GEOG5839.22, Paleofloods
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Transcript of GEOG5839.22, Paleofloods
November 27
Paleofloods
Source: AP Photo/Carolyn Kaster
INSURED LOSSESDUE TO FLOODS EXCEEDED
$6.4 BIN 2010.
Source: Swiss Re
WORLDWIDE
11,027PEOPLE WERE
KILLED BY FLOODS.
Source: Swiss Re
Annual losses* due to floods in the United States
Source: National Weather Service* adjusted for inflation
2005
1993
1972
1927
FUTURE RISKSPAST BEHAVIOR
Photograph: skooksie
“100-year flood”
The 100-year flood refers to a flood that has a 1% chance of being equaled or exceeded in any single year.
The 100-year flood has come and gone, so, by all rights, Tucsonans should enjoy another century of great Southwest weather.“ ”
Metropolitan Tucson Convention and Visitor’s BureauSent immediately a!er a severe flood
WRONG
Paleoflood hydrology uses physical evidence le! behind on the landscape to make inferences about past floods that were not directly observed or recorded by humans.
Photograph: David Snyder
Slackwater deposits Fine-grained sediments laid down by floodwaters
The forts now stand like a castle of romance in the midst of an ocean of deep contending currents, the water extending for at least a mile behind them, and they are thereby only approachable by boats and canoes.”
“Francis HeronHudson Bay Company, 1826
St.. George and Rannie, Canadian Water Resources Journal, 2003
scarring
“flood rings”
injury
microclimatology
ReadingSt. George (2010), Tree rings as paleoflood and paleostage indicators. In Sto"el et al., (eds.), Tree Rings and Natural Hazards.
FLOOD SCARS
Photograph: Mark’s Postcards from Beloit
Photograph: NDSU Ag Comm
FLOOD SCARSThe timing of the flood can be determined by counting the number of rings between the scar and the outside ring, and the height of the scar represents the minimum elevation of high water.
INJURY
Floods can damage trees by tilting or partial uprooting or can uproot them completely, causing their death.
Source: Alex Drainville
MICROCLIMATE
Photograph: Alex Source
Source: ouelle#e001.com
FLOOD RINGS
Winnipeg Manitoba
Winnipeg
The name Winnipeg is a transcription of the western Cree word wi-nipe-k meaning "muddy waters"
Source: Greg Brooks
Source: U.S. Coast Guard, Lt. Brendan Evans
Source: Greg Brooks
Grand Forks, North Dakota 1997 flood and fire
Source: Ma#hew Bietz
Lake Agassiz
How large can Red River floods get and how o!en do the large ones occur?
Are there geological processes that may be changing the Red River flood hazard?
What are the geological controls that govern the character of Red River flooding?
Instrumental and historical estimates of major Red River floods
Erik Nielsen Manitoba Geological Survey
Source: Greg Brooks
2008
1875
Source: Erik Nielsen
54Source: Erik Nielsen
The forts now stand like a castle of romance in the midst of an ocean of deep contending currents, the water extending for at least a mile behind them, and they are thereby only approachable by boats and canoes.”
“Francis HeronHudson Bay Company, 1826
St. George and Rannie, Canadian Water Resources Journal, 2003
Source: St. George and Nielsen, Geographie Physique et Quaternaire, 2002
In hydrology, flood observations reported as having occurred above some threshold are known as censored data sets.
Photograph: USGS
1979 Red River flood Drayton, North Dakota
Source: St. George and Nielsen, Geographie Physique et Quaternaire, 2002
St. George et al. (2002), Tree-Ring Research
How large can Red River floods get and how o!en do the large ones occur?
Are there geological processes that may be changing the Red River flood hazard?
What are the geological controls that govern the character of Red River flooding?
Source: St. George and Nielsen, The Holocene, 2003
350 years of Red River floods
TREES AS PALEOFLOOD INDICATORS
Strengths and limitations
Photograph: David Snyder
Redrawn from Stahle (1990)
Source: Ste"ano A#ardi
scarring
“flood rings”
injury
microclimatology
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