ArticlePublisher preview available

Evaluating Retention Capacity of Infiltration Rain Gardens and Their Potential Effect on Urban Stormwater Management in the Sub-Humid Loess Region of China

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

Recognized as an effective low impact development (LID) practice, rain gardens have been widely advocated to be built with urban landscaping for stormwater runoff reduction through the retention and infiltration processes; but the field performance and regional effect of rain gardens have not been thoroughly investigated. In this paper, we presented a four-year monitoring study on the performance of a rain garden on stormwater retention; hydrological models were proposed to predict the potential effect of rain gardens on runoff reduction under different storms and the future urban development scenarios. The experimental rain garden was constructed in a sub-humid loess region in Xi’an, China; it has a contributing area ratio of 20:1 and depth of 15 cm. During the study period, we observed 28 large storm events, but only 5 of them caused overflow from the rain garden. The flow reduction rate for the overflow events ranged from 77 to 94 %. The runoff coefficient from the contributing area (RC) was reduced to less than 0.02 on annual basis, and 0.008 over the four years average. Field observations also showed that infiltration rate remained stable during the operation period. The predictions based on the future landuse and storm variability of the study area showed that by converting a small fraction of the city land area into rain gardens, the negative hydrological effect from expansion of impervious area can be reduced significantly. The challenge, however, lies in how to plan and build rain gardens as an integral part of the urban landscape.
This content is subject to copyright. Terms and conditions apply.
Evaluating Retention Capacity of Infiltration Rain
Gardens and Their Potential Effect on Urban Stormwater
Management in the Sub-Humid Loess Region of China
S. Tang
1
&W. Luo
2
&Z. Jia
2
&W. Liu
3
&S. Li
1
&Y. Wu
1
Received: 29 September 2015 /Accepted: 25 November 2015 /
Published online: 2 December 2015
#Springer Science+Business Media Dordrecht 2015
Abstract Recognized as an effective low impact development (LID) practice, rain gardens
have been widely advocated to be built with urban landscaping for stormwater runoff reduction
through the retention and infiltration processes; but the field performance and regional effect of
rain gardens have not been thoroughly investigated. In this paper, we presented a four-year
monitoring study on the performance of a rain garden on stormwater retention; hydrological
models were proposed to predict the potential effect of rain gardens on runoff reduction under
different storms and the future urban development scenarios. The experimental rain garden
was constructed in a sub-humid loess region in Xian, China; it has a contributing area ratio of
20:1 and depth of 15 cm. During the study period, we observed 28 large storm events, but only
5 of them caused overflow from the rain garden. The flow reduction rate for the overflow
events ranged from 77 to 94 %. The runoff coefficient from the contributing area (RC)was
reduced to less than 0.02 on annual basis, and 0.008 over the four years average. Field
observations also showed that infiltration rate remained stable during the operation period.
The predictions based on the future landuse and storm variability of the study area showed that
by converting a small fraction of the city land area into rain gardens, the negative hydrological
effect from expansion of impervious area can be reduced significantly. The challenge, how-
ever, lies in how to plan and build rain gardens as an integral part of the urban landscape.
Keywords Rain garden .Storm runoff .Design storm .Infiltration .Overflow.LID
Water Resour Manage (2016) 30:9831000
DOI 10.1007/s11269-015-1206-5
*W. Lu o
luowan@yzu.edu.cn
1
State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area, Xian University of
Technology, Xian, China
2
Department of Agriculture and Water Resources Engineering, Yangzhou University, Yangzhou,
China
3
Department of Biological and Agricultural Engineering, North Carolina State University,
Raleigh, NC 27695-0001, USA
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Water-retention capacity, another critical aspect of urban greening aimed at delaying and mitigating run-off generation, is also strongly influenced by antecedent conditions. The water-retention capacity of urban vegetation during and after rainfall depends on the relatively dry conditions preceding precipitation, as these conditions create the potential for greater water storage within the substrate and soil layers' pores (Kõiv-Vainik et al., 2022;Tang et al., 2016). Despite the commonalities in the underlying mechanisms of water-retention and cooling capacity, there is a significant lack of research systematically assessing their joint environmental benefits or comparing their relative effectiveness across regions with varying climatic differences. ...
