Urbanization increases stormwater runoff and places growing pressure on aging gray infrastructure, such as deteriorating culverts and unmanaged regional detention systems. These challenges have increased interest in green stormwater infrastructure (GSI) as decentralized stormwater control measures. Recent geospatial and computational hydrology models, such as Community-Enabled Lifecycle Analysis of Stormwater Infrastructure Costs (CLASIC), integrate multiple aspects of stormwater planning, including hydrologic responses, stormwater quality, life-cycle costs, triple bottom line (TBL) cobenefits, and climate change factors in a single, user-friendly web-based tool. However, limited guidance exists for determining optimal spatial allocation of distributed GSI installations. This study integrates the CLASIC tool with ArcGIS suitability modeling and Nondominated Sorting Genetic Algorithm II (NSGA-II) to explore alternative GSI deployment within a 64.7-ha (160-acre) pilot study area in the Proctor Creek watershed in Atlanta, Georgia. The analysis is conducted for a 95th percentile storm event, 45.7 mm (1.8-in.), 24-h design storm. Two representative GSI configurations (n=21) were identified with trade-offs between land suitability and flow interception. This study advances green stormwater infrastructure planning from land suitability-based screening toward performance-driven spatial allocation. Future research should validate results against calibrated models, incorporate multistorm evaluation, and incorporate explicit cost surfaces with equity and ownership constraints.
Stormwater runoff from urban areas threatens water quality and ecosystems around the world. For freshwater ecosystems, phosphorus (P) is often a primary concern, as excess P loading can cause eutrophication, symptoms of which include harmful algal blooms and oxygen depletion. Sand filters are stormwater management practices that trap particles and thereby reduce downstream sediment and P loads. However, sand typically has low P sorption capacity. To target both particulate and dissolved P species in stormwater, a P-sorbing material amendment can be added to sand filter media to increase P sorption capacity. This research centered on a field study of two urban stormwater sand filters enhanced with alum-based drinking water treatment residuals (DWTRs) (3%-5% of the sand layer by volume), a byproduct of drinking water treatment, to improve P removal in sand filter media under field conditions in Chittenden County, VT. The composition of influent stormwater was markedly different between sites, dominated by dissolved P at the residential site and mostly particulate P at the more industrial/commercial site. Due to this difference in influent water quality, >99% of the total P removed at the residential sand filter was in the form of dissolved P, while only 4% of the total P load removed at the industrial/commercial site was dissolved P. Because removal of dissolved P by sand filters tends to be negligible, the dissolved P load reductions observed at both sites are likely attributable to the DWTRs. Overall, the two systems reduced total P loads by 65%-78% during monitored events. This field study indicates that adding DWTRs to sand filter media is an effective way to couple both physical and chemical P removal mechanisms and thereby enhance water quality improvement performance. We provide guidance on future use of DWTRs in stormwater infrastructure based on our findings
Erosion and sediment control (ESC) practices are essential for minimizing soil loss from active construction sites and preventing the discharge of sediment-laden stormwater. However, many traditional ESC products rely heavily on synthetic materials (e.g., plastic). Growing awareness of microplastic pollution and increasing concerns over wildlife entanglement have prompted many state departments of transportation (DOTs) to seek alternatives to plastic-based ESC materials. The objective of this study was to investigate the current use of plastics in ESC practices across state DOTs and examine policies and initiatives aimed at reducing or eliminating plastic dependency. A literature review was conducted to gather information on plastic use in ESC products. Findings were used to develop a web-based survey, which was distributed to stormwater professionals in all 50 state DOTs and the Washington, DC DOT. The survey achieved an 82% response rate. Finally, semistructured interviews were conducted with six state DOTs to document their unique approaches to reducing plastic use. Key findings indicate that alternatives are needed for erosion control because netted products can be a substantial source of microplastic pollution and present the greatest risk of wildlife entanglement. Alternative practices such as natural fiber blankets and slash mulch berms have been perceived to have high effectiveness. State DOTs that have transitioned to plastic-free alternatives report no decrease in ESC practice performance and similar efforts for installation when compared with standard practices. Together, the survey results and interviews were used to develop a nine-step framework to support state DOTs transitioning away from plastic-based ESC practices in varying stages.
