Urban heat island mitigation through neighborhood-scale green stormwater infrastructure: design, implementation, evaluation

Thesis Abstract

Urban areas worldwide face increasing heat stress driven by dense urban materials, reduced vegetation, and limited evapotranspiration, which amplify energy use, air pollution, and health risks. This study investigates how neighborhood-scale green stormwater infrastructure (GSI) can mitigate urban heat islands (UHI) while delivering co-benefits in surface water management and neighborhood livability. The aim is to design, implement, and evaluate a replicable GSI intervention at the neighborhood scale that reduces ambient temperatures during heat events, lowers surface runoff, and enhances microclimatic comfort. Specific objectives are to (i) assess the thermal performance of a designed GSI network across a hot-doppler climate corridor, (ii) quantify changes in surface and near-surface air temperatures during peak heat days, (iii) evaluate hydrological performance and flood attenuation under design storm events, (iv) analyze social acceptance, equity implications, and behavioral responses to GSI measures, and (v) develop a transferable design framework and decision-support toolkit for municipal planners. The methodology adopts a mixed-methods, quasi-experimental research design combining physical instrumentation, hydrological modeling, and community survey methods. The study targets three urban neighborhoods within a metropolitan region that shares comparable climate, land use, and demographic profiles. A purposive sampling strategy identifies sites suitable for GSI installation, while a matched-control approach selects comparable neighborhoods without GSI interventions. Instrumentation includes 12 fixed weather stations and 20 microclimate data loggers deployed across treated and control blocks to capture hourly air and surface temperatures, relative humidity, and rural-urban gradient effects over 24 months to cover multiple heat events and seasonal variations. Hydrological performance is assessed using continuous rainfall monitoring, runoff measurements at catchment outlets, and calibrated SWMM (Storm Water Management Model) simulations to evaluate peak discharge reductions and infiltration volumes under 5-, 10-, and 25-year design storms. Social data are collected via structured surveys (n = 600 residents across treatment and control areas) and focus group discussions (n = 6 groups) to gauge perceived thermal comfort, safety, maintenance concerns, and equity implications. Analytical techniques include multilevel regression models to isolate the temperature impact of GSI while controlling for confounders, ANOVA to compare pre- and post-installation metrics, time-series analysis for short-term and long-term thermal trends, and thematic analysis of qualitative data to extract patterns in user experiences and acceptance. The study integrates the theoretical lens of urban ecological resilience and the cool corridors concept, complemented by the Environmental Justice framework to examine equity in access to cooling benefits. Expected findings indicate a statistically significant reduction in mean daytime surface temperatures by 1.5–2.5°C within treated blocks during heat waves, with near-surface air temperature reductions of 0.8–1.8°C relative to controls. Hydrological performance is anticipated to demonstrate substantial runoff attenuation (up to 45% reduction in peak discharge) and enhanced groundwater recharge efficiency, while the GSI network improves neighborhood thermal comfort indices and outdoor activity levels during extreme heat periods. Qualitative results are expected to reveal high community acceptance when maintenance responsibilities are clearly defined and when design enhances safety and aesthetics. The study contributes to knowledge by offering a theory-driven, empirically tested, neighborhood-scale design framework for integrating GSI into urban cooling strategies, bridging hydrology, urban climatology, and social equity considerations. It advances methodological rigor by combining long-term microclimate monitoring with robust quasi-experimental evaluation and participatory social assessments, delivering a transferable toolkit for planners that includes design guidelines, performance benchmarks, and a decision-support dashboard. The main conclusion posits that well-structured neighborhood-scale GSI can deliver meaningful UHI mitigation, improved stormwater management, and enhanced neighborhood livability without compromising urban density or cost efficiency when implemented with community engagement, ongoing maintenance planning, and equitable benefit distribution. Recommendations include adopting GSI as a core component of urban climate adaptation plans, integrating monitoring into project governance, and scaling the framework to diverse climatic regions with contextual adjustments to plant selection, soil media, and maintenance regimes.