Article
Full-text available
Urban green spaces play a crucial role in addressing pressing environmental challenges, such as alleviating the urban heat island effect and enhancing water retention. However, there remains a research gap in understanding the simultaneous benefits of water‐retention and cooling capacities, especially under the diverse climatic conditions across China. Utilizing robust methodologies and remote sensing data, our study evaluates the dynamic interplay between aridity index (AI) and retention‐cooling performances of urban green spaces in both cold and warm season from 2003 to 2018. Results demonstrated that water‐retention capacity is more effective in relatively arid regions, whereas cooling capacity is more pronounced in humid regions, with both effects being largely season‐dependent. In addition, green space proportion significantly influences the relationship between AI and retention‐cooling performances, particularly for cooling capacity, which exhibits opposite trends between cold and warm seasons. Future projection analysis indicate that climate change scenarios could significantly alter retention‐cooling performances, potentially leading to notable deviations from the patterns observed during the historical periods across different climate zones, with an increasing dependence on changes in local climatic conditions. The inconsistent performance of urban green spaces in terms of water‐retention and cooling across seasons and various climate regions, highlighting the importance of context‐specific greening strategies to sustain and enhance urban resilience to future climate change in China.
... RG systems have been widely accepted in the engineering community due to numerous field and laboratory studies that demonstrate a significant reduction in the volume of rainwater runoff from the catchment area, a reduction in the speed and delay of peak flows in the sewer system, groundwater recharge through infiltration, and the removal of pollutants from water before it enters local watercourses [11]. The effectiveness of reducing the volume of runoff and reducing the rate of peak runoff by RGs has been documented in scientific papers from around the world: in Poland [12], Serbia [13], Japan [14], the USA [15], Thailand [16], Brazil [17], China [18], Indonesia [19], Sweden [20], and Norway [21], ranging from 50 to 98% for different studies. ...
Article
Full-text available
Implementing rain garden (RG) designs is widespread worldwide to reduce peak flow rates, promote stormwater infiltration, and treat pollutants. However, inadequate RG design degrades its hydrological behaviour, requiring the development and validation of an appropriate hydrological model for the design and analysis of structures. This study aimed to improve a hydrological infiltration model based on Darcy’s law by taking into account the height of the water column (HWC) at the surface of the RG and the filtration coefficients of soil materials. The model was tested by simulating the hydrological characteristics of a rain garden based on a single rain event of critical intensity (36 mm/h). Using the validated model, design curves were obtained that predict the performance of the RG as a function of the main design parameters of the structure: water column height, ratio of catchment area to structure area, layer thickness, and soil filtration coefficient. The hydrological efficiency of the RG was evaluated in terms of the time of complete saturation, filling of the structure with water, and determining the change in HWC caused by changes in the parameters. The filtration coefficient and thickness of the upper and intermediate infiltration layers of the RG are the main parameters that affect the depth of saturation of the layers of the structure and the HWC on the surface. The model is not very sensitive to the model parameters related to the lower gravel layer. If the top layer’s thickness increases by 10 cm, it takes longer to fill the structure with water, and the HWC on the surface reaches 0.341 m. The rain garden’s performance improves when the filtration coefficient of the top layer is 7.0 cm/h. Complete saturation and filling of the structure with rainwater do not occur within 7200 s, and the water column reaches a height of 0.342 m at this filtration coefficient. However, the rain garden’s effectiveness decreases if the filtration coefficient of the upper and intermediate layers exceeds 15 cm/h and 25 cm/h, respectively, or if the catchment area to RG area ratio decreases to values below 15. The modelling results confirm that considering the HWC in RG hydrological models is essential for designing structures to minimise the risk of overflow during intense rainfall events.
