Session HS5.3.4

[Programme]

HS5.3.4 | Green Infrastructure for Sustainable Urban Hazard Management

Green Infrastructure for Sustainable Urban Hazard Management

Co-organized by SSS7

Convener: Daniel Green | Co-conveners: Lei LiECSECS, Elena Cristiano, Jorge Isidoro

Orals

| Wed, 17 Apr, 16:15–18:00 (CEST)

Room 2.15

Posters on site

| Attendance Wed, 17 Apr, 10:45–12:30 (CEST) | Display Wed, 17 Apr, 08:30–12:30

Hall A

Urban areas are at risk from multiple hazards, including urban flooding, droughts and water shortages, sea level rise, disease spread and issues with food security. Consequently, many urban areas are adapting their approach to hazard management and are applying Green Infrastructure (GI) solutions as part of wider integrated schemes.

This session aims to provide researchers with a platform to present and discuss the application, knowledge gaps and future research directions of urban GI and how sustainable green solutions can contribute towards an integrated and sustainable urban hazard management approach. We welcome original research contributions across a series of disciplines with a hydrological, climatic, soil sciences, ecological and geomorphological focus, and encourage the submission of abstracts which demonstrate the use of GI at a wide range of scales and geographical distributions. We invite contributions focusing on (but not restricted to):

· Monitored case studies of GI, Sustainable Drainage Systems (SuDS), Low Impact Developments (LIDs) or Nature-based Solutions (NbS), which provide an evidence base for integration within a wider hazard management system;

· GIS and hazard mapping analyses to determine benefits, shortcomings and best management practices of urban GI implementation;

· Laboratory-, field- or GIS-based studies which examine the effectiveness or cost/benefit ratio of GI solutions in relation to their wider ecosystem potential;

· Methods for enhancing, optimising and maximising GI system potential;

· Innovative and integrated approaches or systems for issues including (but not limited to): bioretention/stormwater management; pollution control; carbon capture and storage; slope stability; urban heat exchange, and; urban food supply;

· Catchment-based approaches or city-scale studies demonstrating the opportunities of GI at multiple spatial scales;

· Rethinking urban design and sustainable and resilient recovery following crisis onset;

· Engagement and science communication of GI systems to enhance community resilience.

Session assets

Session materials

Orals: Wed, 17 Apr | Room 2.15

Chairpersons: Daniel Green, Elena Cristiano, Lei Li

16:15–16:20

5-minute convener introduction

16:20–16:30

EGU24-214

On-site presentation

Impact of hydraulic conductivity on water quality and microbial ecology of rain gardens

Vernon Phoenix, Erin Corbett, and Umer Ijaz

Rain gardens are a form of sustainable urban drainage which lower flood risk and reduce environmental contamination from stormwater. A combination of processes including filtration, sedimentation and microbial metabolic processes work to remove contaminants from the stormwater. In this study we examined the impact of hydraulic conductivity of raingarden soil on raingarden performance, exploring its impact on the removal of contaminants from the stormwater, as well as microbial community composition and function. This was undertaken as part of a large scale project to install raingardens across the city centre of Glasgow, thus improving the city’s climate resilience. The study utilized four raingardens fed real stormwater from a busy road. All raingardens tested reduced contaminant concentrations in the stormwater, and reductions in contaminant concentrations were greatest when pollutant levels in the input water were higher. Importantly, road salting in the winter did not cause dissolved metals to be released from the raingardens. DNA was extracted from waters and soils for microbial community and function analysis using Illumina 16S sequencing and a bioinformatics suite. A diverse community of bacteria capable of hydrocarbon degradation and metal resilience were found in stormwaters and raingarden soil. Notably, the taxonomic evenness and overall diversity of the stormwater microbial community was increased as it passed through the raingarden. Furthermore, the raingarden soil displayed a greater functional richness compared to the input waters. This demonstrates that the microbes in the raingardens can undertake a greater range of functions than those in the untreated stormwater, and highlights the importance of the raingarden bacteria in treatment of contaminants. Microbial community composition and function showed little difference between rain gardens and PERMANOVA analysis identified that hydraulic conductivity had no significant impact on functional Beta diversity in the soil. Overall, in this study, hydraulic conductivity did not appear to have a significant impact on microbial community composition, nor on the removal of contaminants by the raingarden, with all raingardens performing similarly well.

How to cite: Phoenix, V., Corbett, E., and Ijaz, U.: Impact of hydraulic conductivity on water quality and microbial ecology of rain gardens, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-214, https://doi.org/10.5194/egusphere-egu24-214, 2024.

16:30–16:40

EGU24-19732

ECS

Virtual presentation

Insights on permeable pavement hydraulic performance from large-scale laboratory experiments and physically based modelling

Giulia Mazzarotto, Matteo Camporese, and Paolo Salandin

Among other Sustainable Urban Drainage Systems, Permeable Pavements (PPs) are one can be easily retrofitted in the urban environment. However, they suffer of clogging phenomena that reduces their efficiency over time. Laboratory experiments to assess the hydraulic performance of a newly constructed PP subjected to different rainfall intensities have been conducted using a large-scale laboratory model (2x6 m2 with 1.2\% slope). The surface of the upstream portion (1.7x2 m2) is impermeable to simulate runoff generation over impermeable surfaces, while the downstream portion (4.3x2 m2) is realized with PICP. The downstream vertical side of the PP is made of permeable bricks and two gutter channels are placed crosswise to separately collect runoff and subsurface discharge. The remaining sides, as well as the bottom of the model, are impermeable. The filter package below the PICP consists of three layers: 5 cm bedding (3-6 mm gravel), a 10 cm base layer (8-12 mm gravel) and a 30 cm sub-base layer (20/40 mm gravel), which is laid on top of a 40 cm layer of native sand (silty sand with d50=0.23 mm). A geotextile separates the bedding and base layers and a 4m long drainpipe (D=150 mm) was inserted in the sub-base layer. The facility is equipped with probes on both lateral sides: 6 tensiometers in the native sand, 4 water content reflectometers in the base and sub-base layers, and 3 piezometers to record water table evolution throughout the experiments and degree of saturation of the filter layer package. Runoff and subsurface discharge are separately conveyed to two tipping bucket rain gauges. A rainfall simulator is used to generate quite uniform rainfall distribution (80 - 150 mm/h intensity) for 15 minutes or 30 minutes. Moreover, an Integrated Surface-Subsurface Hydrological model (CatHy) has been used to model the permeable pavement, assess and support data collected from the laboratory experiments.