Urban blue infrastructure-comprising lakes, rivers, canals, and wetlands-plays an essential role in sustaining water resources and enhancing climate resilience in rapidly urbanizing regions. Indian cities, however, face mounting water scarcity and recurrent flooding due to the degradation, encroachment, and fragmentation of their water bodies. This study undertakes a comparative assessment of blue infrastructure dynamics in three major Indian cities-Bengaluru, Chennai, and Delhi-to examine how variations in urbanization patterns, governance structures, and hydrological conditions influence water insecurity. Using geospatial analysis and a review of planning and policy frameworks, the study identifies substantial declines in water spread areas, weakened ecological functions, and governance fragmentation as key drivers of water-related risks. Findings show that Chennai exhibits the highest vulnerability due to drastic contraction of water bodies and monsoon-dependent hydrology; Bengaluru demonstrates significant loss of lake networks despite retaining comparatively higher storage potential; while Delhi's challenges stem primarily from pollution, groundwater depletion, and institutional overlap. The study highlights the need for coherent regulatory frameworks, strengthened interagency coordination, and city-specific strategies that integrate blue infrastructure within formal urban planning systems. The implications emphasize that revitalizing urban water bodies is critical for enhancing long-term climate resilience and water security in Indian metropolitan regions.
A permeable articulating concrete block (P-ACB) pavement (area=218 m2, storage depth=1.2 m) was installed in April 2021 in Colmar Manor, MD. This 1.5-year study analyzed the volumetric stormwater reduction and subsurface infiltration performance for 50 rainfall events at this site. Subsurface infiltration rates were calculated by fitting linear and exponential decay models to depth sensor data. Site soil boring data revealed a heterogenous soil composition, including hydrologic soil group (HSG) A, B, and D soils. The local permitting agency classified soils per the lowest HSG (D), which is not recommended for infiltration-based best management practices. Nonetheless, exponential models revealed a mean subsurface infiltration rate of 2.35 +/- 1.88 cm/h, despite the presence of D soil with low hydraulic conductivity. Balances of rainfall and storage volumes reveal that the pavement fully captures rainfall from a 873 m2 drainage area, 8% greater than anticipated in design stages (809 m2). Study results predict that the P-ACB pavement system is able to fully capture rainfall from storms up to 10.44 cm without reaching overflow into a mid-drain, based on trends from observed data and assuming static volumetric storage with 40% porosity. Considering continuous exfiltration from the storage bed, an additional 0.58 cm can be managed during a 4-h rainfall, for a total capture of 11.02 cm.
Infiltration trenches have been shown to effectively manage stormwater runoff but are reported to have a high risk of clogging when implemented without pretreatment. This study assessed the performance of an infiltration trench (IT) stormwater control measure (SCM) equipped with an R-Tank modular stormwater tank system and a pretreatment surface filtration system (Contech Jellyfish). The IT replaced an older IT without pretreatment that experienced diminished performance after only 1 year of operation due to sediment accumulation. The pretreatment filter system was installed upstream of the IT to minimize the accumulation of sediments that caused the previous IT to fail. The results presented herein document the performance of the filtration system to pretreat stormwater runoff from 541 m2 of an elevated parking deck over the first 29 months of operation with respect to total suspended solids (TSS) removal, as well as the removal of other water quality constituents. Even though the average TSS concentration entering the pretreatment system was relatively low (12.0 +/- 11.3 mg/L, n=31), the pretreatment system decreased the TSS concentration by 59.7%+/- 39.7% (n=15) where influent TSS concentrations were above the minimum reporting limit. In addition, removal percentages of suspended copper (59.7%+/- 21.1%, n=15), dissolved copper (53.1%+/- 27.1%, n=5), and suspended zinc (59.8%+/- 18.8%, n=12) concentrations were comparable to the TSS removal. Total Kjeldahl nitrogen (56.6%+/- 29.3%, n=9) and total phosphorus (39.8%+/- 27.8%, n=7) removal was also observed, and these losses were attributed to particulate organic N and P removal by the filters. Sediment accumulated on the filters at a rate of 20 mg/d/m2 of the parking deck surface area and had a medium particle size (53.3 mu m) and organic content (30.1%+/- 6.2%, n=3) that was comparable to the medium particle size and organic content of sediment that accumulated inside the old IT that failed within 1 year of operation. Recession rates of the IT retrofit were greater than the old IT prior to failure demonstrating that, after removal of the failed infiltration system, the subgrade infiltration function was still viable. No decrease in recession rates was observed in the IT retrofitted with pretreatment filters during the first 29 months of operation. These results indicate that surface filtration pretreatment to remove fine-grain stormwater sediment can play a role in extending IT operation, while also serving to remove pollutants from the watershed.