... Assim, os jardins de chuva, também denominados sistemas de biorretenção, têm se mostrado eficazes para mitigar inundações urbanas (GREKSA et al., 2022;KUMAR e SINGH, 2023). Estudos apontam que a conversão de pequenas áreas urbanas em jardins de chuva pode reduzir significativamente os efeitos hidrológicos negativos da impermeabilização do solo (BURSZTA-ADAMIAK et al., 2023;GREKSA et al., 2023;TANG et al., 2016). Soluções como esta são valorizadas por seu baixo custo e relevante potencial para restaurar o ciclo hidrológico natural, reduzir o escoamento superficial, filtrar poluentes, fomentar a biodiversidade, controlar o microclima e recarregar águas subterrâneas (ASLESON et al., 2009;BURSZTA-ADAMIAK et al., 2023;KASPRZYK et al., 2022). ...
Thesis
Full-text available
Os jardins de chuva, também denominados como sistemas de biorretenção, vêm revelando-se como uma solução eficaz para mitigar os problemas de drenagem urbana. Contudo, a maioria dos estudos concentra-se em regiões de clima temperado, evidenciando a necessidade de investigações em regiões de clima tropical, onde os dados são escassos. Neste contexto, esse trabalho visa investigar a eficácia de um jardim de chuva em ambiente tropical urbano, avaliando critérios de design, capacidade de infiltração, armazenamento hídrico e suporte ao desenvolvimento de espécies vegetais. Experimentalmente foram coletados e analisados dados de 50 eventos de precipitação natural ao longo de cinco meses, calculando-se o balanço hídrico do sistema. Além disso, monitorou-se o desenvolvimento de quatro espécies vegetais (Chlorophytum comosum, Dracaena reflexa, Ruellia simplex e Sansevieria trifasciata) avaliando-se a adaptabilidade dessas espécies ao ambiente da célula de biorretenção e como essas respondem à sazonalidade do regime pluviométrico natural, comparativamente a um jardim controle tradicional. Os resultados mostraram que a eficiência de retenção hídrica da estrutura, durante o período monitorado, foi de 97,3% ± 7,3% com cerca de 78% dos eventos monitorados com eficiência de 100%. As taxas de utilização da estrutura de biorretenção indicaram que o sistema opera dentro do desempenho projetado. As espécies selecionadas demonstraram boa adaptabilidade, exibindo aparência morfológica saudável e crescimento satisfatório sob condições de um jardim de chuva em clima tropical. A Ruellia simplex e a Sansevieria trifasciata apresentaram crescimento estatisticamente superior no jardim de chuva em comparação ao jardim controle. Em contraste, a Dracaena reflexa e a Chlorophytum comosum não mostraram diferenças estatisticamente significativas no crescimento em ambos os jardins. O modelo simplificado de base física elaborado reproduziu adequadamente o nível superficial máximo (H45S, MAX) e a eficiência de retenção de escoamento (Eff), com coeficientes de eficiência de Nash-Sutcliffe (NSE), raiz do erro quadrático médio (RMSE) e coeficiente de determinação (R²) de 0,81, 4,71% e 1,00 para Eff e 0,93, 6,89 cm e 0,96 para H45S,MAX, respectivamente. Em tempo, os resultados deste estudo contribuem para uma melhor compreensão do desempenho de estruturas de biorretenção em áreas de clima tropical, oferecendo diretrizes e recomendações para projetos novos e existentes.
... They are an effective way to reuse water resources and flood control strategies, and can ensure the sustainability, livability and resilience of the urban ecological environment [1]. In recent years, in order to cope with frequent urban waterlogging disasters and repair the urban water cycle pattern of "rainfall-infiltration-evaporation", sustainable stormwater management landscapes represented by rain gardens have been widely used in cities [2,3]. It has the advantages of simple structure, low cost, low maintenance and obvious effect, and has broad application prospects [4]. ...
