the red river valley flood of 1997 : a call for worst-case scenario approaches to flood risk...
TRANSCRIPT
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The Red River Valley Flood of 1997: A Call for Worst-Case
Scenario Approaches to Flood Risk Management
Paul E. TodhunterDepartment of GeographyUniversity of North Dakota
Grand Forks, ND, 58202-9020USA
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Frequency-Magnitude-Damage Relationships
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Extreme Flood Hydroclimatology
• Unique combination of flood-producing processes
• Not sampled in historical record• Flood Flow Frequency Analysis (FFFA)
inadequate to estimate Qpk100
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Global Change
• Global climate change• Global environmental
change• Cultural change• Assumptions of FFFA not
valid
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Clark (2005): Worst-case Thinking
• Preemptive resilience as a national disaster mitigation strategy
• Probabilism• Possibilism
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1997 Red River Valley FloodGrand Forks, ND – East Grand Forks, MN USA
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Source: USGS
Constant Flood Factors
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Flood Forecast-Response System (FFRS)
(Krzysztofowicz, 1983)
1) Data collection
2) Flood forecasting
3) Forecast dissemination
4) Decision-making
5) Action implementation
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FFRS – Step 1Data Collection
• United States Geological Survey• Real-time river stage observations• Telemetry input to NCRFC• Required NWSRFS input data
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Stream Gage
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FFRS – Step 2Flood Forecasting
• National Weather Service River Forecast Centers
• NWS River Forecasting System modeling system
• Numerical Outlook – climatological forecast• Operational Forecasts – NWSRFS for 34
Red River Basin forecast points
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Variable Flood Factors
• Long lead time Fall soil
moisture Seasonally
frozen soils Snow water
equivalent of snowpack
• Short lead time Spring thaw Spring rain-on-
snow events River ice
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1 6 11 16 21 26 31
April 1997
0
10
20
30
40
50
60R
ive
r S
tag
e (
ft)
NCRFC
RR-Grand Forks
CrestApril 22
02:00
Outlookmode
Forecastmode
“Stair-Stepping”
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1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
W ater Year
0
50
100
150
200
250
300
Sn
ow
fall
(cm
)GFU
1892-1997
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Transect of snow depth and snow density in a prairie snowpackPomeroy et al. (1993)
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1-M
ar
8-M
ar
15
-Mar
22
-Mar
29
-Mar
5-A
pr
12
-Ap
r
19
-Ap
r
26
-Ap
r
0
100
200
300
400
M
DD
(C
°)W ahpetonFargoGrand ForksPembina
Bliz
zard
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1979 Flood
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Historical Extrapolation
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18 April 1997 Flood Statement, 2008 LST“This situation is unlike any flooding conditions ever experienced in eastern ND and NW MN. The NWS is working very hard with local, state, and federal agencies to give the public the most accurate information possible.”
USA Today, 14 June 1997, NCRFC Head
“... We really didn’t have an indication we were going to get 54 feet until all the pieces fell into place and we put the puzzle together.”
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FFRS – Step 3Forecast Dissemination
• National Weather Service Eastern North Dakota Forecast Office
• Staff Hydrologist• Flood Statements addressed
hydrological uncertainty to an educated audience
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FFRS – Step 4Decision-Making
• Local governments and agencies• City Emergency Manager• City Engineer• Mayor• Police, Firefighters, Sheriff, etc.
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1997 “The Perfect Snowmelt Flood”
• 1979 Flood: 49 ft• Changes since 1979• Anchoring of perception
• Midplaced concreteness• Unfamiliar with NWS
products / hydrology• Narrow flood-defense strategy
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NWSRFC
Forecast Point
2nd Numerical Outlook (feet)
14 March 1997
1997 Flood Peak
(feet)
Red River – Wahpeton 18.5 19.42
Red River – Fargo 37.5 39.72
Red River – Halstad 39.5 40.74
Red River – Grand Forks 49.0 54.35
Red River – Drayton 44.0 45.60
Red River – Pembina 54.0 54.90
Wild Rice River – Abercrombie 24.5 26.59
Sheyenne River – Lisbon 18.5 19.29
Sheyenne River – Kindred 21.0 22.33
Sheyenne River – West Fargo 22.5 23.30
Sheyenne River – Harwood 894.0 892.0
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NWSRFC
Forecast Point
2nd Numerical Outlook (feet)
14 March 1997
1997 Flood Peak
(feet)
Maple River – Mapleton 14.50 15.50
Pembina River – Walhalla na 16.20
Pembina River – Neche 22.0 24.51
Buffalo River – Hawley 10.0 10.77
Wild Rice River – Twin Valley 13.5 15.90
Wild Rice River – Hendrum 31.5 33.85
Marsh River – Shelly na 25.70
Red Lake River – Crookston 27.0 28.40
Snake River – Alvarado 10.0 10.60
Two Rivers River – Hallock 810.0 810.7
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-101 -100 -99 -98 -97 -96 -95 -94
45
46
47
48
49
50
Flood-of-record by 7 April
Flood-of-record by 15 AprilEventual flood-of-recordNCRFC Forecast Point
NWS NCRFC Forecast Points
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25
-Ma
r2
6-M
ar
27
-Ma
r2
8-M
ar
29
-Ma
r3
0-M
ar
31
-Ma
r1-
Ap
r2-
Ap
r3
-Ap
r4-
Ap
r5
-Ap
r6
-Ap
r7
-Apr
8-A
pr
9-A
pr1
0-A
pr1
1-A
pr1
2-A
pr1
3-A
pr1
4-A
pr1
5-A
pr1
6-A
pr
0
25
50
75
100
125
150S
an
db
ag
s (
x1
00
0)
Bliz
zard
Ha
nn
ah
Dik
es F
ail
Emergency Sandbagging Operations
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FFRS – Step 5Action Implementation
• Local workers• Federal workers – National Guard,
Army Corps of Engineers, Volunteers
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EvacuationSites
Emergency OperationsCenter
10 km1
2
3 3 2 1← . .
.
.
. .
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0 10 20 30 40 50 60 70 80 90 100 110 120
Julian D ay
0
10
20
30
40
50
60
Riv
er
Sta
ge
(ft
)0.90, 0.70, 0.50, 0.30, 0.10 Probabilities
Observed River Stage - 2006
Flood Stage
Outlookmode
Forecastmode
Advanced Hydrologic Prediction System
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Caveant admonitus (Let the forewarned beware)
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Walter M. Kollmorgen (1953) Settlement Control Beats Flood Control. Economic Geography, 29: 208-215.
Gilbert White(1911-2006)