Stormwater Pollution Research Articles

Analyzing Research Trends in Deep-Tunnel Systems and Evaluation of Stormwater Pollutant Removal for Urban Runoff Management

Deep-tunnel systems are increasingly being recognized as an infrastructure solution for mitigating combined sewer overflows (CSOs) and managing urban stormwater, as evidenced by growing research interest. This study employed a bibliometric analysis method using Scopus to evaluate global research trends in deep-tunnel systems. This method revealed that while early studies primarily focused on flood mitigation, recent research has shifted toward exploring water quality improvements. An initial comprehensive review using keywords from the bibliometric analysis was conducted, highlighting the limited data relating deep-tunnel systems to water quality and underscoring a gap in the literature. A subsequent comprehensive review focusing on urban stormwater runoff was conducted to bridge the knowledge gap between flood mitigation and water quality enhancement in urban stormwater management. The analysis indicated that mixed urban areas showed the highest range of TSS concentrations, with a mean of 238.3 mg/L, while urban roads exhibited the highest mean TN and TP concentrations at 93.6 mg/L and 0.49 mg/L, respectively. For deep-tunnel systems, a design approach that considers the characteristics of pollutants in incoming stormwater and their reduction mechanisms is essential. This study’s findings provide foundational data for the development of deep-tunnel systems with integrated water treatment functions. Such systems could enhance urban resilience by addressing both flood risk and water quality challenges in rapidly urbanizing areas.

The Correlation Between Water Sensitive Urban Design and Urban Climate: a Bibliometric Analysis

The rapid population growth in the past two centuries has caused a significant rise in urbanisation, leading to various environmental impacts. To address these negative consequences, the adoption of new technologies is crucial. One such approach is Water Sensitive Urban Design (WSUD), which shows potential in mitigating the Urban Heat Island effect, climate change, and extreme heat, as well as reducing stormwater pollution. Therefore, this research comprehensively examines the correlation between the WSUD and the urban climate by conducting a bibliometric analysis. This study expanded all research from 2014 to 2023 by utilising the similar visualisation software (Vosviewer). A total of 38 publications were analysed as documented in the Scopus database in January 2024, identifying the most compelling subjects covered by the journal. The results indicate a substantial dearth of literature regarding the relationship between water-sensitive urban design (WSUD), low-impact development (LID), sustainable urban drainage (SUD), thermal comfort, cooling, urban heat island (UHI), and urban climate. This highlights the emergence of a potential research topic. The study offers a roadmap for future researchers, focussing on key areas where fruitful investigation is feasible.

Integrating Wetlands as Nature-Based Solutions for Sustainable Built Environments

Wetlands are ecosystems that can provide numerous services critical for sustainable development, especially in urban areas, by ensuring environmental stability. The wetlands receive increasing recognition as Nature-Based Solutions (NBSs) to environmental challenges. This review synthesizes the numerous roles of wetlands as NBSs for promoting sustainability in both rural and urban environments and highlights the potential contributions of multiple wetland services and benefits towards sustainable built environments. The review methodology involved an article search from various databases with the utilization of specific keywords in an organized framework to understand the contribution of wetlands as NBSs. The articles were reviewed to provide a comprehensive analysis of the existing research on the associated topics, focusing on specific sub titles and pre-selected themes. The findings of this review identify various parameters through which wetlands contribute to sustainable built environments, including ecological resilience, storm water management, climate adaptation, biodiversity enhancement, recreational opportunities, pollution control, and cultural values. The review also encompasses case studies of different types of wetland features such as riparian buffer zones, retention ponds, reed beds, bio swales, rain gardens, constructed wetlands, etc. in the urban environment and their contribution as NBSs. These contributions are discussed in terms of integration in urban development planning in different segments. Future work recommendations consist of a holistic integration of wetlands into urban planning and design considerations to promote more resilient, healthy, and sustainable built environments for present and future generations.

Research on the Reusability of Bentonite Waste Materials for Residual Chlorine Removal.

