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Rainwater runoff samples from a range of roofing materials were temporally collected from 19 small-scale roof structures and two commercial buildings through simulated and actual storm events, and the concentrations of polycyclic aromatic hydrocarbons (PAHs), phosphorus flame retardants (PFLs), and pyrethroid insecticides and other water quality parameters were analyzed. In Part I of this research, the concentrations of these contaminants in roof runoff and soils receiving runoff from a range of roofing materials were evaluated. In Part II, recommendations have been developed for a first-flush exclusion to improve the quality of water harvesting for nonpotable uses. Recommendations focus on a first-flush diversion based on mass removals of total suspended solids (TSS) and PAHs linked to conductivity measurements throughout a storm event. Additionally, an upper-confidence limit (UCL) was constructed to determine the minimum diversion required to obtain 50, 75, 90, and 95% mass removal of TSS and PAH contaminants. The majority of TSS were produced during the initial 1.2 mm of runoff. Likewise, the majority of PAHs were removed during the initial 1.2 mm of runoff, except for the asphalt shingle roofs, where high PAHs were observed after 6 mm of runoff. The Texas Water Development Board (TWDB)-recommended first-flush diversion of one gallon for every 100 square feet of rooftop was not always adequate for removing 50% of TSS and PAHs from the roofs. Rainwater runoff conductivity decreased drastically between 1.2 to 2.4 mm of rainwater runoff. Diverting the first flush based on conductivity has the potential to also divert the majority of TSS and PAHs in roof runoff. [ABSTRACT FROM AUTHOR]

Rainfall runoff may be captured and stored for later use, but the quality of this water can be detrimental in some uses without the use of appropriately designed first-flush diverters. The rainfall runoff water quality was measured on nineteen new small-scale and two aged commercial roofs located near high traffic highways. Roof coverings included asphalt shingles, sheet metal, clay tiles, and tar and gravel. Runoff samples were evaluated for polycyclic aromatic hydrocarbons (PAHs), phosphorus flame retardants (PFRs), and pyrethroid insecticides. Eighteen small-scale roofs were subjected to a range of simulated rainfall events, while natural runoff was sampled on the commercial roofs and one small-scale roof. Runoff was analyzed for pH, conductivity, turbidity, total suspended solids, boron, iron, copper, zinc, manganese, sodium adsorption ratio, nitrate-nitrogen, seventeen PAHs, tris(2-chloroethyl) phosphate, tris(1,3-dichloro-2-propyl)phosphate, bifenthrin, cypermethrin, and lambda-cyhalothrin. Samples from four natural storm events were also analyzed for total coliforms and Escherichia coli. In addition, soils below seventeen existing gutter downspouts were sampled to determine long-term pollutant accumulation. Atmospheric deposition was the main contributor of pollutants in the roof runoff. A majority of samples fell within the U.S. EPA guidelines for non-potable urban and agricultural water reuse. Trace levels of PAHs, PFRs, and insecticides were detected, but all detections were three orders of magnitude below the USGS health-based screening level benchmark concentrations. Results indicate that diverting the first flush, based on turbidity, total suspended solids, or conductivity, can improve the overall water quality and reduce the concentrations of PAHs in harvested rainwater. Downspout soil sampling showed potential for the long-term accumulation of PAHs at concentrations exceeding the minimum human-health risk-based screening levels at these high runoff-loading locations. [ABSTRACT FROM AUTHOR]

This study aimed to assess the quality of harvested rainwater from two (aluminum and corrugated zinc) commonly used roof materials in several urban and rural parts of Africa, and particularly in Nigeria for potable use, and to identify and select appropriate water quality indicator sensitive to variations in response to roof types and precipitation sampling time regimes. A total of 36 samples (first-flush and post-flush) were taken from two different urban residential roofs during six rainfall events, within the months of June (3events) and July (3events), and analyzed for selected water quality parameters. The results showed that concentrations were far below recommended guidelines (WHO and NSDWQ). However, concentration levels in First-flush samples for the two roofs were relatively higher than Post-flush. This implies that quality improves with initial roof washoff as traditionally practiced. Results also showed that sampling (interval) time had significant influence on quality parameters than roof material. Multivariate statistical tool was employed to identify a sensitive quality indicator. Factor analysis (FA) was used to group parameters into significant factors that explained over 72% of variations in water quality parameters. Discriminant analysis identified Sulphate and Chloride as the most sensitive parameters for residential roof harvested rainwater, and therefore, may be applied for water quality monitoring in the region. [ABSTRACT FROM AUTHOR]

Rainwater harvesting (RWH) technology are currently utilized in many locations in the world due to the sustainable benefits that it provides to the surrounding community. Their application in tropical countries is still minimal due to high rainfall variability and intensity, making tank design difficult to apply and optimize. This research aims to design and assess the efficiency of stormwater harvesting tanks in three tropical climate types for residential roof runoff management. Ten-year historical rainfall data was collected for assessment in the three study sites in the Philippines: a Type I, Type II/IV, and Type III representative site from different locations in the country, characterized by varying dry and wet seasons throughout the year. To accommodate the 90th and 95th percentiles of historical rainfall, a 0.7-1.1 m³ tank was recommended for construction in each residential site. A total of 59 events were then monitored on the selected sites to recalibrate the original design of the stormwater harvesting tanks. Compared with the initial size estimations, results indicate that nearly similar tank designs are recommended for the Type I and Type II/IV sites, attaining only a 7 % and 2 % decrease respectively, while a much smaller size would be deemed efficient for the Type III site, at least 59 % smaller than the original design. [ABSTRACT FROM AUTHOR]

The first flush occurs during urban runoff events. In this study, we aimed to assess the characteristics of different-sized particles in the first flush of roof runoff, and runoff was collected from an asphalt roof (AR), metal roof (MR), and cement roof (CR) for analysis. There were no clear patterns in the particle size distributions in the runoff from the three roofs and were affected by several factors. The strength of the first flushes differed significantly for particles in different size categories in AR, MR, and CR runoff and were very different from suspended solids (SS). The comparison showed that it would be possible to meet the SS control design expectation required by the Chinese national standard for runoff pollution control (VFF = 3 mm) for particles 45 μm. The methods presented provide an alternative for assessing the ability to control the transport of different-sized particles in runoff. HIGHLIGHTS First flushes of SS, chemical oxygen demand, total nitrogen, and total phosphorus in runoff were stronger for an AR, followed by an MR, and weakest for a CR.; First flushes of different-sized particles were different from those of SS.; First flushes of particles in the different size ranges were influenced by the rainfall characteristics and roof types.; Requirements of the Chinese national standards can be met for particles 45 μm.;

