Analysis of roof greening technology impact on rain and meltwater retention

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.

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Water Resilience by Centipedegrass Green Roof: A Case Study

Buildings ◽

10.3390/buildings9060141 ◽

2019 ◽

Vol 9 (6) ◽

pp. 141 ◽

Cited By ~ 1

Author(s):

Shuai Hu ◽

Lijiao Liu ◽

Junjun Cao ◽

Nan Chen ◽

Zhaolong Wang

Keyword(s):

Soil Moisture ◽

Green Roof ◽

Green Roofs ◽

Saturated Soil ◽

Water Retention Capacity ◽

Water Runoff ◽

Retention Capacity ◽

Runoff Reduction ◽

Eremochloa Ophiuroides ◽

Rain Events

Centipedegrass (Eremochloa ophiuroides) is a low-maintenance turfgrass. The first extensive green roof of centipedegrass was established in TongZhou Civil Squares in 2014. However, storm-water-runoff reduction, water-retention capacity, and plant-water requirements by a centipedegrass green roof has not yet been defined. The soil moisture dynamics, rainwater-retention capacity, runoff reduction, and plant evapotranspiration were investigated by simulated centipedegrass green roof plots, which were constructed in the same manner as the green roofs in TongZhou Civil Squares in 2018. The results showed that the centipedegrass green roof retained 705.54 mm of rainwater, which consisted 47.4% of runoff reduction. The saturated soil moisture was 33.4 ± 0.6%; the excess rainfall over the saturated soil moisture resulted in runoff. The capacity of rainwater retention was negatively related to the soil moisture before rain events and was driven by plant evapotranspiration. Drought symptoms only occurred three times over the course of a year when the soil moisture dropped down to 10.97%. Our results indicate that the rainwater retained in the soil almost met the needs of plant consumption; a further increase of rainwater retention capacity might achieve an irrigation-free design in a centipedegrass green roof.

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Hydrological Performance and Runoff Water Quality of Experimental Green Roofs

Water ◽

10.3390/w10091185 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1185 ◽

Cited By ~ 10

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.

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Heat Transfer Behavior of Green Roof Systems Under Fire Condition: A Numerical Study

Buildings ◽

10.3390/buildings9090206 ◽

2019 ◽

Vol 9 (9) ◽

pp. 206

Author(s):

Gerzhova ◽

Blanchet ◽

Dagenais ◽

Côté ◽

Ménard

Keyword(s):

Heat Transfer ◽

Failure Time ◽

Numerical Study ◽

Fire Hazard ◽

Green Roof ◽

Green Roofs ◽

Heat Transfer Process ◽

Heat Fluxes ◽

Substrate Thickness ◽

Time To Failure

Currently, green roof fire risks are not clearly defined. This is because the problem is still not well understood, which raises concerns. The possibility of plants catching fire, especially during drought periods, is one of the reasons for necessary protection measures. The potential fire hazard for roof decks covered with vegetation has not yet been fully explored. The present study analyzes the performance of green roofs in extreme heat conditions by simulating a heat transfer process through the assembly. The main objective of this study was to determine the conditions and time required for the roof deck to reach a critical temperature. The effects of growing medium layer thickness (between 3 and 10 cm), porosity (0.5 to 0.7), and heating intensity (50, 100, 150, and 200 kW/m²) were examined. It was found that a green roof can protect a wooden roof deck from igniting with only 3 cm of soil coverage when exposed to severe heat fluxes for at least 25 minutes. The dependency of failure time on substrate thickness decreases with increasing heating load. It was also found that substrate porosity has a low impact on time to failure, and only at high heating loads.

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A comparative study on rainfall runoff control indicators of green roof

Water Science & Technology Water Supply ◽

10.2166/ws.2020.076 ◽

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.

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The Potential of Recycled Locally-Sourced Waste Materials for Green Roof Soil Mixtures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.730.445 ◽

2017 ◽

Vol 730 ◽

pp. 445-451

Author(s):

Hartini Kasmin ◽

Siti Nur Ummiah Munir ◽

Nur Syafira Razak ◽

Nor Azizi Yusoff ◽

Rosniza Kassim ◽

...

