Despite decades of research and organized efforts to control nonpoint source nutrient pollution associated with urbanization, waterways continue to be plagued by excess nitrogen, phosphorous, and sediment. This research investigated how urban watersheds can be improved through better stormwater management, explicitly evaluating watersheds in Washington, DC and Baltimore, Maryland that possess different degrees of urban decay and revitalization. This work is timely in investigating key environmental and social drivers of stormwater runoff and nutrient pollution in watersheds, as well as the associated factors related to the socio-ecological matrix of the built environment, urban decay and revitalization, and resident attitudes and behaviors.

Our work quantified how biophysical and social drivers of nutrient pollution and urban greenspace are inequitably distributed across neighborhoods in predictable ways. For example, lower socioeconomic neighborhoods had greenspace dominated by unmanaged plants consisting of higher proportions of invasive species, greater numbers of water-filled trash containers that produce mosquitoes, and the coexistence of mosquito species that were likely to increase disease risks. Household-scale stormwater Best Management Practices (BMPs), including managed trees, rain barrels, and rain gardens, are also more likely to be adopted in watershed areas with higher socioeconomic conditions, including lower renter and poverty rates, higher median household incomes and education levels, and greater tree canopy. Advanced modeling using machine learning approaches showed that greater BMP adoption rates in higher socioeconomic areas would address pollution hotspots more quickly and comprehensively than in lower socioeconomic areas that had lower BMP adoption rates. Many pollution hotspots in lower socioeconomic neighborhoods occurred in open areas characterized by abandonment and vacancy. It is possible that these pollution hotspots may never be addressed by household-scale BMPs unless neighborhoods and communities receive significant investments in infrastructure and social interventions. 

In addition to generating 15 research publications to date, this project supported the development and distribution of outreach on stormwater and mosquito management, training of citizen scientists and watershed stewards, and an intervention experiment to increase household BMP adoption. In low-income neighborhoods, we leveraged an existing urban tree giveaway program to implement and test a targeted social-marketing intervention consisting of distributed emails and flyers promoting tree adoption. The percentage of trees adopted and the percentage of households adopting a tree increased over past years in neighborhoods exposed to the intervention compared to neighborhoods that did not receive the intervention. Engagement with residents indicated four main reasons residents declined free tree planting and giveaways: conflicts with cars, potential damage to sewer lines and sidewalks, trees being too expensive to maintain or causing damage that costs too much to repair, and too much upkeep.

Community engagement through train-the-trainer programs, workshops, and community outreach events were used to educate residents about stormwater and manage nutrient pollution through household-scale stormwater BMPs. Methods included partnering with workforce development/green jobs community organizations to teach train-the-trainer classes, teaching landscape practitioners and public works professionals on how to design, install, and maintain BMPs, and informing the curricula of partnering Watershed Stewards Academies. We delivered education to property and HOA managers on stormwater resources and taught actions that communities can take towards BMP implementation. We partnered with exisitng projects to conduct workshops with K-12 teachers and their students on nutrient pollution, microplastic pollution, and biodiversity, as well as created related education materials and curricula. Workshops educated residents of mosquito-related risks associated with unmanaged greenspace and associated trash, and informed residents of affordable mosquito control methods.

In summary, nutrient pollution and urban greenspace are inequitably distributed across neighborhoods. The loss of infrastructure and a declining resident population in lower socioeconomic neighborhoods can created a negative feedback where open spaces, unmanaged greenspace, and associated trash increase the export of nonpoint source pollution in waterways and support mosquito pests. The adoption of stormwater BMPs also clusters in urban areas across socio-economic boundaries, requiring targeted, community-specific social interventions to implement BMPs on previously unmanaged greenspace to reach nutrient management goals, reduce trash and decrease associated mosquito risks.

Last Modified: 01/27/2025
Modified by: Paul Leisnham