Non-point source pollution from rainwater runoff presents a serious challenge for urban water management in many cities undergoing urbanization and experiencing climate change. To alleviate water resource conflicts in Changsha, China, this study comprehensively evaluated the pollution characteristics and first flush effect (FFE) of runoff from asphalt roads and colored steel plate roofs under seven rainfall events in April–May 2022. The runoff was collected and purified using bioretention ponds. The results showed that the peak runoff pollutant concentrations occurred within the first 20 min of runoff generation and then decreased to relatively stable levels, with maximum total suspended solids (TSS) concentration and chemical oxygen demand (CODCr) reaching 873.5 and 207.32 mg/L, respectively, for road runoff and 162 and 73.31 mg/L for roof runoff, respectively. The main pollutants were TSS and CODCr, followed by ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), total phosphorus (TP), and nitrite nitrogen (NO2−-N). Concentrations of pollutants and FFE for roof runoff were lower than those for road runoff. Road runoff had a more obvious FFE for TP and NH4+-N, whereas the roof runoff showed the presence of TP and NO3−−N. An important implication is that treating the first 30% of surface runoff from rainfall events with long antecedent dry days or high rainfall amounts is necessary to improve water quality before discharge or utilization. The study also found that road and roof runoff, after treatment with bioretention ponds, exhibit good water quality, thus, allowing their use as reclaimed water or for miscellaneous purposes in urban areas. Overall, this study provides useful information for designing management measures to mitigate runoff pollution and reuse in Changsha. [ABSTRACT FROM AUTHOR]

Roof runoff is collected rainwater from a roof using a rainwater harvesting system (RWHS). The construction of an efficient RWHS requires a thorough analysis of the rainwater quality and the appropriate treatment process for its intended use. In line with this, a bibliometric and comprehensive review of studies related to roof rainwater harvesting was conducted. A corpus of 1123 articles was downloaded from the Scopus database and parsed through the CorText Manager to determine the relationships between keywords, journals, and topics related to rainwater harvesting. A comprehensive analysis was also conducted to determine the different designs of RWHS, the quality of harvested rainwater from roof catchments, the efficiency of the system for specific purposes, and its sustainability in terms of economic, environmental, and social aspects. Results show that the effectiveness of a RWHS heavily depends on its installation site, the physicochemical characteristics of the harvested rainwater, and the acceptability of the end users. An effective water treatment process is essential for achieving better water quality for harvested rainwater. Moreover, assessing the financial viability and return on investment of an RWHS is necessary. [ABSTRACT FROM AUTHOR]

Metal roofs have always been in the focus of stormwater runoff contamination. However, other roofing materials are also suspected of releasing metals and other inorganic substances with stormwater runoff. Hence, this review focuses on the impact of commonly used non-metal roofs - vegetated and nonvegetated - on stormwater runoff quality. Results from 42 studies were compiled and assessed to gain an overview of substances in runoff from nine roofing types with a special focus on green roofs. Concentrations of 27 substances including nutrients, heavy metals, and other inorganic substances were compared. Results show that the nine roof types that were assessed can be a potential source for inorganic substances in the runoff. Threshold values for groundwater protection are exceeded especially for PO43-, Cu, Pb, and Zn for some roofing materials. As the concentrations vary strongly for different parameters, no roofing material can be identified as clearly superior or inferior to the others. Gravel roofs act as a sink for NH4+ and can retain some heavy metals. Elevated heavy metal concentrations were found in runoff from wood shingle roofs treated with preservative chemicals and in runoff from most roofing types usually due to the used gutter materials. Green roof runoff shows increased concentrations of Ptot, PO43-, Na, K, Ca, and Mg. The concentrations depend strongly on the green roof age, the growth substrate, and applied fertilizers. In addition to the roofing materials, external factors dependent on the location (rural or urban site) influence the runoff quality. Runoff from the analyzed roofs must be seen as a diffuse source of environmental pollution and requires appropriate treatment before it is released into the environment or used for further applications. Overall, there are only a few studies on the topic so it is not possible to make statistically significant statements. More serious indepth studies are urgently needed. [ABSTRACT FROM AUTHOR]

First flush is a common phenomenon in urban runoff pollution. Typical cement roof and asphalt road runoff in Beijing, China were monitored for 2 years. Based on the M(v) curve, the suspended solids (SS), chemical oxygen demand (COD), total phosphorus (TP) and particulate phosphorus in cement roof runoff presented a stronger first flush than those in asphalt road runoff. The first flush volume (VFF) of SS, COD, total nitrogen (TN) and TP in asphalt road runoff differed slightly from the cement roof. There were also differences in the first flush assessment depending on which method was used. We proposed a new method based on the runoff depth versus pollutant cumulative mass curve. According to the national standards in China (VFF = 3 mm), various masses of different pollutants, such as 91.42 ± 9.80% (cement roof) and 78.49 ± 19.41% (asphalt road) of SS and 86.85 ± 13.54% (cement roof) and 72.80 ± 25.79% (asphalt road) of COD, can be effectively controlled, but our mass control efficiencies were 55.91%–66.65% when VFF = 1 mm. The new method proposed in this study provides an alternative approach for assessing runoff pollution control efficiency of different VFF. HIGHLIGHTS SS, COD, TP and PP exhibited a stronger first flush in cement roof runoff than in asphalt road runoff by M(v) method.; VFF of SS, COD, TN and TP in asphalt road runoff differed slightly from the cement roof.; Differences were found in the first flush assessment results between M(v) and VFF methods.; A new method based on the runoff depth versus pollutant cumulative mass curve was proposed.;

Metal roofs have always been in the focus of stormwater runoff contamination. However, other roofing materials are also suspected of releasing metals and other inorganic substances with stormwater runoff. Hence, this review focuses on the impact of commonly used non-metal roofs - vegetated and non-vegetated - on stormwater runoff quality. Results from 42 studies were compiled and assessed to gain an overview of substances in runoff from nine roofing types with a special focus on green roofs. Concentrations of 27 substances including nutrients, heavy metals, and other inorganic substances were compared. Results show that the nine roof types that were assessed can be a potential source for inorganic substances in the runoff. Threshold values for groundwater protection are exceeded especially for PO43-, Cu, Pb, and Zn for some roofing materials. As the concentrations vary strongly for different parameters, no roofing material can be identified as clearly superior or inferior to the others. Gravel roofs act as a sink for NH4+ and can retain some heavy metals. Elevated heavy metal concentrations were found in runoff from wood shingle roofs treated with preservative chemicals and in runoff from most roofing types usually due to the used gutter materials. Green roof runoff shows increased concentrations of Ptot, PO43-, Na, K, Ca, and Mg. The concentrations depend strongly on the green roof age, the growth substrate, and applied fertilizers. In addition to the roofing materials, external factors dependent on the location (rural or urban site) influence the runoff quality. Runoff from the analyzed roofs must be seen as a diffuse source of environmental pollution and requires appropriate treatment before it is released into the environment or used for further applications. Overall, there are only a few studies on the topic so it is not possible to make statistically significant statements. More serious in-depth studies are urgently needed.

