Hydrologic performance assessment of nature-based solutions: a case study in North-eastern Italy

The consequences of climate change are exacerbated by land-use changes, which influence the rainfall-runoff relations and consequently the flood risk. Effectively, urbanization is steadily contributing to the increase of impervious areas and reducing the time-to-peak. The effect of Nature Based Solutions (NBSs) on the mitigation of these phenomena is recognized. Nevertheless, these kinds of sustainable infrastructures are still barely known and scarcely adopted in many parts of the European Countries. The LIFE BEWARE project aims to enhance hydraulic safety and spread good practices in rainwater management by promoting and facilitating the adoption of NBSs in the Altovicentino area (Northern Vicenza Province, Veneto Region, Italy). To support the dissemination activities, some full-scale NBSs have been created within the municipality areas involved in the project. The hydrological impact of the structures is continuously monitored thanks to the installation of devices measuring inlet and outlet runoff, and rainfall pattern. This study aims to analyse the monitoring data of the first two years of the built NBSs. Results show that the structures managed almost all the water runoff through processes of infiltration and retention, providing additional insights into understanding the real behaviour of NBSs exposed to the specific environmental conditions of a very rainy foothills area. In particular, mean rain intensity and rainfall duration are the variables that mostly affected the structure performance, especially for events prolonged over time (2-3 days) with mean rainfall intensity in the range of 2-3 mm/h. Therefore, the overall outcomes from this analysis resulted as being useful to improve the design of NBSs and further promote their installation in urban areas.