Results from the laboratory experiments performed have proven the efficiency of a newly constructed permeable pavement to very intense rainfall events. The monitoring with spatially distributed sensors allowed to assess the evolution in time of the water table as well the “recovery” phase to pre-event conditions after the event. This is useful to assess the effect of repeated rainfall events at short distance in time. For each experiment performed, a rapid increase of subsurface discharges was recorded by the tipping bucket, whereas surface runoff occurred only for short and intense rainfall events (approximately 150 mm/h for 15 min). The system did not reach saturated conditions in any of the performed experiments due to the high permeability of the filter layer package. The monitoring with spatially distributed sensors also allowed to assess the heterogeneities of the physical processes (synthetic rainfall events, infiltration processes) as well as of the filter layer package.

Future laboratory experiments simulating clogging phenomena will be performed and compared to the results obtained from the developed experiments up to now and of the ISSH model.

How to cite: Mazzarotto, G., Camporese, M., and Salandin, P.: Insights on permeable pavement hydraulic performance from large-scale laboratory experiments and physically based modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19732, https://doi.org/10.5194/egusphere-egu24-19732, 2024.

16:40–16:50

EGU24-1874

Highlight

On-site presentation

Green Panel performance testing – Analysis from one season of monitoring data and implications for urban scale applications

Karina Vink

Most cities have climate goals such as lowering the Urban Heat Island (UHI) effect and reducing flood damages. Green infrastructure (GI) can help mitigate the UHI effects and has the potential to locally delay flood peaks. However, in dense urban infrastructure there is often little space for ground based vegetation. Green roofs are therefore a feasible implementation option even within city centres. While there is a myriad of types of green roofs available for flat roofs, and their performance is tested in various environments, sloped roofs as of yet have few design options available. To this end, Green Panels were developed as a novel type of GI for sloped roofs. As it is a novel design, its performance can be estimated only by literature results of GI applying different designs and materials. To overcome this research gap, in this case study a Green Panel prototype was constructed and its performance was monitored over a period of 3-4 months at the University of Twente, the Netherlands.

The experimental setup consisted of 1 m2 of Green Panels, and 1 m2 of regular roof tiles as control area, both at a slope of 45 degrees. The materials of the Green Panels, mounted on the same railing as solar panels, is High Density Polyethylene, while different substrates were tested: soil, rock wool, recycled fabric, and combinations thereof. Applied sensors were a soil moisture and temperature sensor (Truebner SMT50) and an environmental sensor (BME680), including a thermal sensor, both connected to Sensebox Mini dataloggers. The soil moisture sensors were placed in each of 6 Green Panel trays. The environmental sensors were placed above and below the roof tiles in both control and Green Panel locations, as well as above and below the Green Panels themselves. The measured parameters were air temperature, humidity, atmospheric pressure, VOC, soil temperature, and soil moisture. These values were compared to meteorological data from a local weather station at 5km distance. Other benefits such as increased biodiversity were not monitored, though species such as ladybug (family Coccinellidae) and fly (family Muscidae) were observed.

Analysis of the results shows that there is a small effect of Green Panels on reducing extreme temperatures, and errors in measurement setup and gaps in data continuity did not affect validity. The implications of this analysis were extrapolated to the urban scale for the city of Enschede to help answer what an appropriate performance monitoring scheme is for cities intending to implement GI and still uncertain about when their climate goals are being met.

How to cite: Vink, K.: Green Panel performance testing – Analysis from one season of monitoring data and implications for urban scale applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1874, https://doi.org/10.5194/egusphere-egu24-1874, 2024.

16:50–17:00

EGU24-20460

ECS

On-site presentation

Integration of Nature-based Solutions for stormwater control and management

Noemi Maglia and Anita Raimondi

In the last decades, all over the world, cities have been characterized by the growth of urban population and urbanization. This involves some issues related to water resource management in terms of water supply during drought periods and stormwater control during rainfall events.

In this context, Nature-based Solutions (NBSs) are increasingly encouraged and used as support for traditional urban drainage systems to make urban areas more sustainable and resilient to the effects of climate change. They contribute to runoff control and management and natural water balance restoration, providing several benefits to the environment and communities. Moreover, NBSs meet several Sustainable Development Goals (SDG) of United Nations Agenda 2030, such as Goal 6 (“Clean Water and Sanitation”), Goal 11 (“Sustainable Cities and Communities”), and Goal 13 (“Climate Action”).

The study presents the integration of a rainwater tank with an infiltration system to limit both the water demand for drinking supplies and the overload of sewers. An analytical probabilistic approach is developed to balance the different purposes of the system and to overcome the limits of the traditional methods for performing multi-objective analysis. The proposed method enables the relationship between the main characteristics of the system and a return period and considers the possibility of storage capacity pre-filling from previous rainfall events. It can be applied under different climatic scenarios and management rules of the system.

The goodness of the theoretical framework is verified by applying it to a real case study in Milano (Italy) and successfully tested by comparing the results of its application with those from the traditional methods proposed in the literature. The use of integrated NBSs can be useful for the optimization of both water supply and urban drainage systems in terms of limiting drinking water waste and flood risk and also acting on water resource protection in terms of high-quality source preservation and aquifer recharge.

How to cite: Maglia, N. and Raimondi, A.: Integration of Nature-based Solutions for stormwater control and management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20460, https://doi.org/10.5194/egusphere-egu24-20460, 2024.

17:00–17:10

EGU24-16239

ECS

On-site presentation

Nature-based solution enhances resilience to saturation excess flooding in coastal cities in the Global South

Emmanuel Dubois, Saleck Moulaye Ahmed Cherif, Montana Marshall, Mohamed Mahmoud Abidine, Charlotte Grossiord, and Paolo Perona

Coastal cities are facing a rise in groundwater levels induced by sea level rise, further triggering saturation excess flooding where groundwater levels reach the topographic surface or reduce the storage capacity of the soil, thus putting stress on the existing infrastructure. Lowering groundwater levels is therefore a priority for sustaining the long-term livelihood and resilience of coastal cities. This project discusses the feasibility of using tree-planting as a Nature-based solution to alleviate saturation excess flooding as a result of rising groundwater levels in coastal cities in the Global South. In environments with shallow groundwater, trees uptake groundwater by intercepting water that percolates in the unsaturated zone or reduce groundwater recharge by canopy interception of rainwater. These contributions, in turn, lower groundwater levels and increase the unsaturated zone thickness, further mitigating the risk of saturation excess flooding. A case study was conducted in Nouakchott City (Mauritania) where rising groundwater levels has led to permanent saturation excess flooding for more than a decade, making parts of the city inhabitable and posing long-term health threats. Consequently, this work presents an interdisciplinary approach using both ecohydrogeology and plant physiology to model the dewatering capacity of five local tree species. These species were selected based on their tolerance to the exceptionally challenging conditions for vegetation posed by the hot desert climate and the shallow and brackish groundwater table. Preliminary results from a 3D groundwater model indicate that a city-scale tree-planting program could induce a groundwater drawdown of up to 70 cm within a 40-year horizon. Thus, a tree-planting program is anticipated to lower the groundwater levels, thereby reducing flooding during the wet season. Tree-planting programs constitute long-term solutions, sustained by environmental factors, that complement conventional engineering solutions. The multi benefits of such Nature-based solutions, as well as the expected positive environmental, economic, and social outcomes, makes them particularly promising for alleviation of saturation excess flooding.

