Urban land cover across the globe is projected to expand by 1.3 million square kilometers by 2050, reshaping hydrological and geomorphic processes and intensifying stream degradation. Construction of roads, parking lots, and other impervious surfaces will accelerate runoff, erode stream channels, and change sediment patterns, with major consequences for water quality and aquatic ecosystems.
Now, researchers at the University of Vermont have developed a novel method to identify and map erosion and sediment supply potential (ESSP) along urban stream corridors, offering a scalable approach for understanding sediment dynamics in cities.
The study, led by recent UVM Ph.D. graduate, Suffiyan Safdar, in collaboration with colleagues from UVM’s Department of Civil & Environmental Engineering and the Rubenstein School of Environment and Natural Resources, analyzed nearly 50,000 storm events across 117 urban watersheds throughout the United States.
Using high-resolution topographic data, soil texture information, and impervious surface mapping, the team developed a framework capable of identifying where sediment is likely entering urban streams. Researchers then paired the ESSP analysis with high-frequency turbidity-discharge hysteresis and discharge data to characterize suspended sediment transport during storms.
Publishing their findings in Communications Earth and Environment, the team found that watersheds with more than 40% impervious cover showed significantly lower sediment responses, suggesting that extensive urbanization can suppress sediment supply through surface sealing, stream burial, channel hardening, and other infrastructure modifications. Below the 40% threshold, researchers observed no significant differences in sediment response among watersheds.
“Excess sediment is a major challenge for many urban streams, affecting both water quality and ecosystem function,” said Suffiyan Safdar, lead author of the study. “Our work advances understanding of sediment sourcing and transport in urban watersheds and provides a framework for identifying sediment hotspots within stream corridors. This information can help guide effective urban watershed management.”
Suspended sediment—the fine particles of soil, clay, silt, sand, and organic matter that are carried and remain suspended in the water column—serves as a key indicator of hydrological connectivity, erosion processes, and nutrient transport in watersheds. Determining where these sediments originate and how they move through stream networks is essential for managing water quality, restoring streams, and designing resilient stormwater infrastructure in urban environments.
The study also identified four distinct sediment supply and transport regimes that describe where sediment is sourced and how it is transported through urban watersheds: early-supply, minimal-midstream supply, mixed-supply, and lagged-supply regimes. The most prevalent pattern observed was a “first-flush” response, in which sediment from nearby downstream sources is rapidly mobilized during storms.
As urbanization continues to reshape watersheds, this framework provides a scalable, resource-efficient tool for understanding sediment dynamics—guiding stream restoration efforts, infrastructure planning, riparian management, and watershed decision-making as cities continue to expand globally.