Recyclable construction waste can be used as a low-cost material to reduce stormwater pollution caused by various pollutants. In recent years, studies have reported increased water contamination from chlorine and chlorine compounds and its negative impact on aquatic ecosystems. When assessing the need for waste recycling, circularity, and stormwater reuse, it is worth evaluating the capacities of construction waste materials to reduce stormwater pollution from residual chlorine. Laboratory experiments using bentonite waste material (bentonite clay) and sodium hypochlorite solutions were carried out to analyze the potential of bentonite clay to retain residual chlorine in stormwater and evaluate its capacity to be applied as filtration media in green infrastructure. In the first stage, the particle size distribution and texture of bentonite clay were assessed using laboratory sieve analysis and microscopy. The results of the experiments indicated that the optimal grain size to retain pollutants was 0.8-2.0 mm. The microstructure analysis showed the capacity of bentonite to retain residual chlorine. The results of the static and dynamic experiments (leaching and filtration tests) show that the bentonite clay retained up to 44% of the residual chlorine. The obtained results indicate that bentonite clay might be suitable for application as filtration media in green infrastructure to reduce stormwater contamination.

Evaluation of stormwater runoff pollutant distributions combined with land-use information in a regional karst aquifer in Texas, USA.

Fast urbanization can result in significant stormwater runoff pollution due to changes in land use. A 3-year study on the distribution and temporal variations of urban water pollutants in stormwater runoff was conducted, with a specific focus on the influence of land-use patterns in the recharge zone of a regional karst aquifer in Texas (Edwards Aquifer). The presence and concentration of various water pollutants including total suspended solids (TSS), total dissolved solids (TDS), nutrients (nitrite, nitrate, ammonia and phosphate), total carbon (TC) and total organic carbon (TOC), oil and grease (O&G), and eight heavy metals (Fe, Mg, Cu, Pb, Zn, Ni, Cr, Cd) were measured in stormwater samples collected from three bioswales. Results show that average TSS in site S1 (598.87mg/L) and S2 (628.69mg/L), COD in site S1 (103.97mg/L), phosphate in sites S1 (1.44mg/L) and S3 (0.65mg/L), and O&G (ranging from 50.63 to 84.32mg/L) in all three sites surpassed the national average (NSQD). While residential areas were identified as the main sources of nutrients, roads and parking lots were associated with heavy metals. Temporal variations indicated the effect of antecedent dry days on the concentrations of TSS and phosphate. Growing seasons as well as pet feces were associated with elevated nitrate concentrations in residential areas. Organic carbon was found overall higher during warmer months, while heavy metals during cooler months. The study also identified specific land-use practices that can be enhanced to mitigate stormwater pollution, such as the implementation of permeable pavements, rain gardens, and stricter waste disposal regulations. The results of this study offer valuable insights for enhancing stormwater management strategies to better mitigate stormwater pollution in urban regions.

Perencanaan Green Infrastructure pada Kawasan Transit Oriented Development (TOD) Lebak Bulus, Jakarta Selatan

Transit Oriented Development (TOD) approach is one of the solutions adapted by DKI Jakarta’s Government in order to create a walkable and mass transportation friendly environment in Jakarta. Lebak Bulus TOD in its development will use environmental sustainability approach in order to reduce negative impact from urban development. However, Lebak Bulus TOD is currently lacked of green open space and dominated with impermeable surface that affect the increase of the stormwater runoff. Implementing green infrastructure concept in planning Lebak Bulus TOD site is one of the solution to overcome the problems. This research is aimed to reduce stormwater runoff and pollution in Pasar Jumat Street, Lebak Bulus Raya Street, and RA Kartini Street located in Lebak Bulus TOD. The methods used in this research are descriptive, quantitative analysis, and spatial analysis. Quantitative analysis is used to calculate water quality volume for each location, the results for each location respectively are 832,56 m3, 205,44 m3, dan 205,7 m3. Green infrastructure system used are stormwater tree trench, stormwater planter, green gutter, permeable pavement, and green wall. 285,95 m3 of stormwater runoff can be reduced by the implementation of green infrastructure. Spatial analysis using CITYGreen shows that the planning can reduce pollution by 48,83 kg/year with economic value of $263,49 (Rp3.751.834,11) and reduce runoff volume by 51% with economic value of $2.408,67 (Rp34.348.838).

