Contribució al coneixement de variables geoambientals en l'àmbit de la Costa Brava (Girona)

Resumo

This thesis developed is framed within the scope of the Environmental Sciences. Environmental Geology is applied to understand the geological processes and resources that take place in the area, thus enhancing the management of the territory. All the littoral area within the hydrographical basins of the Aubi, riera de Calonge, Ridaura, riera de Tossa and riera de Lloret (75 km of coast line and an extension of 291 sq.km), a good part of the southern Costa Brava, has been selected as the study zone. This work, with its ability to integrate the concepts and methods of the Environmental and Geological Sciences, has three main objectives: the analysis of the quality and the physical and chemical behaviour of the terrestrial materials in front of human actions and its utilization as resources; the study of the natural processes and the influences that they have on the antropic activity, or the effects that this can cause on those; and as a derivation of the previous objectives, the design and application of preventive instruments for the management of the territory, that is to say, the planning of the uses of the territory. Considering geological factors as helping elements to achieve an integral vision of a territory, different geoenvironmental variables have been studied. It has been tried to translate the acquired knowledge into information which could be used by the planners of this coastal environment for their decision making process. The Geographical Information Systems (GIS) have been a key factor to keep a systemic vision of the territory. They have also made possible the integration of the different geoenvironmental variables, as well as the cartographic production. With regard to the geological processes related to the fluviotorrencial dynamics, the main areas of their action have been mapped. The factors that initiate, favor or increase their occurrence have been analysed as well. The denudation actions, processes of transportation and sedimentation have also been studied. With the integrated study of all these processes and resultant forms, several territorial units characterized by a uniform geomorphic behaviour have been identified. With the analysis of the geological resources, we have contributed to the knowledge of the subterranean water resources, the industrial rocks and the coastal georesources. With regard to the first item we have put most of our efforts in the delimitation of the main aquifer units and subunits, as well as in the study of their geometries and their main hydraulic characteristics. With regard to the mining activity, the fundamental objective has been the cartographic delimitation of those materials which, by their physiochemical properties, are potentially apt for the indicated uses. Finally a study oriented to the factors that limit or condition the geotouristic potential of this littoral area has been done, specifically at the cliffs and in the beaches. The main contributions of this thesis can be framed in regional and phenomenological fields, both of which are key aspects in management and territorial planning. With respect to the regional ones, we would like to emphasize the contribution of geoenvironmental cartographic data related to litostructural variables, dynamic processes or geological resources. Considering the phenomenological aspects we would like to highlight the interaction of the variables inside the hydrographical basins, like the existing relations among the different aquifer formations; the possible participation of groundwater in the hydrologic response of the fluviotorrencial system, or the quality losses of the sand of the beach as a result of the rubble dumping on the creeks margins.