Wet season hydrological performance of green roofs using native species under Mediterranean climate (original) (raw)
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The capacity of green roofs to intercept rainfall, and consequently store and slow runoff resulting in a reduction in flood risk, is one of their main advantages. In this review, previous research related to the influence of green roofs on the hydrological cycle is examined with a special focus on studies for Mediterranean climate conditions (Csa and Csb according to the Köppen–Geiger climate classification). This climate is characterized by short and intense rainfall occurrences which, along with the increased area of impervious surface on Mediterranean regions, intensify the risk of flooding, particularly in the cities. The analysis covers the variables rainfall retention (R, %), runoff delay (RD, min or h), peak delay (PD, min or h), peak attenuation (PA, %), and runoff coefficient (RC, −), in relation to physical features of the green roof such as layers, substrate depth, slope, and vegetation, as well as, weather conditions, such as monthly temperature and monthly precipitation...
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Different mitigation measures with vegetation have been proposed to sustainably manage rainwater, among which green roofs have demonstrated to be a valid solution in urbanized areas. Green roofs have gained interest also in Italy, but their spreading is generally based on application of ready-to-use packages, poorly tested in the specific climate conditions. A study was carried out to evaluate the green roof solution most suitable in the humid, subtropical climate context of Veneto Plain (north-eastern Italy) to reduce outflow volumes from building roofs into the urban drainage systems. Twelve different microcosm combinations of extensive green roof (three plant mixtures × two substrates × two storage/drainage layers) were tested and compared with gravel (considered as a conventional flat roof with gravel ballast). The tested drainage/storage layers were a preformed layer in recycled HDPE (PL) and an expanded perlite mineral layer (ML), and the growth medium layers were recycled bri...
Urban water retention by greened roofs in temperate and tropical climate
Proceedings of the 38th …, 2001
The authors of this paper are working on the ecological effects of greened roofs. What are the ecological functions of plants growing on roofs? Are there any benefits for the inhabitants of cities? Urbanisation is increasing worldwide. As more and more urban areas are paved over, precipitation increasingly runs off directly into surface waters. This does not only change the flow of the waters but also increases the level of nutrients and contaminants led into them. By greening roofs it is possible to reduce such environmental impacts. Green roofs contribute as well to a better microclimate through evapotranspiration, filtering off dust from the air and decreasing temperatures at the rooftop and in the surrounding area. This team's aim of cooperation is to transfer knowledge of greened roofs of Central Europe to the tropics. This project is supported by DAAD (Germany) and CAPES (Brazil) since 2000. Long-term studies in Germany have pointed out water retention by greened roofs. Nowadays, water retention is one important aspect of modern ecological architecture. Retaining rainwater has a lot of further positive effects in the cities of Central Europe, i.e. to improve the urban climate. The above-mentioned scientific group pointed out some first results based on these European studies for tropical countries.
STORMWATER RUNOFF MITIGATION ON EXTENSIVE GREEN ROOF: A REVIEW ON TRENDS AND FACTORS
South East Asian Technical Universities Consortium (SEATUC), 2012
This paper aims to provide a broad overview on research trend and factors contributing towards green roof performance in mitigating urban stormwater runoff. Nineteen papers were selected and examined for trends on research concern and factors attributing towards stormwater runoff mitigation. The factors are then discussed based on stormwater runoff measurements reported and existing literatures in the field. The research trend on green roof stormwater mitigation has evolved around the factors that could delay peak water runoff and increase retention period. Researchers have identified substrate depth, slope, climate, vegetation and green roof age as the significant factors attributing stormwater runoff mitigation. Wide research gap have been identified on the role of vegetation hydrology management and green roof performance on regions other than temperate climate providing opportunity for further research and experiments.
E&S Engineering and Science
Green roofs are recognized as a sustainable infrastructure to improve the environmental quality of cities. Among many benefits, green roofs reduce the rate and volume of runoff helping to improve rainwater management. This study investigated the runoff retention capacity of three pilot extensive green roof assemblies with different vegetation (grass, shrub and intercropping of the two plants). Rainwater runoff data were collected for 18 rainfall events that ranged from a minimum of 1.6 mm to a maximum of 157.9 mm. Average precipitation event retention efficiencies were 46.7, 59.7 and 61.6% for intercropped, shrub and grass green roofs, respectively, while the annual runoff retention rates were 43.8, 57.3 and 59.7%. The difference in retention rates for the green roofs with different vegetation was not statistically significant. The rainfall intensity influenced the retention rates, with the highest retentions for small events (<10.0 mm) followed by medium (10.0-24.9 mm). Retentio...
