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>

Innovative green roof with high water retention and durability

2019 ◽  
Author(s):  
Thomas Cornelius Buch-Hanser ◽  
Guangli Du ◽  
David John Duffus
Keyword(s):  
Water Retention ◽  
Green Roof ◽  
Water Reservoir ◽  
Green Roofs ◽  
High Water ◽  
Water Retention Capacity ◽  
Storm Events ◽  
Concrete Element ◽  
Retention Capacity ◽  
Roof System

<p>Given the rapid increase in urban populations, combined with the effects of climate change, cities are struggling to provide green spaces to address liveability as well as adaptability to new challenges. Water retention and bio-diversity are the main advantages of green roofs. There are, however, limitations to green roofs that impede their acceptance and proliferation. There is for example uncertainty on how much water they retain during major storm events. In terms of building technology, green roofs today aren’t robust, and the risk for leakage through the roof membrane is disproportionally high when compared to the cost. A newly developed innovative green roof system with high water retention capacity and high durability will be presented. The patented prefabricated technology incorporate insulation and membrane into a single concrete element, ensuring improved robustness, quickened building times and a long term durable product. Initial indications for pricing indicate that the system is price-neutral when compared with green roofs as they are built today. The optimized structural performance obtain same loadbearing capacity, as existing systems, in spite of the relatively increased space created for water reservoir, without compromising the insulation capacity, hence the new green roof system further contribute to increased sustainability.</p>

scholarly journals Hydrologic Performance of an Extensive Green Roof under Intensive Rain Events: Results from a Rain-Chamber Simulation

2021 ◽  
Vol 13 (6) ◽  
pp. 3078
Author(s):  
Elena Giacomello ◽  
Jacopo Gaspari
Keyword(s):  
Water Retention ◽  
Green Roof ◽  
Green Roofs ◽  
International Standards ◽  
Dimensionless Number ◽  
Runoff Coefficient ◽  
Retention Performance ◽  
Extensive Green Roof ◽  
Rain Events ◽  
Hydrologic Performance

The water storage capacity of a green roof generates several benefits for the building conterminous environment. The hydrologic performance is conventionally expressed by the runoff coefficient, according to international standards and guidelines. The runoff coefficient is a dimensionless number and defines the water retention performance over a long period. At the scale of single rain events, characterized by varying intensity and duration, the reaction of the green roof is scarcely investigated. The purpose of this study is to highlight how an extensive green roof—having a supposed minimum water performance, compared to an intensive one—responds to real and repetitive rain events, simulated in a rain chamber with controlled rain and runoff data. The experiment provides, through cumulative curve graphs, the behavior of the green roof sample during four rainy days. The simulated rain events are based on a statistical study (summarized in the paper) of 25 years of rain data for a specific location in North Italy characterized by an average rain/year of 1100 mm. The results prove the active response of the substrate, although thin and mineral, and quick draining, in terms of water retention and detention during intense rain events. The study raises questions about how to better express the water performance of green roofs.

scholarly journals Hydrological Performance and Runoff Water Quality of Experimental Green Roofs

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1185 ◽  
Author(s):  
Grzegorz Pęczkowski ◽  
Tomasz Kowalczyk ◽  
Katarzyna Szawernoga ◽  
Wojciech Orzepowski ◽  
Romuald Żmuda ◽  
...  
Keyword(s):  
Total Nitrogen ◽  
Green Roofs ◽  
Control Surface ◽  
Substrate Thickness ◽  
Storm Events ◽  
Runoff Water ◽  
Relative Retention ◽  
Runoff Reduction ◽  
Relative Retention Index

Within the scope of the conducted experiment the authors analysed the efficiency of runoff reduction by the system of extensive type green roofs. The observations were based on storm events in the area of Lower Silesia at the Agro and Hydrometeorology Station Wrocław-Swojec. The authors analysed the thickness of plant substrate, and also estimated the quality of runoff waters under the conditions of periodic atmospheric deposition. Also considered were such indicators as electrolytic conductivity, N, NO3−, NO2−, NH4+, P, PO43−. The experiment included roof substrates designed in two variants, with known hydraulic and physical properties of the soil material. The analysis was performed for models with vegetation layer based on pumice and zelolite, covered with five plant species from the sedum family. The modelling of the hydraulic properties was conducted with variably saturated medium, using the Hydrus 1D software. The performance of systems with primary layer thickness of 11 cm and 9, 8, 7, 6 and 5 cm was estimated. The designed models reduced the average peak flows to 89%, and in addition they caused a delay in the initiation of the runoff which was dependent on the intensity and distribution of rainfalls in time, and on the initial moisture of the profiles. Simulations, performed for variable substrate thickness, permit the conclusion that in the case of thin-layer profiles (5 cm), the relative retention index was decidedly lower and amounted to 35.9% for the substrate with zeolite (originally 60.6%) and 41% for the substrate with pumice (originally 65.7%). In the case of total nitrogen and phosphates, statistical analysis revealed significant differences (p < 0.05) in relation to specific concentrations in the rainwater and in the control surface. The total nitrogen in the runoff from the green roof was nearly twice as high as that in the rainwater and amounted to, on average, 8.3 mg L−1.