Increased nitrogen (N) from urban stormwater runoff aggravates the deterioration of aquatic ecosystems as urbanisation develops. The sources and transport of nitrate (NO3−) in urban stormwater runoff were investigated by analysing different forms of N, water isotopes (δD-H2O and δ18O-H2O), and NO3− isotopes (δ15N-NO3− and δ18O-NO3−) in urban stormwater runoff in a residential area in Hangzhou, China. The results showed that the concentrations of total N and nitrate N in road runoff were higher than those in roof runoff. Moreover, high concentrations of dissolved organic N and particulate N led to high total nitrogen (TN) concentrations in road runoff (mean: 3.76 mg/L). The high δ18O-NO3− values (mean: + 60 ± 13.1‰) indicated that atmospheric deposition was the predominant NO3− source in roof runoff, as confirmed by the Bayesian isotope mixing model (SIAR model), contributing 84–98% to NO3−. Atmospheric deposition (34–92%) and chemical fertilisers (6.2–54%) were the main NO3− sources for the road runoff. The proportional contributions from soil and organic N were small in the road runoff and roof runoff. For the initial period, the NO3− contributions from atmospheric deposition and chemical fertilisers were higher and lower, respectively, than those in the middle and late periods in road runoff during storm events 3 and 4, while an opposite trend of road runoff in storm event 7 highlighted the influence of short antecedent dry weather period. Reducing impervious areas and more effective management of fertiliser application in urban green land areas were essential to minimize the presence of N in urban aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Roof runoff is generally perceived as a relatively clean source of water and is therefore often discharged or used without any treatment. Available data from literature however show that roof runoff can be contaminated by a wide range of (micro)pollutants, and in concentrations often exceeding surface water quality and/or drinking water standards. In this review, information on more than 100 contaminants, including trace metals, polycyclic aromatic hydrocarbons, pesticides, phthalates, alkylphenols and alkylphenolethoxylates, is summarized and a meta-analysis provides quantitative proof that roof runoff is a major contributor to stormwater quality deterioration. The two prime sources of roof runoff contamination are leaching from roofing materials and atmospheric deposition. A detailed discussion on material-pollutant relationships is given and a benchmarking method is presented which ranks roofing materials based on their runoff quality. Treated wood roofing and metallic rooftops (copper and zinc) were found to have the highest impact on water quality. Atmospheric deposition is also discussed in detail and includes a summary on the concentration levels in deposition for more than 400 pollutants such as trace metals, pesticides and polycyclic aromatic hydrocarbons. As a conclusion, it can be argued that the general perception on roof runoff quality is inaccurate and that its quality aspects should not be overlooked when roof runoff is used or discharged. [ABSTRACT FROM AUTHOR]

To identify emerging contaminants （ECs） in rainwater is a topic that has gradually received widespread attention. Rainwater resources, specifically urban roofs, play a crucial role in utilizing rainwater efficiently by understanding the occurrence and migration characteristics of pollutants in precipitation. This study selected a typical roof and studied the differences in rainwater quality and pollution occurrence at different collection stages during six rainfall events from March to May in 2023. Principal component analysis （PCA） and correlation analysis were used to explore the distribution, migration, and transformation of ECs in the collection process of roof rainwater. The findings revealed the presence of 44/54 ECs in wet deposition, dry and wet deposition, and roof runoff processes, with a total concentration range of 63.0 to 432.4 ng·L -1 and an average concentration of 166.8 ng·L -1 . Notably, bisphenol A （BPA） exhibited the highest concentration, ranging from 14.7 to 265.6 ng·L -1 , with an average concentration of 62.5 ng·L -1 , followed by ofloxacin （OFX） and ethylhexyl methoxycinnamate （EHMC）, with detected concentrations up to 45.5 ng·L -1 and 44.8 ng·L -1 . Dissolved organic matter （DOM）, nitrogen pollutants, and particulate matter were important factors affecting the occurrence characteristics of ECs, with a mantel correlation coefficient of up to 0.98 （ P <0.01）. Based on the analysis of different rainfall events and collection stages, variations were observed in the accumulation pathways and contribution ratios of different pollutants. The wet deposition exhibited the highest content of ECs in the initial stage, whereas the dry and wet deposition and roof runoff processes displayed higher ECs content in the later stages. Additionally, the average ECs contribution rates of dry and wet deposition to roof runoff were 21.48% and 78.52%, respectively. Due to the influence of roof material and surface roughness retention performance, over 30% of ECs, including pharmaceuticals and personal care products （PPCPs）, endocrine-disrupting compounds （EDCs）, and pesticides, were deposited on the roof during the runoff collection. The results of this research can provide the theoretical foundation and technical support for the identification and control of ECs in urban roof runoff and for the safe storage of rainwater.

Abstract Shadow area distribution of vertical elements mounted on flat roofs was studied regarding its impact on opportunities for harnessing solar energy and its positive effect on obstructing undesirable heat transfer. Various cases were assumed for the position of a penthouse on flat roofs of dwelling units. In each case the spatial distribution of the shadow was studied on the host roof and its neighbors. The general constant ratio between the average annual shadow and lateral area of a rectangular shape was found to be 0.88. The north direction and the back penthouse position receive the highest quantity of annual shadow on the host's roof (2.85 times its roof area). The left corner roofs offer better opportunities compared to the middle and right corner roofs for collecting solar energy, on average 1.5 and 1.3 times, respectively. Left corner roofs with front penthouse position receive the highest amount of insolation energy per unit area, which makes it the favorable position for harnessing solar energy. The highest positive obstructed insolation is in 0° orientations and 180° penthouse position by 413 kWh/m2/year. Generally, the back penthouse position performs better than the center and front positions in terms of obstructing negative heat transfer. Highlights • Left corner lots perform better by an average of 1.5 times of mid roofs and 1.3 times of right corner roofs to harness solar energy. • The back penthouse position is favorable in comparison to the front and center positions in reference of heating and cooling benefits of shadows. • The average ratio of annual shadow area of a rectangular shape to its lateral area is constant and is approximately 0.88. • The two equinoxes and solstices adequately represent the entire year for studying shadow area. [ABSTRACT FROM AUTHOR]