Urban Water Journal, 2015
11 3 Centre d'études et d'expertise sur les risques, l'environnement, la mobilité et 12 l'aménagement (Cerema), DTer IDF, 15 16 17 Use of green roofs to solve storm water issues at the basin scale -1 Study in the Hauts-de-Seine county (France) 2 3 At the building scale, green roof has demonstrated a positive impact on urban 4 runoff (decrease in the peak discharge and runoff volume). This work aims to 5 study if similar impacts can be observed at basin scale. It is particularly focused 6 on the possibility to solve some operational issues caused by storm water. 7 For this purpose, a methodology has been proposed. It combines: a method to 8 estimate the maximum roof area that can be covered by green roof, called 9 green roofing potential, and an urban rainfall-runoff model able to simulate the 10 hydrological behaviour of green roof. 11 This methodology was applied to two urban catchments affected one by 12 flooding and the other one by combined sewage overflow. The results show that 13 green roof can reduce the frequency and the magnitude of such problems 14 depending on the covered roof surface. Combined with other infrastructures, 15 they represent an interesting solution for urban water management. 16 17
Water, 2019
Green roofs can provide various benefits to urban areas, including stormwater retention. However, semi-arid regions are a challenging environment for green roofs as long dry weather periods are met with short but intense rainfall events. This requires green roofs to retain maximum volumes of stormwater, while being tolerant to minimal irrigation supplies. The objectives of this study are (i) to quantify the stormwater retention of two substrate mixtures with two plant species under natural rainfall; (ii) to assess the performance of two plant species under two levels of deficit irrigation; and (iii) to compute stormwater runoff reduction and reuse by green roofs and rooftop water harvesting systems for three standard residential plot types in urban Nicosia, Cyprus. A rooftop experiment was carried out between February 2016 and April 2017 and results were used to compute long-term performance. Average stormwater retention of the 16 test beds was 77% of the 371-mm rainfall. A survival...
GREEN ROOFS FOR SUSTAINABLE WATER MANAGEMENT IN URBAN AREAS
Environmental Engineering and Management Journal - Gheorghe Asachi” Technical University of Iasi, Romania, 2013
This paper presents the description of a pilot green roof on the engineering laboratories of University of Bologna, Italy. The first results of the monitoring and simulation phase of the green roofs project that has been carried out by University of Bologna in collaboration with the Columbia University of New York aim at providing more evidence on green roof stormwater performance. This project is the first green roof in the city of Bologna as no green roofs have been monitored for annual stormwater retention in this area. Only one green roof in City of Genova, belonging to north Italian climate (the specific climatic context of the Mediterranean region: areas with this climate receive almost all of their precipitation during their winter season, and may go anywhere from 4 to 6 months during the summer without having any significant precipitation.) has been monitored and gave a 70 percent result in retention of the annual runoff (Palla et al., 2009). The main objective was to compare this result to the Bologna pilot green roof and see how it differs from the other climatic area results.
Hydrologic Restoration in the Urban Environment Using Green Roofs
2010
Loss of natural soil and vegetation within the urban environment can significantly affect the hydrologic cycle by increasing storm water runoff rates and volumes. In order to mitigate these modifications in urban areas engineered systems are developed, such as green roofs, to mimic and replace functions (evapo-transpiration, infiltration, percolation) which have been altered due to the impact of human development. Green roofs, also known as vegetated roof covers, eco-roofs or nature roofs, are composite complex layered structures with specific environmental benefits. They are increasingly being used as a source control measure for urban storm water management. Indeed, they are able to re-establish the natural water cycle processes and to operate hydrologic control over storm water runoff with a derived peak flow attenuation, runoff volume reduction and increase of the time of concentration. Furthermore green roofs exhibit the capacity to reduce storm water pollution; they generally act as a storage device, consequently pollutants are accumulated in the substrate layer and released when intensive rainwater washes them out. In order to investigate the hydrologic response of a green roof, the University of Genova recently developed a joint laboratory and full-scale monitoring programme by installing a "controlled" laboratory test-bed with known rainfall input and a companion green roof experimental site (40 cm depth) in the town of Genoa. In the paper, data collected during the monitoring programme are presented and compared with literature data.
Water, 2016
In an urban environment, green roofs represent a sustainable solution for mitigating stormwater volumes and hydrograph peaks. So far, many literature studies have investigated the hydraulic efficiency and the subsurface runoff coefficient of green roofs, showing their strong variability according to several factors, including the characteristics of storm events. Furthermore, only few studies have focused on the hydraulic efficiency of green roofs under Mediterranean climate conditions and defined the influencing hydrological parameters on the subsurface runoff coefficient. Nevertheless, for designing purposes, it is crucial to properly assess the subsurface runoff coefficient of a given green roof under specific climate conditions and its influencing factors. This study intends to, firstly, evaluate the subsurface runoff coefficient at daily and event-time scales for a given green roof, through a conceptual model implemented in SWMM. The model was loaded with both daily and 1-min rainfall data from two Mediterranean climate sites, one in Thessaloniki, Greece and one in Cosenza, Italy, respectively. Then, the most influencing hydrological parameters were examined through a statistical regression analysis. The findings show that the daily subsurface runoff coefficient is 0.70 for both sites, while the event-based one is 0.79 with a standard deviation of 0.23 for the site in Cosenza, Italy. The multiple linear regression analysis revealed that the influencing parameters are the rainfall intensity and antecedent dry weather period with a confidence level of 95%. This study demonstrated that, due to the high variability of the subsurface runoff coefficient, the use of a unique value for design purposes is inappropriate and that a preliminary estimation could be obtained as a function of the total rainfall depth and the antecedent dry weather period by using the validated multi-regression relationship which is site specific.