Assessing the Costs and Benefits of Green Infrastructure Plans Using Agent-Based Modeling and Scenario Analysis: Evaluating Social and Economic Values

While green infrastructures (GIs) are used to address urban flooding and stormwater runoff and enhance sustainability, their implementation faces challenges such as limited funding and competing priorities. Existing studies generally focused on specific/individual GI practices, potentially overlooking the broader benefits or values of comprehensive GI plans that generally are interconnected networks of multiple GI practices. Thus, this paper developed an agent-based model to offer municipalities, planners, and decision makers a structured and systematic modeling approach to: (1) simulate the dynamic nature of GI implementation plans across spatial and temporal dimensions; (2) capture the interplay among regulations that govern GI plans; and (3) conduct scenario and sensitivity analyses to gain deeper insights into the various characteristics of GI plans under different scenarios. The proposed model considered different economic values of GI plans, including stormwater management, carbon sequestration, pollutant removal, energy cost savings, and increased property value, as well as the social values, such as the positive impact on nearby residents/communities. In addition, the developed model considered the following six GI practices: green roofs, rain gardens, community gardens, bioswales, permeable playgrounds, and permeable pavements. These GI practices were modeled across five submodels: school greening, private property greening, park greening, right-of-way property greening, and public housing properties greening. Scenario analysis was conducted to investigate the effect of financial limitations (i.e., funding priorities) on the model's behavior under two scenarios. Finally, the developed model was statistically validated. The results showed that increasing the number of GIs does not guarantee an increase in their economic value, but rather the implementation of GIs should be well planned according to a priority plan. The findings also provided valuable insights into the importance of considering physical and institutional limitations. This paper contributes a practical workflow for evaluating the costs and benefits of GI programs.