How to cite: Dubois, E., Cherif, S. M. A., Marshall, M., Abidine, M. M., Grossiord, C., and Perona, P.: Nature-based solution enhances resilience to saturation excess flooding in coastal cities in the Global South, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16239, https://doi.org/10.5194/egusphere-egu24-16239, 2024.

17:10–17:20

EGU24-17797

ECS

On-site presentation

How has urbanisation already altered a city’s natural water balance? The case study of Hamburg to present a commonly missing step before considering green infrastructure interventions

Ian McNamara, Tim Wolters, Michael Schröder, Nele Wotha, and Frank Wendland

The concept of water-sensitive cities continues to gain traction globally, as the disruptive effects of urbanisation on local hydrological processes and the potential benefits of green infrastructure become increasingly evident. Despite this, in many planning instances, consideration is only given to how the water balance will be altered and hazard risk reduced from the current urbanised state to the state after implementation of green infrastructure. Why is the understanding of the natural water balance in the pre-urbanisation state often not considered as reference point for planning? If urban green infrastructure should provide hydrological and ecosystem services, should these services be similar to those in the natural condition before urbanisation?

For our study, we recreated the daily near-natural water balance for the city of Hamburg to quantify how urbanisation has already affected the water balance, particularly in years of hydrological extremes that represent hydrological hazards. Using the fully-distributed daily water balance model mGROWA, we developed two very high resolution (25 m) models for the city of Hamburg for 1991–2020; one representing the current hydrological situation and one representing a theoretical near-natural situation. To generate the near-natural scenario, the input datasets for topography, soil and land cover were adjusted through the integration of various datasets representing non-anthropogenic conditions, while sealed surfaces and artificially drained areas were removed from the datasets. As expected, due to the lack of runoff from sealed surfaces the actual evapotranspiration is much higher (+40%) in the near-natural scenario than in the current one. Groundwater recharge was also higher in the near-natural scenario (+27%), mainly due to the lack of surface sealing. We then compared the water balance components for the two models against the SPEI meteorological drought index to assess differences in the extremely wet and extremely dry periods that represent potential hydrological hazards. This revealed an increasing divergence in some water balance components between the scenarios for the extreme conditions, quantifying the extent to which the urbanisation of the city has exacerbated hydrological hazard risks. Our study presents a transferable methodology for assessing how urbanisation has affected the natural water balance of a region, which can be used as a starting point for defining targeted solutions for green infrastructure, with the aim of achieving water-sensitive cities.

How to cite: McNamara, I., Wolters, T., Schröder, M., Wotha, N., and Wendland, F.: How has urbanisation already altered a city’s natural water balance? The case study of Hamburg to present a commonly missing step before considering green infrastructure interventions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17797, https://doi.org/10.5194/egusphere-egu24-17797, 2024.

17:20–17:30

EGU24-9959

On-site presentation

Modelling the environmental impact of combined urban drainage systems with a lumped hydrological approach

Roberto Greco, Alessandro Farina, and Rudy Gargano

The management of combined urban drainage systems is a complex task, as it requires detailed knowledge about precipitation regime, hydrological features of the catchment, hydraulic characteristics of the drainage network, and information about the water use by the served inhabitants. Heavy semi-distributed hydrological and physically based hydraulic models are used for network conduits design. However, in many management problems, the knowledge of the hydraulic flow characteristics in all the conduits is not required, and the uncertainty of the available information hampers the use of complex hydrological models. Hence, simple models with few parameters and small computational effort may be preferable, especially for management and planning problems requiring the execution of many simulations.

In this study, a novel approach is proposed for the definition of effective lumped simplified models of urban drainage systems, the parameters of which can be estimated directly from cartographic information. For several case studies, the hydrographs predicted by lumped simplified models result close to those obtained with semi-distributed models in SWMM. The results show that robust relationships linking lumped model parameters with morphological and topological characteristics of the urban catchment can be established (Farina et al., 2023).

The proposed lumped modelling approach is applied to carry out a sensitivity analysis of the effects of parameters characterizing climate, urban catchment, and overflow discharge device, on several indicators of the environmental impact of combined sewer overflows (CSO) (Farina et al., 2024). In fact, pollution from CSO is still not satisfactorily addressed by current management practices and regulations, usually setting a dilution threshold for the discharged overflow, and enforcing limitations to the number of overflow activations per year. The sensitivity analysis indicates that the percentage of impervious surface of the catchment is the most influent parameter on all the indicators, and its reduction can effectively contain the yearly discharged pollutant mass. The overflow activation threshold, instead, results the second least influent parameter, suggesting that its regulation alone would not be a suitable strategy to control CSO pollution. The results also indicate that neither sustainable urban drainage practices, nor interventions on the CSO device, significantly affect the frequency of the overflows, which is indeed controlled by the local precipitation regime. Furthermore, the yearly discharged pollutant mass and the mean concentration of pollutants in the overflow result independent on the overflow activation frequency. Hence, the regulation of this latter does not seem a suitable means to reduce the environmental impact of combined urban drainage systems.

References.

Farina, A., Di Nardo, A., Gargano, R., van der Werf J.A. & Greco, R. (2023). A simplified approach for the hydrological simulation of urban drainage systems with SWMM. Journal of Hydrology, 623, 129757.

Farina, A., Gargano, R., & Greco, R. (2024). Effects of urban catchment characteristics on combined sewer overflows. Environmental Research, 244, 117945.

How to cite: Greco, R., Farina, A., and Gargano, R.: Modelling the environmental impact of combined urban drainage systems with a lumped hydrological approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9959, https://doi.org/10.5194/egusphere-egu24-9959, 2024.