Abstract Since spring 2011 the roof of a building on the Agripolis Campus of the University of Padova (Italy) has been used as a drainage area for two rain gardens with a circular area of about 10% and 20% of the drainage area respectively. To improve soil infiltration, the topsoil was removed up to the depth of 1 m and filled with a mix of 50% sand, 25% compost and 25% of the existing topsoil. Herbaceous perennials were selected and planted to test their adaptability to different soil water conditions in the rain garden. To evaluate the capacity of each rain garden to manage stormwater runoff a simplified water balance was done, estimating actual evapotranspiration using the WUCOLS method. From autumn 2012 runoff volumes were collected just from one pitch of the roof, and directed only into the smaller rain garden that became equal to 15% of the new roof drainage area. We thus had the possibility to test the functionality of rain gardens with three different percentages of roof drainage area: 10, 15 and 20%, even if in different periods. Results are presented relating to a four-year experimental period. Regarding hydrological behaviour, the input water volumes caused a slight overflow only during a few rainfall events. Consequently, the results showed a high capacity to manage stormwater runoff and also in the smaller rain garden almost the total roof runoff volumes infiltrated into the soil. As regards plants, the results indicated that the growth is affected by their position in the rain garden, from the wettest condition in the centre to the driest at the perimeter, except for Hemerocallis hybrida that showed great adaptability in all positions. Aster novi-belgii , Echinacea purpurea, Iris pseudacorus, Molinia caerulea and Rudbeckia fulgida also showed good adaptation, even if not in all rain garden zones, with highly aesthetic results. Lythrum salicaria and Saponaria officinalis plants appeared to be unsuitable for rain gardens. The results of the experiment have shown that, in the Veneto plain environment, rain gardens with a size of 10–15% of the roof drainage area can ensure both the sustainable management of stormwater runoff and a high aesthetic functionality. [ABSTRACT FROM AUTHOR]

Roof runoff pollution has been given considerable attention to ensure the safety of roof rainwater utilization. A residential roof catchment located in Handan, China, was selected as a study site. The water quality of roof runoff was analyzed at 15 storm events during 2014–2016. The median concentrations of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, total phosphorus and sulphane are 104, 8.53, 10.60, 0.21 and 14.31 mg/L, respectively; these values all exceed the class V of environmental quality standards for surface water in China. A strong linear correlation is established between COD and other pollutants. All the Pearson’s coefficients (r) are more than 0.8. COD could be considered surrogates for other pollutants. During storm events, the concentration change of runoff pollutants could be fitted well by the exponential function. The selected storm events present the first flush effect in varying degrees. Approximately 80% of the pollutant load is transported in the first 36%, 53%, 57%, 26% and 38% of the volume for five storm events. The first flush effect is evidently related with rainfall depth and antecedent dry days. Furthermore, water quality depth (WQD) can be used as a definitive parameter for runoff pollution control. WQD presents different values to reach diverse stormwater management targets. [ABSTRACT FROM AUTHOR]

Runoff water is an important medium transporting various types of pollution originating from the atmosphere and washed out from roofing materials. The study presents a quality assessment of runoff from different roofs in the context of trace metal concentrations. The analysed rooftops were covered with copper, tar paper and ceramic tile. The quality of the rain water collected at the same time satisfies the demands of the first grade of cleanliness according to (Journal of Laws, 2016 item1187). The highest content of copper was leached from the copper roof, containing 10.23 mg·dm-3. In the case of zinc, the highest concentration of 15.52 mg·dm-3 was present in the runoff from the roof covered with thermally bonded tar paper. The amount of trace metals in the ceramic roof runoff was the lowest and only for zinc slightly exceeded 1.47 mg·dm-3 - the value determined for II class of purity. In the paper, the different levels of heavy metals leaching from different roofing materials have been confirmed. [ABSTRACT FROM AUTHOR]

Green roofs are increasingly being used among the suite of tools designed to reduce the volume of surface water runoff generated by cities. Plants provide the primary mechanism for restoring the rainfall retention capacity of green roofs, but selecting plants with high water use is likely to increase drought stress. Using empirically-derived plant physiological parameters, we used a water balance model to assess the trade-off between rainfall retention and plant drought stress under a 30-year climate scenario. We compared high and low water users with either drought avoidance or drought tolerance strategies. Green roofs with low water-using, drought-avoiding species achieved high rainfall retention (66–81%) without experiencing significant drought stress. Roofs planted with other strategies showed high retention (72–90%), but they also experienced > 50 days of drought stress per year. However, not all species with the same strategy behaved similarly, therefore selecting plants based on water use and drought strategy alone does not guarantee survival in shallow substrates where drought stress can develop quickly. Despite this, it is more likely that green roofs will achieve high rainfall retention with minimal supplementary irrigation if planted with low water users with drought avoidance strategies. [ABSTRACT FROM AUTHOR]

Rice Husk Ash (RHA), a waste from firing process of clay products, has no proper usage. For this study, roof tile specimens were manufactured by replacing clay with different RHA percentages (i.e., 0%, 5%, 10%, 15% and 20%) in an industrial scale plant, so as to determine the effect of waste RHA from a brick firing process on structural, thermal properties and run-off qualities of clay roof tiles. For 10% replacement of clay with RHA, transverse breaking load was increased by 45.97% indicating higher ductility compared with that of the conventional tiles. Bulk density is reduced with the percentage of RHA added, promising a light-weight roof tile, a favourable tile for a roofing material. With increasing RHA content, water absorption increases. RHA replacement up to 15% is desirable, satisfying the water absorption limit according to standards. RHA replacement up to 20% doesn’t affect on the water penetration property. RHA mixed roof tiles can reduce the indoor temperature, feeling more comfortable for inhabitants. Collected runoff coming along the 10% RHA mixed clay roof tiles has a pH value of 7.22 and total solid concentration of 118.67 mg/L, indicating RHA mixed roof clay tile will not cause any severe impact on the runoff. Hence this harvested runoff can still be utilized for non-potable activities while enhancing the strength and thermal properties of clay roof tiles. [ABSTRACT FROM AUTHOR]

Growth substrate plays an important role in determining the quality of runoff from green roofs. However, no systematic research has been conducted to design a substrate to improve runoff quality. Hence, the present study aimed at designing and developing a green roof substrate using low-cost and environmentally-benign materials. The inorganic fraction of the substrate includes purosil, vermiculite, sand and light-weight clay aggregates (LECA); whereas the organic fraction includes coco-peat andSargassum wightii. Through factorial design, 13 different substrate mixes were prepared and the optimum mix (20% purosil, 30% vermiculite, 10% sand, 20% LECA, 10% coco-peat and 10%S. wightii) was found to have high water holding capacity (67.6%), air filled porosity (21%), hydraulic conductivity (5524 mm/h) and low bulk density (495 kg/m3). The substrate also provided maximum support for the growth ofPortulaca oleracea. Experiments with metal-contaminated influent from the down-flow of a packed reactor revealed that the green roof substrate possesses a high sorption capacity towards various metal ions. [ABSTRACT FROM AUTHOR]

