Summertime Flash Floods in the Southern Appalachians

In this study, a 3D coupled surface-groundwater hydrology model (3D-LSHM) is used to simulate summertime flash floods (time to peak < 6 hours) in headwater catchments in the Southern Appalachians. The focus is on two distinctive types of regionally dominant convective events: tropical storms and isolated thunderstorms. The model has been implemented at 1km×1km, 500m×500m, 250m×250m and 100m×100m resolutions. Model simulations for two ungauged headwater catchments of the French Broad River, the Cataloochee Creek Basin in the Great Smoky Mountains National Park and the West Fork Pigeon River Basin, will be presented. The Quantitative Precipitation Estimation (QPE) Q2 products (Q2RAD_HSR_GC) were adjusted and downscaled using the rainfall data from rain gauge network in the Great Smoky Mountains. Model simulated streamflow agrees well with observations both in terms of timing (peak discharge) and mass balance (overall discharge). The space-time variability of hydrologic response across the two basins is examined in details with particular emphasis on interflow processes which are the dominant mechanisms of flash flood response in the regions. Implications of this study for predicting debris flows and landslides are also presented.