The Impact of Green Infrastructure on the Quality of Stormwater and Environmental Risk

Increasing urbanization and the associated sealing of areas and the use of storm sewer systems for drainage not only increase the risk of flooding but also reduce water quality in streams into which stormwater is discharged. Green infrastructure (GI) measures are applied with the aim of managing this stormwater sustainably and reducing the associated risks. To this end, a quantitative–qualitative approach was developed to simulate GI—namely, rain gardens, bioretention cells, and vegetative bioswales—at the urban catchment scale. The findings highlight the potential of applying GI measures to managing stormwater more effectively in urban environments and mitigating its negative pollution-related impacts. For the housing estate analyzed, a simulated implementation of GI resulted in a reduction in pollution, measured as total nitrogen (N; 9–52%), nitrate-N (5–30%), total phosphorus (11–59%), chemical oxygen demand (8–46%), total suspended solids (13–73%), copper (12–64%), zinc (Zn; 16–87%), polycyclic aromatic hydrocarbons (16–91%), and the hydrocarbon oil index (HOI; 15–85%). Reducing the concentrations of pollutants minimizes the risk to human health determined via the HOI from a low-risk level to zero risk and reduces the ecological risk in terms of Zn pollution from a significant risk to a low risk of adverse effects. The modeling conducted clearly shows that the GI solutions implemented facilitated a quantitative reduction and a qualitative improvement in stormwater, which is crucial from an environmental perspective and ensures a sustainable approach to stormwater management. Lowering the levels of stormwater pollution through the implementation of GI will consequently lower the environmental burden of pollutants in urban areas.

Impacts of climate change on urban stormwater runoff quantity and quality in a cold region

Climate change poses significant challenges to urban environments affecting both flood risks and stormwater pollutant loadings. However, studies on variations in stormwater runoff quantity and quality in cold regions, which are highly sensitive to climate change, are notably limited. Integrating climatic, hydrologic, and hydraulic modelling, the study assesses the potential impacts of climate change on stormwater runoff volume and pollutant dynamics in a Canadian urban watershed (Calgary). A two-year field program was conducted to support the calibration and validation of the Storm Water Management Model (SWMM). Intensity–duration–frequency curves were employed to evaluate the impacts of climate change on peak flow rate and flooding duration. In addition, typical dry, average, and wet years were applied to continuously simulate stormwater runoff quantity and quality during the 2050s and 2080s. The results suggest substantial increases in peak flow rates and flooding durations, particularly for the 5-year return period rainfall, with 1-h, 4-h, and 24-h peak inflow rates increasing by 74.3% (170.7%), 89.2% (158.4%), and 64.1% (102.8%) in the 2050s (2080s) Furthermore, the runoff quantity is projected to rise by 2.4–10.2% in the 2050s and 11.8–17.5% in the 2080s. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) loadings are anticipated to increase by 2.0–36.1%, 3.1–21.4%, and 4.1–20.7%, respectively. As a result, the current stormwater system could overload and stormwater quality is likely to deteriorate under the impact of climate change. The findings are beneficial for cold regions to develop adaptive strategies that enhance urban water security and environmental sustainability under climate change.

Stormwater Management in Urban Coastal Areas—A Review

Stormwater management in coastal urban cities, where drainage networks are influenced by marine dynamics and specific soil and altimetry conditions, has specific challenges that need to be addressed to ensure adequate management in such areas, which are also heavily affected by floods. Their location downstream of drainage basins and the interaction of network outfalls with current and tidal variability increases the vulnerability of populations and should therefore be the target of specific studies. This article presents a literature review, where publications that focus on stormwater management in coastal urban areas were identified and analyzed. The main objective was to present the key issues related to drainage in coastal areas, the most relevant challenges, the solutions and strategies that reveal the greater potential for application and the challenges for modeling this type of case. It is intended to provide a grounded basis for new ways of optimizing stormwater drainage in coastal areas and promote a sustainable urban water cycle. This review reveals the necessity to implement a multidisciplinary approach to minimize three main issues: urban flooding, stormwater pollution and groundwater salinization, including the adaptation of existing infrastructures, complementing them with control solutions at source, correct urban planning and the involvement of populations. For an effective management of urban stormwater drainage in coastal areas, this approach must be carried out on a watershed scale, duly supported by reliable decision support tools and monitoring systems.

