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Floods and Sandbars in the Grand Canyon

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Vol. 9, No. 4 April 1999GSA TODAYA Publication of the Geological Society of AmericaABSTRACTErosion of sandbars and beaches inthe Grand Canyon National Park down-stream from Glen Canyon Dam hasbecome a major problem that needs tobe addressed. Geomorphic and geologicmapping provide a link between sand-bar elevations and discharge measure-ments. This link allows an estimate ofdischarges that will deposit sand farenough above normal high water toprevent frequent depletions by erosion.The sand is needed to protect habitatsand archaeological sites and to main-tain beaches used by recreationists. It isproposed that when the Little Coloradois in flood, discharge at Glen CanyonDam be increased to bring the total dis-charge to the desired high value. Analy-sis of the flow records show that suchopportunities are presented on the aver-age once in eight years, suggesting thatthe proposal has a reasonable chance ofsuccess.INTRODUCTIONThe Colorado River in the GrandCanyon section in Arizona once fluctuatedgreatly in its flow. Year-to-year and season-to-season variability was large. Peak dis-charges ranged from 300000 cfs (cubicfeet per second) to 19200 cfs, a differenceof 16 times. The amount of sedimenttransported as suspended load was verylarge. Measurements carried out at theGrand Canyon for the period December1940 to June 1941 show that, at 50000cfs, about 2000000 tons were moved perday during the rising stage of the flood,1and 500000 tons during the falling stage,whereas almost 5000000 tons per daywere moved during the peak of the floodFloods and Sandbars in the Grand CanyonIvo Lucchitta, 6969 Snowbowl View Circle,Flagstaff, AZ 86001Luna B. Leopold, 400 Vermont Avenue,Berkeley, CA 94707Glen Canyon Dam at high discharge during the June 1983 flood. The dam is 710 ft (216 m) high. Thefour jets of water issuing from near the lower right corner of the dam are from the outlet works.Releases from the right spillway are hidden by the cloud of mist and spray near the lower left corner ofthe dam. The left spillway, whose exit is visible a short distance downstream from the outlet-work jets,was inactive when the photo was taken. Discharge from the powerplant is below river level and notvisible. Photo courtesy of David L. WegnerGrand Canyon continued on p. 2DENVER1999INSIDE• Call for Papers — Page D1• Electronic Abstract Submission — Page D12• Registration Issue — June GSA Today1Sediment transported during the risingstage of a flood is much greater than thattransported during the falling stage (Leopoldand Maddock, 1953).2 GSA TODAY, April 1999Floods and Sandbars in the Grand Canyon ....................... 1In Memoriam .......................... 2Memorial Preprints ..................... 2Environment Matters ................... 3SAGE Remarks ......................... 8Farouk El-Baz Award ................... 10New Service for Bulletin and Geology Authors ....................... 10Washington Report .................... 11Cordilleran Meeting Field Trips ......... 121999 Annual Meeting Call for Papers ... D1Letter ................................. 14Environmental & Engineering GeoscienceContents .............................. 16Bulletin and Geology Contents .......... 18GSAF Update .......................... 19Future GSA Meetings .................. 20 1999 GeoVentures ..................... 21Calendar .............................. 22Classifieds ............................. 23IN THIS ISSUEGSA TODAY AprilVol. 9, No. 4 1999GSA TODAY (ISSN 1052-5173) is published monthlyby The Geological Society of America, Inc., with offices at 3300Penrose Place, Boulder, Colorado. Mailing address: P.O. Box9140, Boulder, CO 80301-9140, U.S.A. Periodicals postagepaid at Boulder, Colorado, and at additional mailing offices.Postmaster: Send address changes to GSA Today, Member-ship Services, P.O. Box 9140, Boulder, CO 80301-9140.Copyright © 1999, The Geological Society of America, Inc.(GSA). All rights reserved. Copyright not claimed on contentprepared wholly by U.S. Government employees within thescope of their employment. Permission is granted to individ-uals to photocopy freely all items other than the science arti-cles to further science and education. Individual scientists arehereby granted permission, without royalties or furtherrequests, to make unlimited photocopies of the science arti-cles for use in classrooms to further education and science,and to make up to five copies for distribution to associates inthe furtherance of science; permission is granted to makemore than five photocopies for other noncommercial, non-profit purposes furthering science and education upon pay-ment of a fee ($0.25 per page-copy) directly to the Copy-right Clearance Center, 222 Rosewood Drive, Danvers,MA 01923 USA, phone (978) 750-8400, http://www.copyright.com; when paying, reference GSA Today, ISSN1052-5173. Written permission is required from GSA for allother forms of capture, reproduction, and/or distribution ofany item in this publication by any means, including postingon authors’ or organizational Web sites, except that permis-sion is granted to authors to post the abstracts only of theirscience articles on their own or their organization’s Web siteproviding the posting includes this reference: “The full paperwas published in the Geological Society of America’s news-magazine, GSA Today [include year, month, and page num-ber if known, where article appears or will appear].” GSAprovides this and other forums for the presentation ofdiverse opinions and positions by scientists worldwide,regardless of their race, citizenship, gender, religion, or polit-ical viewpoint. Opinions presented in this publication do notreflect official positions of the Society.SUBSCRIPTIONS for 1999 calendar year: SocietyMembers: GSA Today is provided as part of membershipdues. Contact Membership Services at (800) 472-1988,(303) 447-2020 or [email protected] for member-ship information. Nonmembers & Institutions: Freewith paid subscription to both GSA Bulletin and Geology,otherwise $50 for U.S., Canada, and Mexico; $60 else-where. Contact Subscription Services. Single copies maybe requested from Publication Sales. Also available on anannual CD-ROM, (together with GSA Bulletin, Geology, GSAData Repository, and an Electronic Retrospective Index tojournal articles from 1972); $89 to GSA Members, otherscall GSA Subscription Services for prices and details. Claims:For nonreceipt or for damaged copies, members contactMembership


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