The GIFLUID Project (Green Infrastructures to mitigate flood risks in Urban and sub-urban areas and to improve the quality of rainwater discharges) addressed the issue related to the onset of flooding events arising due to the impacts of climate change and the anthropic urbanization of the coastal landscape, which are two common challenges for the territories of Sicily and Malta. In the context of the admissible action of the IT-MT program, the project aimed to develop and promote practical tools which integrate the planning and design of Green Urban Infrastructures (GUIs) in critical urban and sub-urban area of Sicily and Malta, to mitigate floods effects, to increase the infiltration of rainwater drainage improving also its quality. The project developed its mitigation framework through the implementation, at real-scale, of three different types of GUIs that are porous pavements, rain gardens and green roofs.
The Green Roof (GR) installed on one of the conventional roofing of the Department of Agriculture, Food and Environment of the University of Catania (Sicily, Italy) is a semi-intensive GR, has an area of about 900 m2 and was planted with 1500 herbaceous and shrubs plants (Figure 1).
Figure 1 – Green Roof installed at the Department of Agriculture, Food and Environment of the University of Catania (Sicily, Italy). A) Conventional roofing ante operam; B) Green roofing post operam.
The GR was installed on the traditional roof taking into account the existing slopes and downpipe locations. The roof was divided into 7 sectors and implemented with 3 different GR technologies, named Draining Modules (4 sectors, 267.5 m2), Experimental (2 sectors, 178 m2) and Green Safe (1 sector, 95.8 m2) (Figure 2a-b). After delineation of the different sectors by means of lightened concrete curbs, the root-resistant bentonite sheathing was laid, before installing the package of the different technologies. An irrigation system was installed to provide emergency irrigation in case of long dry periods. Finally, substrate for vegetation was distributed and plants were planted.
The site was equipped with a weather station made up of a thermometer, a barometer, a hygrometer, an anemometer and a pyranometer, for the monitoring of the main meteorological paramaters, i.e. the air temperature (°C), the air pressure (bar), the relative humidity (%), the wind speed (ms-1) and the solar radiation (Wm-1), respectively (Figure 2c). Moreover, the response of the GR vegetation in the visible and near-infrared spectral domain, and in the thermal spectral domain, is detected by a multispectral and a thermal camera, respectively. The soil volumetric-water content (SWC), temperature, and bulk electrical conductivity (EC) patterns of the GR sectors under study are continuously measured using a set of TEROS-12 probes (METER Group) and a couple of innovative multiparameter smart sensors (CS655, Campbell Sci.). All sensors are connected to a data-logger that manages the data.
Sensors were installed to compare the thermal behaviour of GRs (Figure 2b). The following parameters were monitored: thermal flow between the substrate and drainage layer, substrate surface temperature, temperature in the middle of the substrate (VWC), temperature between the substrate and the drainage layer and water content.
Figure 2 – Green Roof at the Department of Agriculture, Food and Environment of the University of Catania (Sicily, Italy): a) GR plan with the indication of the implemented technologies, the monitored sectors and the weather station; b) technologies sections with the construction details and location of thermal performance sensors (in red and blue the heat flux and surface temperature sensors, respectively, in green the substrate water content and temperature sensors); c) detail of the installed weather station.
Finally, in order to evaluate the effects of the GR technologies on the runoff volumes, the outflow is continuously monitored in 4 sectors in total, 3 equipped with the different technologies and 1 corresponding to the existing roof, used as control. Before to be discharged to the soil, the outflow collected in each of the 4 monitoring downpipes is collected in a system of tubes equipped with valves and ultrasonic volumetric gauges connected to a data logger (Figure 3).
Figura 3 – Sistema di monitoraggio del deflusso del tetto verde dotato di valvole e misuratori volumetrici a ultrasuoni collegati ad un data-logger.
The GIFLUID Project addresses the onset of flooding events in urban and sub-urban areas arising due to the impacts of climate change and the anthropic urbanization of the coastal landscape, which are two common challenges for the territories of Sicily and Malta. These cross-border territories present similar characteristics namely a semi-arid dry climate a prevalence of high intensity rain events, the historic urbanization of the low-lying areas of coastal catchments.
In the context of the admissible action of the Interreg Italia-Malta programme, the project aims to develop and promote practical tools which integrate the planning and design of green urban infrastructures (GUIs) in critical urban and sub-urban area of Sicily and Malta, to mitigate floods effects, to increase the infiltration of rainwater drainage improving also its quality.