Abstract Extreme precipitation events are a major driver of flood risk for urban areas with extensive impervious cover. Existing stormwater management infrastructure, much of which was constructed before our current best estimates for extreme precipitation values, is unlikely to sufficiently address the rising risks. This research modeled several potential broad stormwater management strategies in three different subwatersheds in Minnesota, USA using the US EPA’s storm water management model (EPA-SWMM). The stormwater management strategies included three storage-based approaches, one conveyance approach, and one infiltration approach. The performance of each scenario was measured by reduction in average model node depth from baseline and reduction in peak flow rate at the outlet. Adding new storage ponds ( 2,100 − 5,100 m 3 of live storage) equipped with continuous monitoring and adaptive control (CMAC) systems to the watersheds was the most effective strategy modeled, followed by adding new storage ponds without CMAC, and the amount of storage added by each scenario (on a per area basis) was found to have a positive relationship with performance across precipitation depths and watersheds. The conveyance strategy, uniformly upsizing stormwater pipes, was found to decrease peak depths for upstream nodes while increasing peak depth for downstream nodes and increasing peak outlet flow rates for the 24-h, 100-year storm by 3.8%–16%.
Stormwater best management practices (BMPs) are essential for meeting water quality and flood control goals, but their long-term effectiveness depends on sustained maintenance. In this study we analyzed a large BMP inspection dataset of 17,843 inspections across 2,535 unique BMPs conducted by the Virginia Department of Transportation from 2020 to 2024. We quantified persistent maintenance needs, identified assets with recurring issues, and examined how these issues vary across environmental and geographic conditions. Recurring maintenance is important because it can signal systemic or site-specific problems that are unlikely to resolve without targeted intervention, directly affecting both asset life-cycle costs and ongoing regulatory compliance. Results showed that a subset of the inventory, 45% of all assets, accounted for 80% of routine, 88% of corrective, and 85% of urgent issues. Routine tasks involve low-risk, scheduled upkeep, corrective tasks address moderate-risk conditions that impair function, and urgent tasks involve high-risk failures or safety hazards requiring immediate action. A smaller subset of the inventory with recurring corrective and urgent maintenance issues accounted for only 15% of the total inventory yet was responsible for 69% of all corrective issues and 72% of all urgent issues. Within this smaller group, 284 of the 385 assets (74%) had issues across three or more consecutive years, while the remaining 101 assets (26%) had issues in nonconsecutive years. Land-use setting, defined by the US Census as urban or rural, and environmental conditions, such as slope, influenced maintenance patterns in predictable ways, with erosion more common in high-slope basins and standing water more common in low-slope basins. Furthermore, low-slope and rural basins tended to exhibit a higher occurrence of blocked pipes and animal burrows. Across the inventory, the study found that many corrective maintenance tasks were related to environmental conditions, whereas many urgent tasks were not and appeared in more random patterns. By combining BMP maintenance classifications (routine, corrective, and urgent), recurrence tracking, and spatial risk factors, this study produced a general framework that enables agencies to prioritize chronic issues, target interventions, and strengthen long-term stormwater system resilience.
Bioretention filters (rain gardens) in urban environments that use plants are promoted as a type of green stormwater infrastructure. To better understand how these engineered controls interact with the environment, soil mesofauna extraction was performed on a variety of urban stormwater controls, including bioretention filters and other more traditional vegetated stormwater controls. Wooded areas were used as background comparisons. Soil metrics, including bulk density, loss on ignition (LOI), and soil penetrometer were performed for sampling locations and several ecological indices were calculated. Over a three-year period, 44 sites were sampled and binned into the following three groups: background (i.e., not urban stormwater controls) (10), bioretention filters (21), and other stormwater controls (13). The last grouping of other stormwater controls had statistically relevant subgroups of dry detention basins (6) and wetlands (4). The other stormwater controls group had both lower enumerations of soil fauna and lower diversity than background and bioretention filters. The lower enumerations and diversity indices of other stormwater controls was from observations in the subgroup of dry detention basins that was significantly less diverse than background, bioretention filters, and even the other subgroup of wetlands. Linear regressions of mesofauna sample enumerations and number of taxa to bulk density and LOI were poorly correlated (R-2<0.09). Penetrometer tests indicated bioretention filters had the least compaction while detention basins had the highest. The relatively larger abundance of soil mesofauna (i.e., total count) and number of taxa in bioretention filters versus dry detention basins is probably because of construction practices and water holding capacity since bioretention filters are highly infiltrative and not compacted while dry detention basins are not infiltrative and highly compacted.
