Evaluation of green roof performances for stormwater quantity and quality controls (original) (raw)
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Evaluation of Green Roof as Green Technology for Urban Stormwater Quantity and Quality Controls
Nowadays, people mutually recognise that global warming is actually a fact rather just a scientific theory and it has been fuelled up quickly as resulted from rapid urbanisations. Driven by environmental needs, green building index (GBI) was established in Malaysia to drive the initiative to lead the property industry towards becoming more environmental friendly. Green roofs (roof with vegetated cover), as one of the assessment criteria of GBI, are gaining attention in the Malaysian society as a versatile new environmental friendly mitigation technology. This paper evaluates the qualitative and quantitative performances of extensive green roof at Humid Tropics Center under local tropical climate. Simulations showed that the peak discharge was reduced up to 26% in relation to impervious brown roof. Its reduction ability decreased for storms with intense rainfall. Increment of pH was observed for the green roof runoff and the runoff water quality ranged between class I and II under WQI. High concentrations of phosphate were noticed in the runoff samples and substrates (fertilised planting soil) might be the potential contributor. Findings indicate that there was a reduction of approximately 1.5°C for indoor temperature of the building after installation of the extensive green roof.
Nowadays, Green Building index (GBI) has became a hot issue in society of Malaysia especially for the field of construction and infrastructure works. Government has promoted this index intensively by launching city developments projects which emphases on environmental friendly buildings and infrastructures. Green Building Index is Malaysia first comprehensive rating system for evaluating the environment design and performance of Malaysian buildings. Green roof system is one of the assessment criteria of this rating system which is under category of sustainable site planning and management. Green roof also serves as one of the components of application of Water Sensitive Urban Design (WSUD) in Humid Tropic Center (HTC). This paper portrays evaluations of the performance of extensive green roof at Humid Tropic Center (HTC) on reducing peak discharge for tropical climate. This study also reviews thermal performance of vegetated rooftop in reducing temperature of the building which enables the building consumes less energy. On-site experiments would be carried out to determine the ability of water retention of green roof in HTC by measuring the runoff produced by the green roof. The total amount of runoff measured was compared with standard peak discharge for Kuala Lumpur calculated from Rational Method with referring to Mesra Alam Saliran Manual (MASMA) chapter 13. The temperature of the building was measured by a thermometer which was attached to the inner wall of the surau. Indoor temperature was recorded every 15 minutes daily. Mean maximum temperature recorded before and after installation of green roof was compared. The results indicate that green roof at HTC can reduce peak discharge up to 44% and it is able to induce cooler indoor environment.
GREEN ROOF PERFORMANCE FOR STORMWATER MANAGEMENT IN MALAYSIA
PhD Thesis, 2020
In managing stormwater, Sustainable Urban Drainage Systems (SUDS) has promoted the control-at-source concept. This concept focuses equally on quantity, quality of stormwater and amenity as an integrated approach. Many components in SUDS have different purposes depending on design and location to implement. One of these components is green roof. There are two types of green roof namely extensive and intensive green roof. Many studies overseas have shown that green roof can help not only in slowing down the rainwater to reach the ground and sinking numerous pollutants in its substrate, but also leaching pollutants from the substrate. Notably, the rainfall characteristics in those countries are different compared to the conditions in Malaysia. Malaysia receives high rainfall depth throughout the year from low to severe intensity (1->60mm/hr). High and severe intensity rainfall may cause flash flood in Malaysia particularly in urban and dense areas. Due to the limitation of space, the performance of green roof towards high-intensity rainfall needs to be further studied in Malaysian conditions. It is to determine the performance of this SUDS component in combating flash flood issues and become an alternative for stormwater management in Malaysia. Other than that, the application of green roof can also be considered for a major system in Urban Stormwater Management Manual for Malaysia 2nd Edition (MSMA 2nd Edition) since it is still not included in the manual. This research was carried out in River Engineering and Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia (USM). Through simulated and real rainfall events, the performance of intensive green roof in terms of flow attenuation, volume retention, and green roof outflow water quality were studied. The result showed that green roof testbeds managed to attenuate the inflow and volume retention. Runoff was delayed in the range of 20 to 65 minutes. Green roof was found to successfully reduce peak discharge of rainfall in the range of 68.8% to 95.6% with moderate influence by rainfall depth and rainfall duration with R2=0.5. In simulated high-intensity rainfall (52mm/hr – 1040mm/hr), the green roof managed to retain rainwater from 0.02m3 to 1.22m3. Volume retention was calculated and found to have a significant correlation with rainfall depth, intensity and rainfall duration with R2=0.8. Based on the Water Quality Index of Malaysia (WQI), the quality of green roof outflow was studied and it was found that pH and COD fell in Class I, BOD5 and TSS in Class I-II, AN in Class I-III, and depletion of DO fell in Class I-V. No significant difference was found in green roof vegetation performance in treating these WQI parameters except for TSS (p<0.05). It was confirmed that green roof discharge would not cause a nuisance to water bodies. To conclude, this study believes that the implementation of green roof in Malaysia is very promising.
