Thursday Poster Session - Source control measures - Monitoring & Modelling

Urban densification combined with climate change is increasing pressure on drinking water, wastewater and stormwater systems, which are often already in a fragile state. A review of potential impacts, existing adaptation measures, and the barriers and enablers influencing their implementation, supported by a survey of municipal practitioners in Québec and internationally, helped identify the key issues guiding the next steps of the project. Conducted in collaboration with the Observatoire de la gestion intégrée de l’espace public urbain of the Centre d’expertise et de recherche en infrastructures urbaines (CERIU), this project aims to develop a method for prioritizing interventions on water infrastructure in response to densification and future climate conditions. Because water networks are strongly interdependent, the approach makes it possible to assess cross-impacts between infrastructures and support more integrated planning. The methodology is based on a risk-mapping analysis integrated within a geographic information system (GIS) that combines public and municipal data. It identifies vulnerable infrastructures, evaluates risk levels and targets priority interventions to optimise investment decisions. The tool is accompanied by an operational guide to support its application according to each city’s available data. Two case studies in Québec were used to validate the method. Overall, the approach aims to strengthen the resilience of water networks in small and medium-sized municipalities with limited resources. 

Highway barrier inlets are prone to clogging from roadway debris, creating safety hazards and requiring labor-intensive maintenance to maintain effective roadside drainage. This study evaluated the performance of seven barrier inlet screen designs, four proprietary and three non-proprietary, installed at 24 inlets across Ohio, USA and monitored in real-time over a two-year period using low-cost sensors. A total of 123 kg of debris was blocked from the storm sewer by the screens during the study, which was primarily comprised of sediment, vegetation, and plastic. The non-proprietary screens outperformed proprietary designs, requiring less frequent maintenance (on average, every 125.8d versus 75.7d, respectively), easier installation, and universal fit to barrier inlets with non-uniform dimensions due to wear over time. Field testing of maintenance techniques revealed that pairing an air compressor with a regenerative air street sweeper was the most effective and resource-efficient approach, while street sweepers alone were inadequate for heavy debris loads. Findings highlight the potential for novel barrier inlet screens as a component of highway drainage infrastructure to improve drainage reliability, roadway safety, and downstream environmental outcomes. 

Day-to-day maintenance of stormwater management units and pavement systems significantly reduces pollutant loads contributing to the impairment of receiving waters.  The hypothesis that maintenance matters is quantifiable and represents a foundation to provide load reduction credits from maintenance practices.  These practices remove gross solids (detritus), particulate matter (PM) and associated constituents (such as nutrients) from the urban inventory of PM that is transported through and stored in stormwater systems and urban pavements.  PM is a primary source and sink of chemicals resulting from interaction and imposition of anthropogenic and biogenic activities and urban infrastructure design practices and materials on the hydrologic cycle. This study illustrates a Florida-based tool for nutrients (total nitrogen, TN and total phosphorus, TP) to provide load credits for quantifiable maintenance practices that has resulted in millions of USD of savings per municipality each year for over a decade.  While structural treatment systems are commonly deployed for load separation in stormwater systems worldwide, this study illustrates that such structural systems yield load separation costs, per load recovered on a dry gravimetric basis, that are one to two orders higher of magnitude as compared to quantified and documented urban maintenance activities such as street sweeping. 

This study evaluates the hydraulic behaviour, water quality, and thermal potential of six green roof prototypes incorporating heat exchangers. To this end, different materials (such as expanded clay, aggregates, and mixed CDW) were tested under simulated rainfall events, assessing water retention, the physico-chemical characteristics of the effluent, and the thermal recovery of the system. The results show notable differences in retention capacity between models, as well as high turbidity and electrical conductivity values during the first events, associated with the washing-out of fines from the substrate. Metal concentrations were low, except for occasional traces in one model. The heat exchanger demonstrated the ability to restore its temperature after rainfall, indicating feasibility for combined water–energy applications. This work provides pioneering insights into the hydrological and thermal behaviour of multifunctional green roofs. 