Keyword(s):

Urban Areas ◽

Climatic Factors ◽

Green Roof ◽

Water Storage ◽

Green Roofs ◽

Waste Materials ◽

Peat Moss ◽

Water Runoff ◽

Maximum Water ◽

Soil Mixtures

The increase in surface runoff has become a serious environmental problem and concern in Malaysia. Hence, promoting the use of green roofs in urban areas will potentially allow some storage area and time attenuation for any rainfall. Initial studies on a few substrate mixtures were done in order to find out the properties of green roof media. These included vermiculite (V), perlite (P) and peat moss (PM) together with locally-sourced waste materials such as empty fruit bunches (EFB) and wet diaper gel (D) which are expected to potentially retain more storm water runoff. A test on the substrate mixture properties and evaporation tests were conducted on seven types of soil mixtures. The results show that a basic substrate mixture of PVPM3,5,2 has a maximum water capacity of 50%. The modification and addition of diaper gel in DVPM1,3,2 and empty fruit bunch (EFB) in PEFBPM1,0.3,2 show an increment in both mixtures’ water holding capacity (54%). All the proposed mixtures have shown permeability values larger than 0.0005 cm/s. To investigate the maximum water storage availability, the evaporation tests show that both mixtures could provide 60 - 62 mm of water storage after 34 days without rainfall under ambient climatic condition (32 ̊ to 34 ̊) whereas under extreme heat temperatures (50 ̊), both mixtures took only 1 day to provide the same storage as the ambient condition. Therefore, this study has provided an initial understanding of the properties of the substrate mixture as well as the evaporation rate of the materials tested. This information can be used to demonstrate the relationship between soil characteristics and local climatic factors (temperature).

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Simulation of Thin Green Roof for Summer in Seoul

International Journal of Air-Conditioning and Refrigeration ◽

10.1142/s2010132517500341 ◽

2017 ◽

Vol 25 (04) ◽

pp. 1750034 ◽

Cited By ~ 1

Author(s):

K. H. Byun

Keyword(s):

Numerical Analysis ◽

Simple Model ◽

Green Roof ◽

Experimental Studies ◽

Green Roofs ◽

Weather Data ◽

Climate Conditions ◽

Four Seasons ◽

Planning Experiment ◽

Insulation Status

The purpose of this paper is to simulate the performance of thin green roofs during summer in Seoul, where there are four seasons. Many experimental studies are available for the green roofs, but there have not been many analytical studies. Numerical analysis is applied to a simple model developed for this study. The effects of the parameters affecting green roof performance are studied using several roof types. The weather data from Korea Meteorological Administration for the summer in Seoul have been used as an input for the simulation model. The results agree with the trends reported in previous studies. The importance of insulation status of the roof before applying green roof and the climate conditions is confirmed. Analysis such as this paper is necessary and useful before applying green roof or planning experiment on green roof.

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Evaluating different machine learning methods to simulate runoff from extensive green roofs

Hydrology and Earth System Sciences ◽

10.5194/hess-25-5917-2021 ◽

2021 ◽

Vol 25 (11) ◽

pp. 5917-5935

Author(s):

Elhadi Mohsen Hassan Abdalla ◽

Vincent Pons ◽

Virginia Stovin ◽

Simon De-Ville ◽

Elizabeth Fassman-Beck ◽

...

Keyword(s):

Machine Learning ◽

Green Roof ◽

Green Roofs ◽

Storm Water ◽

Water Runoff ◽

Learning Methods ◽

Retention Model ◽

Machine Learning Methods ◽

Storm Water Runoff ◽

Extensive Green Roofs

Abstract. Green roofs are increasingly popular measures to permanently reduce or delay storm-water runoff. The main objective of the study was to examine the potential of using machine learning (ML) to simulate runoff from green roofs to estimate their hydrological performance. Four machine learning methods, artificial neural network (ANN), M5 model tree, long short-term memory (LSTM) and k nearest neighbour (kNN), were applied to simulate storm-water runoff from 16 extensive green roofs located in four Norwegian cities across different climatic zones. The potential of these ML methods for estimating green roof retention was assessed by comparing their simulations with a proven conceptual retention model. Furthermore, the transferability of ML models between the different green roofs in the study was tested to investigate the potential of using ML models as a tool for planning and design purposes. The ML models yielded low volumetric errors that were comparable with the conceptual retention models, which indicates good performance in estimating annual retention. The ML models yielded satisfactory modelling results (NSE >0.5) in most of the roofs, which indicates an ability to estimate green roof detention. The variations in ML models' performance between the cities was larger than between the different configurations, which was attributed to the different climatic characteristics between the four cities. Transferred ML models between cities with similar rainfall events characteristics (Bergen–Sandnes, Trondheim–Oslo) could yield satisfactory modelling performance (Nash–Sutcliffe efficiency NSE >0.5 and percentage bias |PBIAS| <25 %) in most cases. However, we recommend the use of the conceptual retention model over the transferred ML models, to estimate the retention of new green roofs, as it gives more accurate volume estimates. Follow-up studies are needed to explore the potential of ML models in estimating detention from higher temporal resolution datasets.

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AN ANALYSIS ON THE EFFICIENCY OF GREEN ROOF IN MANAGING URBAN STORMWATER RUNOFF

PLANNING MALAYSIA JOURNAL ◽

10.21837/pm.v19i17.991 ◽

2021 ◽

Vol 19 (17) ◽

Author(s):

Shazmin Shareena Ab. Azis ◽

Muhammad Najib Mohamed Razali ◽

Nurul Hana Adi Maimun ◽

Nurul Syakima Mohd Yusoff ◽

Mohd Shahril Abdul Rahman ◽

...

