PhD Oral Exam - Shuyan Wan, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Green infrastructure (GI) is used to manage stormwater, reduce heat, and support ecological functions and climate adaptation in cities. However, its planning and evaluation remain fragmented: benefits and resource demands are measured in different units, technically preferred designs do not ensure adoption, and facility-level services are rarely compared with citywide resource use. This thesis examines these problems through an assessment–implementation–outcome sequence across project, neighborhood, and city scales, using green roofs as the main policy and infrastructure case. The first study developed an emergy-based multi-objective optimization framework that combined life-cycle cost, stormwater performance, regional climate information, and donor-side resource accounting. Applications in Longueuil, Canada, and Chizhou, China, showed that the sustainability level of optimized layouts was strongly site-dependent. The highest emergy sustainability index (ESI), whose values above 1 are commonly interpreted as indicating sustainable development, was 1.643 in Longueuil but 0.361 in Chizhou, and green roofs and selected combinations with sunken green space or rain gardens generally performed more favorably. The second study explained adoption patterns in Toronto by linking green roof permits with census-based socioeconomic and built-environment variables, then applying interpretable machine learning for rare-event classification at census tract and neighborhood scales. Financial incentives were not a uniform driver: contributions were generally negative at 50 CAD/m2, mixed at 75 CAD/m2, and consistently positive at 100 CAD/m2. Commuting-related variables were the strongest predictors. The third study constructed a 1995–2025 urban emergy account for Toronto and added a green roof benefit layer. Total emergy use increased by 50.4%, purchased and imported inputs remained 98–99% of the total, and the ESI decreased by about 40.4%. Manufactured imports were the largest negative contributor, followed by construction materials, commercial services, and stationary energy. Although the accumulated green roof stock provided measurable energy, stormwater, heat-related, biological, and greenhouse-gas benefits, its 2025 baseline benefit offset only a negligible share of purchased and imported emergy, and wider coverage scenarios did not materially change city-scale EMA indicators. Together, the studies show that GI benefits and resource requirements need to be evaluated at the scale where they occur. Project planning, policy-supported adoption, and city-scale accounting provide different but connected evidence for deciding where GI can produce meaningful environmental outcomes.