1. The Red River Flood of 1997 in Grand Forks, North Dakota
Predicting Flooding based on Snow Accumulation
Jennifer Sorenson
November 21, 2002

2. Location of the Red River

3. Red River Flood April 1997 100-year flood overall
500-year peak flows in some places
95% of residents evacuated
Downtown fire
$4 billion damages total – $3.6 billion in GF/EGF
Pictures taken from the Grand Forks Herald

4. What caused the flood? 8 blizzards brought nearly 100 inches of snow
Colder than normal spring temperatures
Sudden snowmelt
Top: Blizzard Betty with 40-mph winds and 50-below wind chill.
Bottom: Blizzard Elmo left behind 20-foot snow drifts.
Pictures from the Grand Forks Herald

5. Predicting Crest Levels
Satellite and airborne remote sensing
NOHRSC
AVHRR from NOAA
Snow cover
GOES
Surface Air Temp.
Soil Moisture
Gamma radiation detection systems
NWS
Snow Water Equivalent
Crest Levels
Snow model
Rating Curves
Estimate volume of snowmelt runoff

6. SWE along Red River

7. Rating Curve and Crest Level Predictions
Daily Mean Streamflow
Rating Curve
Actual Crest Level on April 15 = 45.3 ft
From USGS water resources website
From “The Red River of the North 1997 Floods – Service Assessment and Hydraulic Analysis” performed by the NWS

8. Grand Forks Prepares NWS predicted crest level of 49.0 feet
Grand Forks prepared for crest of 52.0 feet
Pictures from the Grand Forks Herald

9. The Flood Devastation
Pictures from “Come Hell and High Water”, produced by the Grand Forks Herald

10. NWS Lessons Learned
NWS adjusted crest prediction to 50.5 ft on April 16, 1997
Actual crest occurred at feet
Difference of 3.8 feet attributable to:
Bridge Effects
Unsteady Backwater
Surprise Discharge

11. Acknowledgements Dr. Maidment Dr. Tom Carroll, NOHRSC
Grand Forks Herald