Search Results (9)

In southeast coastal Texas, expansive shrink–swell vertisols limit the effectiveness of infiltration-based green infrastructures (GIs) for stormwater management. Both pervious concrete (PC) and bioretention (BR) were conjunctively deployed at Lamar University (LU) and Montrose Park (MP) to evaluate their performance. The field measurements of drawdown rates indicated that post-event evaporation enhanced the system’s effectiveness by draining the media pore spaces of PC-BR. A SWMM model was developed at LU to verify soil infiltration behavior. A total of 66 water samples have been collected in the PC-BR systems to measure levels of NH₄⁺-N, NO₂⁻-N, NO₃⁻-N, TN, PO₄³⁻, and COD. The results showed that no elevated pollution was observed, and the measurements were compliant with the local river water criteria. Both systems were operated under local weather conditions, without irrigation or other human interference, and are still functioning well after 3 years. Two identical laboratory systems were fabricated to replicate the field system as zero-tension lysimeters. Laboratory testing demonstrated effective removal of nutrients, organic matter, and E. coli, with removal efficiencies generally exceeding 80% for PO₄³⁻ and NH₄⁺-N and reaching up to 95% for E. coli. These findings demonstrate that the PC-BR systems are an effective and sustainable solution for managing stormwater runoff and mitigating nutrient and bacterial pollution, particularly in regions with expansive shrink–swell vertisols and vulnerable to localized nuisance flooding. Full article

Microplastics (MPs) are emerging pollutants of global concern, posing significant ecological and human health risks. They are frequently detected in stormwater systems, with urban runoff serving as a major transport pathway into the environment. Green stormwater infrastructure, particularly bioretention systems (BRSs), offers a promising approach to mitigate these risks by filtering and retaining various contaminants. However, the occurrence of MPs in BRSs and their capacity to retain these pollutants remain largely unexplored in the literature, despite being critical for stormwater management and water quality protection. Therefore, this study attempted to examine the occurrence, vertical distribution, and trapping of MPs within a field-installed BRS, potentially emphasizing their role in reducing microplastic (MP) transport. Therefore, field samples were collected at depths of 2, 12, and 24 inches below the surface and processed in the laboratory for MP detection and quantification. The results revealed an average concentration of 1095 particles per kg of dried sediment, with fragments (microplastics shape) accounting for 78.54% of the total MPs. Although no clear vertical distribution pattern was observed, the initial findings showed that MPs were mostly retained at 24 inches, potentially indicating their transport through the media and the retention capacity of a BRS (surface and middle layer) in capturing microplastics from stormwater environments. However, there is no direct evidence to explain the mechanisms driving the observed concentrations at greater depths. The preliminary findings of this study highlight that the concentrations of different sizes of MPs can vary with soil depth in bioretention media. Integrating a BRS into urban stormwater infrastructure likely provides the dual benefits of improved stormwater management and reduced plastic pollution. This study underscores the importance of optimizing bioretention design and media composition to enhance MP trapping from stormwater. Full article

Effective microclimate regulation and rainwater management have become critical challenges in residential environments. Bioretention (BR) facilities are widely applied low-impact development (LID) measures that provide co-benefits in runoff control and microclimate regulation. However, the effects of BR designs and runoff control targets on microclimate performance remain unclear. Using ENVI-met simulations, this study evaluated the microclimate regulation performance of simple and engineered BR configurations under varying total annual runoff control rates (RCRs) across 28 scenarios in a community in Nanjing, China, considering sunny and post-rainfall conditions. Results showed the following: (1) Simple and engineered BR facilities exhibit distinct microclimate regulation pathways: simple BR shows a stable improvement in microclimate regulation with increasing facility area, whereas engineered BR shows declining effectiveness when RCR exceeds 75%. (2) Rainfall enhances the cooling and humidifying effects of both BR alternatives, enhancing microclimate regulation on post-rainfall conditions. (3) BR selection should be aligned with RCR targets. When RCR ≤ 75%, no substantial difference is observed between the two BR alternatives, while simple BR demonstrates better cooling effectiveness and higher implementation efficiency at higher RCRs. This study provides practical guidance for optimizing bioretention design to balance runoff control and microclimate regulation in residential-scale LID planning. Full article

