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Science for a Changing World

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Science for a Changing World science for a changing world Cover photograph Mount Rainier, Washington, with the flood plain of the Puyallup River in the foreground, 50 kilometers downstream from the volcano. The flood plain is a pathway for debris flows (lahars) from the volcano, most recently by the Electron Mudflow about 500 to 600 years ago. (Photograph by David Wieprecht, U.S. Geological Survey.) Catastrophic Debris Flows Transformed from Landslides in Volcanic Terrains: Mobility, Hazard Assessment, and Mitigation Strategies By Kevin M. Scott, Jose Luis Macias, Jose Antonio Naranjo, Sergio Rodriguez, and John P. McGeehin U.S. Geological Survey Professional Paper 1630 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary U.S. GEOLOGICAL SURVEY CHARLES G. GROAT, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Reston, Virginia 2001 For sale by the U.S. Geological Survey, Information Services Box 25286, Federal Center Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Scott, Kevin M., 1935- Catastrophic debris flows transformed from landslides in volcanic terrains: mobility, hazard assessment and mitigation strategies I by Kevin M. Scott ... [et al.]. p. em.- (U.S. Geological Survey professional paper; 1630) Includes bibliographical references and index. 1. Debris avalanches. 2. Lahars. 3. Catastrophes (Geology). I. Scott, Kevin M., 1935- 11. Series QE75.P9 no. 1630 [QE599.A2] 557.3 s-dc21 [551.3'07] 2001058484 ISBN 0-607-98578-X CONTENTS Abstract. ..................................................................................................................................................... 1 Introduction............................................................................................................................................... 2 Sediment terminology-size and texture . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4 Landslides and volcano collapses . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 6 Debris avalanches. ... .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..................... .. .. .. .. .. .. .. .. .. 6 Debris flows . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 7 Acknowledgments.................................................................................................................................... 8 "La avalancha" in the Rio Paez, Colombia-an archetypal seismogenic debris flow in volcanic terrain......................................................................................................................................... 9 Formation of "la avalancha" .. .. .. ... .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. ... .. .. .. .. ... .. .. .. .. .. .. 10 Dynamics of "la avalancha" .. .. .. ... .. .. .. .. .. .. .. .. .. .. ... .. .. .. ... .. .. .. .. ... .. .. .. .. .. .. 13 Velocity of the wave front ............................................................................................................ 13 Cross-sectional area and discharge. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 14 Flow hydrograph-the rise............................................................................................................. 15 Flow hydro graph-the recession .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 16 Formation of the single wave .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 16 Flow mobility . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 16 Other debris flows transformed from landslides in volcanic terrains . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 16 Rainfall-triggered debris flows ........................................................................................................... 17 Earthquake-triggered debris flows ...................................................................................................... 18 Mexico, 1920 .. ... .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. ... .. .. ... .. .. .. .. 18 Chile, 1960 . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 21 Ecuador, 1987 . ... .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. ... .. .. .. .. .. .. .. 22 Debris flows from landslides and volcano collapses-triggering mechanisms . .. .. .. .. .. 23 Magmatic destabilization .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 23 Rainfall . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 25 Earthquakes .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 26 Gravity ................................................................................................................................................ 26 Hydrovolcanic activity (phreatic and phreatomagmatic)........... .. .. .. .. .. .. .... .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. 27 Triggering mechanisms related to possibility of pre-event warning. .. .. ................. .. .. ... .. 27 Recognition of volcanic debris avalanches and cohesive debris flows (lahars) from deposits ... .. .. 28 Longitudinal transformations and textural changes .. .. .. .. .. .. .. .. .. .. .. .. .. 28 Interpreting flows and their behavior from their deposits .. .. .. .. ... .. ... .. .. .. .. .. ... .. .. .. .. 30 Examples from Mount Rainier .................................................................................................. 3 3 Examples from New Zealand .................................................................................................... 34 Debris flows from landslides and volcano collapses-flow mobility ................................................. 3 4 Debris flows from landslides and volcano collapses-extrapolating case histories . .. .. .. .. .. .. .. .. 3 7 Forensic documentation of flow pathways-Past events and future predictions ............................. 40 Hazard assessments . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4 0 Risk analysis-Example of Mount Rainier .................................................................................... 41 Contents iii Mitigation strategies .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. ... .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. 4 2 Land-use planning . .. ... ... .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4 2 Instrumental event warnings to lowland residents in volcanic terrains.................................... 44 Educating residents of flow hazard zones to recognize the possible initiation or the actual approach of a debris flow . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 45 Recognition of seismic shock as a possible flow trigger......................................................... 45 Recognition of the acoustic signal of an approaching flow . .. .. .. ... ... .. .. .. .. .. ... .. .. .. .. .. .. .. .. ... 45 Education for Self Warning and Evacuation (ESWEV)... .. .. .. .. .. .. .. ... .. .. .. ... .. .. .. .. .. .. .. .. .. ... 4 7 Engineering measures integrating response to volcanic and hydrologic hazards ... .. .. ... .. .. 49 Conclusions . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 50 References cited .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 51 FIGURES 1. Diagram illustrating origin of textural subpopulations of debris flow deposits . .. .. 3 2. Photograph of debris avalanche in the Rio Teno, Chile, showing clast of incoherent, lighter- colored material deforming and mixing with matrix. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 3. Index map showing route of debris flow triggered by the Paez earthquake of June 6, 1994 and flow cross sections illustrating growth and decay of peak discharge . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 9 4-10. Photographs showing: 4. Site of Irlanda looking northwest, showing near-synchroneity and coalescence of flows................................................................................................................................... 10 5. Site of T6ez looking southeast................................................................................................ 11 6. Impact forces of debris flows illustrated by margin of "la avalancha" where 1-2 m of flow inundated animal bam of stone masonry................................................................... 12 7. Margin of "la avalancha" looking downstream where it inundated the only remaining street . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 12 8. Head scarp of individual failure. ·······························································l···························· 13 9. Hillside of Rfo Paez valley upstream of Irlanda showing coalescence of·approxi-I mately synchronous small debris flows and debris avalanches into a larger single flow .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 14 10. Downslope deposits of flow in figure 9 showing intact masses (outlined) of soil and rock 0.7-1.0 min diameter ................................................................................... 14 11. Diagram showing schematic hydrographs of evolving flow wave beginning from upstream of the epicenter near Dublfn through downstream communities of Irlanda, T6ez, and Belalcazar ..............................................................................................................
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