Keyword(s):

Flash Flood ◽

Meta Analysis ◽

Green Roof ◽

Drainage System ◽

Green Roofs ◽

Storm Water ◽

Water Runoff ◽

Extensive Green Roof ◽

Storm Water Runoff ◽

Urban Storm

Modernization has created new impervious urban landscape contributed to major catastrophe. Urban drainage system incapable to convey the excess rainwater resulting in flash flood due to heavy rainfall. The combination of green roof on building have tremendously proved to control stormwater efficiently. This study is conducted to review the efficiency of intensive and extensive green roof in reducing urban storm water runoff. This study identifies characteristic of green roof that contributes to lessening urban storm water runoff. Data was collected based on rigorous literature reviews and analyzed using meta-analysis. Overall, findings revealed intensive green roof performed better in reducing storm water runoff compared to extensive green roof. Green roof performance increases as the depth of substrate increased. Origanum and Sedum plants are both highly effective for intensive and extensive green roofs. The performance of green roof reduces as degree of roof slope increased.

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Green Roof Design Techniques to Improve Water Use under Mediterranean Conditions

Urban Science ◽

10.3390/urbansci3010014 ◽

2019 ◽

Vol 3 (1) ◽

pp. 14 ◽

Cited By ~ 7

Author(s):

Teresa Paço ◽

Ricardo Cruz de Carvalho ◽

Pedro Arsénio ◽

Diana Martins

Keyword(s):

Water Use ◽

Green Roof ◽

Green Roofs ◽

Climatic Conditions ◽

Native Plant ◽

Additional Energy ◽

Climate Conditions ◽

Native Plant Species ◽

Roof Design ◽

Mediterranean Conditions

Green roof typology can vary depending on buildings structure, climate conditions, substrate, and plants used. In regions with hot and dry summers, such as the Mediterranean region, irrigation plays an essential role, as the highest temperatures occur during the driest period of the year. Irrigation might reduce the heat island effect and improve the cooling of buildings during this period, however, the added cost of maintenance operations and additional energy consumption could outrun the benefits provided by the project. Moreover, in situations where water is scarce or primarily channelled to other uses (e.g., domestic, agriculture or industry) during drought occurrence, it is advisable to implement green roof projects with the lowest use of water possible. The objective of the present work is to investigate solutions to optimize water use in green roofs under Mediterranean conditions, such as those of southern Europe. Two case studies are presented for Portugal, and potential techniques to reduce irrigation requirements in green roofs were tested. These addressed the use of native plant species, including the extreme type of a non-irrigated green roof (Biocrust roof) and techniques for plant installation. Plant drought tolerance was found to be an advantage in green roofs under these climatic conditions and, for the species studied, aesthetic value could be maintained when irrigation decreased.

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Growing substrates for aromatic plant species in green roofs and water runoff quality: pilot experiments in a Mediterranean climate

Water Science & Technology ◽

10.2166/wst.2017.276 ◽

2017 ◽

Vol 76 (5) ◽

pp. 1081-1089 ◽

Cited By ~ 5

Author(s):

Cristina M. Monteiro ◽

Cristina S. C. Calheiros ◽

Paulo Palha ◽

Paula M. L. Castro

Keyword(s):

Organic Matter ◽

Plant Species ◽

Urban Areas ◽

Mediterranean Climate ◽

Green Roof ◽

Oxygen Demand ◽

Green Roofs ◽

Water Runoff ◽

Aromatic Plant ◽

Runoff Quality

Green roof technology has evolved in recent years as a potential solution to promote vegetation in urban areas. Green roof studies for Mediterranean climates, where extended drought periods in summer contrast with cold and rainy periods in winter, are still scarce. The present research study assesses the use of substrates with different compositions for the growth of six aromatic plant species – Lavandula dentata, Pelargonium odoratissimum, Helichrysum italicum, Satureja montana, Thymus caespititius and T. pseudolanuginosus, during a 2-year period, and the monitoring of water runoff quality. Growing substrates encompassed expanded clay and granulated cork, in combination with organic matter and crushed eggshell. These combinations were adequate for the establishment of all aromatic plants, allowing their propagation in the extensive system located on the 5th storey. The substrate composed of 70% expanded clay and 30% organic matter was the most suitable, and crushed eggshell incorporation improved the initial plant establishment. Water runoff quality parameters – turbidity, pH, conductivity, NH4+, NO3−, PO43- and chemical oxygen demand – showed that it could be reused for non-potable uses in buildings. The present study shows that selected aromatic plant species could be successfully used in green roofs in a Mediterranean climate.

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