Maintenance is needed to ensure stormwater control measure (SCM) functionality. However, cost data for SCM maintenance can lack detail and/or be limited. This study quantified the costs for bioretention cells, constructed stormwater wetlands, dry ponds, level spreader-filter strips, rainwater harvesting, sand filters, and wet ponds located in North Carolina that were routinely and proactively maintained by SCM maintenance contractors. Routine maintenance was defined as tasks that included litter and debris removal, vegetation management, side slope stabilization, and inspections. Proactive maintenance was defined as tasks that occur less frequently than routine maintenance, but are not intended to restore a SCM's functionality (e.g., forebay dredging). Twelve maintenance companies anonymously participated in the 2018 study, but not all contractors maintained each type of SCM. For each SCM type and survey participant, the data were normalized on an annual basis, using the average footprint maintained. Costs were inflated to 2025 dollars using consumer price index inflation rates. Except for sand filters, on average, SCMs were maintained monthly, and costs were differentiated into two levels of service with respect to mowing. Most, but not all, contractors mowed the immediate landscape in addition to the SCM footprint to reduce the impacts of unstable watersheds. In 2025, the inflated mean cost to routinely maintain SCMs with the additional mowing ranged from $4,640/ha/year (wet ponds) to $8,640/ha/year (above ground sand filters). Routine maintenance costs normalized on an annual basis and watershed area were estimated using typical watershed areas for SCMs in North Carolina. Basin-SCMs (e.g., constructed stormwater wetlands, dry ponds, wet ponds) had lower costs than nonbasin SCMs (e.g., bioretention cells, rainwater harvesting). Entities using these data to predict maintenance costs should exercise caution because site specific conditions (e.g., maintenance access, watershed stability) will influence costs. It is recommended these entities favor the more expensive estimates to account for the impacts of site specific conditions.
This study monitored four bioretention planters installed at Stevens Institute of Technology providing information on the hydrologic mitigation potential of planters and design considerations for future guidance. Monitoring during 18 months spanning 3 calendar years compared performance against several bioretention system design objectives, including fully captured events, peak flow reduction, and runoff retention. Hydraulic loading ratio and media porosity affected the fraction of captured events, with one-fifth of the events completely captured. The captured storms were less than 2.0 mm/m2 of drainage area 77% of the time. The planters halved the peak flow rate for 61% of observations. The entire media volume was wetted in almost half of the events but rarely fully saturated. A modified available water capacity calculation based on the difference between the field capacity and the lowest measured volumetric water content provided a useful estimate of the median retention per event. To use this estimator, it is proposed to estimate the modified available water capacity as the difference between the laboratory-measured field capacity and a laboratory-measured wilting point increased by a factor of safety to account for the practical issue that the planters never dried fully between rain events in the New Jersey temperate climate.
Current equations used to predict the capture efficiency of curb inlets in green stormwater infrastructure (GSI) are mostly based on design equations created by the Federal Highway Administration (HEC-22), as this is the standard in roadway drainage design. These equations were determined using experiments and models based on curb opening sizes traditionally found on highways, which are usually much larger than curb openings found in urban infrastructure. The problem this presents is that urban street curb openings, particularly leading to GSI systems, are specified to be oversized when designing with these equations. There is limited guidance on how a municipality should set its guidance for the construction of curb openings for GSI. The present work set out to measure the capture efficiency of typical curb opening combinations (i.e., opening size and shape) using a physical model. The experimental observations were compared to capture efficiencies calculated using existing design equations. Findings show that the existing design equations can overestimate the expected flow capture and also identify the range of curb opening designs in which the design equations may be accurate.
A growing number of urban surface waters are impaired for high temperatures due to the heat exchange that occurs between the warm urban land surface and stormwater runoff before it enters downstream waterbodies. Green stormwater infrastructure (GSI) has the potential to reduce runoff temperatures; however, it is unclear how specific treatment approaches, such as rock swales, or sequencing of GSI in series can most effectively mitigate temperature in stormwater runoff. The objective of this study is to capture the temperature dynamics of a GSI treatment train consisting of rock swales leading to bioretention that captures runoff from an elevated highway interchange in Milwaukee, WI. Temperature was observed continuously during 17 runoff events at nine locations, including the primary influent from overpass downspouts, rock swale effluent, bioretention media, and bioretention underdrain effluent. Results indicate that rather than mitigate temperature, rock swales warmed runoff to a greater degree than that of highway overpass decks. However, the sequencing of bioretention practices at the end of the GSI system resulted in temperature reductions of 0.9 degrees C-2.4 degrees C on average to levels below thresholds for downstream trout species. Overall, this study demonstrates the importance of effective sequencing of GSI practices for effective temperature mitigation, which is a leading water body impairment in many states in the United States.