Two rainwater harvesting systems, which included first-flush diversion devices, connected to the roofs of two adjacent buildings, were monitored for water quality. The roofs were constructed from different materials, i.e., one roof was covered with ceramic tiles and the other was made of concrete. Water quality samples from the two storage tanks and the first-flush devices were collected and analyzed, showing satisfactory water quality in the tanks for residential non-potable use, while the water in the first-flush device was of poorer quality. Between the two collection surfaces, statistically significant differences were found only in the concentrations of NH-N, orthophosphate, and Ca. Total coliforms were detected in both the storage tanks and the first-flush devices, indicating that disinfection of harvested rainwater may be necessary if it is collected for potable uses. Finally, first-flush water quality was related to antecedent dry days, showing that when the number of dry days increased, the accumulation of materials on the concrete roof was reduced while it was increased on the ceramic tile roof. This is attributed to the fact that the concrete roof is nearly horizontal (very slightly sloped), and the wind action easily removes various materials which accumulate on it. [ABSTRACT FROM AUTHOR]

Roof runoff is an important source of urban stormwater and a main source of rainwater harvesting. Deposition of pollutants on rooftops can have a negative impact on runoff quality and, therefore, on harvested rainwater. Laboratory experiments with simulated rainfall were performed in order to study the washout of fine sand particles deposited on a ceramic tile roof, by runoff, considering the effect of the particle position, particle areal load, particle connectivity and roof slope. Results indicated that particle washout was influenced by the particle position on the roof; particle transport peak and transported mass was higher for the particle mass positions closer to the outlet. Increase in particle areal load decreased particle transport whereas particle connectivity had no effect on particle transport. However, roof slope was a dominant aspect in the particle washout; increase in roof slope greatly increased particle transport peak and transported mass. It also remarkably increased the first flush effect. [ABSTRACT FROM AUTHOR]

The present study evaluated the ability of 2 different bioretention storm water control measures (SCMs), planter boxes and swales, to decrease the toxicity of sheet copper (Cu) roofing runoff to Daphnia magna. The present study quantified changes in storm water chemistry as it passed through the bioretention systems and utilized the biotic ligand model (BLM) to assess whether the observed D. magna toxicity could be predicted by variations found in water chemistry. Laboratory toxicity tests were performed using select storm samples with D. magna cultured under low ionic strength conditions that were appropriate for the low ionic strength of the storm water samples being tested. The SCMs decreased toxicity of Cu roof runoff in both the BLM results and the storm water bioassays. Water exiting the SCMs was substantially higher than influent runoff in pH, ions, alkalinity, and dissolved organic carbon and substantially lower in total and dissolved Cu. Daphnids experienced complete mortality in untreated runoff from the Cu roof (the SCM influent); however, for planter and swale effluents, survival averaged 86% and 95%, respectively. The present study demonstrated that conventional bioretention practices, including planter boxes and swales, are capable of decreasing the risk of adverse effects from sheet Cu roof runoff to receiving systems, even before considering dilution of effluents in those receiving systems and associated further reductions in copper bioavailability. Environ Toxicol Chem 2017;36:1680-1688. © 2016 SETAC [ABSTRACT FROM AUTHOR]

This study investigates the temporal variability of zinc concentrations from zinc roof runoff. The influence of rainfall characteristics and dry period duration is evaluated by combining laboratory experiment on small zinc sheets and in situ measurements under real weather conditions from a 1.6-m zinc panel. A reformulation of a commonly used conceptual runoff quality model is introduced and its ability to simulate the evolution of zinc concentrations is evaluated. A systematic and sharp decrease from initially high to relatively low and stable zinc concentrations after 0.5 to 2 mm of rainfall is observed for both experiments, suggesting that highly soluble corrosion products are removed at early stages of runoff. A moderate dependence between antecedent dry period duration and the magnitude of zinc concentrations at the beginning of a rain event is evidenced. Contrariwise, results indicate that concentrations are not significantly influenced by rainfall intensities. Simulated rainfall experiment nonetheless suggests that a slight effect of rainfall intensities may be expected after the initial decrease of concentrations. Finally, this study shows that relatively simple conceptual runoff quality models may be adopted to simulate the variability of zinc concentrations during a rain event and from a rain event to another. [ABSTRACT FROM AUTHOR]

Sediment and heavy metals in stormwater runoff are key pollutants of urban waterways, and their presence in stormwater is driven by climatic factors such as rainfall intensity. This study describes the total suspended solids (TSS) and heavy metal concentrations found in runoff from four different urban surfaces within a residential/institutional catchment, in a climate where rainfall is typically of low intensity (< 5.1 mm·h − 1 ). The results were compared to untreated runoff quality from a compilation of international studies. The road runoff had the highest TSS concentrations, while copper and galvanized roof runoff had the highest copper and zinc concentrations, respectively. Pollutant concentrations were found to be significantly different between surfaces; quantification and prediction of pollutant contributions from urban surfaces should thus take account of the different surface materials, instead of being aggregated into more generalized categories such as land use. The TSS and heavy metal concentrations were found to be at the low to medium end of ranges observed internationally, except for total copper and zinc concentrations generated by dissolution of copper and galvanized roofing material respectively; these concentrations were at least as high as those reported internationally. TSS wash-off from the roofs was seen to be a source-limited process, where all available TSS is washed off during the rain event despite the low intensity rainfall, whereas both road TSS and heavy metals wash-off from roof and road surfaces appeared to all be transport-limited and therefore some carryover of pollutants occurs between rain events. A first flush effect was seen from most surfaces for TSS, but not for heavy metals. This study demonstrates that in low intensity rainfall climates, quantification of untreated runoff quality from key individual surface types in a catchment are needed to enable development of targeted and appropriately sized stormwater treatment systems. [ABSTRACT FROM AUTHOR]

Roofs surfaces are frequently used to catch water for drinking in many countries, so the presence and mobilisation of material into runoff water can be an important process to consider. This paper investigates the origin and mobilisation of trace elements from roofing tiles. Our work suggests that trace elements can mobilise into roof runoff. However, lead by contrast, appears to have accumulated at the surface of tiles exposed to busy automobile traffic that used leaded fuel (confirmed by X-ray fluorescence). Although lead is relatively immobile on the tile surface, the potential for leaching by acidic rain (pH < 4) means that the guidelines for lead in drinking water may be exceeded during some rainfall events. [ABSTRACT FROM AUTHOR]