Migration of naphthalene in a biochar-amended bioretention facility based on HYDRUS-1D analysis

Biochar has been proved as a promising and efficient filler in bioretention facilities for enhancing the stormwater pollutants removal. However, the migration behaviors of stormwater pollutants in biochar filled bioretention facilities is unclear. In this study, as one of the most typical stormwater pollutants, naphthalene was selected as an example and a HYDRUS-1D model was first used to understand the migration behavior of naphthalene in a bioretention facility. In comparison with the conventional bioretention soil media (sandy loam), the amended biochar filled bioretention cell showed that the naphthalene removal rate was enhanced by up to 10.1%. Meanwhile, the experimental data was well-fitted by the “two-site sorption model” in HYDRUS-1D model. Another, the effect of rainfall intensity on the naphthalene migration in both bioretention columns was further investigated. The HYDRUS-1D model fitting indicated that the increase in rainfall intensity promoted naphthalene migration by increasing hydraulic conductivity and water flux. In addition, static batch experiments revealed that the biochar filled fillers achieved about 50% higher adsorption capacity than sandy loam. The sensitivity analysis from the HYDRUS-1D model data verified adsorption coefficient Kd and longitudinal dispersivity λ are the main factors affecting naphthalene migration. Finally, the model simulation displays that the proportion of naphthalene retained by the fillers was highest during high rainfall intensities, indicating that the fillers remain the most important fate for naphthalene. This study presents research on the behavior and mechanisms of stormwater pollutant transport through improved bioretention facilities.

Analyses of Bioretention Systems for Removal of Stormwater Pollutants

Analyses of Bioretention Systems for Removal of Stormwater Pollutants

Effective Storm Water Management in The Urban Area – A Case Study

Urbanization and climate change have negative effects on the changes of natural precipitation and runoff regime, which results with more frequent floods and landslides. Besides of the increased quantity of the stormwater that drainage channels have to collect, neg- ative consequences of urbanization are also evident through increased pollution of runoff stormwater. Stormwater has immense impacts on urban flooding and water quality, leaving the marginalized and the impoverished disproportionately impacted by and vulnerable to stormwater hazards. However, the environmental health concerns of socially and econom- ically marginalized individuals are largely underestimated. Therefore stormwater manage- ment should be adapted to these changes so that the negative effects of new hydrological conditions of precipitation and runoff and stormwater pollution in the urban areas are mitigated. By 2050 the world population will grow to about 9 billion contributing to deep changes in urban areas structure. This would increase the effect of water deficiency and along with projected climate changes the impact of urban flooding, urban heat islands or drought. Stormwater threats can be mitigated with the application of stormwater management meth- ods named differently such as ‘Sustainable (Urban) Drainage Systems’ (SUDS), ‘Low Impact Development’ (LID) or ‘Best Management Practices’ (BMPs). This method includes differ- ent techniques such as Green roof, Rain barrels and cisterns, Infiltration basin, Detention Ponds, Retention Ponds, Green walls, Porous pavements, Bioretention basins, Bioswales. The aim of the research includes a study of the effectiveness of urban stormwater manage- ment techniques for the case study area. The concept of urban stormwater management techniques refers to the ability to provide and manage this primary resource in quantitative and qualitative terms in order to satisfy the future needs of population. The storm wa- ter management techniques provides several benefits: mitigation of the urban heat island effects, reduction of air pollution, additionally, It induces important hydraulic advantages acting as an effective tool for reducing flood risk in urban area with runoff reduction, attenuation and delay of the peak flow. The results confirm that bioretention basin, Permeable pavement, Grassed swale, Infiltration basin are effective techniques for the reduction of total runoff volume of rainwater falling on their area.

Temporal and spatial distribution of microplastics in green infrastructures: Rain gardens

Rain gardens, a type of green infrastructure (GI), have been recognized for mitigating flooding and improving water quality from minor storms by trapping stormwater pollutants. Yet, the capability of these systems to retain microplastics (MPs) from stormwater, especially in size <125 μm, remains inadequately understood. This study investigated the spatial and temporal distributions of MPs in three rain gardens located in Newark, New Jersey, USA. The rain gardens have been in operation for ∼7 years and located in different land uses: low-density residential (Site 1), commercial (Site 2), and high-density residential (Site 3). The sediment samples were collected during May 2022, August 2022, and February 2023 at various soil depths and horizontal distances of rain gardens. The MPs were quantified and characterized using Fourier transform infrared (FTIR) spectrometer and a Raman microscope. The overall mean concentration varied between sampling sites, with 469 ± 89.8 pkg−1 in Site 1, 604 ± 91.4 pkg−1 in Site 2, and 997 ± 64.3 pkg−1 in Site 3, with Polypropylene as the dominant polymer, followed by nylon and polyethylene. In the vertical direction, larger MPs (250 μm–5 mm) were effectively retained within the top 5 cm and their concentration declined exponentially with the increasing depths. Small-sized MPs (1–250 μm) were prevalent at deeper depths (≥ 10 cm), and no MPs were found below 15 cm. In the horizontal direction, the highest MP concentration was observed near the stormwater inlet, and the concentration decreased away from the inlet. Over the nine-month period, a notable increase in concentration was observed at all sites. These findings contribute valuable knowledge towards developing effective measures for retaining MPs from stormwater and monitoring GIs in urban environments.