Evapotranspiration (ET) from vegetation is a key component of urban water and energy budgets. The moisture loss occurring between storm events creates storage capacity for rainfall, thereby reducing flood risk and mitigating combined sewer overflow events in urban watercourses. However, uncertainties surrounding ET estimations from green infrastructure remain a barrier to broader implementation and performance prediction. This study investigates the capability of the Bowen Ratio method for estimating ET rates from a testbed-scale vegetated Sustainable Drainage System (SuDS) device in an urban environment. Rainfall-runoff, net radiation, soil heat flux, wind speed, air temperature, and relative humidity were continuously monitored over a six-month period at 1-minute intervals. Temperature and humidity measurements at three heights were used to calculate ET for both an unvegetated control test bed and vegetated test beds using the Bowen Ratio approach. These estimates were compared with ET values calculated from the standard FAO-56 Penman-Monteith equation. The results show that ET estimates generated by the two methods were consistent for both the vegetated and unvegetated test beds. The Bowen Ratio method produced reasonable ET estimates for the vegetated test bed, indicating its potential suitability for wider application, particularly when integrated with remote sensing data for larger-scale ET assessment. Future work will examine the method’s performance across a broader range of green infrastructure types. 

This study investigates runoff water quality from an extensive 10-year-old green roof (GR) compared with a conventional ceramic roof (CR) during the dry winter season in São Paulo, Brazil (Cwa climate). Three rainfall events (>40 mm) occurring in 2024 were monitored, representing all significant winter storms. Runoff was analyzed for nitrogen species, phosphorus, organic matter (BOD, TOC), pH and total suspended solids (TSS). The GR showed higher concentrations of nitrate, total nitrogen and phosphorus relative to the CR, indicating continued nutrient release in aged systems under low vegetation activity. TOC progressively decreased over the season, whereas BOD/TOC ratios suggested shifts in organic matter quality. The CR exhibited greater first-flush effects after long dry periods, whereas TSS remained consistently low in the GR, highlighting effective particulate retention. This dataset provides a first reference for dry-season runoff quality from an aged GR in Brazil, contributing to the characterization of nutrient and carbon dynamics in subtropical conditions. 

Urban runoff is a major source of microplastics in aquatic environments. However, in contrast to road runoff, the contribution of building materials, including roofing, remains poorly documented. This study assesses microplastic emissions from two green roof systems using a large-scale rain simulator (8x12 ft) that reproduces heavy rainfall events over short (1.5 hours) or long (6 hours) periods. Runoff water was collected to analyze microplastics (25 to 300 µm) using micro-FTIR spectroscopy. The results reveal very high concentrations (10^3 MP/L), with most microplastics composed of synthetic rubbers (EPDM or EPR), which form the waterproofing membrane of the roofs. Most of the particles measured were less than 100 µm, and the maximum concentrations peaked at the maximum runoff. In addition, the detention system roof, which had the highest number of synthetic layers, released more particles than the retention system. These results provide the first controlled experimental evidence that roofing materials can be a significant source of microplastics in urban environments. 

Sensors mounted streams do not only record concentrations of a substance but also indirectly the impacts of driving processes and boundary conditions in the waterbody on the analyte. In this abstract we want to show how diurnal patterns of dissolved oxygen (DO), pH, Temp and CO2 change within an urbanized subcatchment of a stream. Therefore, we compare sensor recordings from two monitoring stations, one in the city of Dresden and another one before the streams reaches the city. We link these findings to differences in the appearance of the stream, alterations in the cross-sections and riverbanks as well as the availability of nutrients. All recorded diurnal patterns in the city show an increase in daily amplitude, the daily maxima and minima reach higher and lower levels than in the rural sub catchment while mean values do not differ much. Using Fourier transformation and regression analysis we created a subset of data for days that were only exposed to clear weather conditions. These days were analysed for changes in seasonality, the occurrence time of daily maximum values and how these times differ from parameter to parameter. We observed that distances between maxima of parameters were longer in the winter season while in summer they decreased. Differences between the two stations are obvious as well with significantly shorter lag times at the urban monitoring site for all parameters. We assume that higher metabolic activities (expressed by O2 and CO2 patterns) have strong effects on the calcium carbonate equilibrium and thereby on the pH value. We envisage that these relations can be used to detect effects of increasing availability of nutrients as well as for the assessment of renaturation efforts in urban streams. 

