Predicting Localized Flooding during the 2015 North Alabama Christmas Flood Event Using WRF-Hydro Simulated Streamflow

The 2015 North Alabama Christmas Flood Event resulted from a combination of high antecedent soil moisture and over 250 mm of rainfall during the 72-hour period of 1200 UTC 23-26 December 2015.  An additional 25-50 mm of rain was recorded on 28 December 2015, further exacerbating flood conditions.  The Tennessee River south of Huntsville, Alabama, reached moderate flood stage, recording a crest over 22 feet, up from 9 feet prior to the event.  The Paint Rock River, Flint River, and Indian Creek watersheds in Madison and Jackson counties also reached moderate and major flood stage.  To investigate the link between soil moisture and flood potential, as well as determine the utility of the Weather Research and Forecasting hydrological extension package (WRF-Hydro) in predicting localized flooding in hilly, county-scale watersheds, WRF-Hydro was coupled with the Noah Land Surface Model with Multi-Parameterization Options (Noah-MP) to model the North Alabama flood event on a 1 km land surface grid and a 100 m routing grid.  After a spin-up duration of three years for both the land surface and hydrological components of the model using hourly North American Land Data Assimilation System (NLDAS) meteorological forcing, hourly Multi-Radar Multi-Sensor gauge-corrected precipitation was used in place of the NLDAS precipitation for the duration of the event beginning 0000 UTC 23 December 2015.  Simulated streamflow along the Paint Rock River, Flint River, and Indian Creek was compared to recorded streamflow measurements from United States Geological Survey (USGS) stream gauges located within these watersheds.  This presentation will examine the results of this comparison and discuss the performance of WRF-Hydro for hilly, county-scale watersheds.