scholarly journals Analysis of roof greening technology impact on rain and meltwater retention

2020 ◽  
Vol 175 ◽  
pp. 11023
Author(s):  
Elena Sysoeva ◽  
Margarita Gelmanova
Keyword(s):  
High Efficiency ◽  
Green Roof ◽  
Experimental Studies ◽  
Green Roofs ◽  
Climatic Conditions ◽  
Water Runoff ◽  
Substrate Thickness ◽  
Runoff Reduction ◽  
The Usa ◽  
Analytical Review

Over the past 20 years, a large number of studies have been published on reducing storm runoff by various types of green roofs. This article analyzes the results of experimental studies presented in 39 publications on green roof runoff reduction in a climate similar to the climate of Russia: in Canada, the USA, Finland, Norway, France. An analytical review found that the ability of green roofs to retain rainfall varies from 20 to 99.5% depending on climatic conditions (duration and intensity of rains, duration of dry periods, solar radiation, temperature and humidity, wind conditions), the properties of green roof layers (moisture capacity of the substrate and a drainage layer, the substrate thickness), the type of vegetation, the geometry of a green roof (slope and orientation). Green roofs can be a useful tool for reducing urban storm water runoff. However, in order to ensure high efficiency, it is necessary to use green roof technology with other measures to reduce runoff.

scholarly journals A comparative study on rainfall runoff control indicators of green roof

2020 ◽  
Vol 20 (6) ◽  
pp. 2036-2042
Author(s):  
Ke Zhou
Keyword(s):  
Comparative Study ◽  
Green Roof ◽  
Reduction Rate ◽  
Green Roofs ◽  
Mean Value ◽  
Rainfall Runoff ◽  
Control Effect ◽  
Runoff Reduction ◽  
Runoff Control ◽  
Reduction Effect

Abstract The rainfall runoff reduction effect on green roofs was analyzed and tested by comparative rainfall runoff monitoring on impermeable roofs (sloping, plane). The evaluation index of rainfall runoff interception benefit (relative runoff reduction rate, rainfall control rate) on green roofs was studied. The results show that compared with sloping and level roofs, the change range of green roof runoff reduction rate relative to level and sloping roofs is 20.0–98.3% and 3.8–92.3%, and the mean value is 48.4% and 34.3% respectively. It is obvious that the green roof has better rainfall runoff reduction effect. It can be seen from the single rainfall control effect that the variation range of green roof rainfall runoff control rate is 36.0% to 99.0%, and the total rainfall control rate is 57.6%, which reflects that the green roof has the better rainfall control effect. Through comparative study, it can be concluded that the rainfall runoff control rate is more suitable for the design index of green roofs.

scholarly journals Lessons from New York High Line Green Roof: Conserving Biodiversity and Reconnecting with Nature

Urban Science ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 2
Author(s):  
Kawar Salih ◽  
Zaid O. Saeed ◽  
Avar Almukhtar
Keyword(s):  
New York ◽  
Urban Design ◽  
Urban Expansion ◽  
Green Roof ◽  
Green Roofs ◽  
Urban Spaces ◽  
Climate Change Research ◽  
Study Approach ◽  
High Line

The concept of sustainable urban design has appeared in different perspectives to minimize and reduce the negative impacts of urban expansion in terms of climatic and environmental drawbacks. One of the undeniable approaches of sustainable urban design is the adoption of green urban roofs. Green roofs are seen to have a substantial role in addressing and resolving environmental issues in the context of climate change. Research investigations have indicated that green roofs have a remarkable impact on decreasing rainwater runoff, reducing the heat island effect in urban spaces, and increasing biodiversity. Nevertheless, green roofs in urban spaces as a competent alternative to nature remains a standing question. To what extent can green roofs mimic the biodiversity that is seen in nature? Moreover, to what level is this approach practical for achieving a tangible reconnection with nature, or so-called biophilia? This study attempts to discuss the essence and impact of green roofs in urban spaces based on a case study approach. The study reflected lessons from the New York High Line Green Roof regarding biophilia and biodiversity in this case study. It concludes with key lessons that can be transferred to other urban spaces with similar settings.

