scholarly journals Evaluation of Green Roof Performance in Mitigating the Impact of Extreme Storms

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 815 ◽  
Author(s):  
Liu ◽  
Chui
Keyword(s):  
Hong Kong ◽  
Hydraulic Conductivity ◽  
Return Period ◽  
Green Roof ◽  
Design Parameters ◽  
Soil Thickness ◽  
Rainfall Characteristics ◽  
Runoff Reduction ◽  
Peak Runoff ◽  
The Impact

Green roofs are used in urban areas to mitigate the adverse effects of stormwater. Through numerical modeling, this study evaluates the impacts of design parameters on green roof hydrological performance under different rainfall characteristics. A calibrated model is run with long-term precipitation data series for three locations (Hong Kong, China; Beltsville, MD, USA; and Sidney, NY, USA). The results show that the amount of peak runoff reduction increases with the duration of the storm return period in Beltsville and Sidney; while the trend is opposite in Hong Kong. Percentage peak reduction generally shows a decreasing trend with the storm return period in three locations. For average runoff reduction, the amount of reduction increases with the storm return period, whereas the percentage reduction presents an opposite trend in all three locations. The actual values vary between the three locations due to differences in rainfall characteristics. Both peak and average runoff reduction increase with green roof thickness, but in practice, it is not cost effective or feasible to increase the thickness beyond a certain threshold. The hydraulic conductivity can then be optimized for peak runoff reduction and it is found to increase with the return period. However, hydraulic conductivity has a minimal effect on average runoff reduction. Overall, this paper studies green roof hydrological performance in response to different rainfall characteristics and provides recommendations on green roof designs related to soil thickness and hydraulic conductivity.

scholarly journals Analysis of Stormwater Retention on Green Roofs / Badania Retencji Wód Opadowych Na Dachach Zielonych

2012 ◽  
Vol 38 (4) ◽  
pp. 3-13 ◽  
Author(s):  
Ewa Burszta-Adamiak
Keyword(s):  
Life Sciences ◽  
Green Roofs ◽  
Retention Capacity ◽  
Runoff Reduction ◽  
Science And Education ◽  
Peak Runoff ◽  
The Impact ◽  
Stormwater Retention ◽  
Maximum Runoff ◽  
Sewage Systems

Abstract This study presents the results of tests conducted in 2009 and 2010 on experimental sites installed on the roof of the Science and Education Building of the Wroclaw University of Environmental and Life Sciences. The aim of the analysis was to determine the retention capacity of green roofs and the runoff delays and peak runoff reduction during rainfall recorded in Wroclaw conditions. The research shows that green roofs allow to reduce the volume of runoff stormwater in comparison to conventional roofs, that they delay the runoff in time and influence the reduction of the maximum runoff intensity, and thus may limit the impact of stormwater on the stormwater drainage and combined sewage systems.

scholarly journals Effects of Extensive Green Roofs on Energy Performance of School Buildings in Four North American Climates

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 6 ◽  
Author(s):  
Milad Mahmoodzadeh ◽  
Phalguni Mukhopadhyaya ◽  
Caterina Valeo
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Plant Height ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Design Parameters ◽  
Soil Thickness ◽  
Area Index ◽  
Roof Design

A comprehensive parametric analysis was conducted to evaluate the influence of the green roof design parameters on the thermal or energy performance of a secondary school building in four distinctively different climate zones in North America (i.e., Toronto, ON, Canada; Vancouver, BC, Canada; Las Vegas, NV, USA and Miami, FL, USA). Soil moisture content, soil thermal properties, leaf area index, plant height, leaf albedo, thermal insulation thickness and soil thickness were used as design variables. Optimal parameters of green roofs were found to be functionally related to meteorological conditions in each city. In terms of energy savings, the results showed that the light-weight substrate had better thermal performance for the uninsulated green roof. Additionally, the recommended soil thickness and leaf area index for all four cities were 15 cm and 5 respectively. The optimal plant height for the cooling dominated climates is 30 cm and for the heating dominated cities is 10 cm. The plant albedo had the least impact on the energy consumption while it was effective in mitigating the heat island effect. Finally, unlike the cooling load, which was largely influenced by the substrate and vegetation, the heating load was considerably affected by the thermal insulation instead of green roof design parameters.

scholarly journals Hydrologic performance of bioretention in an expressway service area

2018 ◽  
Vol 77 (7) ◽  
pp. 1829-1837 ◽  
Author(s):  
Jianping Gao ◽  
Junkui Pan ◽  
Ning Hu ◽  
Chengzuo Xie
Keyword(s):  
Water Balance ◽  
Reduction Rate ◽  
Service Area ◽  
Annual Rainfall ◽  
Design Parameters ◽  
Effective Measure ◽  
Bioretention System ◽  
Runoff Reduction ◽  
The Impact ◽  
Hydrologic Performance

