allowed to reconstruct the morphological and topographic setting, that had characterized the coastal area before the human impact could upset and disfigure a landscape that, originally, was to present high natural values as observable from a cartographic and pictorial representation by Schmettau, dating back to 1720. Particularly, of extraordinary beauty was to be dune systems that were extended far to the south of the railway line, in some cases, reaching the base of the Quaternary marine terraces; the latter had a thick cover of forest type and were affected by few or any gravitational phenomena.The setting of the shoreline has been heavily modified from the realization of port facilities and the reduction of sediment transport from the River San Bartolomeo; also, as well as a widespread and uncontrolled human activities affected the entire coastal strip so as to making it appearing today as a densely urbanized area. All this has led to a heavy modification of the hydrographic setting of area; in fact, the water courses were first laterally confined and forced to move in very small channel and then forced to flow through undersized pipelines, along alignments very different from the original paths. As a consequence, during pluviometric critical events, widespread phenomena of flooding in adjacent areas occur, triggering also numerous mass movements of soil slip type, on slope. A lot of damages have been recently produced to structures and infrastructure, during the floods of August 1997 and February 2009. The risk conditions in the area are, therefore, related to the hazard for flooding of almost all the streams, for gravitational phenomena affecting the slopes which border the terraced deposits, also as a result of intense excavation and earth moving which have changed the overall morphometry of slopes, and for accelerated water erosion, following the replacement of forest cover with productive essences. Therefore, only after identification of the most vulnerable sectors it will be possible to proceed with appropriate interventions, which are to be correctly planned and systematically extended to the whole coastal strip in order to obtain a mitigation of risk and a general recovery of the environment.
Original languageEnglish
Pages147-148
Number of pages2
Publication statusPublished - 2009

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