... Os jardins de chuva são um exemplo de solução baseada na natureza e com tipologia de sistema de biorretenção com função de reter as águas pluviais e permitir a infiltração da água no solo, minimizando os impactos advindos do escoamento superficial, enquanto elemento mitigador de pico de vazão de chuva (Melo et al., 2014). Além disso, são uma prática eficaz de desenvolvimento de baixo impacto , e têm sido amplamente defendidos para serem construídos como elementos do paisagismo urbano associado a redução do escoamento de águas pluviais a partir dos processos de retenção e infiltração (Tang et al., 2016). Iftekhar et al. (2021) abordam que os jardins de chuva são elementos importantes da infraestrutura urbana sensível à água nos Estados Unidos, em Cingapura e na Austrália (em Sydney e em Melbourne, as duas cidades australianas mais populosas). ...
Article
Full-text available
Os impactos negativos ao meio ambiente decorrentes da urbanização acelerada são cada vez mais severos, inclusive as inundações urbanas. A busca por alternativas de desenvolvimento sustentável reforçam a importância da redução das áreas impermeáveis e os sistemas de biorretenção surgem como dispositivos eficazes na redução dos volumes de escoamento e minimização das inundações. Dentre os dispositivos, os jardins de chuva funcionam com retenção das águas pluviais e infiltração. Eles constituem-se como elementos da paisagem urbana e beneficiam a saúde humana por tornar locais mais agradáveis e melhorar o conforto térmico local. Este estudo objetivou apresentar um projeto piloto e a execução de um jardim de chuva na cidade de Recife-PE, com avaliação da sua eficiência hidráulica. Optou-se também por utilizar um material reciclado de resíduos da construção civil, tornando o dispositivo de drenagem ainda mais sustentável. A metodologia consistiu em caracterização do local de instalação, determinação da chuva de projeto, escolha da geometria do jardim e da cobertura vegetal, determinação do volume útil necessário, execução e simulação dos eventos de chuva. Foi verificado que a camada permeável de solo encontrava-se na profundidade de 1,25 m, a partir dos ensaios de infiltração com anel simples e foi dimensionada a camada núcleo do jardim com 90 cm de espessura. Nas simulações, o dispositivo apresentou-se eficiente para a chuva mais crítica de 156,63 mm/h, sem atingir a máxima capacidade de utilização do jardim. O dispositivo se mostrou eficiente enquanto potencial mitigador de pico de vazão de chuva e redução das inundações urbanas.
... China proposed in December 2013 to "build a sponge city with natural accumulation, natural infiltration and natural purification" [5]. A sponge city is inspired by the concept of "Low Impact Development (LID)" [6], a sustainable stormwater management concept that minimizes disasters caused by urban rainfall, prevents water loss, enhances groundwater infiltration and recharge, reduces pollutant discharges, improves urban stormwater storage and utilization, and increases urban resilience [7][8][9]. With the rapid advancement of ecological civilization construction, prioritizing a green stormwater infrastructure to address urban stormwater management issues has become a crucial strategy for emphasizing ecological priorities and fostering green development in sustainable urban planning [10]. ...
Article
Full-text available
To investigate the quantitative relationship between the volume capture of rainfall and carbon emissions from bioretention facilities, this study introduces the concept of the carbon intensity of volume capture of rainfall. The influence of four key factors—climatic conditions, aquifer height, permeability coefficient, and facility area—was investigated using a residential neighborhood in Tianshui, China, as an example. The results reveal that the carbon intensity value is influenced not only by external environmental changes but also by the inherent attributes of bioretention facilities, such as aquifer height, permeability coefficient, and facility area. The maximum carbon intensity value for the volume capture of rainfall was −0.0005 kg CO2/m³, while the minimum was −0.0852 kg CO2/m³, representing a substantial difference of approximately 169 times. Orthogonal experiments identified the facility area as the most significant influencing factor on carbon intensity, with a correlation coefficient of 0.0520. The area of bioretention facilities can be prioritized to meet deployment requirements, taking into account volume capture reduction effects and carbon emissions. For facilities with a high carbon intensity, an emphasis should be placed on enhancing carbon reduction benefits, and various initiatives can be implemented to achieve this goal.
