Navigating environmental, economic, and hydrologic tradeoffs in the design of green infrastructure for stormwater management in urban settings

With growing urbanization and an increase in impermeable land uses, our stormwater infrastructure are becoming increasingly strained. The impending impacts of climate change will only worsen the situation, causing more extreme rain events resulting in flooding and in many of the United States’ cities, combined sewer overflows (CSOs). These CSOs dump untreated sewage and stormwater into local water bodies when the flow becomes too large due to extreme wet weather events. The impacts of CSOs and localized flooding can be extreme for a community, economically, environmentally, and with regards to human health. Green infrastructure has the potential to alleviate some of these issues by infiltrating more water and reducing pollutant loading in the water. This study analyzed six green infrastructure technologies against a gray alternative and found that there is not one universal solution that performed the best across all objectives. But rather there are trade-offs between objectives for every technology. One can use the information gathered about these trade-offs and the more in-depth information embedded in the model to understand where to target to reduce the negative impacts or increase the positive impacts of a technology. The sensitivity analysis using Morris’s one at a time method also provides useful information to help direct research and design attention to the most pressing design inputs for desired solutions. For example, green infrastructure maintenance is one of the highest contributors to cost, posing a barrier to entry for some projects on tighter budgets; however, knowing this allows for targeting ways to reduce need for maintenance through different plant species or media materials. The implications of this study focus on how green infrastructure can best be utilized to achieve sustainability across multiple dimensions. One of the critical takeaways is the need to involve a wide range of stakeholders early in a project to understand the objectives of interest and locally specific constraints of a project. The study also identified several areas that require further study to reduce emissions and cost to make these technologies more universally sustainable