Climate Resilient Management of Urban Stormwater and Wastewater Systems: a Pilot Study in the Pittsburgh, Pennsylvania Metropolitan Region

Pittsburgh, Pennsylvania's metropolitan region currently faces a major challenge in effectively managing its water resources. The region's combined stormwater and wastewater system needs substantial upgrade and reinvestment in order to eliminate untreated sewer overflows and reduce the risk of flooding in low lying areas. The billion-dollar investment decisions currently faced by local decision makers are further complicated by a changing climate, with recent projections suggesting that the northeastern United States is expected to see increased precipitation and more heavy rainfall events. These challenges could also be exacerbated by continued conversion of forested areas to impervious cover for new development.

In this talk, we present an initial evaluation of the region's vulnerability to future climate and land use change, one of three pilot studies focus on new tools for urban climate adaptation. Specifically, the study applies Robust Decision Making (RDM) to evaluate and improve the performance of improved storm and wastewater management strategies across a range of plausible future scenarios. We describe the results from a significant combined sewer system simulation modeling effort to consider how proposed infrastructure resilience strategies might better meet water quality and flood risk reduction goals and reduce the likelihood of future vulnerabilities. A range of approaches are evaluated for the region, including wastewater system upgrades, pipe repair, operational changes, and flow reduction from large-scale, regional implementation of green stormwater infrastructure (GSI).

The study represents an important early application of methods for decision making under deep uncertainty using a high-resolution, computationally intensive hydraulics and hydrology model in a complex urban context. It provides important insights on how regional storm and wastewater strategies might be improved and made more robust to uncertain future conditions. It also illustrates how methods like RDM can be used to support planning in cities and regions facing challenges from sewer overflows and urban rainfall flooding who have previously not had the capacity to address deep uncertainty.