Green infrastructure (GI) provides essential ecosystem services for urban sustainability in the face of urbanization and climate change, including stormwater management, heat mitigation, and reduction in carbon dioxide (CO₂) concentration levels. Existing studies often focus on single-dimensional ecological effects, lacking a systematic investigation of their synergies and trade-offs. This study developed a coupled framework integrating scenario design, model simulation, and multi-indicator evaluation. Fifty-six scenarios, varying by GI combinations, weather conditions, and total annual runoff control rate (RCR), were applied to a high-density industrial district in Nanjing. The results showed that: (1) GI combinations enhanced comprehensive benefits, with the combination including bioretention (BR), permeable pavement (PP), and green roof (GR) performing most effectively. This was followed by the combination of BR and PP, then by BR and GR, while the use of BR alone provided the lowest effectiveness. (2) PP was a key synergistic component, improving heat mitigation and reducing CO₂ concentration levels through the beneficial effects of rainfall events. (3) Exceeding the optimal RCR threshold for some GI combinations diminished tree space and three-dimensional green volume, shifting synergies into trade-offs. (4) Three-dimensional green volume was positively correlated with reductions in Physiological Equivalent Temperature (PET) and CO₂ concentration, confirming its core role. (5) Rainfall boosted carbon sinks, while a significant cooling enhancement required PP. This study elucidates the water–heat–carbon synergy in small-scale GI, supporting multi-objective optimization in high-density urban renewal. Full article

To address the challenges of the twenty-first century, particularly the negative effects of climate change, mitigation measures such as Nature-based Solutions (NbS) are being employed. Vegetation, being a part of various NbS interventions, provides different ecosystem services that help combat current climate-related vulnerabilities. This research aims to illustrate the connection between plants’ contribution to adapting to climate change and the creation of more sustainable spaces, focusing on the usage of bioretention systems (BRs) as an example of NbS. Some of the main aspects of how vegetation is selected for BRs according to qualities that may contribute to developing sustainable landscapes, along with providing key features of plants’ adaptation, different taxonomic data, and specific plant species that have been demonstrated to be good candidates for planting in BRs, are also discussed. Therefore, the importance of this paper is in providing a comprehensive systematization of vegetation with insightful suggestions on plant species for future BR implementation. Full article

Low-impact development (LID) is increasingly used to reduce stormwater’s quality and quantity impacts associated with climate change and increased urbanization. However, due to the significant variations in their efficiencies and site-specific requirements, an optimal combination of different LIDs is required to benefit from their full potential. In this article, the multi-objective genetic algorithm (MOGA) was coupled with the stormwater management model (SWMM) to identify both hydrological and cost-effective LIDs combinations within a large urban watershed. MOGA iteratively optimizes the types, sizes, and locations of different LIDs using a combined cost- and runoff-related objective function under both past and future stormwater conditions. The infiltration trench (IT), rain barrel (RB), rain gardens (RG), bioretention (BR), and permeable pavement were used as potential LIDs since they are common in our study area—the city of Renton, WA, USA. The city is currently adapting different LIDs to mitigate the recent increase in stormwater system failures and flooding. The results from our study showed that the optimum combination of LIDs in the city could reduce the peak flow and total runoff volume by up to 62.25% and 80% for past storms and by13% and 29% for future storms, respectively. The findings and methodologies presented in this study are expected to contribute to the ongoing efforts to improve the performance of large-scale implementations of LIDs. Full article

