Analisi Evolutiva del Sistema Spiaggia-Duna in Emilia-Romagna: Processi Morfodinamici e Trasporto Eolico

Several studies have been carryout to highlight the scientific community about the importance of coastal beach-dune system in coastal dynamics recognizing. Their ecological and environmental value is very important, they play a fundamental rule in coastal defense protecting hinterland from flooding with their raised morphology, contrasting the salt wedge’s intrusion with their water table and moreover they constitute an important reservoir of sand for beaches This aspect in the Emilia-Romagna region seems to be particularly important: many coastline features are characterized by emergency conditions because they are exposed more frequently and dangerously to phenomena of submersions for sea storm’s events and to a diffuse and intense marine erosion. Actually, along 130 km of the Emilia-Romagna coastline, 29 km are characterized by the presence of coastal dunes, of which, approximately 9,5 km belong to the province of Ferrara, approximately 18 km to Ravenna’s and remaining to the more to south coastal part of the region. In this paper the results of a regional research are presented trough the application of a methodological integrated approach (System’s Theory), that aims to analyze and to point out the evident morphoevolutionary state of crisis in which the Emilia Romagna dunes today are (2008). Another objective is to try to optimize the management’s policies of natural sedimentary resources, which are today very important for the new philosophical approaches to coastal problems. The final result is a tool able to supply indications about the priorities to front and the actions methodologies finalized to the safeguard and the defense of these delicate environmental subsystems. It becomes fundamental to have the correct perception of the phenomena in action and to quantify the “weight” that the several morphodynamic’s agents have in the coastal dune system’s evolution. The parameterization of such factors, the spatial analysis, the multi-scale and temporal analysis (from 2000 to today) helps us to identify the relations of mutual interaction between such parameters. Therefore, it’s possible to extract an Instability beach-Dune system Index (IDI) to establish the state of system’s instability, and a space-temporal variability allowing their possible future evolution forecasting. Among all the factors, the anthropic impact of the several tourist activities on the management of coastal spaces, in the Emilia Romagna region seems to be the most important: only for the province of Ferrara, for example, from 2000 to today, the areas lacking in vegetation developed on dunes, have increased of approximately 11%. The majority have become unvegetated ground knots (blowouts), full of recreational structures, or transformed in tourist’s beaches. Through the overlap of several classes of land cover distributions (change detection), it is possible to gain important indications on the dunes erosive trends: of the 9,5 km of the Ferrara’s dune’s coastal strip, nowadays approximately 4,2 km, is developed through an erosion escarpment with height greater than 1m. This demonstrates that the exposure to wave action is intense and frequent. In these cases the processes can reach to abrupt accelerations, till to assume speed and various intensities also from point to point for a same system; in a short time, the opening of crosses and the development of blowouts can put in crisis the whole dune’s system and expose the inlands to a risk. In 11 cases on 23, the front beach highlights an erosion trend and the width is less then 20m with the dune’s foot which is often constituted by temporary accumulation generated by landslides of the erosion walls. Therefore, this job has been integrated with a study on the wind’s “potentialities” to contribute to the maintenance and/or the development of dunes, by applying a conceptual model (Kadib, 1983; Bagnold, 1941) that allows to gain an annual potential sedimentary budget for each system, in relation to the medium climate and to the morphological and sedimentary characteristics of the system. Such aspect can supply important indications during all the steps of a coastal action, beginning from the planning and realization of sedimentary traps, till their positioning and direction. Moreover, the obtained results above all demonstrate as such methodological approach can represent a real, useful, regional scale instrument to all policies of coastal land management, to the research on new technical of actions or to program and optimize the resources.