Geomorphology of the Lower Copper River, Alaska ByTlMOTHY P. BRABETS U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1581 Prepared in cooperation with the Alaska Department of Transportation and Public Facilities U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Mark Schaefer, Acting Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Government. Library of Congress Cataloging in Publications Data Brabets,Timothy P. Geomorphology of the lower Copper River, Alaska / by Timothy P. Brabets p. cm. - (U.S. Geological Survey professional paper ; 1581) "Prepared in cooperation with the Alaska Department of Transportation and Public Facilities." Includes bibliographic references (p. - ). ISBN 0-607-87206-3 (pbk.) 1. Geomorphology-Alaska-Copper River Valley. I. Alaska Dept. of Transportation and Public Facilities. II. Title. Ill. Series. GB428.A4B7 1997 551.41'09798'7--dc21 97-40451 CIP ISBN 0-b07-8720b-3 For sale by U.S. Geological Survey, Branch of Information Services Box 25286, Federal Center Denver. CO 80225 CONTENTS Abstract .................................................................................................................................................................................. Introduction ........................................................................................................................................................................... Purpose and Scope ....................................................................................................................................................... Methods of Study ......................................................................................................................................................... Acknowledgments ....................................................................................................................................................... Description and History of the Study Area ............................................................................................................................ Physical Characteristics ............................................................................................................................................... Early Expeditions ........................................................................................................................................................ Copper River and Northwestern Railway and the Copper River Highway ................................................................. Great Alaska Earthquake of 1964 ............................................................................................................................... Geomorphology of the Lower Copper River ......................................................................................................................... Van Cleve Lake Breakout Floods ............................................................................................................................... Miles Lake ................................................................................................................................................................... Discharge ..................................................................................................................................................................... Statistical Analysis ............................................................................................................................................. Synthesized Flow Statistics of the Copper River at the Million Dollar Bridge ................................................ Discharge at Bridges Along the Copper River Highway ................................................................................... Sediment Transport ...................................................................................................................................................... Suspended Sediment .......................................................................................................................................... Bedload .............................................................................................................................................................. Bed Material ..................................................................................................................................................... Cross Sections of the Copper River ............................................................................................................................ Historical Data ................................................................................................................................................... 1993 Data ........................................................................................................................................................... Water-Surface Profiles ....................................................................................................................................... Entrainment of Bed Material ....................................................................................................................................... Aerial Photography ..................................................................................................................................................... 1950 to 1965 ...................................................................................................................................................... 1965 to 1971 ...................................................................................................................................................... 1985 to 1991 ...................................................................................................................................................... Future Trends of the Copper River .............................................................................................................................. Probability Analysis ........................................................................................................................................... Markov Analysis ................................................................................................................................................ Summary and Conclusions ................................................................................................................................................... References Cited ................................................................................................................................................................... Glossary ................................................................................................................................................................................. Appendixes: Appendix 1. Suspended-Sediment Data for the Copper River at Bridges Along the Copper River Highway ................. Appendix 2 . Suspended-Sediment and Particle-Size Analyses for the Copper River at Bridges Along the Copper River Highway .......................................................................................................................... Appendix 3 . Bedload Analyses for the Copper River at Bridges Along the Copper River Highway .............................. Appendix 4 . Bedload and Suspended-Sediment Data for the Copper River at Bridges Along the Copper River Highway .......................................................................................................................... Contents Ill FIGURES 1.3 . Maps showing: 1. The lower Copper River Delta ........................................................................................................................ 2 . Locations of bridges along the Copper River Highway. 1991 ........................................................................ 3 . The Copper River Basin .................................................................................................................................. 4 . Graphs showing comparison of drainage area, average discharge, and unit discharge of large river basins in Alaska........................................................................................................................................................ 5-8 . Photographs showing: 5 . The lower Copper River in 1944..................................................................................................................... 6 . The Million Dollar Bridge on the Copper River Highway, 1991 ................................................................... 7 . Van Cleve Lake, August 1969......................................................................................................................... 8. Van Cleve Lake, September 1991 and September 1992 ................................................................................. 9 . Graph showing discharge of the Copper River at the Million Dollar Bridge during the breakout of Van Cleve Lake, August 4-12, 1992 ........................................................................................................................ 10. Graph showing water-surface elevation of the Copper River at the Million Dollar Bridge during Van Cleve Lake breakouts of 1909 and 1992 .........................................................................................................