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

GEOG5839NEXT CLASS