National Water ModelDavid R. Maidment1 (maidment@utexas.edu)

1Center for Research in Water Resources, The University of Texas at Austin

S u m m e r I n s t i t u t e a t t h e

N a t i o n a l W a t e r C e n t e r

The National Weather Service is collaborating with the academic community throughCUAHSI to support a National Flood Interoperability Experiment (NFIE). A seven weekSummer Institute is being held in June-July 2016 for 34 graduate students from 22universities to help advance the research supporting the National Water Model. TheSummer Institute will take place at the National Water Center, a newly opened facilityon the Tuscaloosa campus of the University of Alabama.

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N a t i o n a l H y d r o f a b r i c

The National Water Modeloperates on top of the NHD Plus,which is a geospatial hydrologicframework providing a detailednational-scale stream networkconsisting of more than 2.7million reaches for thecontinental United States. Eachreach is labelled by a uniqueidentifier and associated with itssurrounding local catchment.

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N a t i o n a l W a t e r M o d e l3The National Water Model startswith a precipitation andmeteorology forecast, processesthese through a land-atmospherewater balance and routes theresulting runoff continuouslythrough the nation’s streamnetwork. This is a single flowcontinuum, atmosphere to theoceans and coast to coast. TheWeather and Climate OperationalSupercomputer System (WCOSS)is used to do the computations.

C o n t i n e n t a l S c a l e F l o o d

I n u n d a t i o n M a p p i n g4

F r o m F o r e c a s t s t o E m e r g e n c y R e s p o n s e 5

Strategic Overview Map Flood Preplanning Map (Minor, Moderate, Major Floods)

Harry Evans, former Chief of Staff of Austin Fire Department

The address point system is a dataset that uniquely defines and locates residential geographic locations, which isadopted by the emergency response system. There are about 100 million such address points in the U.S.Discharge forecasts from the National Water Model are converted into water levels and then used to generatereal-time inundation maps. The inundation map is intersected with the address point layer to evaluate floodimpacts and guide flood emergency response actions.

Work with the first response community to define flood strategy for stream reaches

Address Points in Travis County (355,000)

Elevation-Indexed Inundation Mapping NHDPlus-HAND

Take blue line network, raise it andflood it out, continue for incrementsof elevation

Coastal Mapping

Riverine Mapping

Elevation-indexed flood inundation mapping

Flood water surface elevation modeling and forecasting

Inundation map library for each NHDPlus Reachfor coastal and riverine reaches

Real-Time Flood Inundation Mapping Existing System Proposed System

Existing Proposed Ratio

Number of Mapped Reaches 130 2691344

Total Mapped Length (Km) 2256 5192824 2302

Average Reach Length (Km) 17.4 1.93 0.11

Total Mapped Length (Mile) 1402 3226671 2302

Average Reach Length (Mile) 10.8 1.20 0.11

NHDPlus-HAND Raster –Version 0.1Computed at the CyberGIS facility,University of Illinois at Urbana-Champaign,by Yan Liu and colleagues using softwaredeveloped by David Tarboton andcolleagues at Utah State UniversityApril 15, 2016

NHDPlusCatchments and Flowlines

DEM

Height Above Nearest Drainage (HAND)

(relative elevation of land surface cell above cell in NHDPlus stream to which it flows)

Inundation map(HAND< 15 ft)

Water surface elevation h = z + y

z

y

h z:DEM

y:HAND

In June 2016, the National WeatherService will start operation of theNational Water Model, a continuouslyoperating near real-time hydrologicsimulation and forecasting system forthe continental United States. This willuse 1 km cells for the land-atmospherewater balance and 2.7 million NHDPlusstream reaches for the streamflowrouting. Four forecast models will berun using hourly and daily time steps.