Determining the Relative Contributions of Runoff and Coastal Processes
to Flood Exposure across the Carolinas during Hurricane Florence
Abstract
Estimates of flood inundation from tropical cyclones (TCs) are needed to
better understand how exposure varies inland and at the coast. While
reduced-complexity flood inundation models have been previously shown to
efficiently simulate the drivers of TC flooding across large regions, a
lack of detailed validation studies of these models, which are being
applied globally, has led to uncertainty about the quality of the
predictions of inundation depth and extent and how this translates to
exposure. In this study, we complete a comprehensive validation of a
reduced-complexity hydrodynamic model (SFINCS) for simulating pluvial,
fluvial, and coastal flooding. We hindcast Hurricane Florence (2018)
flooding in North and South Carolina, USA using high-resolution
meteorologic data and coastal water level output from an ocean
recirculation model (ADCIRC). We compare modeled water levels to
traditional validation datasets (e.g., water level gages, high-water
marks) as well as property-level records of insured damage to draw
conclusions about the model’s performance. We demonstrate that SFINCS
can accurately simulate coastal and runoff drivers of TC flooding at
large scales with minimal computational requirements and limited
calibration. We use the validated model to attribute flood extent and
building exposure to the individual and compound flood drivers during
Hurricane Florence. The results highlight the critical role runoff
processes have in TC flood exposure and support the need for broader
implementation of models that are capable of realistically representing
the compound effects resulting from coastal and runoff processes.