Green roofs are an increasingly important component of water-sensitive urban design systems that can potentially improve the quality of urban runoff, reduce the energy consumption of buildings, and add esthetic value to the environment. The most important green roof abilities, which appear as a key feature in urban catchments are the ability of rainwater detention and retention and reduction in energy consumption. This paper aims to provide an overview of the effects of the application of the green roof strategy on the quality of runoff water and the reduction of energy consumption. The components of a green roof are discussed, and the advantages and disadvantages of different types of green roofs are assessed. In addition, the origins and concentrations of the main pollutants are discussed, moreover environmental cost-benefits of green roofs are also considered. In addition, the main factors that affect the quality of green roof runoff water, e.g., plant species, fertilization, pH, growth media as well as how green roofs could reduce energy consumption are discussed. Green roofs are considered as sustainable approach for runoff management with achieved aesthetical values and in combination with energy saving on heating/cooling. Hence, green roof causes a sufficient decrease in energy consumption and consequently in the related energy costs. It can help to improve the micro climate around the buildings and save money and also improve water quality. Therefore, green roofs may turn into a profitable investment. Some recommendations for future study also are proposed.
Proceedings IAHR World Congress 2015
Receiving an average 3000mm of rainfall depth with high intensity, Malaysia is known as a tropical climate country. Currently, Malaysia proactively promotes the use of Sustainable Urban Drainage Syatem (SUDS) as indicated in the Malaysian's Stormwater Management Manual namely the Urban Stormwater Management Manual of Malaysia (MSMA) 1 st and 2 nd version. The manual is promoting the implementation of SUDS facilities whether as a single facility or integrated ones which is a combination of two or more SUDS facilities. However green roof is not included in this manual. Thus the objectives of this paper are to share the preliminary study of intensive green roof tested under high intensity rainfall (159mm/hr) using rainfall simulator and four intensive green roof test bed with different vegetations. Three species selected for each test bed namely Kalanchoe pinnata (K.pinnata), Axonopus compressus (A.compressus) and Arachis pintoi (A.pintoi). Another test bed is to leave in a baren condition without vegetation as a control unit. Media or substrate use for these test beds are similar which consists of drainage cells, geotextile, river sand and top soils. Parameters studied are potassium (K), Total Phosphate (TP), Total Nitrogen (TN) and Ammoniacal Nitrogen (AN). Results show that K.pinnata performed well in the reduction of TP (37.50%-89%) and AN (68.90%-95.34%) followed by A.pintoi(TP: 36.68%-82.50%, AN: 59.92%-92.68%) and A.compressus (TP: 20.11%-80.15%, AN: 89.52%-93.44%).Another studied parameters (K and TN) show leaching in outflow of test bed. It is believed due to the fertilizer used for plant growth.In term of quantity control, all test beds showed reduction percentage of runoff hydrograph in the range of 9% to 67. 1. INTRODUCTION Malaysia located near to the equator consists of two major parts namely Peninsular Malaysia and East Malaysia (Sabah and Sarawak) which is located in Borneo Island. By receiving high rainfall depth throughout the year Malaysia notable has tropical climate and also has big area of tropical rainforest as a water catchment area. Even though average of rainfall per year is 3500mm, Malaysia facing major stormwater problems like flash flood, water shortage and water pollution. Year by year the problems getting worse, thus holistic methods need to be applied. Conventional method in stormwater management like using concrete drain in new development area cannot fulfill the expectation in control the volume and quality of runoff water. It is due to the concept applied by concrete drain known as rapid disposal. Rapid disposal means stormwater runoff have to convey to downstream as soon as possible. This scenario will cause the failure of existing concrete drain in downstream area due to the high amount of water compare than the drain was designed. Hence, flash flood will occur in the area and will bring whether tangible or intangible loss to the community. Flash floods also sweep away all litter, debris, dead leaves and etc to the nearest water bodies. So obviously it will cause deterioration the quality of water bodies and affect the water resource of the community. Therefore, management of stormwater need to improve and solve these three major problems as a whole. Related to the issues, Department of Irrigation and Drainage, Malaysia (DID) launch a new Urban Stormwater Manual of Malaysia (USWM) in 2001 and second edition of USWM was launched in August 2012. This manual introduces the new perception in stormwater management. The integrated approach have been promote where quantity, quality and amenity of stormwater runoff and surrounding catchments area are taken equally into consideration for design the urban drainage system. This integrated approach known as Sustainable Urban Drainage System (SUDS) or Best Management Practices (BMPs). SUDS replace the concept of rapid disposal in conventional method to the new paradigm called control at source. 6730
GREEN ROOF: RESPONSE TOWARDS EL-NINO AND IMPACT ON RUNOFF WATER QUALITY
IAHR 2017 Congress Proceedings, 2017
Sustainable Urban Drainage Systems (SUDS) promoting numerous type of facilities in stormwater management. The facilities fall in three major group functions namely source control, site control and regional control. Control at source facilities like green roofs, permeable surface and so forth are purposely built to manage rainfall close to where it falls. Benefits of green roof around the globe are very noticeable. This paper will discuss the performance of green roof during El-Nino period and runoff water quality from high intensity rainfall. Intensive green roof is constructed on the top of car parking roof. It was observe daily for one year. Results found that green roof’s contribution in cooling the indoor area of car park in tropical climate region varies during El-Nino period. Its performance relies to the surrounding temperature which during El-Nino, it can increase the surrounding temperature in the range 0.5oC to 2.0oC compared to normal period. However, during normal climate, green roof manage to reduce indoor area temperature in the range of 0.2oC to 2.0oC. This study shows the green roof manage to perform very well in delaying the outflow during high intensity rainfall. It can retain 100% of rain water or up to 6 months ARI event. However, it depends on the frequency of the events. In term of improving the rain water quality, vegetation used did not gave significance difference in improving runoff water quality. Nonetheless the parameters studied still did not permit according to the National River Water Quality Standard for Malaysia and Malaysia Drinking Water Quality Standard (Raw Water). This study concluded that application of green roof in urban infrastructure like parking areas and bus stops is very promising method for tropical climate countries.