17:30–17:40

EGU24-13624

ECS

On-site presentation

Role of Vegetation in mitigating urban heat risk in Twelve American Cities - Applying the ARIES Modelling Approach

Sudeshna Kumar, Alba Marquez, Celina Aznarez, G Darrel Jenerette, Marco Bidoia, Peter C Ibsen, Ken Bagstad, Stefano Balbi, and Ferdinando Villa

The anthropogenic urban realm exacerbates surface urban heat island (UHI) effects, triggering health hazards, such as mortality attributable to heat exposure in cities. The study makes a concerted effort to unravel the complex interplay between various spatial, quantitative, and qualitative attributes of vegetation, aiming to comprehend its pivotal role in mitigating urban heat risks within urban environments. The UHI risk is related to land surface temperature (LST). The study models UHI risk in twelve American cities in diverse Köppen-Geiger Climate zones spanning the contiguous USA. To address this, the Integrated Modelling approach by the ARtificial Intelligence for Environment & Sustainability (ARIES) initiative has been adopted in the study. This approach based on FAIR (Findable, Accessible, Interoperable, and Reusable) principles is accessible at https://aries.integratedmodelling.org/. Utilizing the k.LAB software with semantic reasoning our modeling approach assesses the UHI risk. It maps the spatial distribution of UHI considering hotspots of anthropogenic heat, vegetation, land cover, and land surface temperature. UHI risk is assessed at a resolution of 30 meters alongside census tract-level data using an ordered weighted approach. The study found variations in the relationship between greenness, as indicated by the Normalized Difference Vegetation Index (NDVI), and Land Surface Temperature (LST) across 12 different cities. The findings highlight the cooling effect of the water bodies, especially in areas near the port and green spaces. Linear parks such as roadside tree plantations typically feature uniform tree species and often lack smaller trees and shrubs, making them susceptible to heat infiltration from surrounding areas and resulting in a lesser overall temperature reduction. It identifies at least 30 percent of census tracts across 12 cities necessitate urban greening intervention. The study provides scientific insight into the cooling effects of urban parks, offering valuable guidance for urban planning and aiding decision-makers in addressing the UHI effect and enhancing overall urban sustainability. The study also underscores the significance of open science in developing environmental models addressing global sustainability challenges concerning the pressing issue of assessing urban climate risks. Models and scientific artifacts often face challenges in reusability, transferability, and sharing across diverse programming languages or modeling systems, revealing a significant lack of interoperability. By delving into the factors of LAI, NDVI, and Landscape Shape Index (LSI), the study aims to enhance understanding of the role of vegetation in ameliorating the adverse effects associated with UHI, thus paving the way for more effective urban heat management strategies.

How to cite: Kumar, S., Marquez, A., Aznarez, C., Jenerette, G. D., Bidoia, M., Ibsen, P. C., Bagstad, K., Balbi, S., and Villa, F.: Role of Vegetation in mitigating urban heat risk in Twelve American Cities - Applying the ARIES Modelling Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13624, https://doi.org/10.5194/egusphere-egu24-13624, 2024.

17:40–17:50

EGU24-607

ECS

On-site presentation

Ecosystem services supply-demand mismatches for urban heat mitigation

Celina Aznarez, Sudeshna Kumar, Alba Márquez-Torres, Unai Pascual, and Francesc Baró

Urban areas, characterized by dense construction, often exhibit elevated land surface temperatures, leading to the formation of urban heat islands (UHIs). These UHIs pose significant environmental hazards, contributing to issues such as heat-related mortality, degraded air quality, and elevated heat stress on biodiversity and ecosystems. Moreover, the impact of UHIs is not uniformly distributed due to the heterogeneous nature of urban landscapes and socio-spatial inequities influencing factors like impervious surfaces and vegetation cover. Urban green infrastructure is increasingly valued as a nature-based solution to mitigate UHIs, offering essential ecosystem services (ES) like urban heat mitigation. To analyze the relationship between users' access and dependence on these benefits, we propose a modeling approach that integrates remote sensing, field, and socio-demographic data, along with Artificial Intelligence for Environment and Sustainability (ARIES) and GIS tools. This approach incorporates: i) indicators of UHI exposure and urban heat vulnerability indices; ii) spatial quantification of the supply and demand of urban green infrastructure related to ES for UHI mitigation; iii) spatially explicit (mis)matches of ES supply and demand balance and iv) coupled modelling. We applied it in the ‘green’ city of Vitoria-Gasteiz, in the Basque Country as a case study. Our findings evidence the unequal distribution of UHI burdens, with individuals vulnerable to heat experiencing disproportionate impacts, including higher exposure and limited access to temperature-regulating ES. This mismatch between the supply and demand of ES particularly affects disadvantaged communities. Conversely, areas associated with higher income levels indicate reduced vulnerability to heat. Incorporating environmental justice principles into UHI mitigation strategies is essential to ensure equitable outcomes for all residents. By considering the socio-spatial inequalities associated with supply-demand mismatches in ES and their impact on vulnerability to heat, our approach enables evidence-based decision-making and spatial prioritization to address the specific needs of vulnerable populations.

How to cite: Aznarez, C., Kumar, S., Márquez-Torres, A., Pascual, U., and Baró, F.: Ecosystem services supply-demand mismatches for urban heat mitigation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-607, https://doi.org/10.5194/egusphere-egu24-607, 2024.

17:50–18:00

EGU24-11013

ECS

On-site presentation

An analysis to interpret the heterogeneous resident's willingness to pay for green roofs to improve the understanding of decision heterogeneity

Pan Yang and Jiahong Wu

Urban waterlogging has become a frequent and threatening issue in recent years due to rapid urbanization and extreme weather conditions, resulting in economic losses and health hazards. In this context, green roofs (GRs) emerge as a sustainable and innovative solution to mitigate these issues by absorbing rainfall, reducing runoff, and enhancing urban biodiversity. Despite the apparent benefits, the adoption of GRs remains limited, largely due to a lack of quantitative understanding of the factors that influence urban residents' GR adoption willingness.

This study aims to fill this knowledge gap via a survey approach, and distribute and collect survey responses from 999 residents in Shenzhen, a rapidly developing coastal city in China. The survey is designed to capture a range of variables that may influence residents' decision-making regarding GR adoption, including demographic information, housing characteristics, waterlogging experiences, roof utilization preference, knowledge of and preference for GR, and willingness to adopt GR. The GR adoption willingness is collected assuming two policy scenarios, one with government subsidy and the other without. By leveraging a machine learning model for data analysis, the study identifies five key predictors that commonly influence GR adoption willingness with and without subsidy: recognition of the advantages of GRs (GR_advantage), whether a resident lives on the top floor (Top_floor), the degree of concern about GRs (GR_concern), the duration of waterlogging experienced in and around the community (WL_time), and the individual's level of education (Education). Interestingly, the study also reveals that GR adoption willingness is affected differently under scenarios with and without policy incentives. In the absence of subsidies, the property fee (Pro_fee) is a significant factor; conversely, when policy incentives are present, age and house ownership (House_own) emerge as influential factors.

The complexity of these influencing factors is further evaluated using the SHAP (SHapley Additive explanation) model, which provides a nuanced interpretation of how these factors interact and exert nonlinear impacts on residents' willingness to adopt GRs. The insights derived from this analysis are critical for policymakers and urban planners who are looking to promote GRs as part of an integrated urban water management strategy. Specifically, a combination of long-term subsidies and one-time subsidies can be combined to motivate residential adoption. Recognizing the general unfamiliarity with GRs and related policies among residents, relevant outreach and education programs are essential. In addition, targeted subsidy levels could be helpful in stimulating more GR adoptions. An important consideration in this targeting process is the frequency of waterlogging events, which has been shown to significantly influence residents' willingness to pay for GRs.

