Assessing the Impact of Green Infrastructure on Urban Stormwater Management Efficiency

Thesis Abstract

Rapid urbanization has significantly increased the prevalence and severity of stormwater runoff, leading to frequent urban flooding, water quality deterioration, and infrastructural damage. Traditional grey infrastructure approaches often fall short in sustainably managing stormwater, prompting a critical need to evaluate the effectiveness of alternative solutions such as green infrastructure (GI). This study aims to assess the impact of green infrastructure on the efficiency of urban stormwater management within metropolitan areas, with specific objectives including quantifying the reduction in runoff volume attributable to GI installations, evaluating improvements in water quality parameters, and analyzing the cost-effectiveness of green versus conventional systems. The research employs a mixed-methods approach, integrating quantitative field measurements with qualitative stakeholder interviews to provide a comprehensive understanding of GI's performance and acceptance. The study adopts a correlational research design to establish relationships between the extent of green infrastructure implementation and stormwater management outcomes. The population comprises urban neighborhoods where green infrastructure measures—bioswales, rain gardens, permeable pavements, and green roofs—have been implemented over the past five years. A stratified random sampling technique is used to select 15 neighborhoods out of a total of 50, ensuring representation across different socioeconomic and land-use categories. From each neighborhood, data is collected from 30 stormwater catchments, resulting in a sample size of 450 sites, which provides sufficient statistical power for analysis. Data collection instruments include installed flow meters and water quality sensors for real-time measurement of runoff volume, turbidity, suspended sediment, and nutrient concentrations during storm events, as well as pre- and post-implementation hydrological data. Supplementary qualitative data are obtained through semi-structured interviews with urban planners, environmental engineers, and residents. The study ensures validity and reliability through calibration of instruments, pilot testing of survey questionnaires, and triangulation of quantitative and qualitative data sources. Quantitative data analysis involves descriptive statistics, paired t-tests to compare pre- and post-implementation parameters, and multiple regression analysis to identify the influence of green infrastructure on stormwater management indicators. The theoretical framework is grounded in the Sustainable Urban Drainage Systems (SUDS) theory, complemented by the Theory of Planned Behavior to understand stakeholder acceptance. A conceptual model illustrating the relationships among green infrastructure characteristics, stormwater runoff reduction, water quality improvements, and social factors is developed. Expected findings indicate a statistically significant reduction (at least 40%) in stormwater runoff volume and substantial improvements in water quality parameters (reductions in turbidity and nutrient loads) associated with green infrastructure utilization. The analysis anticipates identifying key factors such as design specifications, maintenance practices, and community engagement levels as determinants of GI performance. These outcomes will demonstrate that green infrastructure is a cost-effective, environmentally sustainable, and socially acceptable alternative to conventional stormwater management systems. The study contributes to urban hydrology and sustainable infrastructure literature by providing empirically validated measures of green infrastructure effectiveness in diverse urban contexts, as well as insights into implementation barriers and enablers. It highlights the importance of integrated planning and community participation in optimizing GI benefits. The main conclusion underscores green infrastructure’s vital role in enhancing urban flood resilience and water quality, recommending policymakers incorporate green solutions into comprehensive urban drainage plans. Future research should explore long-term maintenance impacts, climate change resilience, and scalability of green infrastructure interventions across broader metropolitan regions.