Thesis
Full-text available
Climate change response of green stormwater infrastructure as a system. https://www.proquest.com/dissertations-theses/identifying-responses-changing-climate-conditions/docview/3121746377/se-2
Article
Full-text available
Bioretention, or variations such as bioinfiltration and rain gardens, has become one of the most frequently used storm-water management tools in urbanized watersheds. Incorporating both filtration and infiltration, initial research into bioretention has shown that these facilities substantially reduce runoff volumes and peak flows. Low impact development, which has a goal of modifying postdevelopment hydrology to more closely mimic that of predevelopment, is a driver for the use of bioretention in many parts of the country. Research over the past decade has shown that bioretention effluent loads are low for suspended solids, nutrients, hydrocarbons, and heavy metals. Pollutant removal mechanisms include filtration, adsorption, and possibly biological treatment. Limited research suggests that bioretention can effectively manage other pollutants, such as pathogenic bacteria and thermal pollution, as well. Reductions in pollutant load result from the combination of concentration reduction and runoff volume attenuation, linking water quality and hydrologic performance. Nonetheless, many design questions persist for this practice, such as maximum pooling bowl depth, minimum fill media depth, fill media composition and configuration, underdrain configuration, pretreatment options, and vegetation selection. Moreover, the exact nature and impact of bioretention maintenance is still evolving, which will dictate long-term performance and life-cycle costs. Bioretention usage will grow as design guidance matures as a result of continued research and application.
Article
Full-text available
The transportation and urban infrastructure relies heavily on impervious surfaces. Unmitigated rainfall runoff from impervious surfaces can lead to a myriad of environmental problems in downgradient areas. To address this issue, novel stormwater control measures (SCMs) are being emphasized and implemented widely to mitigate some of the impacts of impervious surface. Bioretention is a soil/media-based SCM that is often used for this purpose, but current design practices are highly empirical. This study compiles work from three research sites in three states to provide some fundamental underpinnings to bioretention design. Although all sites demonstrate different levels of performance, water volumetric performance trends are common to all. These trends are based on the available storage in the bioretention cell, termed herein as the Bioretention Abstraction Volume (BAV). The BAV is directly related to available media porosity and storage in the surface bowl. A finite capacity to completely store all runoff from smaller events is defined by the BAV. Normalization for this storage provides prediction for volumetric performance. Recommendations for bioretention design are provided.
Article
Full-text available
In response to water quality and quantity issues within the Stroubles Creek watershed in Blacksburg, Virginia, a retrofit bioretention cell (BRC) was installed to collect and treat runoff from an existing parking lot. The BRC was completed in July 2007, and 28 precipitation events were monitored between October 2007 and June 2008. For each storm, inflow and outflow flow-weighted composite samples were collected and analyzed for suspended sediment, total nitrogen, and total phosphorus. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were analyzed to evaluate BRC efficiency. Overall, the BRC successfully reduced flow volumes and peak flow rates leaving the parking lot by 97 and 99%, respectively. Cumulative mass reductions for sediment, total nitrogen, and total phosphorus all exceeded 99% by mass. The findings of this study have significant implications for areas with karst geology: (1)current design recommendations of lining the bottom of BRCs with clay may not be sufficient to prevent large amounts of water from infiltrating into surrounding soils; and (2)in areas with significant elevation changes, designing BRCs deeper than the typical 0.6-1.2m increases the feasibility of retrofits and provides substantial water quality and quantity benefits.
