Impacts of Anthropogenic Change on Streamflow: Runoff Generation and Stormwater Timing

Authors: Chen-Ling J. Hung*, University of South Carolina, L. Allan James, University of South Carolina, Gregory J. Carbone, University of South Carolina
Topics: Geomorphology, Water Resources and Hydrology, Anthropocene
Keywords: urban flood hydrology, runoff generation, hydrograph, instream flow, rainfall-runoff process, land use
Session Type: Paper
Day: 4/10/2018
Start / End Time: 8:00 AM / 9:40 AM
Room: Balcony K, Marriott, River Tower Elevators, 4th Floor
Presentation File: No File Uploaded

Fluvial systems are vulnerable to changes in urban land use that affect flood flows. Not only is urbanization and urban flooding continuing to spread rapidly with a global migration to cities, but also surface inland flooding has grown greatly in recent years in response to extreme precipitation events. More research is needed to understand how much urbanization increases runoff generation, stormflow volumes, and peak stormflow discharges. This study presents results of a field measurement study in Columbia, South Carolina that demonstrate the impacts of anthropogenic change on stormwater generation and storm hydrographs. Hydrologic responses in two small, highly urbanized watersheds are contrasted with a small, rural control watershed. The urban watersheds experience serious repetitive flooding with extensive damages and threats to public safety, whereas the control watershed is of similar size but forested and lacking in development. Comparisons of runoff volumes, runoff coefficients, peak discharges, stormflow peak arrival times, and shapes of dimensionless unit hydrographs between the watersheds indicate that stormflow depths and peak instantaneous discharges are more than an order of magnitude greater in the urban watersheds than in the rural watershed, but that changes in hydrograph shapes, as measured by skewness, kurtosis, and time-to-peak, are more subtle. Urbanization of hilly forested areas with sandy soils, such as the study watersheds, may cause pronounced increases in runoff that result in substantial increases in flood risks and the potential for geomorphic change.

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