Abstract Bioretention can be an effective measure for stormwater treatment. However, there is a lack of systematic analysis of the impact of bioretention design parameters on hydrologic performance. Herein, SWMM and RECARGA models were applied to generate the typical annual rainfall runoff and simulate the water balance of the bioretention system in an expressway service area. The purpose of the investigation was to identify key design parameters for the bioretention system and delineate the priorities in developing the design. Results showed that the average groundwater recharge ratios for bioretention basins with and without an underdrain were 58.29% and 92.27%, respectively, the average overflow ratios were 4.13% and 4.19%, the average evapotranspiration ratios were 4.48% and 4.47%, and the average outflow ratio for bioretention with an underdrain was 33.94%. The ratio of the bioretention area to drainage area, and the saturated infiltration rates of planting soil and native soil were the main factors influencing water balance, while the underdrain diameter and gravel layer depth exerted little effect. Based on the impact analysis, multivariate nonlinear regression models of runoff reduction rate for two types of bioretention basin were established, which both exhibited high determination coefficients and acceptable Nash–Sutcliffe coefficients.

scholarly journals Modelling the impact of retention–detention units on sewer surcharge and peak and annual runoff reduction

2015 ◽  
Vol 71 (6) ◽  
pp. 898-903 ◽  
Author(s):  
Luca Locatelli ◽  
Søren Gabriel ◽  
Ole Mark ◽  
Peter Steen Mikkelsen ◽  
Karsten Arnbjerg-Nielsen ◽  
...  
Keyword(s):  
Retention Volume ◽  
Stormwater Runoff ◽  
Annual Runoff ◽  
Reduction Peak ◽  
Peak Reduction ◽  
Small Catchment ◽  
Runoff Reduction ◽  
Impervious Area ◽  
Peak Runoff ◽  
The Impact

Stormwater management using water sensitive urban design is expected to be part of future drainage systems. This paper aims to model the combination of local retention units, such as soakaways, with subsurface detention units. Soakaways are employed to reduce (by storage and infiltration) peak and volume stormwater runoff; however, large retention volumes are required for a significant peak reduction. Peak runoff can therefore be handled by combining detention units with soakaways. This paper models the impact of retrofitting retention–detention units for an existing urbanized catchment in Denmark. The impact of retrofitting a retention–detention unit of 3.3 m3/100 m2 (volume/impervious area) was simulated for a small catchment in Copenhagen using MIKE URBAN. The retention–detention unit was shown to prevent flooding from the sewer for a 10-year rainfall event. Statistical analysis of continuous simulations covering 22 years showed that annual stormwater runoff was reduced by 68–87%, and that the retention volume was on average 53% full at the beginning of rain events. The effect of different retention–detention volume combinations was simulated, and results showed that allocating 20–40% of a soakaway volume to detention would significantly increase peak runoff reduction with a small reduction in the annual runoff.

scholarly journals In-situ monitoring of energetic and hydrological performance of a semi-intensive green roof and a white roof during a heatwave event in the UK

2019 ◽  
Vol 30 (1) ◽  
pp. 56-69 ◽  
Author(s):  
Yangang Xing ◽  
Phil Jones
Keyword(s):  
Air Temperature ◽  
Indoor Air ◽  
Performance Monitoring ◽  
Green Roof ◽  
Weather Conditions ◽  
Green Roofs ◽  
In Situ Monitoring ◽  
Runoff Reduction ◽  
Peak Runoff ◽  
The Uk

Due to the increasing magnitude and high frequency of urban heatwaves, recently, there has been a surge of interest in the reflective roofs and the vegetative green roofs. Along with the rising temperature, there are also more frequent droughts and rainfall which have led to wider changes in weather conditions subsequently affecting the performance of green roofs and white roofs. However, there is still a lack of research in comparing dynamic energetic and hydrological performance of green roof and white roofs during heatwave events. This paper introduces a newly constructed outdoor test rig (installed with a semi-intensive green roof and an aluminium white roof) and a few initial monitoring results. The hydrological performance monitoring results showed that, although a noticeable peak runoff reduction of the white roof was observed, more significant water retention of green roofs had been established. The energetic performance monitoring results indicated that the green roof performed better than the white roof during the heatwave event reducing solar heat gains by 76% during day time, improving U-value by 28% and reducing indoor air temperature by 2.5°C. The peak indoor air temperature reduction in the green roof space occurred during late afternoons (around 7 pm).

scholarly journals Soil Moisture Dynamics in Response to Precipitation and Thinning in a Semi-Dry Forest in Northern Mexico

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 105
Author(s):  
Argelia E. Rascón-Ramos ◽  
Martín Martínez-Salvador ◽  
Gabriel Sosa-Pérez ◽  
Federico Villarreal-Guerrero ◽  
Alfredo Pinedo-Alvarez ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Forest Management ◽  
Water Availability ◽  
Dry Forest ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Northern Mexico ◽  
The Difference ◽  
The Impact ◽  
Moisture Dynamics

