Tuesday Poster Session - Source control measures - Understanding & management

Bioretention systems are increasingly used in municipalities to manage stormwater, yet little is known on the contribution of plants and growing media on the performance of these infrastructures. The objectives of this project are to compare the impact of two growing media used in bioretention systems (media for water infiltration – NF or for water treatment – NS) on the growth of three groups of perennial species and on the hydrologic performance of the system. Nine perennial plant species were divided in three groups based on their water needs: high (Group E: Anemonastrum canadense, Astilbe x arendsii, Trollius chinensis), moderate (Group M: Symphyotrichum dumosum, Iris sibirica, Veronica spicata) and low (Group F:Chelone obliqua, Hylotelephium spectabile, Nepeta x faassenii). Unplanted controls for each media were also included. Results show that, for a given species, plants grown in NS were significantly larger than plants grown in NF. NF resulted in lower evapotranspiration but also had a lower TSS in the lixiviate compared to NS. The combination of plants and growing media that resulted in the best hydraulic performance was Group E in the NS media. Results from this project will help municipalities design more efficient bioretention systems by selecting better performing combinations of plant species and growing medias. 

Soil sealing reinforces the need for effective stormwater treatment systems, among others for removing trace metals elements (MTEs) that accumulate in urban runoff. Nature-based solutions (NBS) rely on interactions between plants and microorganisms to retain TMEs, but the respective roles and interactions of vegetation, microbial communities and metal inputs have rarely been investigated. This study examined how Phragmites australis and Plantago lanceolata, combined with natural or reduced microbial communities, influence the removal of copper, zinc, nickel and cadmium in controlled microcosms. Plants were grown in autoclaved (Mi-) or non-autoclaved (Mi+) sediments, and with or without MTEs enrichment. Plant growth, MTEs concentrations in effluents, and microbial community structure were determined over 12 weeks. Plant growth was higher under Mi- conditions. Effluent analyses revealed no differences between plant species, but higher concentrations of Cu and Zn were observed under Mi- conditions. After three weeks, root-associated bacterial communities were influenced by sediment autoclaved. Overall, preliminary results suggest that sediment autoclaved has a greater impact than metal inputs on plant performance, metal dynamics and microbial communities. 

Blue Green Infrastructure (BGI) is widely adopted as an adaptive strategy for stormwater management, helping to reduce flood risk in urban areas. However, expanding urban greenery increases urban water demand during prolonged droughts, largely due to elevated evaporation rates. To sustain vegetation and enhance climate resilience, it is essential to understand the minimum water input required to prevent plant mortality, as well as the soil moisture thresholds needed to support effective evaporative cooling. Defining these two critical thresholds is essential for effective urban water management in water-limited conditions. The first threshold ensures plant survival by providing the minimum necessary water to maintain physiological functions. The second threshold identifies the soil moisture levels required to maximize cooling efficiency, optimizing the evaporative benefits of urban greenery. Balancing these thresholds is particularly important as cities face increasing water constraints while expanding urban greening initiatives. Understanding and quantifying these ranges will support sustainable water management strategies, ensuring that BGI remains functional and effective in mitigating urban heat stress under changing climate conditions. 

As we face more intense and frequent rainfall events many traditional drainage systems, such as drains and pipes, struggle to cope resulting in surface water flooding. To address this, a Sustainable Drainage Systems planter can be used to slow water diverted from a roof. Sensors evidence that the planter distributes water over time allowing the traditional system to cope. It achieves this by using the multiple internal layers designed to slow the water down. Trees can also be introduced into urban spaces to help manage the water while also providing multiple benefits to the community. Tree water demand and the soil-tree-atmosphere interaction is being established via monitoring campaign across Newcastle-upon-Tyne, UK. Instrumentation includes sap flow meters, soil moisture sensors and meteorological stations across the city. This research initiative is expanding, from a preliminary trial (tree planted within a rain garden) to other sites exploring the impact of tree maturity, species and context. Evidence-based guidance will then allow stakeholders to better implement both trees and Sustainable Drainage Systems to better reduce surface water flooding. Overall, this research provides a pathway for city-scale greening projects to incorporate nature as an active part of the city’s drainage network.