Resilience of the Urban Drainage System in Brescia (Northern Italy) to Climate Change: A Preliminary Analysis

Changes in weather types and features caused by climate change in Northern Italy might lead to more frequent hydrometeorological events, besides urban floods and droughts. Namely, climate change is expected to alter the magnitude and frequency of extreme meteorological events forcing the urban drainage infrastructure. Future changes in rainfall intensity will then require higher performances of the hydraulic infrastructure. In fact, without an upgrade of the sewerage more frequent urban flooding and surcharging of waterways will occur. In recent years it clearly emerged that the "conventional" solutions, as the collection of rainwater through road drains and its delivery into the sewer system, are not adequate to handle the problem. First of all, they are not robust solutions, since they are sized for the extreme events expected in the future and can therefore discharge very high flow rates into the waterways and increase the downstream hydraulic risk. Secondly, because most of the Italian urban sewerage system is combined, so the pipes collect both wastewater and stormwater and during heavy storm discharge through the spillways most of the flow directly into the water bodies, bringing a significant polluting load. Accounting for climate change requires a radical change in the approach used to plan and design drainage infrastructure. This should foster development features and sustainable urban drainage systems that provide multiple benefits, such as surface runoff reduction, water quality improvement, rainwater collection and reuse, as well as mitigation of the urban heat island effect. In this perspective, sustainable urban drainage represents a useful and necessary solution to reduce the impact of climate change effects especially in highly urbanized areas. In this study, a preliminary analysis was carried out for the Brescia case study, an Italian city that is developing a strategy to adapt to climate change. A multi criteria scenario analysis was used to generate and evaluate the effectiveness of sustainable adaptation strategies under the deep uncertainties due to climate change. In addition, different solutions were investigated to find those which better fit the specific urban context of the city, where free space is seldom available.