How to cite: Yang, P. and Wu, J.: An analysis to interpret the heterogeneous resident's willingness to pay for green roofs to improve the understanding of decision heterogeneity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11013, https://doi.org/10.5194/egusphere-egu24-11013, 2024.

Posters on site: Wed, 17 Apr, 10:45–12:30 | Hall A

Display time: Wed, 17 Apr, 08:30–Wed, 17 Apr, 12:30

A.31

EGU24-5209

Retention capacity and thermal properties of a multilayer blue-green roof in Sardinia: two years of monitoring

Francesco Viola, Elena Cristiano, Salvatore Urru, and Roberto Deidda

Many different nature-based solutions have been proposed in the literature to contribute to the sustainable development of the urban environment. Among them, multilayer blue-green roofs are becoming more and more popular, thanks to their multiple benefits. As traditional green roofs, the multilayer ones guarantee high retention capacity during rainfall events, contributing to the pluvial flood mitigation. Thanks to the additional storage layer, not only the mitigation capacity is increased, but there is the possibility to store the collected water, and reused it for some urban purposes, such as garden irrigation. Moreover, these nature-based solutions ensure thermal insultation for the underneath buildings and they help lowering the air temperature, contributing to the mitigation of the urban heat island effects. Finally, they improve the air quality, promote the biodiversity, and increase the aesthetic value of the overall city. In June 2019, a multilayer blue-green roof prototype has been installed at the university of Cagliari, and subsequently equipped with multiple sensors to monitor and evaluate the ecohydrological and thermal dynamics. The multilayer blue-green roof, with a surface of 16 m2, presents an 8 cm layer of soil, classified as sand, and a 10 cm additional storage layer. It is characterized by Cactaceae vegetation, which shows resistance to the high temperature and low water availability and does not require additional maintenance. The prototype has been equipped with a Smart Mill, that beside opening and closing of the valve to control the storage layer, enables to measure climatological variables, such as rainfall, air temperature and wind speed, and the water level in the additional layer. Four HOBO thermometers have been installed to measure the temperature in the soil, underneath the structure and on the lateral side. Two soil moisture sensors have been placed at opposite sides of the multilayer blue-green roof. Finally, a tank with a sensor to measure the water level have been collocated at the valve opening, to measure the outflow from the additional storage layer. The collected data have been used to model the ecohydrological and thermal dynamics, with the aim to quantify the potential benefits in terms of pluvial flood mitigation and thermal insulation. Results, collected during two full years of monitoring the prototype in Cagliari, are discussed, highlighting the potential benefits of a large-scale installation for the sustainable development of urban areas.

How to cite: Viola, F., Cristiano, E., Urru, S., and Deidda, R.: Retention capacity and thermal properties of a multilayer blue-green roof in Sardinia: two years of monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5209, https://doi.org/10.5194/egusphere-egu24-5209, 2024.

A.32

EGU24-2833

ECS

Highlight

How do multilayer blue-green roofs affect the runoff water quality?

Elena Cristiano, Alessandra Carucci, Martina Piredda, Emma Dessì, Salvatore Urru, Roberto Deidda, and Francesco Viola

To ensure a sustainable urban development, the large-scale implementation of green roofs and, more in general, of several nature-based solutions is an essential aspect to be considered. Thanks to their multiple benefits (e.g., pluvial flood mitigation, acoustic and thermal insulation of building, urban heat island reduction, air quality improvement, increase of biodiversity and additional aesthetic value) green roofs have been widely investigated. Among them, the multilayer blue-green roofs present an additional storage layer, that enables to accumulate the rainwater that percolates from the soil when it reaches saturation. This water can potentially be used for several domestic non-potable purposes, such as garden irrigation, street cleaning or flushing the toilets. To identify the possible rainwater reuse, it is fundamental to know the physical and chemical properties of this unconventional resource and evaluate whether they respect the regulations limits. Many studies investigated the effects of traditional green roofs on the runoff quality, without reaching a complete agreement. Moreover, the influence of the additional storage layer on the water quality has not been explored yet. In this context, the multilayer blue-green roof prototype installed at the University of Cagliari has been used as case study to analyze the quality of the outflow during three artificial and three natural rainfall events, comparing the runoff with the one obtained from a traditional roof. The prototype is constituted by 8 cm of soil (classified as sand) and 10 cm of storage layer, and it is characterized by Cactacee vegetation, that does not require additional irrigation or maintenance. For each artificial event, three samples every five minutes have been collected from both traditional roof and multilayer blue-green roof, to evaluate how the water quality varies during time. For the natural events only one sample has been collected as representative of the average quality of the accumulated water. The collected samples have been analyzed, evaluating temperature, pH, conductivity, total and volatile suspended solids, Chemical Oxygen Demand (COD), most common cations and anions and heavy metals concentrations. Results showed that suspended solids and heavy metal concentrations observed in the multilayer blue-green roof outflow are lower than by the traditional roofs, underlying the beneficial effects of this Nature-based solution. On the other hand, multilayer blue-green roof outflow presents high COD concentrations, caused by the accumulation of organic matter in the additional storage layer. Hence, the collected water can be used only for irrigation either of the multilayer blue-green roof itself or of gardens. It is important to notice that results obtained in this work are limited to one single soil (sand) and vegetation (Cactacee) type: the response with different vegetation, soil type and thickness, and fertilizer should also be investigated, as well as under different climatological conditions.

How to cite: Cristiano, E., Carucci, A., Piredda, M., Dessì, E., Urru, S., Deidda, R., and Viola, F.: How do multilayer blue-green roofs affect the runoff water quality? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2833, https://doi.org/10.5194/egusphere-egu24-2833, 2024.

A.33

EGU24-14278

ECS

Sensitivity Analysis of Bioretention Cells for Stormwater Management: A Study in Secondary Cities of India

Indra Mani Tripathi and Pranab Kumar Mohapatra

The present study conducts a comprehensive sensitivity analysis of bioretention cells, a green stormwater management infrastructure, in the context of urban stormwater systems in secondary cities of India (Bhopal and Kozhikode). The research aims to enhance our understanding of the performance and effectiveness of bioretention cells in mitigating the impacts of urbanization on stormwater runoff. Utilizing the Storm Water Management Model (SWMM), the study employs a systematic approach to assess the sensitivity of bioretention cells to various design and environmental parameters. The initial screening of diverse design parameters is performed using the one-factor-at-a-time (OAT) sensitivity analysis method. Subsequently, pivotal parameters, namely, conductivity, berm height, vegetation volume, suction head, porosity, wilting point, and soil thickness, are identified for further sensitivity analysis. Around 500 randomly and uniformly distributed samples for each sensitive design parameter are simulated using a Python wrapper for the Storm Water Management Model (PySWMM). These simulations are conducted under varying design storm scenarios. This research contributes valuable insights into the optimal design and configuration of bioretention cells tailored to the specific challenges posed by stormwater in secondary cities of India. By systematically analyzing the sensitivity of these green infrastructure elements, the study aims to inform urban planners, engineers, and policymakers about effective stormwater management strategies.