Article
Full-text available
Bioretention systems are increasingly being used to control the adverse effects of urbanization on stormwater quantity and quality. The stormwater capture efficiency of a bioretention system, defined as the fraction of stormwater volume captured by the system, can be used as an important index of its stormwater management performance. In this paper, an analytical probabilistic expression (APE) is derived for estimating the long-term average stormwater capture efficiency of bioretention systems. The derivation is based on the probability distribution functions of the input rainfall event characteristics and the rainfall-runoff-overflow transformations occurring on a bioretention system and its contributing catchment. In the derivation, instead of simply adopting the Howard’s conservative assumption as used in many previous studies, an approximate expected value of the surface depression water contents of a bioretention system at the end of a random rainfall event [denoted as E(S dw )] is derived and used. The accuracy of the resulting APE is verified by comparing its results with those determined from continuous simulations. The use of E(S dw ) is proven to be advantageous than the use of the Howard’s conservative assumption, it demonstrates that similar methods may be developed to analytically evaluate the stormwater management performance of other types of storage facilities for which the Howard’s conservative assumption was employed previously.
Article
Hydraulic conductivity of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of stormwater characteristics on the clogging of stormwater filters. Effect of five different operational regimes has been tested in this study of sediment concentration; pollutant concentrations; stormwater sediment size; loading rate and stormwater loading/dosing regime and compared with the Base case. For each operational condition, five column replicates were tested. Results suggest that sediment concentration in stormwater is a significant parameter affecting hydraulic and treatment performance, eventually affecting longevity of these stormwater treatment systems. Further, the size of sediments (and their relation to the size of filter media grains) in stormwater was found to be an important parameter to be considered in design of coarse filters with high infiltration rates that are used for stormwater treatment. As expected, the addition of metals and nutrients had limited or no contribution to changes in hydraulic or sediment removal performance of the studied stormwater filters. Whilst loading rate was found to be an important parameter affecting the hydraulic and treatment performance of these systems, any variation in the stormwater loading regime had a limited effect on their performance. This study therefore develops an understanding of the effect of catchment characteristics on design of filters and hence their longevity and maintenance needs.
Article
Hydraulic performance of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of physical characteristics of filter media and flow-through rates on the clogging of stormwater filters. Five replicate experimental columns were constructed using zeolite, scoria, riversand and polymeric glass beads, and different flow-through rates were achieved using restricted outlets. The systems were dosed with semi-synthetic stormwater and the evolution of hydraulic performance and sediment removal rate was observed (for four filter media and across four flow rates) to investigate impacts of media type and flow rate. It was found that shape and smoothness of filter media grains had limited effect on clogging and sediment removal rate. All media except scoria clogged after similar volumes of stormwater but scoria-based filters were found to be highly variable in performance, most likely due to breakdown of its particles. Conversely, flow-through rate significantly affected clogging and sediment removal rate. For instance, in the case of zeolite filters, the systems with the lowest flow rate clogged after application of over 30 m of stormwater, while the unrestricted zeolite columns (with 200 times the flow rate) clogged after only 10 m of applied stormwater. At the same time, the zeolite filters with the lowest flow rate had an overall treatment efficiency of 88% compared with the unrestricted design’s efficiency of 59%. Further work is needed to analyse the influence of filter bed design, stormwater inflow characteristics and drying and wetting regimes on clogging and to understand the location of the clogged material in these filters.
Article
Flows into and out of two bioretention facilities constructed on the University of Maryland campus were monitored for nearly 2 years, covering 49 runoff events. The two parallel cells capture and treat stormwater runoff from a 0.24 ha section of an asphalt surface parking lot. The primary objective of this work was to quantify the reduction of hydrologic volume and flow peaks and delay in peak timing via bioretention. Overall, results indicate that bioretention can be effective for minimizing hydrologic impacts of development on surrounding water resources. Eighteen percent of the monitored events were small enough so that the bioretention media captured the entire inflow volume and no outflow was observed. Underdrain flow continued for many hours at very low flow rates. Mean peak reductions of 49 and 58% were noted for the two cells. Flow peaks were significantly delayed as well, usually by a factor of 2 or more. Using simple parameters to compare volume, peak flow, and peak delay to values expected for undeveloped lands, it was found that probabilities for bioretention Cell A to meet or exceed volume, peak flow, and peak delay hydrologic performance criteria were 55, 30, and 38%, respectively. The probabilities were 62, 42, and 31%, respectively, for Cell B.
