| Title | Factors controlling the hydraulic efficiency of green roofs in the metropolitan area of milan (Italy) |
| Abstract | Green roofs (GRs) are considered sustainable solutions for the adaptation of urban water management to climate change. The use of GRs is particularly promising in urban environments like the Metropolitan Area of Milan, the most urbanized area in Italy. In this work, we evaluated the subsurface runoff coefficient at the event-time scale, for more than one year of observations, of 68 small-scale test beds comprising different configurations of green roofs (e.g., different vegetations, types and depths of growing media, and different slopes) installed in the Metropolitan Area of Milan. The objectives of this study are three-fold. Firstly, the controlling factors of the hydraulic have been assessed for efficiency. We calculated a mean drainage flow rate of 51%, finding that growing media play a significant role in determining the drainage flow during the spring, at the beginning of the vegetative period. During this season, water retention in fertilized beds increases significantly. At the beginning of the summer, the vegetation cover is able to significantly reduce the drainage flow, playing an even more crucial role with respect to the growing medium material. However, we found that the vegetation type (grass field and Sedum) does not play a significant role in the retention processes. Secondly, the delay of the peak flow rate was determined. We found a precipitation peak delay from 1 to 2 h, which would be sufficient to guarantee environmental benefits for urban drainage. Finally, the factors controlling the hydraulic efficiency of GRs for individual precipitation events were assessed. We found that soil moisture and cumulated precipitation are both significant factors determining the drainage flow rate. In conclusion, we point out that soil moisture is one of the main parameters characterizing GR drainage and should be further considered in future research efforts devoted to the analysis of GR performance. |
| Source | Sustainability (Basel) 13 (24) |
| Keywords | Green roofPeak flow delaySoil moistureUrban hydrologyWater retention |
| Journal | Sustainability (Basel) |
| Editor | MDPI, Basel, |
| Year | 2021 |
| Type | Articolo in rivista |
| DOI | 10.3390/su132413638 |
| Authors | Salerno, Franco; Valsecchi, Lucia; Minoia, Riccardo; Copetti, Diego; Tartari, Gianni; Guyennon, Nicolas; Colombo, Nicola; Pirola, Niccolò; Barozzi, Benedetta; Bellazzi, Alice; Marziali, Laura |
| Text | 461563 2021 10.3390/su132413638 Scopus 2 s2.0 85120937196 Green roof Peak flow delay Soil moisture Urban hydrology Water retention Factors controlling the hydraulic efficiency of green roofs in the metropolitan area of milan Italy Salerno, Franco; Valsecchi, Lucia; Minoia, Riccardo; Copetti, Diego; Tartari, Gianni; Guyennon, Nicolas; Colombo, Nicola; Pirola, Niccolo; Barozzi, Benedetta; Bellazzi, Alice; Marziali, Laura Istituto di Ricerca sulle Acque, Italy; Consiglio Nazionale delle Ricerche; Universita degli Studi di Torino; Istituto Trentino di Cultura Centro per la Ricerca Scientifica e Tecnologica Green roofs GRs are considered sustainable solutions for the adaptation of urban water management to climate change. The use of GRs is particularly promising in urban environments like the Metropolitan Area of Milan, the most urbanized area in Italy. In this work, we evaluated the subsurface runoff coefficient at the event time scale, for more than one year of observations, of 68 small scale test beds comprising different configurations of green roofs e.g., different vegetations, types and depths of growing media, and different slopes installed in the Metropolitan Area of Milan. The objectives of this study are three fold. Firstly, the controlling factors of the hydraulic have been assessed for efficiency. We calculated a mean drainage flow rate of 51%, finding that growing media play a significant role in determining the drainage flow during the spring, at the beginning of the vegetative period. During this season, water retention in fertilized beds increases significantly. At the beginning of the summer, the vegetation cover is able to significantly reduce the drainage flow, playing an even more crucial role with respect to the growing medium material. However, we found that the vegetation type grass field and Sedum does not play a significant role in the retention processes. Secondly, the delay of the peak flow rate was determined. We found a precipitation peak delay from 1 to 2 h, which would be sufficient to guarantee environmental benefits for urban drainage. Finally, the factors controlling the hydraulic efficiency of GRs for individual precipitation events were assessed. We found that soil moisture and cumulated precipitation are both significant factors determining the drainage flow rate. In conclusion, we point out that soil moisture is one of the main parameters characterizing GR drainage and should be further considered in future research efforts devoted to the analysis of GR performance. 13 Published version https //doi.org/10.3390/su132413638 Articolo in rivista MDPI 2071 1050 Sustainability Basel Sustainability Basel Sustainability Basel Sustainability. Basel lucia.valsecchi VALSECCHI LUCIA gianni.tartari TARTARI GIANNI diego.copetti COPETTI DIEGO franco.salerno SALERNO FRANCO benedetta.barozzi BAROZZI BENEDETTA alice.bellazzi BELLAZZI ALICE laura.marziali MARZIALI LAURA nicolasdominique.guyennon GUYENNON NICOLAS DOMINIQUE DIT.AD015.022.008 I ZEB |
