Question of the day: How is a Tucson flood like a redneck divorce?

Rainfall in southern ArizonaA Case of Famine and Feast

April May June July Aug Sept Oct Nov Dec Jan Feb March

Precipitation Seasons in Southern Arizona

Monsoon Pacific storms

Pacific tropical storms

Digital Elevation Map

Mogollon Rim

ColoradoPlateau

Basin and Range

You are here.

General airflow from Pacific

Annual Precipitation

Sky Islands of SE Arizona

Anatomy of River Valley• Main channel is normal course of river.• Floodplain is area covered during flood.• Over geologic time, river meanders over floodplain.

Typical flood hazard is water covering the floodplain.

Major Drainages of Tucson Basin

Flow Gauge Records, Santa Cruz River

More frequent record flows post 1960

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

Record Flows on Santa Cruz River

stre

am g

aug

ein

stal

led

191

31965 1977

1983

1983 flow = 53,000 cfs(Equivalent to 16 backyard swimming pools per second!)25% above previous 100-year flood estimates.

1914

1983 Santa Cruz River @ Congress

Santa Cruz River @ Congress

Rillito at First Avenue, Oct. 1983Bank erosion along the outside of a meander bend

Active river channel moves by bank erosion. This is principle flood hazard in Tucson.

Rillito Creek at First Avenue, Tucson, 1983

October, 1983 flood: 8 deaths, ~1000 injuries; $250 million damage.

Increased frequency of record Santa Cruz flows since 1960.A. Climatic effect? Global warming? Enhanced El Nino?B. Urbanization? Urbanized desert increases runoff by four times compared to undeveloped desert.

Effects of Urbanization on Stream FlowD

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Time

Lag time

Rai

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Streamflow

TimeD

isch

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Lag time

StreamflowRai

nfa

llUrbanization decreases lag time and increases maximum flow.

Before After

Flood Forecasting

Recurrence Interval (yr)

1 10 10010

100

1000

10000S

trea

m D

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ft3 /

sec)

??

100-year flood projections depend on models of climate and hydrology.

Flood Control MeasuresA. Structural Dams Channelization Diversion channelsB. Nonstructural Zoning and land-use restrictions Land acquisition programs Flood forecasting Public education

Pima County

Soil cementing, Rillito @ Campbell

Confine the flow. Move the water out of Tucson ASAP.

Q: How is a Tucson flood like a redneck divorce?

A: Sooner or later, someone’s going to loose a trailer.

Teton Dam on Snake River

Beginning of water piping and erosion of earthfill.

Complete failure

Permeable volcanic rock in footings of Teton Dam