SAI: Examining Long-Term "Success" of Green Stormwater Infrastructure

Strengthening American Infrastructure (SAI) is an NSF Program seeking to stimulate human-centered fundamental and potentially transformative research that strengthens America’s infrastructure. Effective infrastructure provides a strong foundation for socioeconomic vitality and broad quality of life improvement. Strong, reliable, and effective infrastructure spurs private-sector innovation, grows the economy, creates jobs, makes public-sector service provision more efficient, strengthens communities, promotes equal opportunity, protects the natural environment, enhances national security, and fuels American leadership.

To achieve these goals requires expertise from across the science and engineering disciplines. SAI focuses on how knowledge of human reasoning and decision-making, governance, and social and cultural processes enables the building and maintenance of effective infrastructure that improves lives and society and builds on advances in technology and engineering.

Stormwater runoff is a major source of water pollution and flooding in cities, and up to $150 billion is needed to manage stormwater in the U.S. over the next 20-years. To manage stormwater cost-effectively, many communities, including those within the Chesapeake Bay watershed, have been investing in "green stormwater infrastructure" (GSI) practices.

These include rain gardens, which reduce and treat stormwater runoff by mimicking natural hydrologic processes. GSI can provide environmental and societal benefits beyond stormwater management and may help address environmental injustices while reducing economic costs for cities. However, these practices must be maintained to continue providing ecologic, hydrologic, and social benefits; without maintenance, these practices may become a burden to communities instead.

GSI practices are a relatively new stormwater management tool, but some of the oldest practices have been installed for a decade or more, particularly in the Chesapeake Bay region. In light of this, a pressing question is: to what extent are these practices a continued "success" ecologically, hydrologically, and socially 10+ years after installation? Furthermore, to what extent can we predict the "success" of aging GSI practices?

This project analyzes the ecologic, hydrologic, and social performance of residential rain gardens that are 10+ years old within the District of Columbia's Department of Environment & Energy (DOEE) RiverSmart Homes program. First, a database of visual inspection reports that have been performed on these practices since 2021 is analyzed to determine ecological success.

Next, a survey of the residents with rain gardens on their property is conducted to evaluate to what extent they see these practices as a success, how they maintain their rain gardens and at what frequency, and what factors influence their willingness to do this maintenance; this will determine social success and the role of maintenance in this success. The project also evaluates how quickly water drains through rain garden soils and running hydrologic models of each inspected rain garden which will be used to assess hydrologic success.

Lastly, survey responses and publicly available data are used to model residents' decision-making with respect to maintenance and to evaluate where "successful" 10+ year old residential rain gardens are likely to occur. This will yield helpful insights to other stormwater managers in the Chesapeake Bay and beyond regarding how site design and maintenance behaviors interact, and how to best support residents in maintenance behavior so that aging GSI practices maintain their ecological, hydrologic, and social benefits.

This award is supported by the Directorate for Social, Behavioral, and Economic (SBE) Sciences and the Directorate for Geosciences.

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.