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Urban stormwater is contaminated by a wide range of substances whose concentrations vary greatly between locations, as well as between and during rain events. This literature review evaluates advantages and limitations of current methods for using continuous water quality monitoring for stormwater characterization and control. High-temporal-resolution measurements have been used to improve the understanding of stormwater quality dynamics and pollutant pathways, facilitate the performance evaluation of stormwater control measures and improve operation of the urban drainage system with real-time control. However, most sensors used to study stormwater were developed for either centralized water treatment or natural water contexts and adaptation is necessary. At present, the primary application of interest in stormwater – characterization of pollutant concentrations – can only be achieved through the use of indirect measurements with site-specific relationships of pollutants to basic physical-chemical parameters. In addition, various problems arise in the field context, associated with intermittent or variable flow rates, the accumulation of debris and sediment, adverse conditions for electrical equipment and human factors. Obtaining reliable continuous stormwater quality data requires the adoption of best practices, including the calibration and regular maintenance of sensors, verification of data and accounting for the considerable uncertainties in data; however, the literature review showed that improvement is needed among the scientific community in implementing and documenting these practices., Validerad;2024;Nivå 2;2024-03-27 (hanlid);Full text license: CC BY 4.0

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's concentration. Such information can be used in a risk management context and to design smart monitoring campaigns., Validerad;2024;Nivå 2;2024-08-15 (hanlid);Full text license: CC BY 4.0

Due to large spatial and temporal variations of soil properties that govern swale infiltration capacities, traditional methods for estimating saturated hydraulic conductivity (ksat) values could potentially lead to erroneous estimation of the total system infiltration capacity. To increase the knowledge of grassed swale infiltration performance and the relationship between hydraulic properties related to the spatial variation within the swale, two methods were applied to estimate ksat values: 1) point measurements using the Modified Philip Dunne (MPD) Infiltrometer, and 2) a full-scale infiltration test (FSIT). A large variation in calculated ksat values was found, ranging from 22 to 1382 mm/hr, with lower/higher values at the swale bottom, and right swale slope respectively. Infiltration point measurements, with a geometric mean of 81 mm/hr, showed higher infiltration rates than those obtained from FSIT, which yielded 34 and 22 mm/hr (for test 1 and 2 respectively). Moreover, FSIT results showed an agreement with ksat values obtained from MPD infiltrometer at the swale bottom. In addition, infiltration rates are significantly reduced as the groundwater mound gets closer to the bottom of the grassed swale., En raison des grandes variations spatiales et temporelles des propriétés du sol qui régissent les capacités d'infiltration des noues, les méthodes traditionnelles d'estimation des valeurs de conductivité hydraulique saturée (ksat) pourraient potentiellement conduire à une estimation erronée de la capacité d'infiltration totale du système. Afin d'accroître la connaissance des capacités d'infiltration des noues enherbées et de la relation entre les propriétés hydrauliques liées aux classes de texture du sol, deux méthodes ont été appliquées pour estimer les valeurs de ksat : 1) des mesures ponctuelles à l'aide de l'infiltromètre Philip Dunne modifié (MPD), et 2) un test d’infiltration à pleine échelle (FSIT). Une grande variation dans les valeurs calculées de ksat a été trouvée, allant de 22 à 1382 mm/h, avec des valeurs inférieures/élevées au fond de la noue et à droite de la pente de la noue respectivement. Les mesures des points d'infiltration, avec une moyenne géométrique de 81 mm/h, ont montré des taux d'infiltration plus élevés que ceux obtenus à partir du FSIT, avec 34 et 22 mm/h (pour les tests 1 et 2 respectivement). De plus, les résultats du FSIT ont montré un accord avec les valeurs de ksat obtenues au fond de la noue. De plus, les taux d'infiltration diminuent considérablement à mesure que le niveau de la nappe phréatique se rapproche du fond de la noue enherbée.

Current gully pot maintenance strategies lack a robust evidence base and clear aims against which performance can be benchmarked. To facilitate discussions, questions on their long-term in-situ performance in trapping sediments and associated contaminants - and how they are impacted by various factors - require robust interrogation. As a contribution, this paper presents sediments data from 27 gully pots located at sites with various street layouts (roundabout; straight road; road crossing) and traffic intensities (<1000-23666 vehicles/day), over two accumulation periods: winter-spring and summer-autumn 2020-2021. On an annual basis, gully pots retained 0.54–44.2 (median: 10.95) kg (dry mass) over 151–189 days, corresponding to a solids accumulation rate of 2.5–1140.6 (median: 69.4) g/m2/year. Of the 27 gully pots, 18 gully pots showed significant seasonal variations in solids accumulation rates though the dominant season was not consistent. For example, roundabouts exhibited a significantly higher solids accumulation rate over the summer-autumn period in comparison to road crossing and straight road gully pots where accumulation was typically higher in the winter-spring season. Further, in contrast to the latter street layouts, a significant negative correlation between traffic intensity and solids accumulation rate was identified at roundabout gully pots, with the turning action of vehicles generating higher levels of sediment resuspension suggested as a possible contributing factor., Les stratégies actuelles d'entretien des avaloirs ne disposent pas de données robustes ni d'objectifs clairs permettant d'évaluer leurs performances. Pour faciliter les discussions, leurs capacités in situ àpiéger les sédiments sur le long terme en fonction de divers facteurs nécessitent un examen approfondi. Cet article présente des données sur les sédiments de 27 avaloirs situés dans différentes configurations de chaussée (giratoire, route droite, croisement) avec différentes intensités de trafic (<1000-23666 véhicules/jour), sur deux périodes d'accumulation : I’hiver-printemps et I’été-automne 2020-2021. Sur une base annuelle, les avaloirs ont retenu 0,54-44,2 (médiane : 10,95) kg (masse sèche) sur 151-189 jours soit un taux d'accumulation de solides de 2,5-1140,6 (médiane : 69,4) g/m2/an. 18 des avaloirs ont montré des variations saisonnières significatives de taux d'accumulation de solides, bien que la saison dominante ne soit pas constante. Par exemple, les ronds-points présentaient un taux d'accumulation de solides significativement plus élevé pendant l’été-automne, en comparaison avec les avaloirs des croisements de routes et des routes droites où l'accumulation était typiquement plus élevée pendant l’hiver-printemps. De plus, une corrélation négative significative entre l'intensité du trafic et le taux d'accumulation des solides a été identifiée dans les avaloirs situés à des giratoires. Une des explications envisagées est qu’en tournant, les véhicules remettent davantage en suspension les sédiments.

