Giuseppina Garofalo

A distributed real-time approach for mitigating CSO and flooding in urban drainage systems

In an urban environment, sewer flooding and combined sewer overflows (CSOs) are a potential risk to human life, economic assets and the environment. To mitigate such phenomena, real time control systems represent a valid and cost-effective solution. This paper proposes an urban drainage network equipped by sensors and a series of electronically movable gates controlled by a decentralized real-time system based on a gossip-based algorithm which exhibits good performance and fault tolerance properties. The proposal aims to exploit effectively the storage capacity of the urban drainage network so as to reduce flooding and CSO. The approach is validated by considering the urban drainage system of the city of Cosenza (Italy) and a set of extreme rainfall events as a testbed. Experiments are conducted by using a customized version of the SWMM simulation software and show that the CSO and local flooding volumes are significantly reduced. HighlightsWe propose a distributed real-time control of urban drainage system.A gossip-based algorithm is exploited together with local PID controllers.The case study confirms the approach reduces effectively local flooding and overflow.

A Cyber-Physical System for Distributed Real-Time Control of Urban Drainage Networks in Smart Cities

This paper focuses on a distributed real time control approach applied to drainage networks. The increasing of urbanization and climate change heightens the challenge for new technologies to be developed for drainage networks. Higher runoff volume, produced by the increase in impervious surfaces and intense rain events, overwhelms the existing urban drainage systems. Recent technical improvements have enabled the exploitation of real-time control on drainage networks. The novelty in this paper regards the use of a totally decentralized approach based on a proper combination of a Gossip-based algorithm, which ensures a global correct behaviour even if local faults occur, and a classic controlling technique (PID) used for local actuations.

Green Roofs in the Mediterranean Area: Interaction between Native Plant Species and Sub-Surface Runoff

Green roofs (GRs) may represent a solution for minimizing the impact of urbanization on the hydrological cycle and for sustainably managing water resources in urban environment. Several studies have shown that GRs effectively control the surface runoff conveyed into the combined sewer systems, by reducing overall volumes and peak flow rates. The hydrological/hydraulic performance of a GR is strongly dependent upon vegetation species used. In this study the influence of plants on the sub-surface runoff is investigated by monitoring two experimental GRs in wet weather conditions. It is hypothesized that although plants reduce sub-surface runoff, they may also boost the formation of preferential flow paths. The results showed that the sub-surface runoff is strongly influenced by vegetation. While for smaller storm events the GR highly retains stormwater due to the plant interception, for larger storm events the GR’s performance decreases due to the increase of sub-surface runoff. This may be due to the presence of the plant root which produces preferential macropores flow through the substrate.

Experimental Testing for Evaluating the Influence of Substrate Thickness on the Sub-Surface Runoff of a Green Roof

Green roofs (GRs) represent one of the most widespread Low Impact Development (LID) techniques, although the lack of adequate modeling tools is a limiting factor in the diffusion of such practices. GRs may represent a solution for minimizing the impact of urbanization on the hydrological cycle and for sustainably managing water resources in urban environment. Several studies have shown that GRs effectively control surface runoff in urban drainage system reducing overall volumes and peak flow rates. The performance of a GR is strongly dependent upon substrate soil depth. The understanding of infiltration phenomena in soil medium is one of the most important factors in the LID’s hydrological behavior analysis. In this study the hydrologic/hydraulic behavior of a GR for varying substrate thicknesses and constant rainfall intensities, ranging from 45 to 130 mm/h is tested. The results show that sub-surface runoff is linearly influenced by substrate thickness.

Sampling, testing and modeling particle size distribution in urban catch basins

The study analyzed the particle size distribution of particulate matter (PM) retained in two catch basins located, respectively, near a parking lot and a traffic intersection with common high levels of traffic activity. Also, the treatment performance of a filter medium was evaluated by laboratory testing. The experimental treatment results and the field data were then used as inputs to a numerical model which described on a qualitative basis the hydrological response of the two catchments draining into each catch basin, respectively, and the quality of treatment provided by the filter during the measured rainfall. The results show that PM concentrations were on average around 300 mg/L (parking lot site) and 400 mg/L (road site) for the 10 rainfall-runoff events observed. PM with a particle diameter of <45 μm represented 40-50% of the total PM mass. The numerical model showed that a catch basin with a filter unit can remove 30 to 40% of the PM load depending on the storm characteristics.