Deriving discharge strategies to reduce CSO in urban drainage systems

1997 ◽  
Vol 36 (8-9) ◽  
pp. 259-263
Author(s):  
K.-J. Breur ◽  
P. E. R. M. van Leeuwen ◽  
N. P. Dellaert
Keyword(s):  
System Performance ◽  
Major Part ◽  
Design Procedure ◽  
Urban Drainage ◽  
Specific Situation ◽  
Storm Events ◽  
Maximum Reduction ◽  
Actual Design ◽  
Heavy Storm

This paper discusses the design of discharge strategies for urban drainage operation. The design procedure applies a tuneable strategy which can be adjusted to a specific situation by adjusting a few parameters which reflect the discharge priority of the various districts of the system. The actual design procedure, a procedure of simulation and analysis of the system performance, is explained in a case study. Apart form the method, the case study shows that a near optimal performance (maximum reduction of overflow volume) can be realised by applying an “event” average strategy (one strategy for all type of inflow events). Furthermore, the case study shows that the major part of the total overflow volume is caused by very heavy storm events.

scholarly journals A Comparison between Conceptual and Physically Based Models in Predicting the Hydrological Behavior of Green Roofs

Proceedings ◽  
2019 ◽  
Vol 48 (1) ◽  
pp. 8
Author(s):  
Mirka Mobilia ◽  
Antonia Longobardi
Keyword(s):  
Urban Areas ◽  
Goodness Of Fit ◽  
Green Roof ◽  
Green Roofs ◽  
Storm Events ◽  
Climate Conditions ◽  
Hourly Data ◽  
Test Beds ◽  
Fit Indexes ◽  
Flooding Risk

The evolving climate conditions contribute to increase flooding risk in urban areas. Green roofs are effective tools for controlling and managing stormwater runoff. With the aim to prevent these damaging events, an accurate modelling of the response of green roofs to storm events becomes essential. The goal of this research is to compare the accuracy of two hydrological models in predicting the behavior of two green roof test beds in terms of runoff production. The test beds are located in the campus of University of Salerno, in a typical Mediterranean climate and they differ in the composition of the drainage layer. The selected models are the Storm Water management model (SWMM) model and the Nash model. They have been calibrated against hourly data of 25 rainfall-runoff events observed at the experimental site and compared using a number of goodness of fit indexes. The Nash cascade model aims to be a very simple but effective approach. No substantial differences were observed in the behavior of the two green roof plots, though they differ in their design characteristics. Finally, the existence of a relationship between the errors and the rainfall characteristics has been found.

scholarly journals The GREENROOF module (v7.3) for modelling green roof hydrological and energetic performances within TEB

2013 ◽  
Vol 6 (6) ◽  
pp. 1941-1960 ◽  
Author(s):  
C. S. de Munck ◽  
A. Lemonsu ◽  
R. Bouzouidja ◽  
V. Masson ◽  
R. Claverie
Keyword(s):  
Water Content ◽  
Green Roof ◽  
Green Roofs ◽  
Model Interaction ◽  
Drainage Layer ◽  
Extensive Green Roof ◽  
Hydrological Characteristics ◽  
Drainage Layers ◽  
The Impact

Abstract. The need to prepare cities for climate change adaptation requests the urban modeller community to implement sustainable adaptation strategies within their models to be tested against specific city morphologies and scenarios. Greening city roofs is part of these strategies. In this context, the GREENROOF module for TEB (town energy balance) has been developed to model the interactions between buildings and green roof systems at the scale of the city. This module, which combines the ISBA model (Interaction between Soil Biosphere and Atmosphere) and TEB, allows for one to describe an extensive green roof composed of four functional layers (vegetation – grasses or sedums; substrate; retention/drainage layers; and artificial roof layers) and to model vegetation-atmosphere fluxes of heat, water and momentum, as well as the hydrological fluxes throughout the substrate and the drainage layers, and the thermal fluxes throughout the natural and artificial layers of the green roof. TEB-GREENROOF (SURFEX v7.3) should therefore be able to represent the impact of climate forcings on the functioning of green roof vegetation and, conversely, the influence of the green roof on the local climate. An evaluation of GREENROOF is performed for a case study located in Nancy (France) which consists of an instrumented extensive green roof with sedums and substrate and drainage layers that are typical of this kind of construction. After calibration of the drainage layer hydrological characteristics, model results show good dynamics for the substrate water content and the drainage at the green roof base, with nevertheless a tendency to underestimate the water content and overestimate the drainage. This does not impact too much the green roof temperatures, which present a good agreement with observations. Nonetheless GREENROOF tends to overestimate the soil temperatures and their amplitudes, but this effect is less important in the drainage layer. These results are encouraging with regard to modelling the impact of green roofs on thermal indoor comfort and energy consumption at the scale of cities, for which GREENROOF will be running with the building energy version of TEB – TEB-BEM. Moreover, with the green roof studied for GREENROOF evaluation being a type of extensive green roof widespread in cities, the type of hydrological characteristics highlighted for the case study will be used as the standard configuration to model extensive green roof impacts at the scale of cities.

Sign in / Sign up

Export Citation Format

Share Document