Soil releasing as key to rethink water spaces in urban planning

Abstract

Soil sealing processes that involved European cities in the twentieth century have reduced the quantity and quality of permeable soils (open land for agricultural and leisure resources). These processes have also weakened the ability of urban areas to manage natural events, of all evidence regarding the water cycle. This intense phase was supported by a cycle of growth that showed signs of an irreversible crisis only in the last decade, starting a new and unprecedented season. However, soil sealing development constitutes the most intense form of land degradation and affects all ecosystem services (Tobias et al. in Land Degrad 29:2015–2024, 2018). This is particularly true for spaces and territories along main rivers where the presence of sealed areas and concrete channels (riverbed and riverbanks) represents a problem regarding hydrogeological, ecological, and landscaping aspects. To safeguard urban systems, by restoring “landscape river” (and its surroundings), increasing green areas and more efficient management of the rainwater, it is fundamental to enhance the “removing sealing layers” (EU 2012) according to a holistic approach. This paper explores the de-sealing concept and highlights some international and Italian cases, in particular the River Contracts experience promoted in the Lombardy Region, including actions proposed by public policies and urban planning tools. All these experiences have proposed de-sealing processes of river environments and urban systems ensuring a new integration between urban areas and “water landscapes”. To underline some characteristics this exploration allowed: to highlight different de-sealing approaches, between direct or indirect conditioning; to recognize river elements and “environments” in which these initiatives are activated; to recognize in these initiatives a multi-scale attitude both the expected effects and the type of involved institutional subject involved; to identify the main subjects, with specific roles and responsibilities, in this type of process; to recognize limits and critical issues. River restoration, combined with de-sealing actions inside the urban structures, shall be performed by answering to several needs: increasing the green open space quantity and ecosystem services recovery; contributing to biodiversity by restoring ecosystems and ecological processes; balancing the soil-sealing negative externalities; improving the flood-risk mitigation and management in urban areas. In particular, the voluntary instrument of the River Contract includes a territorial area that is adequate for the treatment of the phenomenon but is struggling to be codified in the local planning instruments with cogency. The assumption of different spaces and the recognition of the same in the spatial devices of urban planning instruments could define more clearly the need to face the water-city relationship effectively, for the benefit of urban security and the quality of the inhabitants’ living environment.