National Water Model-Based Diagnoses of Recent High-Impact Floods

The NOAA National Water Model (NWM) began producing officially operational hydrologic forecasts
in August of 2016. The multiple spatial frameworks and multiple forecast configurations
of the NWM are now enabling a wealth of new forecast information related to floods and their
potential impacts on society including things like critical infrastructure (e.g. transportation
and built facilities). In this presentation we provide a quantitative diagnosis of the first versions
of the NWM (versions 1.0, v1.1 and v1.2) in their depiction of flood events both with respect to
aggregate flood statistics performance and for selected case studies. Aggregate statistical analysis
will focus on assessing the regional performance of the NWM to predict threshold-based high streamflow amounts
as well as terrain undergoing episodic inundation. A set of more in-depth analyses will focus on both
qualitative and quantitative assessment of selected recent high impact flood events. Event analyses will
focus on aspects of overall model fidelity in capturing peak flow and recession characteristics, areal
extents of inundation and forecast lead time dependency.