Green roofs for stormwater mitigation in Hong Kong
2009
Hong Kong often faces stormwater problems during the rainy season. The heavy rainstorm could cause flooding and serious damages to the society. To tackle this, the Government has to make large investment in drainage and flood control projects which have significant socioeconomic implications. The research findings in other countries indicated that green roofs can be an effective tool to help mitigate stormwater problems. The application of green roofs in the buildings can delay the starting time of the stormwater runoff and reduce the magnitude of peak runoff and the total amount of rainwater discharged from the buildings. Also, the roof greening method in urban areas can improve the quality of the built environment and provide useful spaces for community functions. This paper explains the major findings of a research project to study the potential of green roofs for stormwater mitigation in Hong Kong. The rainfall characteristics and stormwater issues in Hong Kong are evaluated. Th...
EVALUATING THE PERFORMANCE OF GREEN ROOF FOR STORMWATER MANAGEMENT OPTIONS FOR GREEN TECHNOLOGY
Green roof is reasonably new concept introduced in Malaysia as part of green technology initiatives in the construction industry. It minimizes the degradation of the environment; zero or low green house gas (GHG) emission is safe for use and promotes healthy and improved environment for all forms of life; conserves the use of energy and natural resources; and promotes the use of renewable resources. Nowadays, Green Building index (GBI) has became a hot issue in society of Malaysia especially for the field of construction and infrastructure works. Green Building Index is Malaysia's first comprehensive rating system for evaluating the environment design and performance of Malaysian buildings. Green roof system is one of the assessment criteria of this rating system which is under category of sustainable site planning and management. Green roof was designed to be one of the components of application of Water Sensitive Urban Design (WSUD) in Humid Tropic Center (HTC) study area. This paper portrays evaluations of the performance of extensive green roof at Humid Tropic Center (HTC) on reducing peak discharge for tropical climate. This study also reviews thermal performance of vegetated rooftop in reducing temperature of the building which enables the building consumes less energy. Onsite experiments would be carried out to determine the ability of water retention of green roof in HTC by measuring the runoff produced by the green roof. The total amount of runoff measured was compared with standard peak discharge for Kuala Lumpur calculated based on MSMA Manual. The temperature of the building was measured by a thermometer which was attached to the inner wall of the selected building. Indoor temperature was recorded every 15 minutes daily. Mean maximum temperature recorded before and after installation of green roof was compared. The results indicated that green roof at HTC capable to reduce peak discharge up to 44% and it is able to induce cooler indoor environment to reduce usage of energy.
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.
Effect of Green Roof Configuration and Hydrological Variables on Runoff Water Quantity and Quality
Green roofs (GRs) are a feasible solution for mitigating increased runoff volumes in urban areas. Though many studies have focused their analysis on the quantity and quality of GR runoff, with respect to the relevance of specific site conditions in GR performance, the information gathered for the tropical Andes is not sufficient. This study assessed the hydrological performance and runoff water quality of 12 green roof modular systems located at the Universidad de los Andes campus (Bogotá, Colombia). Based on 223 rainfall events spanning a 3-year period, average rainfall retention was 85% (coefficient of variation = 29%). t-tests, the Welch Test, multiple linear regressions, and correlation analysis were performed in order to assess the potential effect of air temperature, substrate type, vegetation cover, relative humidity, antecedent dry weather period (ADWP), rainfall duration, and rainfall maximum intensity. In some cases, GR design variables (i.e., substrate type and vegetation cover) were found to be significant for describing rainfall retention efficiencies and, depending on the GR type, some hydrological variables were also correlated with rainfall retention. Rainfall and GR runoff from 12 rainfall events were also monitored for total Kjeldahl nitrogen (TKN) polyaromatic hydrocarbons (PAHs). The results obtained confirmed that GR systems have the ability to neutralize pH, but are a source of the rest of the aforementioned parameters, excluding PAHs (with concentrations below detection limits), ammonia, TSS, selenium and lithium, where differences with control cases (rainfall and plastic panel runoff) were not statistically significant. Substrate type, event size, and rainfall regime are relevant variables for explaining runoff water quality.