How to cite: Tripathi, I. M. and Mohapatra, P. K.: Sensitivity Analysis of Bioretention Cells for Stormwater Management: A Study in Secondary Cities of India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14278, https://doi.org/10.5194/egusphere-egu24-14278, 2024.

A.34

EGU24-14353

Radiation budget and surface energy balance of green roofs using flux profile method

Yongwon Seo and Woo Chang Jeong

One of the primary advantages offered by a green roof is its ability to regulate indoor temperatures more effectively in response to changing outdoor temperatures, in contrast to a traditional concrete roof on a building. This advantage aids in decreasing the amount of energy needed to cool the building during warm seasons and heat it in colder seasons. This investigation gathered data from four recently constructed detached buildings: one with a bare concrete roof, another with a highly reflective paint roof, and two with green roofs. The focus was on examining the complete radiation budget and surface energy balance of green roofs compared to other roof types during a summer season in Korea. The thorough data collected allowed for a quantitative assessment of how green roofs behave in terms of energy balance, particularly when compared to bare concrete roofs. The monitoring period for this study took place over a week, from July 21, 2021, to July 28, 2021. Results indicated that, on average, green roofs reduced the maximum indoor temperature by 6.83℃ compared to buildings with bare concrete roofs, potentially resulting in significant energy savings required for cooling. Additionally, the analysis of energy balance using the flux profile method highlighted the significance of the difference in ground heat flux in determining indoor building temperature. The findings also revealed that green roofs utilized a substantial portion of net radiation for latent heat flux (70.7%), but a minimal amount for ground heat flux (0.5%). Conversely, bare concrete roofs used a larger portion of net radiation for ground heat flux (16.2%) and sensible heat flux (45.3%), resulting in greater warming of both indoor building areas and the air near the surface. These outcomes illustrate that green roofs not only stabilize indoor temperature fluctuations but also directly assist in mitigating the heat island effect.

How to cite: Seo, Y. and Jeong, W. C.: Radiation budget and surface energy balance of green roofs using flux profile method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14353, https://doi.org/10.5194/egusphere-egu24-14353, 2024.

A.35

EGU24-15236

ECS

Balancing Urban Heat, Flood and Water Scarcity: Blue-Green Infrastructure in Alpine Cities

Lisa Ambrosi, Manfred Kleidorfer, Thomas Einfalt, Yannick Back, Alrun Jasper-Tönnies, Claudia Fennig, Martina Hauser, Fabian Funke, and Georg Leitinger

In Alpine cities, water management needs to be adapted to the challenges of climate change, including altering temperature and precipitation patterns. Blue-green infrastructure (i.e., the combination of nature-based and technical solutions) can help to improve the water and energy balance, to increase the evaporative cooling effect, to maintain sufficient soil water availability and to reduce runoff peaks. Thus, it can reduce the risks of heat, drought and flooding, and improve the overall quality of life in cities. The implementation of blue-green infrastructure requires an interdisciplinary approach, as mechanisms of urban water management and ecohydrology (i.e., energy balance and soil-plant-atmosphere continuum) must be optimized with regard to the common goal.

In the research project 'BlueGreenCities', ecological and technical disciplines are integrated to close knowledge gaps regarding (1) land-atmosphere interactions in ecological, hydrological and meteorological systems, and (2) the performance of blue-green adaptation measures under different climate scenarios in alpine urban areas. We present first results of measurement campaigns and eco-hydrological modelling to better understand the energy budget of various green spaces in the city of Innsbruck, Austria. Moreover, we give first insights if the specialty of the alpine setting (increasing summer droughts, but still cold winter temperatures) will be a chance or a burden for the current urban vegetation in the future.

The outcomes of our project underpin the importance of climate-friendly and future-proof planning of urban green spaces to ensure proper functioning of the blue-green infrastructure concept. The results support scientists as well as urban planners, land developers and policy stakeholders in decision-making for sustainable and flexible water management systems that maintain human well-being, economic development and environmental protection. This work is funded by the Austrian Climate and Energy Fund in the project BlueGreenCities (Project No. KR21KB0K00001), funding period: October 2022 until September 2025.

How to cite: Ambrosi, L., Kleidorfer, M., Einfalt, T., Back, Y., Jasper-Tönnies, A., Fennig, C., Hauser, M., Funke, F., and Leitinger, G.: Balancing Urban Heat, Flood and Water Scarcity: Blue-Green Infrastructure in Alpine Cities , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15236, https://doi.org/10.5194/egusphere-egu24-15236, 2024.

A.36

EGU24-16057

Examining the Impact of Regulatory Measures on the Implementation of Nature-Based Solutions in Urban Water Management: Insights from Finland

Aino Saarinen, Piia Leskinen, Aleksi Reini, and Elina Kasvi

Climate adaptation and climate change prevention have become essential aspects of city planning. Urbanization and changing climatic conditions pose a threat to the sustainability of cities, and excess stormwater exacerbates these challenges by causing flooding and pollution of the receiving water bodies. To address these issues, cities must enhance the sustainability and climate resilience of their stormwater management systems. Nature-Based Solutions (NBS) offer a sustainable alternative to traditional grey infrastructure by providing water retention, detention, and pollutant reduction capabilities. Despite their numerous benefits, the adoption of NBS lags behind, with conventional solutions often being favored. Effective policy measures are crucial for promoting the integration of NBS into urban water management systems and aligning them with overall sustainability goals.

This study uses multilevel analysis that begins with an examination of EU policies and national legislation to understand the regulatory landscape. The focus then shifts to local stormwater regulation practices, which are explored through interviews with stormwater experts from various cities. These interviews provide insights into the practicalities, functionality, and shortcomings of stormwater regulation practices. Finally, this study focuses on Turku, analyzing the impact of the Blue-Green Index (BGI), which has been used to direct new constructions to use Green Infrastructure and NBS. The analysis of Turku's construction plans serves as a real-world case study to evaluate the actual effects of BGI on NBS implementation.

This research adds to the academic conversation by examining the complex relationship between regulatory measures and the practical application of Nature-Based Solutions (NBS) in urban water management. By analyzing decision-making processes at various levels, this study offers detailed insights into the difficulties and potential opportunities associated with promoting environmentally sustainable water solutions in cities. The findings of this research have significant implications for policymakers, urban planners, and environmental practitioners and could help inform strategies that encourage the adoption of NBS and create more resilient and sustainable urban water management systems.