Green infrastructure (GI) protects aquatic ecosystems from stormwater runoff caused by urban development. Bioretention (BR) is a typical GI system wherein stormwater runoff is routed to a soil basin planted with vegetation and has been shown to reduce deicing salt loads in surface runoff, but the removal mechanism of salt is poorly understood. This study explores the potential of different vegetation types to reduce deicing salt released from a BR by transpiration. Six engineered soil media columns were built in a laboratory greenhouse to simulate a 1012 m² BR basin along Lorton Road, Fairfax County, VA, USA. The effect of vegetation type (Blue Wild Indigo and Broadleaf Cattail) and influent salt concentration on flow volume and salt mass reduction were quantified for multiple storm events. For all storm events, chloride inflow concentrations, and vegetation types, Cl⁻ load reduction ranged from 26.1% to 33.5%, Na⁺ load reduction ranged from 38.2% to 47.4%, and volume reductions ranged from 11.4% to 41.9%. Different inflow salt concentrations yielded different removal rates of deicing salt, and for a given column, salt removal decreased over sequential storm events. For each influent salt concentration, columns planted with Broadleaf Cattail (BC) performed better for volume and salt mass reductions than columns planted with Blue Wild Indigo (BWI), which in turn performed better than the controls. Full article

Studies on the assessment of green infrastructure (GI) practice implementation effect and cost efficiency on an urban watershed scale helps the GI practice selection and investment decisions for sponge city construction in China. However, few studies have been conducted for these topics at present. In this study, the Long-Term Hydrologic Impact Assessment—Low Impact Development (L-THIA-LID) 2.1 model was applied to assess the effectiveness and cost efficiency of GI practices on surface runoff volume reduction in an urban watershed—the Hexi watershed, Nanjing City, China. Grassed swales, bioretentions, green roofs, rain cisterns, permeable pavements, wet ponds, dry ponds, and wetlands were chosen as potential GI practices for sponge city construction based on feasibility analysis. Results showed that grassed swales were the most cost-effective practice (0.7 CNY/m³/yr), but the total implementation effect of grassed swales was not obvious due to the small area of suitable locations. Permeable pavements performed best on runoff reduction, but the cost efficiency was much lower. Correspondingly, bioretentions were compromise practices. Green roofs were the least cost-effective practices, with the cost efficiency at 122.3 CNY/m³/yr, but it was much lower for rain cisterns, which were 3.2 CNY/m³/yr. Wet ponds, dry ponds, and wetlands were potential practices implemented in development areas, of which dry ponds were the most cost-effective (2.7 CNY/m³/yr), followed by wet ponds (10.9 CNY/m³/yr). The annual runoff volume of the total area could be reduced by up to 47.01% by implementing GI practices in buildup areas. Rain cisterns (RC) and permeable pavements (PP) were the best combination for this area, and bioretentions (BR) and green roofs (GR) followed. Grassed swales (GS₁), dry ponds (DP), wet ponds (WP), and wetlands (WL) were not wise choices due to the small suitable location areas. This study also demonstrated the feasibility of the L-THIA-LID 2.1 model for the evaluation of GI practice implementation effects and cost efficiency on urban runoff in sponge city construction in China. Full article

To address regional flooding in the United States, federal and state agencies are adopting strict drainage policies in any large-scale commercial development within the watershed boundary. The conventional approach of implementing a wet detention pond (WP) reduces the land cover and causes operation and maintenance challenges eventually. The present study developed a decision-support system (DSS) in the Lower Rio Grande Valley region of South Texas for optimal selection of Best Management Practices (BMPs) by substituting a portion of the WP footprint with three regionally promising low-impact development practices, namely, porous concrete pavement (PCP), bioretention (BR), and bioswale (BS). Source Load Assessment and Management Model for Windows (WinSLAMM) was used as the foundation for the DSS database and algorithm development. This tool suggested that the implementation of bioswale alone can considerably reduce the footprint and construction cost. Less than 0.95 ha of installation of BR and BS can mitigate 79–91% of runoff from a maximum of 5 ha of commercial development. A combination of BR, BS, and WP was found to reduce runoff significantly (~100%), which suggests that the successful adoption of DSS might support better planning of the urban stormwater management in the Lower Rio Grande Valley (LRGV). Full article