Hydraulic efficiency of a Sustainable Urban Drainage System in Turin.

As urban environments continue to expand to accommodate the increasing global population, there is an ongoing necessity to measure and characterize the effects of urbanization on natural processes. Particularly, the development of impervious surfaces disrupts natural hydrologic cycle as well as affecting the efficiency of drainage systems. Consequently, modifications in slopes, soils, and land cover will result in dramatic alterations in runoff peak, maximum volume involved, flow routes and timing related. Because of the mentioned changes, there is an increase of possible flooding, pollution, and erosion problems. Therefore, it is of paramount importance to find solutions not only to reduce surface runoff effects, but also to do so at a sustainable level. Hence, Sustainable Urban Drainage Systems (SUDS) rise as a significant alternative to counteract some of the mentioned impacts on the water cycle. The philosophy of these systems relies on slowing down and reducing the quantity of surface water runoff by infiltrating, storing, and conveying water excess. In the framework of urban drainage issues, the present thesis aims to model the hydraulic response of an urban basin, represented by a half-block street located in Turin, Italy; in order to determine the efficiency of an existing SUDS. To do so, Hydrologic Modeling System (HEC-HMS) software was required to simulate precipitation-runoff process. Throughout the model construction, the mentioned software allows to consider the most significant and influencing factors involved in the surface runoff process such us: elevations and slopes, through the utilization of a Digital Surface Model (DSM), soil characteristics, using specific loss methods considering infiltration rates as well as impervious areas, and including different options for representing the transformation of precipitation into surface runoff. Once finished the hydraulic modeling, and after choosing appropriate precipitation data according to IFD curves from Turin involved area, a base scenario without the contribution of the SUDS was set as a reference point. Therefore, the desired efficiency was obtained comparing the base scenario with the ones under the influence of the existing SUDS, which were represented considering specific infiltration rates and impervious area. As a result, it is possible to reflect about how much these systems collaborate to reduce both peak runoff and volume at the basin outlet, as well as the influence of some factors related to the SUDS design such as: material, contributing areas and street slope.