Hydrologists are concerned with high-intensity rainfall and peak runoff rates for stormwater infrastructure designs, post-event assessments, and mitigation of environmental impacts. In the southwestern United States the need for accurate information about these rates is increasingly important as population growth and associated development are projected to exceed national averages. Design storm totals for various durations and return period frequencies are routinely derived from the National Oceanic and Atmospheric Administration (NOAA) Atlas 14 and are commonly used as input to hydrologic models to estimate peak runoff rates and runoff volumes. For the southwestern United States during the North American Monsoon, NOAA relies on sparse rain gauge networks to measure rainfall from limited area convective storms primarily at daily time steps and estimates of subdaily event intensities are derived by temporal downscaling from a few point locations. The USDA, Agricultural Research Service, Southwest Watershed Research Center (SWRC) operates the Walnut Gulch Experimental Watershed (WGEW) in the vicinity of Tombstone, Arizona. SWRC maintains a database of 60 years of subdaily, high temporal-precision rainfall intensities and runoff rates for WGEW. Updated, temporally extended, rainfall intensity-duration-frequency relations for WGEW are presented. The current analysis includes intensity-duration-frequency relations for July, August, and September for 53 years, 1961-2013, for durations of 2, 5, 10, 15, 30, and 60 min and return periods of 2, 5, 10, 25, 50, 100, and 1,000 years. The 149 km² WGEW is large enough to select groups of four rain gauges whose event totals are independent. This allows combining of the four independent gauges' 53-year time series into a longer time series of 212 years. A comparison of WGEW-generated intensity-duration-frequency curves to those of NOAA Atlas 14 indicated good agreement. However, across the range of durations, many observed events on WGEW from gauges not used in the frequency analysis are much greater than the estimated 100-year event. The dense gauge network appears to capture a substantially greater number of low-frequency, extreme rainfall events not typically observed in sparse networks. To assess the hydrologic consequences of these extreme events they were used as input to a well-tested watershed model for a small gauged watershed that did not experience events of similar magnitude. Simulated runoff volumes and peak discharge rates were up to four times as large as the largest observed runoff event of record. These analyses offer insights into the benefit of long-term watershed research with spatially dense and high temporal resolution observations. [ABSTRACT FROM AUTHOR]

In this research, the mobilization and distribution of lead originating in roof dust and wet deposition were investigated within a roof dust-rooftop-runoff system. The results indicated that lead from roof dust and wet deposition showed different transport dynamics in runoff system and that this process was significantly influenced by the rainfall intensity. Lead present in the roof dust could be easily washed off into the runoff, and nearly 60 % of the total lead content was present in particulate form. Most of the lead from the roof dust was transported during the late period of rainfall; however, the lead concentration was higher for several minutes at the rainfall beginning. Even though some of the lead from wet deposition, simulated with a standard isotope substance, was adsorbed onto adhered roof dust and/or retained on rooftop in runoff system, most of it (50-82 %) remained as dissolved lead in the runoff for rainfall events of varying intensity. Regarding the distribution of lead in the runoff system, the results indicated that it could be carried in the runoff in dissolved and particulate form, be adsorbed to adhered roof dust, or remain on the rooftop because of adsorption to the roof material. Lead from the different sources showed different distribution patterns that were also related to the rainfall intensity. Higher rainfall intensity resulted in a higher proportion of lead in the runoff and a lower proportion of lead remaining on the rooftop. [ABSTRACT FROM AUTHOR]

Understanding the sources of chemical components in roof runoff can help to prevent water quality problems in rooftop rainwater harvesting. To identify the contribution of wet deposition to the mass of components in roof runoff, the samples from air, rainwater, dust buildup and roof runoff were collected from an urban site in Shenzhen of China in 2011-2012. The results indicate that: (1) wet deposition has a dominant contribution to the mass of total organic carbon (TOC), NH4+, NO3-, Cl- and organic acids in the roof runoff, while the mass of NH4+, acetic acid and formic acid in the roof runoff may be greatly reduced by the neutralization between the components with alkaline dust buildup on the rooftop; and (2) wet deposition partially contributes to the mass of Na+, K+, Mg2+, Ca2+, F- and SO42- in the roof runoff, while other factors like dust buildup on the rooftop and chemical reactions also have a non-negligible impact. Furthermore, TOC, NH4 NO3- and organic acids in the wet deposition are mainly influenced by the atmospheric pollution due to fast increase in fossil fuel consumption (e.g. vehicle emissions). Therefore, the effects of wet deposition should be carefully considered for rooftop rainwater harvesting in urbanized areas. [ABSTRACT FROM AUTHOR]

Roofs and roads, accounting for a large portion of the urban impervious land surface, have contributed significantly to urban nonpoint pollution. In this study, in Beijing, China, roof and road runoff are sampled to measure the suspended solids (SS), nitrogen (N), and phosphorus (P) contained in particles with different sizes. The SS content in the road runoff (151.59 mg/L) was sevenfold that in the roof runoff (21.13 mg/L, p < 0.05). The SS contained more coarse particulates in the roof runoff than in road runoff. The small particulates in the range of 0.45-50 μm consisted of 59 % SS in the roof runoff and 94 % SS in the road runoff. P was mainly attached to particle sizes of 10-50 μm in the roof (73 %) and road (48 %) runoffs, while N was mainly in a dissolved phase state in both runoffs. So, the different associations of N and P raise a challenge in preventing stormwater pollution in urban environments. [ABSTRACT FROM AUTHOR]

The article discusses multiuse trails have been a prominent feature of park lands for many years. Now, multiuse rain gardens may become a prominent feature of many parks. Rain gardens have traditionally been used for catchment, retention, and filtration of impervious surface storm water runoff. County park districts and other agencies across Ohio (and elsewhere) are being pushed more and more toward finding inexpensive creative multi-solutions to issues as a result of limited budgets.

To assess the contribution of five toxic metals from new roofing materials to stormwater, runoff was collected from 14 types of roofing materials and controls during 20 rain events and analyzed for metals. Many of the new roofing materials evaluated did not show elevated metals concentrations in the runoff. Runoff from several other roofing materials was significantly higher than the controls for arsenic, copper, and zinc. Notably, treated wood shakes released arsenic and copper, copper roofing released copper, PVC roofing released arsenic, and Zincalume® and EPDM roofing released zinc. For the runoff from some of the roofing materials, metals concentrations decreased significantly over an approximately one-year period of aging. Metals concentrations in runoff were demonstrated to depend on a number of factors, such as roofing materials, age of the materials, and climatic conditions. Thus, application of runoff concentrations from roofing materials to estimate basin-wide releases should be undertaken cautiously. [ABSTRACT FROM AUTHOR]

Green roof has a significant influence on reducing runoff volume, delaying runoff-yielding time, reducing the peak flow and improving runoff quality. This paper addressed the related research around the world and concluded from several aspects, i.e., the definition of green roof of different types, the mechanism how green roof manages runoff quantity and quality, the ability how green roof controls roof runoff, and the influence factors of green roof toward runoff quantity and quality. Afterwards, there was a need for more future work on research of green roof toward roof runoff, i.e., vegetation selection of green roof, efficient construction model selection of green roof, the regulating characteristics of green roof on roof runoff, the value assessment of green roof on roof runoff, analysis of source-sink function of green roof on the water pollutants of roof runoff and the research on the mitigation measures of roof runoff pollution. This paper provided a guideline to develop green roofs aiming to regulating roof runoff. [ABSTRACT FROM AUTHOR]

