Assessing Nutrient Export and Stormwater Retention Amid Urban Growth in Greenville, North Carolina

abstract: Urban expansion alters hydrology and impacts nutrient export and runoff retention, but understanding the effects of these processes requires consideration of local context and physical geography. Toward this end, this study spatially examines ecosystem services and tradeoffs linked to land use changes over 20 years (2001–2021) in five sub-watersheds in Greenville, North Carolina. Using the InVEST® modeling suite, specifically the Nutrient Delivery Ratio (NDR) and Urban Stormwater Retention (USR) models, this study explores how urban growth and land use change affect nutrient delivery and stormwater runoff. The NDR model estimates nutrient loads based on land cover and USR assesses stormwater retention and avoided nutrient loads. Results indicate increased impervious surfaces reduce stormwater retention and amplify nutrient export, leading to greater flood risks and water quality degradation. These effects are particularly pronounced in rapidly urbanizing regions where natural retention features are diminished or removed. Findings highlight the importance of ecosystem-based retention services, such as wetlands, forests, and green infrastructure, in mitigating urban hydrological impacts. They also emphasize the need for integrating these features into sustainable land-use planning and urban design. Additional data collection and further refinement of biophysical inputs would enhance the translational value of InVEST modeling.