Modelling landfill location using Geographic Information Systems (GIS) and Multi-Criteria Decision Analysis (MCDA): Case study Bo, Southern Sierra Leone

Green roofs can be an attractive strategy for adding perviousness in dense urban environments where rooftops are a high fraction of the impervious land area. As a result, green roofs are being increasingly implemented as part of urban stormwater management plans in cities around the world. In this study, three full-scale green roofs in New York City (NYC) were monitored, representing the three extensive green roof types most commonly constructed: (1) a vegetated mat system installed on a Columbia University residential building, referred to as W118; (2) a built-in-place system installed on the United States Postal Service (USPS) Morgan general mail facility; and (3) a modular tray system installed on the ConEdison (ConEd) Learning Center. Continuous rainfall and runoff data were collected from each green roof between June 2011 and June 2012, resulting in 243 storm events suitable for analysis ranging from 0.25 to 180 mm in depth. Over the monitoring period the W118, USPS, and ConEd roofs retained 36%, 47%, and 61% of the total rainfall respectively. Rainfall attenuation of individual storm events ranged from 3 to 100% for W118, 9 to 100% for USPS, and 20 to 100% for ConEd, where, generally, as total rainfall increased the per cent of rainfall attenuation decreased. Seasonal retention behavior also displayed event size dependence. For events of 10‐40 mm rainfall depth, median retention was highest in the summer and lowest in the winter, whereas median retention for events of 0‐10 mm and 40C mm rainfall depth did not conform to this expectation. Given the significant influence of event size on attenuation, the total per cent retention during a given monitoring period might not be indicative of annual rooftop retention if the distribution of observed event sizes varies from characteristic annual rainfall. To account for this, the 12 months of monitoring data were used to develop a characteristic runoff equation (CRE), relating runoff depth and event size, for each green roof. When applied to Central Park, NYC precipitation records from 1971 to 2010, the CRE models estimated total rainfall retention over the 40 year period to be 45%, 53%, and 58% for the W118, USPS, and ConEd green roofs respectively. Differences between the observed and modeled rainfall retention for W118 and USPS were primarily due to an abnormally high frequency of large events, 50 mm of rainfall or more, during the monitoring period compared to historic precipitation patterns. The multi-year retention rates are a more reliable estimate of annual rainfall capture and highlight the importance of long-term evaluations when reporting green roof performance.

https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024036/pdf

Hydrological performance of extensive green roofs in New York City: observations and multi-year modeling of?three full-scale systems

Green roof hydrologic performance and modeling: a review.

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.

/pdf/performance-of-green-roofs-with-respect-to-water-quality-and-4wyo09mcjv.pdf

Performance of green roofs with respect to water quality and reduction of energy consumption in tropics: A review

A review of cleaner production in electroplating industries using electrodialysis

The design of a green roof plays a significant role in performance. In a ground-level field study, 28 built-in-place green roof models, four modular units, and four roof decks with standard black membrane were arranged in a completely randomized design. Storm-water runoff quantity and quality were monitored from September 2005 through June 2008. Results indicate that green roof systems significantly reduced storm-water runoff and that system design, growth media depth, and presence of plants impacted storm-water retention. In a second study on a building roof, two modular systems were used to evaluate water loss through evapotranspiration. Water loss of both systems was significant and influenced by system design, growth media type, and presence of plants. Finally, runoff quality analyses from the ground-level field study and from a laboratory pot experiment indicate that nitrate, total suspended solids, and turbidity are generally low in runoff after a first-flush event. Runoff water quality was ...

Green Roof Storm-Water Runoff Quantity and Quality

Green roof technology is used to reduce the quantity of stormwater runoff, but questions remain regarding its impact on quality. This study analyzed the total suspended solids (TSS) in and the turbidity of runoff from green roof growth media mixed with composted pine bark in an indoor pot study. The results showed that there were elevated levels of TSS and turbidity in the runoff that decreased over time for all growth media. Both TSS and turbidity are affected by the type of growth media. Lava and haydite had higher mean TSS and mean turbidity than arkalyte and bottom ash. Vegetation reduced the mean turbidity and mean TSS of the first flush by an average of 53% and 63%, respectively, but generally had no statistically significant effect thereafter. The results indicate that the media, rather than the vegetation, has a greater effect on TSS and turbidity in the runoff. In areas with stringent water quality regulations for stormwater runoff from developed sites, media selection may be an important conside...

/pdf/suspended-solids-in-and-turbidity-of-runoff-from-green-roofs-38njer4don.pdf

Suspended Solids in and Turbidity of Runoff from Green Roofs

A life-cycle cost model for noise barrier walls was developed based on survey data and field observations. The model includes all costs required to construct the noise barriers and uses service-life estimates based on field observations and surveys. The results indicate that earth berms represent the lowest cost alternative and metal barriers with absorptive panels are the most expensive. The life-cycle costs of wood, concrete, Carsonite, and Durisol fall within a relatively narrow range near $323/m2 ($30/ft2), approximately twice the cost of earth berms. A sensitivity analysis of the model indicated that the two most important variables are initial construction cost and service life. The difficulty in obtaining data is the primary reason many state transportation departments do not use life-cycle cost analysis to select noise barrier materials. Because of the importance of the costs associated with the frequency of maintenance and replacement, and the difficulty in obtaining reliable data, life-cycle cos...

Study of Noise Barrier Life-Cycle Costing

Green roofs are a technology used to control the quantity of the storm-water runoff and reduce energy consumption. Questions remain about their effect on water quality. Total suspended solids and turbidity are of the main parameters for water quality. This study investigated whether turbidity could produce a satisfactory estimation for total suspended solids (TSS) in the storm-water runoff from green roofs. Measuring turbidity is much faster than measuring TSS; a log-linear model showed strong positive correlation between TSS and turbidity (R2=0.9374) with a regression equation of [ln (TSS)=0.979 ln (Turb.)+0.574]. This equation shows that turbidity is a suitable monitoring parameter for TSS when TSS sampling and testing are impractical or not feasible.

Using Turbidity to Determine Total Suspended Solids in Storm-Water Runoff from Green Roofs

The feasibility of using landfill gas (LFG) for electricity generation at four St. Louis, Mo., area landfills was explored using the U.S. EPA's E-PLUS (Energy Project Landfill Gas Utilization Software). The estimated break-even generation price of the electricity was about 4¢/kW ? h. This price is higher than the current avoided cost provided by utilities. These results are consistent with the current situation for the entire renewable energy industry. Renewable technologies, in general, are characterized by relatively high capital costs and low operation and maintenance costs, and with the development of electricity deregulation throughout the United States, renewable energy is facing more competitive challenges. With the loss of federal tax incentives and relatively low electricity prices, fewer LFG-to-electricity projects are being im- plemented. LFG-to-energy facilities may be able to take advantage of increasing demands for green energy and markets for greenhouse gas emission reductions, but to make LFG projects economically feasible, it appears that some type of subsidy will be necessary to take into account the pollution reduction benefits derived from utilizing LFG.

Susan Morgan

Papers

Green Roof Storm-Water Runoff Quantity and Quality

Suspended Solids in and Turbidity of Runoff from Green Roofs

Study of Noise Barrier Life-Cycle Costing

Using Turbidity to Determine Total Suspended Solids in Storm-Water Runoff from Green Roofs

Use of Landfill Gas for Electricity Generation