Robust Stormwater Management in the Pittsburgh Region
From the RAND Corporation - a global nonprofit research organization - this report addresses stormwater management and sewer overflow issues in the Pittsburgh, Pennsylvania metropolitan region within Allegheny County. The research behind this project provided the baseline science needed first to address this system future, in the face of climate change. This research is designed to support improved stormwater, wastewater, and climate resilience planning in the Pittsburgh region - and offers a robust framework for other cities facing these issues.
According to the report, Allegheny County’s water management system is inadequately sized to handle precipitation events, so that nearly every time it rains - a sewer overflow occurs somewhere in the system. In addition, the vulnerability analysis found that sewer overflow volumes are up to 15 percent higher than previously estimated.
RAND has developed new analytical approaches to derive long-term solutions for these impacts. Their approach to stakeholder engagement included a planning process called Robust Decision Making (RDM), that is designed to support decision making in the face of future uncertainties. RDM was used for the first scoping stage of the project in which stakeholders and partners helped define goals, performance metrics, policy levers, uncertain factors, and the relationships among these elements - for a research agenda.
The second stage involved a vulnerability assessment through a scenario analysis approach to understand the risks to Pittsburgh’s future sewer system. Climate change assumptions were developed as part of this study, in which the team created a recent historical rainfall scenario using observed data from 2004 through 2013, and then developed two climate-adjusted rainfall and temperature scenarios using projections from 2038 through 2047.
Chapter Three describes potential future sewer system vulnerabilities if no additional actions are taken, and Chapter Four provides preliminary simulation modeling results from a range of source reduction policy levers. The report goes on to detail the costs and benefits of some source reduction strategies which are evaluated using a range of scenarios representing current and future uncertainty about wastewater customer demand, climate and land-use changes, and infrastructure capital costs.
Along with key takeaways and strategies, RAND offers the following final recommendations:
- Plausible future change should inform near-term planning and design for stormwater and wastewater infrastructure investments.
- Evaluations of GSI should consider co-benefits beyond sewer overflow reduction, such as such as flood risk reduction, ecosystem services, and economic development.
- Source reduction could help reliably reduce overflows, but additional research is needed to fully define a long-term, adaptive stormwater and wastewater management strategy.
Publication Date: 2017
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