WP1 concerns project management and WP2 dissemination and communication activities (seminars, training courses, workshops, etc.).
WP3 and WP4 promote the realization of green infrastructures in some demonstration plants.
WP5 includes modelling activities to evaluate the effects of green infrastructures on the reduction of hydraulic risk in urban and sub-urban areas, and the final editing of a master plan for the implementation of GUIs in some target areas located in Sicily and Malta.
In particular, the WP3 and WP4 envisage the construction of demonstration plants to promote some green infrastructures such as porous pavements (PP), rain gardens (RGs) and green roofs (GRs) in the territories of Sicily and Malta.
WP3 will promote Low Impact Development (LID) technologies, like innovative porous pavement (PP) and rain gardens (RGs) for storm water management.
PPs are able to address both water quantity and quality issues. PP is a particular Hydraulic Best Management Practices (BMPs) allowing storm water to seep directly into the ground (if the water quality permits) rather than running off into storm drains. As rain falls on the pavement, it infiltrates down into the storage basin where it is slowly released in the underground environment or conveyed to surface discharge systems.
RGs are landscaped depressions designed to infiltrate and filter storm-water runoff, containing vegetation and sometimes a drainage system. RGs are designed specifically to withstand high amounts of rainfall, storm-water runoff, as well as high concentrations of nutrients typically found in storm-water runoff – particularly nitrogen and phosphorus, minimizing the amount of rainwater that enters storm drains. They also help to trap silt and other pollutants that are carried by the runoff – as the water percolates through, it is treated by a number of physical, chemical and biological processes, removing loads of heavy metals and sediments, and thereby improving water quality and protecting local waterways from pollution.
These type of green urban infrastructures (GUIs), relatively cheap and easily implementable by the Public Authorities, can be designed starting from the urban planning stage, in order to reduce the flooding risk, and also settling of solids.
In Sicily a PP will be implemented in Aci Castello and a RG will be implemented in an area of UNICT. In Malta PP and RG demonstration sites will be implemented within the administrative area of the Rabat Local Council.
WP4 will promote the use of green roofs (GRs) in Mediterranean regions to mitigate the effects of the increased runoff peaks, volumes, and velocity. In particular, GRs are constructed of a lightweight soil media, underlain by a drainage layer, and a high quality impermeable membrane to protect the building structure. They are also passive cooling systems, which reduce incoming solar radiation from reaching the building structure. Green roofs are increasingly being used as a source control measure for urban storm water management as they detain and slowly release rainwater. Due to their water storage capacity, green roofs may significantly mitigate the runoff generation of most rainfall events. The mitigation consists in delaying the initial time of runoff due to the enhanced infiltration of water in the green roof system, reducing the total outflow volume by retaining part of the rainfall and evapotranspirating through vegetation, and distributing the outflow over a longer time period thanks to a relatively slow release of the excess water that is temporarily stored in the high porosity structure of the growing and drainage layers.
The objectives of WP4 are to provide detailed information about green roof performances in the Mediterranean climate (retained volume, peak flow reduction, runoff delay) and to identify a suitable modelling approach for describing the associated hydrologic response. A very important aspect will be also the identification of suitable plants in Mediterranean climate.
Two GR demonstration sites will be designed and realized in Catania and Malta. The sites in Catania will be an existing roof within the building of University of Catania where is located the Department of Agriculture, Food and Environment; in Malta, the roof will be realized within a public administrative building.
In WP5 the results from implemented demonstration GUIs (measures) will be integrated in a GIS-based model which will enable the modelling of runoff flows (and flooding) under different scenarios of GUI application (outputs). A policy paper on the application of GUIs as well as communication and dissemination activities will contribute to the promotion of the capacity building of GUIs in order to increase awareness of policy makers, public authorities/municipalities and other interested stakeholders (beneficiaries). A masterplan based on a GIS model and including a cost benefit assessment aimed at developing a methodology for the identification of the economically optimal application level of GUIs will be developed for two target areas.
The masterplan will also outline a methodology (tool) which can be used by agencies as blueprints for flood mitigation in similar scenarios. The adoption of GUIs will also provide an opportunity for addressing a cultural change in the population, by increasing awareness levels of critical hydrological events and how these can be managed (innovation) by adopting environmental sustainable options.
