Collaborative Research: Reimagining Urban Watershed Management: A Systems Approach to Stormwater Control and Ecological Rehabilitation

It is expected that a greater number of larger and denser cities will manifest more potent and pervasive pressures on stream ecosystems worldwide. Urbanization leads to greater stormwater runoff, which can result in a slate of ecological impairments that collectively have been identified as the “urban stream syndrome” (USS). Stormwater control is thus central to protecting and rehabilitating urban waterways, but stormwater management has largely prioritized objectives motivated by societal concerns, like flood control and protecting infrastructure, over consideration of ecological functions in receiving waters.

Consequently, little progress has made towards ‘solving the syndrome’. This project aims to transform how urban runoff is managed by designing and demonstrating a systems approach to upland interventions to rehabilitate in-stream ecological conditions. The expectation is that the work will yield fundamental technological and conceptual advances to realize much-needed next generation stormwater infrastructure, addressing the grand challenge laid out by the National Academy of Engineering to Restore and Improve Urban Infrastructure.

The project could substantively improve the condition of surface waters across the US and abroad. According to the US EPA, urban runoff is the probable source of impairment for over 49,000 miles of rivers and streams that have been assessed in the US, a staggering number that illustrates the potential impact of innovative stormwater management solutions.

It is the goal of the project to provide the foundation for transforming how urban runoff is managed by creating a new framework for rehabilitating and protecting surface waters. The project will recast stormwater runoff as an environmental flows problem that can be addressed by upgrading traditional stormwater infrastructure into cyber-physical ‘smart stormwater’ systems capable of adaptively meeting ecological and regulatory objectives.

Static and decentralized replacement of grey stormwater infrastructure with green alternatives (e.g., bioswales, wet ponds) has not provided corrective remedies of USS. This has led to increasing advocacy for operational shifts towards basin-scale coordination of stormwater interventions and conceptual shifts towards viewing urban stormwater management through the lens of environmental flows.

Recent advances in sensors and controls now allow stormwater infrastructure to be operated as a ‘smart’ system for managing how and when runoff is discharged into a receiving stream, affording unprecedented opportunities to (re)establish desired flow regimes based on a set of multiple objectives. In this project, the target is to determine and demonstrate how stormwater systems can be tuned to achieve environmental flows as an objective function to meet ecological and regulatory goals.

The project will combine model parameterization and simulations with empirical tests, with the aim of assessing whether achieving environmental flows (1) is possible using a ‘smart stormwater’ approach; (2) alters ecosystem attributes and functioning in urban streams; and if so, (3) alleviates impairments characteristic of USS. This will entail (1) identifying and defining ecologically-informed performance objectives for urban watersheds; (2) using a systems approach to optimize stormwater interventions that leverage controllable outlets and adaptive control algorithms; and (3) empirically demonstrating and evaluating site- and system-level smart stormwater management at two experimental testbeds.

The project also will also pursue public outreach through educational partnerships. The project team will continue to work with Tennessee's Knox County Schools to host biannual “Meet the Creek” citizen science events that offer students opportunities to learn about the effects of urbanization on streams and automation of storm water control, as well as collect physical and biological data on in-stream conditions that will support K-12 curricular goals.

Additionally, aspects of this study will be integrated into topical courses taught by the investigators at their respective institutions, including a graduate seminar on ecological restoration and engineering courses focusing on modeling and analytics. The project will help advance diversity, equity and inclusion in STEM fields by involving students from underrepresented groups, who will be recruited through organizations like the UTK Engineering Office of Diversity Programs, and will afford excellent opportunities for graduate education and career advancement.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.