First Advisor

Vivek Shandas

Term of Graduation

Spring 2025

Date of Publication

6-3-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.) in Urban Studies

Department

Urban Studies and Planning

Language

English

Subjects

Climate Change Adaptation, Geospatial Analysis, Green Infrastructure, Spatiotemporal Variation, Urban Forestry, Urban Heat

Physical Description

1 online resource (viii, 166 pages)

Abstract

This dissertation provides a comprehensive analysis of the interaction between urban heat and green infrastructure (GI) in terms of dynamic aspects, spatiotemporal variation across various spatial scales, temporal phases, and socioeconomic contexts. By integrating a national-scale longitudinal analysis, street-level structural assessments, and neighborhood-specific resilience frameworks, this study enhances our understanding of how cities can utilize existing ecological assets to mitigate increasing heat risks while addressing systemic inequities.

Urban areas face unprecedented thermal challenges due to climate change and the urban heat island effect, with marginalized communities disproportionately affected. Although cities are increasingly adopting GI expansion for heat mitigation, significant knowledge gaps remain regarding the spatiotemporal complexity of thermal dynamics and their socio-ecological implications. This research utilized a unique pedestrian-level air temperature dataset from the National Integrated Heat Health Information System (NIHHIS) Heat Watch Campaign to explore these dynamics through three interconnected studies.

The first study investigated decadal changes (2013/14-2022/23) in urban greenery across 33 U.S. cities, employing satellite-derived vegetation indices and high-resolution urban air temperature maps. The findings revealed accelerated greenery loss in the hottest neighborhoods, with 69.7% of cities showing inverse relationships between heat burden and conservation efforts. A 150m grid-cell analysis highlights systemic preservation failures, indicating that current urban forestry policies inadequately protect vegetation in thermal hotspots.

The second study, conducted across four mid-latitude cities (Portland, Washington D. C., Philadelphia, and Boston), integrates vehicle-collected air temperature data with municipal tree inventories to assess cooling performance. These results indicate that tree diameter at breast height (DBH) is a significant predictor of microclimate cooling. Neighborhoods with the coolest microclimates have trees with an average DBH 2.87 inches (7.29 cm) larger than those in warmer neighborhoods, which tend to be less affluent areas, suggesting a temporal disparity of over a decade in tree maturity.

The resilience framework for the Portland Metro area distinguishes between resistance (afternoon-evening cooling) and recovery phases (evening-morning cooling). Through clustering analysis, seven neighborhood typologies were identified, revealing phase-dependent effects of urban characteristics. Areas with 30% canopy coverage optimized both resilience phases, whereas those with coverage exceeding 40% hindered overnight cooling. Socioeconomic disparities were apparent, with lower-income areas experiencing elevated temperatures, and low recovery cooling was correlated with racial demographics. The resilience framework offers planners a tool to evaluate neighborhood thermal performance, such as the "cumulative heat exposure" introduced in the study, and to identify phase-specific intervention needs.

By bridging the spatial and temporal scales, this dissertation offers evidence-based recommendations to assist cities in addressing heat inequities while enhancing ecological resilience. As urban temperatures rise, so must our commitment to stewarding existing ecological assets in the communities that need them most. The path to urban heat resilience lies not in planting our way out of crisis, but in protecting what already exists.

Rights

© 2025 YunJae Ock

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/43788

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