How to cite: Saarinen, A., Leskinen, P., Reini, A., and Kasvi, E.: Examining the Impact of Regulatory Measures on the Implementation of Nature-Based Solutions in Urban Water Management: Insights from Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16057, https://doi.org/10.5194/egusphere-egu24-16057, 2024.

A.37

EGU24-4670

Investigation on Flood Resistance Characteristics of Waterfront Plants: A Case Study of Baxi Stream in Fujian Province, China

Jinn-Chyi Chen, Feng-Bin Li, Jian-Qiang Fan, Xi-Zhu Lai, Gui-Liang Li, and Wen-Sun Huang

Urban waterfront green spaces are pivotal in maintaining urban-rural landscape patterns, enhancing habitats and biodiversity, modulating temperature and humidity, purifying air, mitigating noise, and improving the urban microclimate. They play a crucial role in regulating the urban ecological environment and enhancing natural environmental capacity. Several waterfront plants demonstrate a high adaptability to local hydrological and climatic conditions, and are resilient to drastic water level changes. Their roots can stabilize riverbanks or riverbeds during abnormal floods. However, there is a dearth of empirical research data on these native plants. This study focuses on the flood that occurred on June 13, 2022, in Baxi Stream, Yong'an City, Fujian Province, China, causing damage to revetments, sidewalks, plants, roads, and disrupting urban traffic. Utilizing this flood event as a case study, we collected terrain data via real-time kinematic (RTK) surveying and unmanned aerial vehicles (UAV). We examined flood traces on structures, buildings, and trees to determine the water level, water surface slope, and inundation depth of waterfront green space during the flood event. We also investigated several common invasive natural plants, including Gramineae, Cyperaceae, and Polygonaceae families, and artificially cultivated plants like Cannaceae. Using the plant type survey data, we calculated the shear stress and flow velocity during the flood event to comprehend the anti-flow characteristics of waterfront plants in the study area. Our findings revealed that naturally invasive Gramineous plants, such as Saccharum spontaneum L. and Phragmites australis, possess a high flood resilience, withstanding mean flow velocity exceeding 5m/s. This study can provide a valuable reference for the selection of greening plants for waterfronts or plant engineering methods to safeguard waterfronts or riverbeds.

How to cite: Chen, J.-C., Li, F.-B., Fan, J.-Q., Lai, X.-Z., Li, G.-L., and Huang, W.-S.: Investigation on Flood Resistance Characteristics of Waterfront Plants: A Case Study of Baxi Stream in Fujian Province, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4670, https://doi.org/10.5194/egusphere-egu24-4670, 2024.

A.38

EGU24-5811

ECS

Understanding Soil Characteristics and Hydrology to Optimise FloodWall®: Another Step Towards Effective Green Infrastructure

Devakunjari Vadibeler, Joseph Holden, Fleur Loveridge, Andrew Sleigh, and Gerbren Haaksma

With rising urbanisation and environmental concerns, green infrastructure has become increasingly used to address a range of environmental issues, including flood hazards. By incorporating green infrastructure into their innovation strategies, cities may achieve a better balance between development and environmental conservation. In accordance with these global initiatives, Andel Ltd.’s FloodWall® stands out as an affordable, green substitute for perimeter flood defence made primarily of non-porous, post-industrial plastic waste, reinforced at the posts with steel pipes for added durability. This flood defence system, made from recycled materials and powered by renewable energy, can be installed in new constructions, existing buildings, and commercial settings. With the goal to maximise the potential of FloodWall® as a sustainable flood defence system, a collaborative effort has been made to develop specific site investigation methods to better understand the local soil hydrology and other characteristics that will control excess water flow beneath the wall and hence determine its effectiveness. Integrated methods are used including analysing geographic information system (GIS) data alongside in-situ and controlled laboratory findings to improve the efficiency of FloodWall® while cutting down its cost. For such green infrastructure solutions to be effectively and successfully implemented, a thorough understanding of site-specific soil properties such as permeability, soil water holding capacity, and the precise location of underground water pipelines and electrical equipment is vital. Accurate temporal and geographical soil hydraulic data are also critically needed for strategic management and accurate flood predictions. Precise soil moisture change measurements across larger areas can be difficult due to the dynamic nature of soil moisture levels. Although AI tools have a lot of potential in tackling this issue, the effectiveness of this approach is restricted by data availability. As a result, it is critical to prioritise localised research and modelling to maximise flood defence design, reliability, and cost. The main objective of this study is to determine an efficient evidence-based workflow that enables key decisions on how to implement installation of sustainable and cost-effective flood walls around properties in locations where public or private funding for community defences are not viable. Our study uses (i) analysis of satellite imagery, (ii) controlled laboratory experiments, (iii) in-situ analysis using cutting-edge sensors, and (iv) appropriate machine learning (ML) and artificial intelligence (AI) techniques to investigate site-specific soil hydraulic properties. Data feeds a suitable numerical model to estimate soil water flow and water seepage beneath flood defence structures. With this integrated approach, environmental stakeholders and flood researchers are provided with extensive site-specific data as well as comprehensive reports that will allow well-informed decisions regarding the implementation of sustainable flood defence technologies in cities, with a particular focus on the FloodWall®.

How to cite: Vadibeler, D., Holden, J., Loveridge, F., Sleigh, A., and Haaksma, G.: Understanding Soil Characteristics and Hydrology to Optimise FloodWall®: Another Step Towards Effective Green Infrastructure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5811, https://doi.org/10.5194/egusphere-egu24-5811, 2024.

A.39

EGU24-7564

ECS

Evaluation of the Performance of Green Roof Substrates with Recycled Materials: A Three-Year Comparative Study

Barbora Rybova, Marek Petreje, Petra Heckova, and Michal Snehota

The aim of this study was to test newly developed green roof substrates with a significant content of recycled materials under real conditions and to compare them with a commercially available substrate.

A two-layer extensive green roof of 7×5 m² was constructed in 2020 and divided into four sections, two of which had top layers based on new substrates. These two substrates contained the same amount of crushed brick from demolition waste (37.5% by volume) but differed in the amount of pyrolyzed sewage sludge biochar (9.5% by volume in one and none in the other). The commercial substrate was mostly based on expanded shale, lava, and pumice. Hydrophilic mineral wool was used as the bottom layer of the green roof system to improve the water retention layer. Vegetation was established with sedum carpets.

Undisturbed substrate samples were taken in 2021, 2022 and 2023 to monitor changes in hydrophysical properties (retention curves, saturated hydraulic conductivity, grain size). At the same time, vegetation development over time was monitored visually, and substrate temperature and humidity were continuously measured by autonomous sensors.