Each winter, the Rideau Canal in Ottawa, Ontario, is transformed into the world’s largest naturally frozen skating rink. However, climate change is threatening the viability of the Skateway as warmer winter temperatures shorten the skating season. The 7.8 km Skateway winds through several historic Ottawa neighbourhoods and receives stormwater from hundreds of outfalls ranging in size from <375 mm to 2100 mm. Faced with increasingly challenging ice-forming conditions, stormwater is becoming more problematic to the Skateway as Ottawa experiences more frequent rain-on-snow and winter thaw conditions. This project examines the quantity and quality of stormwater entering the canal from one large downtown outfall to determine if stormwater inputs to the Skateway impact the ice formation. Conductivity, temperature, and flow rate were measured via sensors installed into the canal and storm sewer. This study found that 80% of stormwater entering the canal from the Cooper drain entered during a high flow day (49 out of 116 days). The quantity and quality of the stormwater entering the canal on these high flow days had a larger respective impact on the canal water than the rest of the winter season. As well as there being significant increases in water temperature and conductivity further downstream. Any remediation methods implemented should focus on treating or mitigating the quantity of stormwater outputs on these high flow days and the later canal segment to maximize impact on canal ice formation. 

Each winter, the Rideau Canal in Ottawa, Ontario, is transformed into the world’s largest naturally frozen skating rink. However, climate change is threatening the viability of the Skateway as warmer winter temperatures shorten the skating season. The 7.8 km Skateway winds through several historic Ottawa neighbourhoods and receives stormwater from hundreds of outfalls ranging in size from <375 mm to 2100 mm. Faced with increasingly challenging ice-forming conditions, stormwater is becoming more problematic to the Skateway as Ottawa experiences more frequent rain-on-snow and winter thaw conditions. This project examines the quantity and quality of stormwater entering the canal from one large downtown outfall to determine if stormwater inputs to the Skateway impact the ice formation. Conductivity, temperature, and flow rate were measured via sensors installed into the canal and storm sewer. This study found that 80% of stormwater entering the canal from the Cooper drain entered during a high flow day (49 out of 116 days). The quantity and quality of the stormwater entering the canal on these high flow days had a larger respective impact on the canal water than the rest of the winter season. As well as there being significant increases in water temperature and conductivity further downstream. Any remediation methods implemented should focus on treating or mitigating the quantity of stormwater outputs on these high flow days and the later canal segment to maximize impact on canal ice formation. 

Reducing urban macro-waste is a major challenge for local authorities, particularly due to its transfer to aquatic environments. In this context, a systemic approach has been developed as part of a research project led by Cerema, Métropole de Lyon and WAO Nature & Conservation. The approach is based on the construction of a Forrester-type dynamic model, developed from a conceptual model, causal analysis and data from workshops with operational stakeholders. The model simulates the production, dispersion and accumulation of six types of macro-waste in urban compartments (surface, networks, outlets) and allows different management scenarios to be compared. The results show that, without actions, certain types of waste accumulate heavily on the surface (cigarette butts, paper) or underground (wipes), and that a significant proportion ends up directly in the Saône river. The evaluation of several experimental actions highlights the effectiveness of surface measures and the complementary effect of underground actions. The combination of the two allows for the greatest reduction in simulated accumulations. The model, which can be fed and improved by the acquisition of future data (diagnostics, expert opinions), is an operational decision-making tool and paves the way for an integrated regional strategy to reduce macro-waste. 

India is one of the worlds most adversely affected by climate change, with strong impacts on both water supply and urban drainage. Sometimes it causes both more frequent water shortages and more frequent urban flooding events. One way to resolve it is by adopting rainwater harvesting for reducing the urban sprawl at the source and using it for recharging the underground water to turn it into a resource. A dwelling unit with a rooftop area of 150m2 in a total land area of 900 m2 in Pratapganj in East Delhi, where six adult persons reside, was selected for the implementation of the scheme of rooftop rainwater harvesting from June to September 2024. The water table in Pratapganj is found to be at 5.5m in the hand pump of the dwelling unit, which goes further down to about 7.0m during the dry season. The collected rooftop rainwater is channelled through a 10cm diameter pipe to the existing borehole to recharge the aquifer, and it was observed that the water level in the hand pump has not only risen in the month of September but also reduced the urban sprawl. This technique of roof-top rainwater harvesting is the most appropriate in this area because not much land is available due to increased urban activities. It has not only recharged the aquifer, turning it into a source, but also reduced the flooding at the source