Debris Flows and Floods in Southeastern Arizona from Extreme Precipitation in July 2006—Magnitude, Frequency, and Sediment Delivery
Total Page:16
File Type:pdf, Size:1020Kb
Debris Flows and Floods in Southeastern Arizona from Extreme Precipitation in July 2006—Magnitude, Frequency, and Sediment Delivery Open-file Report 2008-1274 U.S. Department of the Interior U.S. Geological Survey Cover Photograph. (November 21, 2006) Debris-flow initiation and transport zones on the western side of Sabino Canyon, southern Santa Catalina Mountains, as seen from the Sabino Canyon road close to its end. (R.H. Webb, Stake 3803x). ii Prepared in Cooperation with the Pima County Regional Flood Control District Debris Flows and Floods in Southeastern Arizona from Extreme Precipitation in July 2006—Magnitude, Frequency, and Sediment Delivery By Robert H. Webb, Christopher S. Magirl, Peter G. Griffiths, and Diane E. Boyer Open-file Report 2008-1274 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia 2008 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Suggested citation: Webb, R.H., Magirl, C.S., Griffiths, P.G., and Boyer, D.E., 2008, Debris flows and floods in the southeastern Arizona from extreme precipitation in July 2006—Magnitude, frequency, and sediment delivery: U.S. Geological Survey Open- file Report 2008-1274. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. ii Contents Contents ........................................................................................................................................................................ iii Figures ........................................................................................................................................................................... iv Abstract ......................................................................................................................................................................... 1 Introduction .................................................................................................................................................................... 2 Definitions ...................................................................................................................................................................... 9 Data Sources and Methods ..........................................................................................................................................10 Precipitation and Streamflow ....................................................................................................................................10 Repeat Photography of Slope Failures .....................................................................................................................11 Sediment Yield from Slope Failure and Debris Flow .................................................................................................12 Identification of Slope Failures ..............................................................................................................................12 Sediment Volume and Mass..................................................................................................................................12 Particle-Size Distribution .......................................................................................................................................13 Stochastic Modeling of Debris Flows (LAHARZ) .......................................................................................................13 Synoptic-Scale Meteorology of the Storm .....................................................................................................................14 Debris Flows and Floods in the Santa Catalina Mountains ...........................................................................................15 Storm Dynamics on July 31 ......................................................................................................................................15 Rainfall Magnitude and Frequency ...........................................................................................................................15 Streamflow Flooding .................................................................................................................................................17 Sabino Creek.........................................................................................................................................................17 Rillito Creek ...........................................................................................................................................................20 Slope Failures and Debris Flows ..............................................................................................................................20 Geologic Deposits .....................................................................................................................................................37 Event Recurrence Interval .........................................................................................................................................37 Debris Flows at Coronado National Memorial ..............................................................................................................37 Floods and Debris Flows in Aravaipa Canyon ..............................................................................................................38 Rainfall ......................................................................................................................................................................39 Streamflow Flooding .................................................................................................................................................40 Slope Failures and Debris Flows ..............................................................................................................................42 Debris Flows in the Vicinity of Bowie Mountain ............................................................................................................43 Slope Failures and Sediment Yields in the Santa Catalina Mountains .........................................................................46 Slope Failure Area and Density ................................................................................................................................46 Failure Type and Depth.............................................................................................................................................47 Debris-Flow and Streamflow Particle-Size Distributions ...........................................................................................48 Sediment Yield ..........................................................................................................................................................51 Debris-Flow Mobility and Stochastic Modeling..............................................................................................................53 Stochastic Modeling with LAHARZ ...........................................................................................................................57 LAHARZ Results .......................................................................................................................................................58 Discussion and Conclusions .........................................................................................................................................66 Relation to Precipitation Magnitude and Frequency ..................................................................................................66 Relation to Wildland Fires .........................................................................................................................................68 Sediment Yield from Slope Failures and Debris Flows .............................................................................................70 Acknowledgments ........................................................................................................................................................70 References Cited ..........................................................................................................................................................71 iii Figures Figure 1. Map of southeastern Arizona. .................................................................................................................. 3 Figure 2. Map of slope failures that occurred on July 31, 2006 in the southern Santa Catalina Mountains. ........... 5 Figure 3. Annual flood series of three streams in southeastern Arizona ................................................................. 6 Figure 4. Hydrograph of flow at two gaging stationsfrom July 27 through August 1, 2006. ..................................... 7 Figure 5. Slope failures in Bear Canyon.................................................................................................................