scholarly journals Vegetation Survival in Green Roofs without Irrigation

2020 ◽  
Author(s):  
Anita Raimondi ◽  
Mariana Marchioni ◽  
Umberto Sanfilippo ◽  
Gianfranco Becciu
Keyword(s):  
Storage Capacity ◽  
Irrigation System ◽  
Probabilistic Approach ◽  
Green Roofs ◽  
Design Parameters ◽  
Urban Drainage ◽  
Rainfall Events ◽  
Peak Runoff ◽  
A Chain

The Sustainable Urban Drainage Systems on stormwater management provide benefits for sewer networks, treatment plants and environment and should be encouraged. Green roofs are part of these systems and can contribute both to delay and cut peak runoff and reduce discharged volumes. In this paper the probability of vegetation survival without irrigation has been proposed as a guide to operators on selecting vegetation and irrigation system as well as design parameters. An analytical probabilistic approach has been proposed; a chain of consecutive rainfall events has been considered to take into account the possibility that storage capacity is not completely available at the beginning of the considered event but pre-filled from previous rainfalls, as typical of green roofs. Finally, an application to a case study has been proposed to validate proposed equations.

scholarly journals Vegetation Survival in Green Roofs without Irrigation

2020 ◽  
Author(s):  
Anita Raimondi ◽  
Mariana Marchioni ◽  
Umberto Sanfilippo ◽  
Gianfranco Becciu
Keyword(s):  
Probabilistic Approach ◽  
Green Roofs ◽  
Design Parameters ◽  
Dry Period ◽  
Rainfall Events ◽  
Average Return ◽  
Growing Medium ◽  
A Chain ◽  
Proper Values ◽  
Stormwater Control

The implementation of green roofs as sustainable urban drainage systems provides benefits for stormwater control and the environment and is always more encouraged. In this paper, the estimation of the probability of vegetation survival without irrigation has been proposed as a guide to choose the proper values for the design parameters; in particular the growing medium thickness has been related to the average return interval of the water content at the end of the dry period. Moreover the study represents an improvement of the analytical probabilistic approach since a chain of consecutive rainfall events has been considered, in order to take into account the possibility that the storage capacity is not completely available at the beginning of each event because of the pre-filling from more than one previous rainfall as typically happens for green roofs. Finally, developed equations have been validated by means of their application to two case studies, respectively in northern and southern Italy.

scholarly journals Probabilistic Modelling of Sustainable Urban Drainage Systems

2022 ◽  
Author(s):  
Anita Raimondi ◽  
Maria Gloria Di Chiano ◽  
Mariana Marchioni ◽  
Umberto Sanfilippo ◽  
Gianfranco Becciu
Keyword(s):  
Control Systems ◽  
Probabilistic Approach ◽  
Urban Drainage ◽  
Rainfall Events ◽  
Drainage Systems ◽  
Effective Strategies ◽  
Urban Drainage Systems ◽  
Rainwater Management ◽  
A Chain ◽  
And Control

Abstract Sustainable Urban Drainage Systems (SuDS) gatherer effective strategies and control systems for stormwater management especially in highly urbanized areas characterized by large impervious surfaces that increase runoff peak flow and volume. The main goal is to restore the natural water balance by increasing infiltration, evapotranspiration and promoting rainwater reuse. This paper proposes an analytical probabilistic approach for the modelling SuDS applicable to different structures and goals. Developed equations allow to estimate the probability of overflow and the probability of pre-filling at the end of dry periods, to evaluate the efficiency of the storage in rainwater management and its ability to empty between consecutive events. A great advantage of the proposed method is that it allows to consider a chain of rainfall events; this aspect is particularly important for control systems SuDS characterized by low outflow rates which storage capacity is often not completely available at the end of a dry period because pre-filled by previous events. Suggested formulas were tested to two cases studies in Milan and Genoa, Italy.

scholarly journals Hydraulic characteristics of stepped spillway dropshafts for urban deep tunnel drainage systems: the case study of Chengdu city

2019 ◽  
Vol 80 (8) ◽  
pp. 1538-1548
Author(s):  
Lei Liao ◽  
Ruidong An ◽  
Jia Li ◽  
Wenmin Yi ◽  
Xiaofan Liu ◽  
...  
Keyword(s):  
Extreme Rainfall ◽  
Stepped Spillway ◽  
Urban Drainage ◽  
Deep Tunnel ◽  
Hydraulic Characteristics ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Fluctuating Pressure ◽  
Air Explosion

Abstract Cities in southwestern China experience urban drainage and overflow pollution after extreme rainfall events, which are major problems. In this study, a type of stepped spillway dropshaft suitable for drainage by deep tunnels in Chengdu was proposed and the hydraulic characteristics were investigated experimentally. The results showed that the nappe flow and strong turbulent deflected jet flow in the stepped spillway allowed the dropshaft to greatly dissipate energy. According to the distribution of the time-averaged pressure on the steps, the flow on the steps could be divided into a recirculating region, a wall-impinging region and a mixing region. The time-averaged pressure on the outside of the step was higher than that on the inside due to the centrifugal force effect of the water. The fluctuating pressure distribution of the step approximated the normal distribution. It was acceptable to calculate the minimum pressure with 3 times the root mean square (RMS). The vibration of the flow on the stepped spillway did not resonate with the step. When the outflow tunnel was under submerged outflow conditions, the aeration in the stepped spillway was exhausted through air holes and only a small amount of air entered the outflow tunnel, thereby avoiding an air explosion.