Bark and biochar in horizontal flow filters effectively remove microplastics from stormwater

Organic materials such as bark and biochar can be effective filter materials to treat stormwater. However, the efficiency of such filters in retaining microplastics (MPs) – an emerging stormwater pollutant – has not been sufficiently studied. This study investigated the removal and transport of a mixture of MPs commonly associated with stormwater. Different MP types (polyamide, polyethylene, polypropylene, and polystyrene) were mixed into the initial 2 cm material of horizontal bark and biochar filters of 25, 50, and 100 cm lengths. The MP types consisted of spherical and fragmented shapes in size ranges of 25–900 μm. The filters were subjected to a water flow of 5 mL/min for one week, and the total effluents were analyzed for MPs by μFTIR imaging. To gain a deeper insight, one 100 cm bark filter replica was split into 10 cm segments, and MPs in each segment were extracted and counted. The results showed that MPs were retained effectively, >97%, in all biochar and bark filters. However, MPs were detected in all effluents regardless of filter length. Effluent concentrations of 5–750 MP/L and 35–355 MP/L were measured in bark and biochar effluents, respectively, with >91% of the MP counts consisting of small-sized (25 μm) polyamide spherical particles. Combining all data, a decrease in average MP concentration was noticed with longer filters, likely attributed to channeling in a 25 and 50-cm filter. The analyses of MPs in the bark media revealed that most MPs were retained in the 0–10 cm segment but that some MPs were transported further, with 19% of polyamide retained in the 80–90 cm segment. Overall, this study shows promising results for bark and biochar filters to retain MPs, while highlighting the importance of systematic packing of filters to reduce MP emissions to the environment from polluted stormwater.

Embracing epistemic uncertainty: a risk evaluation method for pollutants in stormwater.

In this study, we show that pollutants of emerging concern are, by nature, prone to the emergence of epistemic uncertainty. We also show that the current uncertainty quantification methods used for pollutant modelling rely almost exclusively on parameter uncertainty, which is not adequate to tackle epistemic uncertainty affecting the model structure. We, therefore, suggest a paradigm shift in the current pollutant modelling approaches by adding a term explicitly accounting for epistemic uncertainties. In a proof-of-concept, we use this approach to investigate the impact of epistemic uncertainty in the fluctuation of pollutants during wet-weather discharge (input information) on the distribution of mass of pollutants (output distributions). We found that the range of variability negatively impacts the tail of output distributions. The fluctuation time, associated with high covariance between discharge and concentration, is a major driver for the output distributions. Adapting to different levels of epistemic uncertainty, our approach helps to identify critical unknown information in the fluctuation of pollutant concentration. Such information can be used in a risk management context and to design smart monitoring campaigns.

Removal of Residual Chlorine from Stormwater Using Low-Cost Adsorbents and Phytoremediation

In recent decades, the pollution of water with micropollutants has become an increasing environmental concern. Since 2019, increased stormwater pollution from chlorine-based disinfectants has been recorded due to the COVID-19 pandemic. Runoff from disinfected areas and the residual chlorine present in stormwater are transported to surface water bodies, posing a risk to aquatic flora and fauna. The objectives of this study were (1) to evaluate the efficiency of different low-cost and recyclable filter materials in removing residual chlorine, and (2) to test plants’ ability to reduce residual chlorine concentrations through phytoremediation. Experiments were conducted in the laboratory (column and batch) and in the field (raised garden bed) to assess the efficiency of various filter materials (peat, wood chips, sawdust and the lightweight aggregates) in retaining residual chlorine to be implemented in green infrastructure. The best retainers of chlorine were sawdust (96%) and the LWA Leca (76%). No harmful effects of residual chlorine (changes in growth, color, leaf size, etc.) on plants (Tagetes patula or Pisum savitum) were observed and the residual chlorine in the leachate samples was below the equipment’s detection limit. Our research results will contribute to future studies aiming to remove various micropollutants from stormwater using remediation technologies.

