No abstract

Lura stream flows in the populated and industrialized\ud conurbation North of Milan, Italy. The area suffers a sprawling\ud urbanization which is leading to major alterations in water\ud quality, hydrology and morphology of streams. These water\ud bodies are known as effluent-dominated streams, because most\ud of the baseflow is given by Wastewater Treatment Plant\ud (WWTP) discharges. In this paper, a 5 year long assessment of\ud Lura stream is presented and the collected data is discussed to\ud understand overall ecological quality. Multivariate analysis\ud carried out on macroinvertebrate assemblages and\ud environmental variables suggests that invertebrate communities\ud suffer severe alteration both upstream and downstream WWTP\ud discharges. Results indicate that the high polluting loads coming\ud from WWTP discharges affect seriously the stream water\ud quality, but the most important cause of impairment are pulse\ud perturbations related to the modified hydrology, causing\ud droughts and flash floods, and to the spills of untreated sewage\ud from overflows during rain events

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The implementation of green roofs as sustainable urban drainage systems provides benefits for stormwater control and the environment and is more and more encouraged. A model for the estimation of the probability of vegetation survival without irrigation is proposed. The model, developed through a probabilistic analytical derivation procedure, can also consider the effects of chained rainfall events, without the need of continuous simulation of hydrological processes. The model equations can be useful in the design of green roofs, allowing to determine the growing medium thickness in terms of an assumed risk of vegetation withering in dry periods. The proposed model is also able to identify the optimal thickness of the growing medium, over which the survival performances can be increased only with irrigation. Model performances were tested by the application to two case studies in Italy. Comparison between the probabilities and the cumulative frequencies from a continuous simulation of water content in the growing medium shows a good agreement and provide a first confirmation of reliability.

In the last few decades, the use of sustainable urban drainage systems is largely spreading and encouraged, because they provide lots of benefits for sewer networks, wastewater treatment plants and the environment. In this context, green roofs can be an effective tool to both delay and attenuate stormwater runoff peaks, reducing runoff at the same time. Their proper design is a key element for stormwater management in highly urbanized cities. The aim of this paper is to propose an analytical probabilistic approach, to evaluate green roof performance in terms of runoff and vegetation's survival without irrigation, to guide planners in choosing proper values for their design parameters. A great advantage of the method is that it can be applied to different sites and climate conditions; moreover, it involves a significant improvement of the typical analytical probabilistic approach, as a chain of consecutive rainfall events was considered, in order to take into account the possibility that storage capacity is not completely available at the beginning of each event, because of pre-filling from previous rainfalls, as typically happens with green roofs. Finally, to verify the goodness of our developed equations, we applied them to a case study.