The albedo of a roof determines the fraction of incoming sunlight that is reflected, which affects heat transfer into the building and exchange of energy between the built environment and the atmosphere. While the albedo of individual roofs can be easily measured, roof albedo at the city scale is unknown. In this paper we characterize the albedos of roofs in seven cities in California: Los Angeles, Long Beach, Bakersfield, San Francisco, San Jose, Sacramento, and San Diego. The fraction of urban area covered by roofs ranged by city from 10% to 25%. City-wide average roof albedo ranged from 0.17 ± 0.08 to 0.20 ± 0.11 (mean ± standard deviation) for five of the cities; values were higher in Sacramento (0.24 ± 0.11) and San Diego (0.29 ± 0.15). Buildings with small roofs were found to constitute a large fraction of city roof area and to have low mean albedos. This suggests that efforts to increase urban albedo through the use of reflective roofs should include small roofs, which are presumably mostly residential. Roof albedos derived for Bakersfield were used in a regional climate model (Weather Research and Forecasting Model) to estimate temperature changes attainable by converting the current stock of roofs to “cool” high albedo roofs. It was found that seasonal mean afternoon (15:00 LST) temperatures could be reduced by up to 0.2 °C during both the summer and winter. Changes in precipitation were not significant at the 95% confidence level. [ABSTRACT FROM AUTHOR]

Cool roofs reflect sunlight and therefore can reduce cooling energy use in buildings. Further, since roofs typically cover about 20–25% of a city, widespread deployment of cool roofs could mitigate the urban heat island effect and partially counter urban temperature increases associated with global scale climate change. The magnitude of these potential benefits for a given city depends on the increase in albedo that can be achieved using reflective roofs. Assessing this increase requires knowledge of roof albedo at the city scale, which until now has been hindered by a lack of reflectance data with sufficient spatial coverage, spatial resolution, and spectral detail. In this work we use multiband aerial imagery to derive the albedos of individual roofs in seven California cities: Los Angeles, Long Beach, San Diego, Bakersfield, Sacramento, San Francisco, and San Jose. The radiometrically calibrated, remotely sensed imagery has high spatial resolution (1 m) and four narrowband reflectances: blue, green, red, and near-infrared. First, we locate roof pixels within GIS building outlines. Next, we use laboratory measurements of the solar spectral reflectances of 190 roofing products to empirically relate broadband solar reflectance to reflectances in the four narrow bands; this empirical relationship well predicts solar reflectance, as indicated by a low root-mean-square of the residuals of 0.016. Albedos computed from remotely sensed reflectances are calibrated to ground measurements of roof albedo in each city. The error (accuracy) at 90% confidence interval of the calibrated albedos is found to vary by city, from 0.00–0.01 at low albedo and 0.06–0.14 at high albedo. [ABSTRACT FROM AUTHOR]

The contribution of ecotoxic dissolved metals from metallic roofs into urban waterways is a global issue. Identifying the specific origin of dissolved metals is critical to enabling appropriate stormwater management approaches that can provide the intended outcome of cleaner urban waterways. An event load pollutant model, Modelled Estimates of Discharges for Urban Stormwater Assessments (MEDUSA2.0), was used to predict the zinc load contributed from individual roof surfaces, under a wide range of rainfall conditions. Zinc was chosen as the pollutant of most concern given the extensive area of zinc-based roof surfaces, and the prevalence and mobility of zinc within urban waterways. The model categorized each roof by surface material and condition, and was run for individual rain events across multiple years to illustrate the influences on zinc loads from both surface type and rainfall conditions. Scenarios of future management were also assessed through the model to compare their benefits in terms of load reductions against the current baseline loadings. To understand how the load prediction and scenario modelling can provide valuable guidance for stormwater management decision-makers, the model was applied to a large urban catchment in Christchurch, New Zealand. Seven representative subcatchments of the varying proportions of industrial, commercial and residential land use type were also modelled to compare zinc loads generated. Results showed that an individual catchment's composition of roof types was the main driver of zinc load generation rather than the catchment's land use type. The modelled management scenarios demonstrated that reductions of 30% zinc could be achieved by changing only 4–13% of a subcatchment's unpainted zinc-based roof surfaces. • MEDUSA2.0 model used to determine Zn runoff from individual roof type and condition. • Composition of roof types, not land-use, is main driver of catchment's zinc load. • Scenario modelling can guide selection of optimal management strategy. • Load reductions of up to 30% can be achieved by targeting 4–13% of roof surfaces. • Multi-year modelling informs expected load responses under future climate change. [ABSTRACT FROM AUTHOR]