scholarly journals Rainwater retention effect of extensive green roofs monitored under natural rainfall events – a case study in Beijing

2018 ◽  
Vol 49 (6) ◽  
pp. 1773-1787 ◽  
Author(s):  
Yongwei Gong ◽  
Dingkun Yin ◽  
Xing Fang ◽  
Dandan Zhai ◽  
Junqi Li
Keyword(s):  
Green Roofs ◽  
Northern China ◽  
Regression Equations ◽  
Peak Reduction ◽  
Retention Capacity ◽  
Rainfall Events ◽  
Natural Rainfall ◽  
Rainfall Depth ◽  
Reduction Effect ◽  
Peak Runoff

Abstract The rainwater retention and peak flow reduction effect of seven extensive green roof (EGR) modules were studied in Beijing under natural rainfall events from May to September 2015. Monitored EGR modules had a layer of vegetation widely planted in northern China and a substrate layer with a thickness of 20 or 50 or 100 mm. The EGRs effectively retained rainwater, and regression equations of the potential retention capacity as a function of rainfall depth were developed for five EGR modules, which show that generally the capacity decreased as rainfall depth increased. The EGR with Sedum lineare Thunb and 100 mm improved soil had relatively higher average retention capacity (61.8%) than others, but all EGR modules had similar retention for an extraordinary rainfall event of 114.4 mm. For rainfall events less than 15 mm, EGR modules had 100% rainfall retention most of the time. The reduction in peak runoff rate ranged from 30.8% to 85.4%. The EGRs with Sedum lineare Thunb using 20 mm improved soil and 50 mm either pastoral soil or ultra-low weight substrates have similar peak reduction (51.3–58.2%). The EGRs with Sedum lineare Thunb have better rainfall retention and peak reduction than EGRs with Angiospermae or Sedum aizoon L.

scholarly journals Analysis of the retention capacity of green roofs

2012 ◽  
Vol 16 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Ewa Burszta-Adamiak
Keyword(s):  
Urban Areas ◽  
Soil Surface ◽  
Green Roofs ◽  
Retention Capacity ◽  
Local Conditions ◽  
Rainfall Events ◽  
Runoff Reduction ◽  
Education Centre ◽  
Peak Runoff ◽  
Rain Events

Abstract Green roofs are one of the modern solutions used to achieve sustainable stormwater management in urban areas. These structures are still more often designed for newly constructed buildings in Poland, based on the observations of changes in urban areas that result in the increased sealing of soil surface and thus in the limitation of natural stormwater infiltration and retention sites. In spite of a growing interest in green roofs, the data related to their retention capacity in Polish conditions is still insufficient. This study presents the results of the author’s tests, conducted in the years 2009-2010 on experimental sites located on the roof of the Science and Education Centre building of the University of Environmental and Life Sciences in Wrocław. The aim of these tests was to determine the retention capabilities of green roofs and the runoff delay and peak runoff reduction during rainfall events recorded in local conditions. The results show that green roofs can play a significant role in the reduction of total outflow volume of stormwater falling on their surface. Multi-layered structure of green roofs contribute also to a slowdown in the outflow of stormwater and to reduction in the peak runoff volume in comparison to the maximum recorded intensity of rainfall. Mean retention for 153 analysed rainfall events amounted from 82.5% to 85.7% for green roofs. In the case of rain events up to 1 mm a day, the retention for green roofs reached nearly 100%.

Effectiveness of green roofs in reduction of rainfall-fed runoff: A case study in Dublin, Ireland

2021 ◽  
Author(s):  
Bidroha Basu ◽  
Arunima Sarkar Basu ◽  
Srikanta Sannigrahi ◽  
Francesco Pilla
Keyword(s):  
Flood Control ◽  
Water Retention ◽  
Green Roof ◽  
Green Roofs ◽  
City Centre ◽  
Urban Drainage ◽  
Storm Events ◽  
Land Area ◽  
Runoff Reduction

<p>Increase in extreme rainfall and storm events due to climate change and decrease in water retention in soil due to urbanization has increased the risk of flooding in cities globally. Since majority of the cites are mostly developed, expanding the conventional urban drainage system to account for the excess runoff produced by the rainfall event has limited scope. The challenge is to develop sustainable urban drainage systems (SUDS) to reduce runoff and create a flood control system in major cities. One of the SUDS that are becoming popular is the use of nature-based solutions (NBSs). A set of conventional NBSs to mitigate flood risk include bioswales, bio-retention, tree pits, infiltration trenches. However, even though their performance in flood control is found to be effective, they require considerable land area for deployment, which might be difficult to obtain in cities. For this purpose, green roofs have becoming popular as an alternative NBS in flood control, as it does not require any additional land area for deployment. This study investigates the effectiveness of a green roof in reduction of runoff via real-world case study. A green roof deployed in the CHQ building located at the city centre in Dublin, Ireland has been considered for the study. The green roof has a total size of 70 sq. m. Performance of the green roof in runoff reduction was measured based on rainfall and water retention data collected at four modular units, each having 1 sq. meter area, located at the centre of the roof with an IoT weight scale. The data has been collected for 1 week at 3-minute interval, and the reduction in runoff with and without the presence of the green roof has been estimated. The performance of the green roofs in runoff reduction was found to vary between 20-40% depending on the intensity of storm events.</p>

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