As urbanization accelerates, stormwater management in cities has shifted from focusing strictly on water quantity to addressing water quality. Traditionally implemented systems, such as stormwater ponds, while offering effective solutions, often require large land areas to implement, making them impractical for dense urban environments. Underground stormwater systems, like EcoVault, offer a more compact solution; however, they lack scientific studies under real-world conditions to prove their effectiveness in treating pollutants. This study evaluates the treatment performance of two parallel EcoVault systems with the same design, consisting of a sedimentation step and a filtration step. These facilities were retrofitted into two different stormwater sewer networks draining two urban catchments. The systems were assessed for their ability to treat total suspended solids, metals, nutrients, and organic pollutants from urban runoff. Over 15 rain events, the average total suspended solids (TSS) removal rate was 40% for EcoVault A and 46% for EcoVault B. The removal rates for metals varied, with EcoVault B showing better performance for average metal treatment (53% for Cu and 58% for Zn). However, neither EcoVault system removed dissolved metals, often with an increase of dissolved metal concentration in the effluent. The filtration step did not contribute to pollutant treatment, likely due to clogging and high hydraulic loading rates. The study highlighted the potential of underground stormwater treatment in areas with limited space availability, while identifying challenges such as treatment of dissolved pollutants.
Best management practices (BMPs) are designed to manage stormwater and reduce pollution, but their effectiveness and compliance with regulatory requirements depend on consistent maintenance. Despite their importance, there is limited research on how stormwater practitioners allocate resources and navigate operational challenges to maintain BMPs under regulatory and budgetary constraints. To address this knowledge gap, this study conducted an open-ended survey of stormwater professionals across eight districts of the Virginia Department of Transportation (VDOT). Paired with a review of 17,874 BMP inspection records from 2020 to 2024, the survey data provided insights into how reported maintenance issues from surveys align with inspection-based observations of BMP conditions, how resource constraints shape maintenance priorities, and which strategies may improve long-term maintenance outcomes. Thematic comparisons between survey responses and inspection data revealed strong alignment for sediment and vegetation concerns but underreporting of erosion and structural issues in narrative responses. The findings also show how resource limitations, such as insufficient staffing, lack of flexible funding mechanisms, and administrative burden, lead districts to make trade-offs when addressing corrective and urgent maintenance tasks. Districts employed a variety of strategies to mitigate these constraints, including severity-based repair prioritization and creative use of roadside or compliance-linked funding. The study further highlights how institutional structures, such as the presence of a dedicated stormwater manager or the design of contractor agreements, significantly influence maintenance outcomes. Enhancements to VDOT's geospatial BMP database are proposed as a way to centralize the system to streamline task bundling, prioritize repairs, and enhance cross-district coordination. By analyzing district-level adaptations, this study highlights practical approaches for maintaining stormwater BMPs despite limited resources.
Traditional trash capture devices that can be installed in upstream locations such as storm drains or curb inlets are of limited use in highway environments due to potential flooding, hydroplaning, safety, and maintenance-personnel exposure issues. There is a need for a trash capture system that can be retrofitted easily into existing highway drainage infrastructure or included in newer projects. To address this issue proactively, the California Department of Transportation (Caltrans) Division of Environmental Analysis (DEA) initiated a trash capture device development and testing project in early 2020. The DEA Stormwater staff developed the initial idea for a capture housing device. Computational fluid dynamics modeling was used first to assess the feasibility and performance. Next, the hydraulic capacity, trash capture characteristics, operation, and ease of maintenance were tested using a full-scale physical model. After successful testing, standard plans and design guidance were developed. The full-scale model physical test demonstrated the following: (1) the device can pass the 1-year, 1-h storm intensity specified in the regulations without overflowing or causing roadway flooding; (2) the device can pass the 25-year 5-min-duration return period storm drain system design storm event without causing roadway flooding; (3) the device will trap trash sizes of 5 mm or larger for the 1 year, 1-h storm intensity specified in the regulations; and (4) the device has the storage capacity for the quantity of trash generated from a typical 0.405 ha (1-acre) highway drainage area.