Stormwater management in urban areas requires continuous water quality data of high-temporal resolution to better understand and control pollutant loads and dynamics. However, the difficult analytical context of stormwater may lead to significant uncertainties and/or biases in data produced by online water quality sensors. In order to provide insights into the alignment of continuous data with discreet data collected through conventional sampling and analysis, 25 grab samples were collected and analysed for pH, conductivity and turbidity in parallel with the continuous monitoring using sensors installed in a gully receiving road runoff. Analysis has shown that while differences in laboratory and field-measured pH could be explained by instrumental uncertainty alone, there were significant differences in conductivity and turbidity, meaning the presence of additional errors. This study highlights the need for further investigation of data-quality-related matters in the stormwater field.

Dimensioning green infrastructure (GI) to achieve different stormwater targets (e.g., runoff volume reductions) is essential at city scale under conditions of limited resources and space. Traditional GI sizing criteria are based on the hydrology of moderate climates. However, cold climate conditions represent an additional challenge for GI design. This paper presents an assessment of the bioretention cell (BC) area required to achieve a given runoff volume reduction (RVR), accounting for seasonal variations in infiltration rates in the Swedish cities of Gothenburg, Orebro, and Kiruna. Clear seasonal differences were found in Kiruna for the areas required to achieve 80% of RVR under winter and summer conditions. However, non-significant seasonal differences were found in Orebro and Gothenburg. For an efficient BC adoption, sizing needs to be completed in the context of the precipitation for the entire year, including the effect of snowmelt, rain-on-snow, and frozen soils.

In subarctic regions, a significant part of annual precipitation occurs as snow. This creates challenges since (a) the occurrence of rain on snow during melting season might increase runoff peak flow and cause flooding in urban areas and (b) snow needs to be removed from roofs and streets. Current snow management practice includes removal of snow to large deposits outside of cities. Downsides of this approach are the carbon footprint and air pollution caused by transport and the release of untreated polluted melt water to nearby water bodies. One strategy to reduce transport and increase treatment of meltwater could be to integrate snow deposits with existing green infrastructure that manages stormwater within the urban environment, i.e. multifunctional areas. When studying the potential performance of multifunctional areas with respect to snow management it is important to consider the flood risk that comes with increased snowmelt and rain on snow. Prior studies have evaluated the combined effect of frozen soils, snowmelt and rainfall during the melting season on runoff from urban catchments, but there are no similar studies on facility scale. Hydrological models can be used to investigate these factors and the snow deposit potential, without risking flooding. It is, however, unclear to what extent current urban hydrological models are suited to this purpose. This study aims to explore how hydrological models can be used to predict snow deposition volumes in multifunctional areas and the effect on runoff. This study used EPA SWMM because it is a commonly used urban hydrological model with a relatively advanced snow management module. The modelled facility was a grassed swale in Luleå, Northern Sweden, receiving runoff from a 60 ha catchment with commercial and light industrial land use. The swale was separated into 6 identical parts to test different scenarios for the amount and distribution of snow deposited in the swale. The long-term performance of the swale wi

Urban drainage systems have developed way beyond the traditional piped combined or separate sewer systems. Many ‘new’ systems are being introduced, ranging from stormwater infiltration facilities to green roofs. However, the widely advocated blue-green infrastructures are typically overlooked by asset managers, which will very likely have detrimental effects on their performance, service life, and wider adoption. In this paper, the working group on Urban Drainage Asset Management (UDAM – https://udam.home.blog/) of the IWA and IAHR Joint Committee on Urban Drainage discusses whether the state-of-the-art knowledge based on conventional sewer asset management is sufficient to develop asset management for blue-green infrastructures (BGIs). The discussion is structured around the five preconditions for effective control and asset management. Results show that asset management for BGIs is still underdeveloped due to a lack of monitoring techniques covering the broad range of BGI benefits and performance indicators, inspection techniques covering relevant failure mechanisms and models describing these mechanisms, maintenance and rehabilitation options, and sufficient support tools to aid inhabitants in the operation and maintenance of their individual BGIs such as green roofs or vegetated swales., Sanitary Engineering