Plants in the biochar and demolition debris plots rooted faster into the substrate and achieved higher cover. While plants in plots with commercial substrate or without biochar turned red in response to stress during periods of lower rainfall or more extreme temperatures, plants in the biochar-containing plot remained lush green longer. In the following year, a greater number of emergent plants (primarily grasses) that spread from the surrounding area were observed on the biochar-amended substrate. This was thought to be due to the increased availability of nutrients from biochar.

Surface temperature amplitudes were higher than substrate and mineral wool temperatures, locally influenced by the plant biomass surrounding the sensors. Temperatures of the substrate and hydrophilic mineral wool were more stable. Differences in substrate temperatures were observed particularly between substrates containing recycled materials and the commercially available substrate.

How to cite: Rybova, B., Petreje, M., Heckova, P., and Snehota, M.: Evaluation of the Performance of Green Roof Substrates with Recycled Materials: A Three-Year Comparative Study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7564, https://doi.org/10.5194/egusphere-egu24-7564, 2024.

A.40

EGU24-11423

ECS

Phytoremediation for mitigating soil heavy metal contamination: A strategic approach to enhance groundwater resilience in vulnerable shallow aquifer systems

Dhritilekha Deka, Karangat Ravi, and Archana M Nair

Groundwater, as the predominant freshwater resource globally, faces a growing scarcity challenge amid the rising global population, making it a critical resource in developing nations. Understanding the key factors influencing groundwater availability under current climatic and human-driven conditions is vital for achieving the sustainable development goals (SDGs). In regions like Assam's shallow alluvial aquifers, located in northeastern India along the flood-prone Brahmaputra River and the Himalayan foothills, the quality of groundwater is of paramount concern for managing its extraction and recharge. Despite its huge water potential, the region accounts for some of the most water-stressed pockets of the country, emphasising the need for thorough groundwater resource assessment for effective protection and management. The present study delves into the high vulnerability of groundwater in Assam due to both natural hydrogeological conditions and human-induced factors using geospatial models. Utilising DRASTIC and Risk Index (RI) models, we discovered that shallow groundwater tables and alluvial deposits are particularly susceptible to adverse effects from unplanned changes in land use and land cover (LULC). The findings indicate a significant correlation between urban-induced LULC changes and groundwater quality deterioration. This highlights the likelihood of industrial and domestic pollutants seeping from the soil into the underground aquifers, thus elevating the vulnerability of groundwater. To remediate the non-biodegradable and persistent heavy metal contaminants exposed to the soil from LULC activities, we propose a Nature-based Solution (NbS): phytoremediation using Chrysopogon zizanioides (vetiver grass). Laboratory-controlled experiments were conducted for two months with initial metal concentrations of lead (Pb), cadmium (Cd), and zinc (Zn) at 500 mg/kg. Results from the atomic absorption spectrometer showed selective metal absorption by the plants. The highest extraction capacity observed was 43% for Zn in the plant shoots, likely due to its role in plant metabolism, while 31% Cd and 35% Pb were removed. The study notes phytotoxicity signs, such as leaf chlorosis and shedding, indicating the plant's response to metal stress. However, with survival rates over 50%, the vetiver grass demonstrates significant metal tolerance. By integrating geospatial vulnerability assessment with the ecological technique of phytoremediation, this research presents a comprehensive strategy to enhance groundwater resilience. It showcases the efficacy of vetiver grass in developing green infrastructure solutions, offering a scalable and eco-friendly approach to mitigate soil and groundwater contamination. This study provides valuable insights for environmental policymakers and advocates, promoting sustainable NbS practices for regions facing similar challenges in groundwater management.

Keywords: Groundwater, LULC, Vulnerability, Phytoremediation, Heavy Metals, Vetiver Grass

How to cite: Deka, D., Ravi, K., and Nair, A. M.: Phytoremediation for mitigating soil heavy metal contamination: A strategic approach to enhance groundwater resilience in vulnerable shallow aquifer systems , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11423, https://doi.org/10.5194/egusphere-egu24-11423, 2024.

A.41

EGU24-9991

ECS

Study of Filtralite Depletion and pH Influence on Nickel Removal

Marlon Mederos, Concepción Pla, and Javier Valdes-Abellan

This work delves into the efficiency of Filtralite in managing Sustainable Urban Drainage Systems (SUDS) for nickel (Ni) removal from urban runoff water. It addresses the optimization of green infrastructure in relation to water pollution and public health, due to the toxicity of heavy metals in general and Ni in particular, and their potential accumulation in living organisms (Ricco et al., 2015). The study's relevance lies in the growing need for innovative and sustainable solutions in urban water management, particularly in semi-arid and urbanized areas where runoff carries heavy metals into water sources (Wang et al., 2017).

The experimental procedure was carried out using flow tests in 10 cm-length columns filled with Filtralite. This porous medium has proven effective in removing heavy metals, including Ni (Pla et al., 2021b) jointly with the requirement of a high hydraulic conductivity. A Ni pulse was introduced into the column and the breakthrough curve was continually monitored at the outflow. The laboratory experiment is underpinned by a numerical model in HYDRUS-PHREEQC-1D (HP1), incorporating three Ni removal processes: Dispersion, Chemical Precipitation, and Adsorption, achieving a determination coefficient (R2) of 98%. With the calibrated HP1 model, it is feasible to analyze the impact of pH as a key element in metal removal.

The interaction between the contaminated solution and Filtralite leads to a rapid and noticeable increase in the solution’s pH. Ni solubility is highly dependent on pH (Amiri & Nakhaei, 2021); an increase in pH causes the Saturation Index of Ni to decrease, thereby facilitating its precipitation as hydroxide. The results demonstrated that the final concentration of the pollutant directly depends on pH values, with the lowest concentrations occurring at the highest pH (Pla et al., 2021a).

Laboratory tests were conducted to analyze Filtralite's wear over time in its capacity to modify the pH of the circulating water. Distilled water circulated for 100 days in continuous flow. When Ni was injected at two different pH levels, 9.27 and 8.28, removal efficiencies of 94% and 47% were observed, respectively. This confirms the relationship between pH and pre-removal efficiency, underscoring the importance of pH control for process effectiveness. Representing Filtralite's depletion over time, a gradual decrease in pH is observed as water circulates. Polynomial adjustments with an R2 of 93% help to determine the relationship between pH, time, and flow rate.

This finding is significant for SUDS design, which aims not only for water regeneration but also for the reduction of metal pollution (Ghadim and Hin, 2017). The research underscores the importance of green infrastructure in managing urban risks, demonstrating how nature-based solutions can effectively mitigate complex environmental challenges. The Filtralite study provides a firm foundation for integrating these systems into a broader urban risk management framework, aligned with green infrastructure and sustainability guidelines.

How to cite: Mederos, M., Pla, C., and Valdes-Abellan, J.: Study of Filtralite Depletion and pH Influence on Nickel Removal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9991, https://doi.org/10.5194/egusphere-egu24-9991, 2024.