Repurposing spent biomass of vetiver grass used for stormwater treatment to generate biochar and ethanol

Stormwater pollution is a key factor contributing to water quality degradation, posing substantial environmental and human health risks. Although stormwater retention ponds, also referred to as wet ponds, are commonly implemented to alleviate stormwater challenges by reducing peak flow and removing suspended solids, their effectiveness in removing heavy metals and nutrients is limited. This study evaluated the performance of floating treatment platforms (FTPs) featuring vetiver grass (Chrysopogon zizanioides), a non-invasive, nutrient- and metal-accumulating perennial grass, in removing heavy metals (Cu, Pb, and Zn) and nutrients (P and N) in stormwater retention ponds. Furthermore, the potential for utilizing the spent vetiver biomass for generating biochar and bioethanol was investigated. The study was conducted in a greenhouse setup under simulated wet and dry weather conditions using pond water collected from a retention pond in Stafford Township, New Jersey, USA. Two FTPs with vetiver (vegetated FTPs) were compared with two FTPs without vetiver (non-vegetated FTPs), which served as controls. Results showed that the removal of heavy metals and nutrients by the FTPs with vetiver was significantly higher (p < 0.05) than the FTPs without vetiver. Notably, vetiver showed resilience to stormwater pollutants and hydroponic conditions, displaying no visible stress symptoms. The biochar and bioethanol generated from the spent vetiver exhibited desirable yield and quality, without raising concerns regarding pollutant leaching, indicated by very low TCLP and SPLP concentrations. This study provides compelling evidence that the implementation of vetiver-based FTPs offers a cost-effective and environment-friendly solution for mitigating stormwater pollution in retention ponds. Furthermore, the utilization of vetiver biomass for biofuel and biochar production supports clean production and fostering circular economy efforts.

Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.

Modeling the impact of future rainfall changes on the effectiveness of urban stormwater control measures

The convergence of urban expansion, deteriorating infrastructure, and a changing climate will escalate the risks of stormwater pollution and urban flooding in the coming decades. Using outputs from an ensemble of global climate models to drive a high spatial resolution stormwater model, we analyzed climate change impacts on urban stormwater runoff and control measures for 23 cities across the United States. Runoff model outputs for two future emissions scenarios ending in 2055 were compared against a historical scenario to assess changes. All cities showed increases in average annual stormwater runoff, with changes up to 30% over the next 30 years due to a greater frequency of high intensity storm events. Runoff model outputs showed substantial variation across cities with untreated stormwater runoff increasing by as much as 48%. Patterns of future runoff impacts within cities will affect the performance of distributed treatment strategies such as Green Stormwater Infrastructure (GSI) to meet municipal water quality improvement and runoff reduction goals. Results indicate that adoption of adaptable design standards and decision support tools that readily accommodate projected precipitation changes are critical for supporting more resilient designs of stormwater control measures.

Enterococci pathways to coastal waters and implications of sea level rise

Highly urban coastal communities in low lying areas and with high water tables are vulnerable to sea-level rise and to corresponding increases in coastal groundwater levels. Stormwater conveyance systems are under increased risk. Rising groundwater levels affect the hydraulics of the stormwater system thereby increasing contaminant transport, for example the fecal indicator bacteria enterococci, to coastal waters. This study offers a unique opportunity to evaluate the impacts of increased contaminant transport on marine coastal environments. Here we assessed historic and recent coastal water quality, stormwater sampling data, groundwater monitoring and tidal elevations near the coastline, in the context of altered hydraulics within the system. Two pathways of enterococci to marine waters were identified. Direct discharge of contaminated stormwater runoff via the stormwater outfalls and tidally driven contaminated groundwater discharge. As sea level continues to rise, we hypothesize that a diminished unsaturated zone coupled with altered hydraulic conditions at the coastal groundwater zone will facilitate the transport of enterococci from urban sediments to the study site (Park View Waterway in Miami Beach, FL USA). We recommend improvements to the stormwater conveyance system, and maintenance of the sanitary sewer system to mitigate these impacts and minimize transport of enterococci, and other stormwater pollutants to coastal waters. The results of this study can be useful to interpret high enterococci levels in low lying coastal areas where groundwater is influenced by rising sea water levels.