Reimagining Urban Leftover Spaces Under Overpasses: Mitigating Urban Heat Islands and Heatwaves Through Green Space Transformation

The urban thermal environment is deteriorating due to the constructed urban space and climate change, which negatively impacts public health, especially in the Urban Canopy Layer (UCL). Recent research has investigated the contribution of microclimate parametric in specific urban typologies such as plazas and streets. However, the wasted under-bridge space, which is hard to utilize and usually deemed an obstacle to community connection, is lacking in the investigation. Therefore, this research aims to study the thermal mitigation and adaptation design strategy in terms of the thermal benefit of space, eventually transforming the space with a thermal comfort perspective to the community. The site was chosen under the Williamsburg Bridge in Lower Manhattan, a highly populated and dense low-income community. The method of study is research by design. Firstly, I used open-source GIS data and community reports to investigate the neighborhood's socioeconomic status and functional outdoor space. Secondly, we conducted a site visit and thermal walk in August to measure the microclimate parameters, including air temperature, Relative Humidity (RH), wind speed, and direction, to understand the impact of different heights of under-bridge space on thermal comfort. Thirdly, we use open-source Climate Studio and Ladybug to stimulate the thermal environment of under-bridge space and interpret it with the Universal Thermal Climate Index (UTCI). Based on the thermal environment analysis, measurement, and investigation to tailor the mitigative and adaptative design strategy for transforming the under-bridge. Eventually, the strategy will guide design implementation via proposed outdoor activity, planting strategies, and pavement patterns in the under-bridge space design, and it will evaluate the impact of thermal comfort with the implemented strategy on the space. The result revealed that the under-bridge space limited sunlight hours and the Sky view factor (SVF). It correlated with the space change, resulting in different stress levels on the UTCI scale. The evaluation result highlighted the tailored strategy in the design process can help alleviate the specific stress level of UTCI levels to zero or less thermal stress, especially in space with extremely low SVF conditions. This study can be a reference case for a similar under-bridge space transformation with a semi-open space, limited sunlight hours, low SVF, and close to the residential area. The study provides urban designer planners and landscape architects with a toolkit and approach from the pedestrian thermal comfort perspective rather than the aesthetic environment design in waste space reclamation strategy.

Name thesis:degree_name

Master of Landscape Architecture

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Landscape Architecture

Department dc:contributor.department

Landscape Architecture

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2025

Author dc:creator

• Zhao, Jiahua

Chair dc:contributor.committeechair

• Engelke, Jennifer Ann

Committee members dc:contributor.committeemember

• Kim, Mintai
• Ha, Jaeyoung

• Thermal comfort
• Urban Leftover Space
• Mitigation
• Adaptation strategy
• Under-overpass space

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:42242

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/124258