Question of the day How is a Tucson

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

Rainfall in southern Arizona A Case of Famine and Feast

Digital Elevation Map General airflow from Pacific You are here. Mo Colorado Plateau gol lo n. R im Basin and Range

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 1914 1983 1965 1977 1983 flow = 53, 000 cfs (Equivalent to 16 backyard swimming pools per second!) 25% above previous 100 -year flood estimates. More frequent record flows post 1960

1983 Santa Cruz River @ Congress

Santa Cruz River @ Congress

Rillito at First Avenue, Oct. 1983 Bank 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 Flow Before After Urbanization decreases lag time and increases maximum flow.

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

Flood Control Measures A. Structural Dams Pima County Channelization Diversion channels B. Nonstructural Zoning and land-use restrictions Land acquisition programs Flood forecasting Public education

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