Wear processes in architectural heritage: definition, studies, contrasting measures. The case of UNESCO World Heritage Site “Venice and its Lagoon”

Since 1987 the site “Venice and its Lagoon” is included in the UNESCO World Heritage List and recently adopted its own Management Plan. The Plan doesn't overlay the usual planning tools and techniques, but it's aimed at identifying possible resources for site development and possible threats to the site integrity, and at defining pre-requirement necessary for a better coordination between authorities and institutions responsible for management. One of the finality of the Management Plan is the study of criticalities and potential stress conditions for the urban system, which are able to originate wear processes both physical and perceptual, in the short, medium and long period. The other target is the identification of causes of wear, its dynamics of appearance and development, its influence on protection of monuments and landscape, and the possible contrasting actions. The term “wear” is not only related to process of material decay, but also to process of immaterial one, such as the loss of socio cultural identity, the reduction in the quality of life or the increase of problems in the fruition (or perception) of cultural heritage and urban peculiarities, due to overcrowding or saturations of paths. Analysis related to Venice risk conditions connects wear phenomena to different dynamics, such as: tourism flows, people congestion, progressive conversion of buildings from residential use into services for tourists, widespread of licenses for the so-called plateatici, increasing decay of dockside elements, presence of high water, gradual erosion of canal’s shore due to growing wave motion and pollution, presence of waste, commital of acts of vandalism on built heritage, presence of pigeons or other colonizing animals. Although tourism represents a source of wealth for the city, certainly it can be considered as one of the most critical elements responsible for urban consumption, being an accelerator for all factors connected to wear process and to urban consumption. Since wear dynamics are surely diversified - due to natural or anthropic agents - the identification of effective strategies for controlling those processes and of solutions for mitigating impacts can not be limited to a sectorial approach, but needs to be developed into a wider framework, in which mutual interaction between different phenomena are taken into account. The paper will deeply illustrate the themes above mentioned, referring to the research “Evaluation of wear processes and critical situations in Venice and its Lagoon due to mass tourism and of the relative effect on the site protection: some emblematic cases”, launched by an initiative of the Venice Municipality and under the guidance of the government department responsible for the environment and historical buildings of Venice and its Lagoon (Soprintendenza per i Beni Architettonici e Paesaggistici).