Suspended sediment supply and transport regimes in urban watersheds across the United States

Urbanization reshapes hydrological and geomorphic processes, and intensifies stream channel erosion and sediment supply. However, urban suspended sediment production and transport understanding remains poorly generalized at continental scales, due to lack of scalable tools. Here we develop a novel method to estimate erosion and sediment supply potential (ESSP) along stream corridors using high-resolution DEMs, soil texture, and impervious cover. We integrate ESSP and high-frequency turbidity-discharge hysteresis from 50,000 storm-events across 117 urban US watersheds. Variation in source proximity and transport patterns governing first-flush and delayed responses is captured by four sediment regimes. An impervious cover threshold of 40%, beyond which suspended sediment response significantly declined, indicates reduction in sediment supply, likely associated with channel hardening. These findings underscore the importance of geomorphology and longitudinal position of sediment sources in controlling urban suspended-sediment dynamics. ESSP identifies these longitudinal positions with applications to stream restoration siting, infrastructure design, ecology, and watershed planning. Urban streams show four suspended-sediment regimes and declining responses beyond 40% impervious cover, according to a study integrating an erosion–sediment supply potential metric with turbidity–discharge hysteresis from 50,000 storm events across 117 US watersheds.