ABSTRACT
In the last decades, land-use changes and urbanization have enhanced flood risk in urban areas in most of the Italian territory and worldwide. In some cases, climate change is claimed as a factor possibly playing a not negligible role and it may additionally exacerbate the vulnerability of urban areas in the future, according to potential projected changes of rainfall characteristics. To efficiently protect cities and increase their resilience to climate change, nature-based solutions are proposed in several frameworks, including the national adaptation strategy to climate change and the UNESCO World Water Program. These solutions are expected to bring a wider spectrum of benefits, when compared to conventional technology-based solutions, involving some socio-economic aspects beyond the obvious ecological benefit. Thanks to their variety, they are also helpful in planning several distributed interventions instead of a few concentrated ones, which would require more space and are difficult to place in historical settlements. To cope with the increased projected flood risk in urban areas, several Italian regional governments approved laws and standards on so-called ‘hydraulic invariance’ requiring that new urban settlements maintain the outlet flow in the stormwater drainage system at the pre-urbanization value. This is actually in line with the national climate change adaptation strategy and gives a chance to implement also nature-based solutions. A review of case studies of structural and non-structural measures being implemented in Regione Lombardia, together with an assessment of actual trends of extreme rainfall at an hourly scale, is presented.