• Culture and molecular methods were used to examine roof runoff microbial quality. • The impact of several factors on roof runoff microbial quality was explored. • Salmonella spp., Campylobacter spp., and Giardia were found in roof runoff. • The occurrence of potential pathogens is correlated with meteorological parameters. • Assessment of microbial quality will inform treatment targets based on end use. Roof runoff has the potential to serve as an important local water source in regions with growing populations and limited water supply. Given the scarcity of guidance regulating the use of roof runoff, a need exists to characterize the microbial quality of roof runoff. The objective of this 2-year research effort was to examine roof runoff microbial quality in four U.S. cities: Fort Collins, CO; Tucson, AZ; Baltimore, MD; and Miami, FL. Seven participants, i.e., homeowners and schools, were recruited in each city to collect roof runoff samples across 13 precipitation events. Sample collection was done as part of a citizen science approach. The presence and concentrations of indicator organisms and potentially human-infectious pathogens in roof runoff were determined using culture methods and digital droplet polymerase chain reaction (ddPCR), respectively. The analyzed pathogens included Salmonella spp., Campylobacter spp., Giardia duodenalis , and Cryptosporidium parvum. Several factors were evaluated to study their influence on the presence of potentially human-infectious pathogens including the physicochemical characteristics (total suspended solids, volatile suspended solids, total dissolved solids, chemical oxygen demand, and turbidity) of roof runoff, concentrations of indicator organisms, presence/absence of trees, storm properties (rainfall depth and antecedent dry period), percent of impervious cover surrounding each sampling location, seasonality, and geographical location. E. coli and enterococci were detected in 73.4% and 96.2% of the analyzed samples, respectively. Concentrations of both E. coli and enterococci ranged from <0 log 10 to >3.38 log 10 MPN/100 mL. Salmonella spp. invA, Campylobacter spp. ceuE , and G. duodenalis β – giardin gene targets were detected in 8.9%, 2.5%, and 5.1% of the analyzed samples, respectively. Campylobacter spp. mapA and C. parvum 18S rRNA gene targets were not detected in any of the analyzed samples. The detection of Salmonella spp. invA was influenced by the geographical location of the sampling site (Chi-square p -value < 0.001) as well as the number of antecedent dry days prior to a rain event (p -value = 0.002, negative correlation). The antecedent dry period was negatively correlated with the occurrence of Campylobacter spp. ceuE as well (p -value = 0.07). On the other hand, the presence of G. duodenalis β–giardin in roof runoff was positively correlated with rainfall depth (p -value = 0.05). While physicochemical parameters and impervious area were not found to be correlated with the presence/absence of potentially human-infectious pathogens, significant correlations were found between meteorological parameters and the presence/absence of potentially human-infectious pathogens. Additionally, a weak, yet significant positive correlation, was found only between the concentrations of E. coli and those of Giardia duodenalis β-giardin. This dataset represents the largest-scale study to date of enteric pathogens in U.S. roof runoff collections and will inform treatment targets for different non-potable end uses for roof runoff. However, the dataset is limited by the low percent detection of bacterial and protozoan pathogens, an issue that is likely to persist challenging the characterization of roof runoff microbial quality given sampling limitations related to the volume and number of samples. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents the results of a hydrological investigation of four medium scale green roofs that were set up at the University of South Australia. In this study, the potential of green roofs as a source control device was investigated over a 2 year period using four medium size green roof beds comprised of two growth media types and two media depths. During the term of this study, 226 rainfall events were recorded and these were representative of the Adelaide climate. In general, there were no statistically significant differences between the rainfall and runoff parameters for the intensive and extensive beds except for peak attenuation and peak runoff delay, for which higher values were recorded in the intensive beds. Longer dry periods generally resulted in higher retention coefficients and higher retention was also recorded in warmer seasons. The average retention coefficient for intensive systems (89%) was higher than for extensive systems (74%). It was shown that rainfall depth, intensity, duration and also average dry weather period between events can change the retention performance and runoff volume of the green roofs. Comparison of green and simulated conventional roofs indicated that the former were able to mitigate the peak of runoff and could delay the start of runoff. These characteristics are important for most source control measures. The recorded rainfall and runoff data displayed a non-linear relationship. Also, the results indicated that continuous time series modelling would be a more appropriate technique than using peak rainfall intensity methods for green roof design and simulation. [ABSTRACT FROM AUTHOR]

As urbanization increases, urban runoff is an increasingly important component of total urban nonpoint source pollution. In this study, the properties of urban runoff were examined in Shenyang, in northeastern China. Runoff samples from a tiled roof, a concrete roof and a main road were analyzed for key pollutants (total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), Pb, Cd, Cr, Cu, Ni, and Zn). The event mean concentration, site mean concentration, M(V ) curves (dimensionless cumulative curve of pollutant load with runoff volume), and mass first flush ratio (MFF30) were used to analyze the characteristics of pollutant discharge and first flush (FF) effect. For all events, the pollutant concentration peaks occurred in the first half-hour after the runoff appeared and preceded the flow peaks. TN is the main pollutant in roof runoff. TSS, TN, TP, Pb, and Cr are the main pollutants in road runoff in Shenyang. There was a significant correlation between TSS and other pollutants except TN in runoff, which illustrated that TSS was an important carrier of organic matter and heavy metals. TN had strong positive correlations with total rainfall (Pearson's r = 0.927), average rainfall (Pearson's r = 0.995), and maximum rainfall intensity (Pearson's r = 0.991). TP had a strong correlation with rainfall intensity (Pearson's r = 0.940). A significant positive correlation between COD and rainfall duration (Pearson's r = 0.902, significance level = 0.05) was found. The order of FF intensity in different surfaces was concrete roof >tile roof > road. Rainfall duration and the length of the antecedent dry period were positively correlated with the FF. TN tended to exhibit strong flush for some events. Heavy metals showed a substantially stronger FF than other pollutant. [ABSTRACT FROM AUTHOR]

Pollution of hazardous elements in roof runoff has been a potential danger to aquatic ecosystem as documented in previous studies. In this study, concentrations of lead (Pb), zinc (Zn), arsenic (As), and cadmium (Cd) in roof runoff were measured for short-term rainfall events. The concentrations of the selected elements varied to a high degree during the rainfall period, and the well-known first-flush phenomenon was not observed due to the short-term rainfall patterns. Based on event mean concentrations (EMCs) and fluxes, the elemental pollution may be ranked as Zn >> Pb > As > Cd. The average levels of Pb and Zn exceeded the fourth class value and fifth class value of the environmental quality standards for surface water in China. The relative high pollution could be caused by atmospheric deposition and the erosion of crust steel appurtenance installed above the rooftop. Furthermore, elements in particulate form dominated the roof runoff pollution, and the ratios of elements in particulate form to total amounts were 0.6 (As), 0.9 (Pb), 0.7 (Cd), and 0.5 (Zn). This study cleared the pollution characteristics of hazardous elements in short-term storm water roof runoff; it was useful for the selection of best management practices. [ABSTRACT FROM PUBLISHER]

Siphonic roof drainage systems are an efficient method of removing rainwater rapidly from roofs. Siphonic roof drainage systems are designed to run full-bore, resulting in sub-atmospheric system pressures, higher driving heads and higher system flow velocities. Hence, siphonic roof drainage systems normally require far fewer downpipes, and the depressurised conditions also mean that much of the collection pipework can be routed at high level, thus reducing the extent of any underground pipework. But, they work properly at only one roof run-off rate and therefore suffer from sizing and operational problems that limit their performance. Climate change is creating situations where normal ranges of rainfall intensity are being frequently exceeded, and this may have an impact on the performance of siphonic roof drainage systems. A multiple parallel pipe siphonic roof drainage system appears to offer benefits and avoids sizing problems associated with current siphonic roof drainage systems. A movable cap covering the inlet to a small bank of parallel pipes has the potential to avoid noise associated with making and breaking siphonic action through flow modulation. Laboratory scale tests demonstrate the basic feasibility of the multiple parallel pipe system and indicate that handover of flow between pipes occurs smoothly and that the flow modulation cap functions reliably. This technology includes moving parts and smaller diameters (19 mm ID) than are currently accepted (32 mm ID) in the British Standards and product development will be required.Practical application: Original research detailing an innovative development of a multi-pipe siphonic roof drainage system. This provides a wide design flow rate range and flow modulation caps reduce noise significantly by avoiding priming failure. Potentially extends the technique to a smaller building size than with current siphonic systems and offers climate change resilience potential. [ABSTRACT FROM PUBLISHER]