Article
Three bioretention field sites in North Carolina were examined for pollutant removal abilities and hydrologic performance. The cells varied by fill media type or drainage configuration. The field studies confirmed high annual total nitrogen mass removal rates at two conventionally drained bioretention cells 40% reduction each. Nitrate-nitrogen mass removal rates varied between 75 and 13%, and calculated annual mass removal of zinc, copper, and lead from one Greensboro cell were 98, 99, and 81%, respectively. All high mass removal rates were due to a substantial decrease in outflow volume. The ratio of volume of water leaving the bioretention cell versus that which entered the cell varied from 0.07 summer to 0.54 winter. There was a significant p0.05 change in the ratio of outflow volume to inflow volume when comparing warm seasons to winter. Cells using a fill soil media with a lower phosphorus index P-index, Chapel Hill cell C1 and Greensboro cell G1, had much higher phosphorus removal than Greensboro cell G2, which used a high P-index fill media. Fill media selection is critical for total phosphorus removal, as fill media with a low P-index and relatively high CEC appear to remove phosphorus much more readily.
Article
Urban stormwater has negative environmental and ecological effects. Bioretention systems are starting to be used in efforts to mitigate these effects. A bioretention system receiving water from a light industrial catchment and a busy road was designed, built and monitored for changes in soil physics as well as hydrological and hydrochemical efficiency. The soils in the bioretention system were designed to have high metal removal potential and high permeability to compensate for undersized bioretention volume. The inflow hydrograph was a series of sharp peaks with little baseflow, typical of runoff from impervious surfaces. The bioretention system smoothed the hydrograph by reducing peak flow and volume for all 12 events monitored in detail. Overflow occurred in 10 events indicating the increased permeability did not fully compensate for the undersized volume. Runoff was heavily polluted with sediment and heavy metals, in particular zinc. The majority of the zinc, lead and Total Suspended Sediments were removed from the stormwater that flowed through the bioretention system, with TSS and total zinc concentrations reducing by orders of magnitude. Despite high removal efficiency, median concentrations of zinc exiting the bioretention system still exceeded ecosystem health guidelines and the bioretention system was both a source and sink of copper.
Article
Storm water control measures (SCMs), also known as best management practices (BMPs), such as rain gardens, are designed to infiltrate storm-water runoff and reduce pollutant transport to surface waters. The life span of these SCMs may be limited depending on the composition of sediments in runoff water. Settling of fine sediments may clog soil pore spaces, reducing the infiltration capacity of the soil and reducing the potential benefits of this SCM. A study was conducted on a Villanova campus rain garden that accepts runoff from an adjacent parking lot to determine if there was a relationship between the accumulation of fine sediments over time and the infiltration capacity. The soil textural profile within the rain garden was characterized prior to SCM installation (2001), after installation, after five years, and after seven years of receiving storm-water runoff. Infiltration data were collected by the single-ring infiltrometer method in 2006 and 2009. Differences in soil texture were found between locations within the infiltration basin, and accumulation of fines smaller than 0.1 mm was observed at both locations sampled in 2009. Infiltration rates were significantly different between the two locations measured within the rain garden, but infiltration rates did not change significantly over time within those regions. This SCM was designed at a 10:1 watershed to SCM area ratio, which is twice what is recommended by the PA DEP BMP Manual. The data collected over the seven years since installation indicate that while fines have accumulated in the SCM there has been no significant change in infiltration potential.