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Lava Falls Rapid in Grand Canyon: Effects of Late Holocene Debris Flows on the Colorado River

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Lava Falls Rapid in Grand Canyon: Effects of Late Holocene Debris Flows on the Colorado River science for a changing world Lava Falls Rapid in Grand Canyon: Effects of Late Holocene Debris Flows on the Colorado River Professional Paper 1591 U.S. Department ef the Interior U.S. Geological Survey Availability of Publications of the U.S. Geological Survey Order U.S. Geological Survey (USGS) publications from the Documents. Check or money order must be payable to the offices listed below. Detailed ordering instructions, along with Superintendent of Documents. Order by mail from— prices of the last offerings, are given in the current-year issues of the catalog "New Publications of the U.S. Geological Superintendent of Documents Survey." 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Minerals information is available electronically at http://minerals.er.usgs.gov/minerals/ Electronically Subscription to the catalog "New Publications of the U.S. Some USGS publications, including the catalog "New Publica­ Geological Survey" tions of the U.S. Geological Survey" are also available elec­ tronically on the USGS's World Wide Web home page at Those wishing to be placed on a free subscription list for the http://www.usgs.gov catalog "New Publications of the U.S. Geological Survey" should write to— Preliminary Determination of Epicenters U.S. Geological Survey Subscriptions to the periodical "Preliminary Determination of 903 National Center Epicenters" can be obtained only from the Superintendent of Reston, VA 20192 Lava Falls Rapid in Grand Canyon: Effects of Late Holocene Debris Flows on the Colorado River By ROBERT H. WEBB, THEODORE S. MELIS, PETER G. GRIFFITHS, JOHN G. ELLIOTT, THURE E. CERLING, ROBERT J. POREDA, THOMAS W. WISE, and JAMES E. PIZZUTO U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1591 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Any use of trade, product, or firm names in this report is for identification purposes only and does not constitute endorsement by the U.S. Government. Reston, Virginia 1999 Library of Congress Cataloging in Publications Data Lava Falls Rapid in Grand Canyon : effects of late Holocene Debris flows on the Colorado River / by Robert H. Web ... [et al.]. p. cm. — (U.S. Geological Survey professional paper : 1591) Includes bibliographical references. ISBN 0-607-88966-7 Supt. of Docs, no.: I 19.16: 1591 1. Debris avalanches—Arizona—Grand Canyon. 2. Geology, Stratigraphic-Holocene. 3. Rapids-Arizona-Grand Canyon. 4. Lava Falls Rapid (Ariz.) I. Webb, Robert H. II. Series. QE599.U5L38 1999 551.48'3'097132-dc21 99-2717 CIP For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225 CONTENTS Abstract .................................................................................................................................................................... 1 Introduction................................................................................................................................................................ 2 Purpose and Scope............................................................................................................................................ 3 Acknowledgments............................................................................................................................................. 3 The Debris-flow Process .................................................................................................................................. 4 Characteristics of Debris Flows in Grand Canyon........................................................................................... 6 Age Dating of Debris Flows............................................................................................................................. 7 Effects of Debris Flows on the Colorado River............................................................................................... 8 Methods .................................................................................................................................................................... 11 The Prospect Valley Drainage Basin................................................................................................................ 11 Mapping of Debris-flow Surfaces .................................................................................................................... 11 Age Dating of Debris Flows............................................................................................................................. 12 Repeat Photography.................................................................................................................................... 12 %e...................................................................._ 12 14C ................................................................................................................................^ 13 137Cs..........................._ 13 Pedogenic Calcium Carbonate.................................................................................................................... 13 Desert Plant Assemblages........................................................................................................................... 14 Clonal Rings of Creosote Bush................................................................................................................... 15 Climatic and Hydrologic Data.......................................................................................................................... 15 Characterization of Debris Flows and Debris Fans.......................................................................................... 18 Discharge Estimates and Water Content.................................................................................................... 19 Debris-fan Area and Volume...................................................................................................................... 19 Debris-fan Frequency................................................................................................................................. 20 Constrictions of the Colorado River........................................................................................................... 20 River Velocities and Reworking................................................................................................................. 20 Surficial Geology of the Prospect Canyon Debris Fan............................................................................................. 21 General Characteristics of Debris Fans............................................................................................................ 21 Upper Debris-flow Surfaces............................................................................................................................. 22 tua..............................................................................................................................................................
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