Understanding soil moisture behavior in semi-dry forests is essential for evaluating the impact of forest management on water availability. The objective of the study was to analyze soil moisture based in storm observations in three micro-catchments (0.19, 0.20, and 0.27 ha) with similar tree densities, and subject to different thinning intensities in a semi-dry forest in Chihuahua, Mexico. Vegetation, soil characteristics, precipitation, and volumetric water content were measured before thinning (2018), and after 0%, 40%, and 80% thinning for each micro-catchment (2019). Soil moisture was low and relatively similar among the three micro-catchments in 2018 (mean = 8.5%), and only large rainfall events (>30 mm) increased soil moisture significantly (29–52%). After thinning, soil moisture was higher and significantly different among the micro-catchments only during small rainfall events (<10 mm), while a difference was not noted during large events. The difference before–after during small rainfall events was not significant for the control (0% thinning); whereas 40% and 80% thinning increased soil moisture significantly by 40% and 53%, respectively. Knowledge of the response of soil moisture as a result of thinning and rainfall characteristics has important implications, especially for evaluating the impact of forest management on water availability.

scholarly journals Seismic Performance of a Green Roof Structure

2021 ◽  
Vol 13 (8) ◽  
pp. 4278
Author(s):  
Svetlana Tam ◽  
Jenna Wong
Keyword(s):  
Green Roof ◽  
Time History ◽  
Green Roofs ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Roof Structure ◽  
Nonlinear Time History Analyses ◽  
Vegetated Roofs ◽  
Nonlinear Time History ◽  
The Impact

Sustainability addresses the need to reduce the structure’s impact on the environment but does not reduce the environment’s impact on the structure. To explore this relationship, this study focuses on quantifying the impact of green roofs or vegetated roofs on seismic responses such as story displacements, interstory drifts, and floor level accelerations. Using an archetype three-story steel moment frame, nonlinear time history analyses are conducted in OpenSees for a shallow and deep green roof using a suite of ground motions from various distances from the fault to identify key trends and sensitivities in response.

scholarly journals Share Contract Revisited: A New Transaction Cost Approach

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jian Ding ◽  
Yixiao Zhou
Keyword(s):  
Hong Kong ◽  
Transaction Cost ◽  
Empirical Studies ◽  
Theoretical Explanation ◽  
Empirical Testing ◽  
Cost Approach ◽  
Satisfactory Answer ◽  
The Impact

Abstract The purpose of this paper is to explore how sharecropping contracts are chosen over fixed-rent contracts. There are two concerning issues. First, theoretical explanation has been criticized for not providing a satisfactory answer to the question as to why share contracts are chosen. Second, among the existing empirical studies, there are great controversies about the impact of variance of output. Inspired by the latest insights from (Cheung, S. N. S. 2014. Economic Explanation. Hong Kong: Arcadia Press.), this paper not only provides an explanation for the choice of share contract that is suitable for empirical testing, but also solves the puzzle over variance of output.

Design of a Robust Memristive Spiking Neuromorphic System with Unsupervised Learning in Hardware

2021 ◽  
Vol 17 (4) ◽  
pp. 1-26
Author(s):  
Md Musabbir Adnan ◽  
Sagarvarma Sayyaparaju ◽  
Samuel D. Brown ◽  
Mst Shamim Ara Shawkat ◽  
Catherine D. Schuman ◽  
...  
Keyword(s):  
Unsupervised Learning ◽  
Recognition Task ◽  
Single Layer ◽  
Process Variations ◽  
Spike Timing ◽  
System Level ◽  
Design Parameters ◽  
Digital Pulse ◽  
Neuromorphic System ◽  
The Impact

Spiking neural networks (SNN) offer a power efficient, biologically plausible learning paradigm by encoding information into spikes. The discovery of the memristor has accelerated the progress of spiking neuromorphic systems, as the intrinsic plasticity of the device makes it an ideal candidate to mimic a biological synapse. Despite providing a nanoscale form factor, non-volatility, and low-power operation, memristors suffer from device-level non-idealities, which impact system-level performance. To address these issues, this article presents a memristive crossbar-based neuromorphic system using unsupervised learning with twin-memristor synapses, fully digital pulse width modulated spike-timing-dependent plasticity, and homeostasis neurons. The implemented single-layer SNN was applied to a pattern-recognition task of classifying handwritten-digits. The performance of the system was analyzed by varying design parameters such as number of training epochs, neurons, and capacitors. Furthermore, the impact of memristor device non-idealities, such as device-switching mismatch, aging, failure, and process variations, were investigated and the resilience of the proposed system was demonstrated.

scholarly journals The impact of SARS and COVID-19 on major trauma in Hong Kong

2021 ◽  
Author(s):  
Joseph Harold Walline ◽  
Kevin Kei Ching Hung ◽  
Janice Hiu Hung Yeung ◽  
Priscilla P. Song ◽  
Nai-Kwong Cheung ◽  
...  
Keyword(s):  
Hong Kong ◽  
Major Trauma ◽  
The Impact
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