452 Advancements in Estimating and Validating Bankfull Flow and Inundation in the National Water Model

Tuesday, 9 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Laura K. Read, NCAR, Boulder, AL; and D. N. Yates, D. J. Gochis, F. Salas, Z. Li, and S. Khan

The National Water Model is an operational, distributed, hydrologic model that runs in forecast and analysis modes across the Continental United States using the Weather Research and Forecasting– Hydro framework. One goal of the NWM is to provide continuous estimates of inundation on the land surface and over-bankfull flow from channels, by enabling 2-way coupling ofthe overland flow with channel flow and quantifying the exchange. This research describes the methodology for this advancement in two-way coupling the overland flow to the channel to quantify bankfull depth estimates and over-bankfull flow fluxes for each reach in the 2.7 million reaches of the National Water Model. River stage above bank-full-depth interacts with the median overland flow depth along the reach, allowing for diffusive inundation across the terrain and upstream propagation of the channel wave. Initial validation results are presented using existing hyper-resolution, nested model runs to compare inundation for specific events. Emphasis is placed on quantifying the accuracy of the new 2-way coupled inundation formulation with respect to streamflow rates and inundation depths for specific selected events. The computational impacts of the various overbank flow formulations will be discussed.
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