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Flood Risk Management ant! the American River Basin An Evaluation Committee on Flood Control Alternatives in the American River Basin Water Science and Technology Board Commission on Geosciences, Environment, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1995
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sci- ences, the National Academy of Engineering, and the Institute of Medicine. Support for this project was provided by the United States Army Corps of Engineers under Contract Number DACW05-93-C-0087. Library of Congress Catalog Card No. 95-70294 International Standard Book Number 0-309-05334-X Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, N.W. Box 285 Washington, D.C. 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan Area) B-661 Copyright 1995 by the National Academy of Sciences. All rights reserved. Printed in the United States of America The cover shows a floodplain map depicting 100- and 400-year floodplains of the Sacramento and American rivers with the 1995 level of protection provided by Sacramento Area Flood Control Agency and the Sacramento District, U.S. Army Corps of Engineers.
COMMITTEE ON FLOOD CONTROL ALTERNATIVES IN THE AMERICAN RIVER BASIN RUTHERFORD H. PLATT, Chair, University of Massachusetts, Amherst KENNETH W. POTTER, Vice Chair, University of Wisconsin, Madison LEO M. EISEL, McLaughlin Water Engineers, Denver, Colorado JAMES D. HALL, Oregon State University, Corvallis L. ALLAN JAMES, University of South Carolina, Columbia WILLIAM KIRBY, U.S. Geological Survey, Reston, Virginia NANCY Y. MOORE, RAND, Santa Monica, California JOHN W. MORRIS, J.W. Morris Ltd., Arlington, Virginia ANN L. RILEY, Coalition to Restore Urban Waters, Berkeley, California LEONARD SHABMAN, Virginia Polytechnic and State University, Blacksburg HSIEH WEN SHEN, University of California, Berkeley JERY R. STEDINGER, Cornell University, Ithaca, New York Staff CHRIS ELFRING, Study Director MARY BETH MORRIS, Senior Project Assistant ROSEANNE PRICE, Consulting Editor 111
WATER SCIENCE AND TECHNOLOGY BOARD DAVID L. FREYBERG, Chair, Stanford University, Stanford, California BRUCE E. RITTMANN, Vice Chair, Northwestern University, Evanston, Illinois LINDA ABRIOLA, University of Michigan, Ann Arbor J. DAN ALLEN, Chevron USA, Inc., New Orleans, Louisiana PATRICK L. BREZONIK, University of Minnesota, St. Paul WILLIAM M. EICHBAUM, The World Wildlife Fund, Washington, D.C. WILFORD R. GARDNER, University of California, Berkeley WILLIAM L. GRAF, Arizona State University, Tempe THOMAS M. HELLMAN, Bristol-Myers Squibb Company, New York CHARLES C. JOHNSON, U.S. Public Health Service (retired), Bethesda, Maryland CAROL JOHNSTON, University of Minnesota, Duluth WILLIAM M. LEWIS, JR., University of Colorado, Boulder CAROLYN H. OLSEN, Brown and Caldwell, Pleasant Hill, California CHARLES R. O'MELIA, The Johns Hopkins University, Baltimore, Maryland IGNACIO RODRIGUEZ-ITURBE, Texas A&M University, College Station HENRY VAUX, JR., University of California, Riverside Staff STEPHEN D. PARKER, Director SHEILA D. DAVID, Senior Staff Officer CHRIS ELFRING, Senior Staff Officer GARY D. KRAUSS, Staff Officer JACQUELINE A. MACDONALD, Senior Staff Officer ETAN GUMERMAN, Research Associate JEANNE AQUILINO, Administrative Associate ANITA A. HALL, Administrative Assistant ANGELA F. BRUBAKER, Senior Project Assistant MARY BETH MORRIS, Senior Project Assistant GREGORY K. NYCE, Senior Project Assistant IV
COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES M. GORDON WOLMAN, Chair, The Johns Hopkins University, Baltimore, Maryland PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh, Pennsylvania EDITH BROWN WEISS, Georgetown University Law Center, Washington, D.C. JAMES P. BRUCE, Canadian Climate Program Board, Ottawa, Canada WILLIAM L. FISHER, University of Texas, Austin EDWARD A. FRIEMAN, Scripps Institution of Oceanography, La Jolla, California GEORGE M. HORNBERGER, University of Virginia, Charlottesville W. BARCLAY KAMB, California Institute of Technology, Pasadena PERRY L. MCCARTY, Stanford University, Stanford, California S. GEORGE PHILANDER, Princeton University, Princeton, New Jersey RAYMOND A. PRICE, Queen's University at Kingston, Ontario THOMAS A. SCHELLING, University of Maryland, College Park ELLEN K. SILBERGELD, Environmental Defense Fund, Washington, D.C. STEVEN M. STANLEY, The Johns Hopkins University, Baltimore, Maryland VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, Florida Staff STEPHEN RATTIEN, Executive Director STEPHEN D. PARKER, Associate Executive Director MORGAN GOPNIK, Assistant Executive Director JAMES MALLORY, Administrative Officer GREGORY SYMMES, Reports Officer SANDI FITZPATRICK, Administrative Associate SUSAN SHERWIN, Project Assistant v
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal govern- ment on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of out- standing engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Harold Liebowitz is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineer- ing communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. Harold Liebowitz are chair- man and vice chairman, respectively, of the National Research Council.
Preface The headwaters of California's American River lie in the high Sierra Ne- vada. The river's three forks descend through a series of challenging rapids amid scenic canyons to merge just before flowing into Folsom Reservoir, about 23 miles upstream of Sacramento. Below Folsom Dam, the American River flows largely between levees to its convergence with the Sacramento River close to downtown Sacramento. Since its founding at the time of the Gold Rush in the 1850s, Sacramento has been battling to protect itself from floods, even as the city has continued to expand within the floodplain. The Sacramento Metropolitan Statistical Area reached a population of 1.4 million in 1990, an increase of 75 percent since 1970. Much of this population lives behind levees along the Ameri- can River. Today, there are plans for a major new expansion in the Natomas Basin, a 55,000 acre expanse of low-lying, former marshland now drained for agriculture that lies within a 41-mile ring of levees across the American River from downtown Sacramento. In February 1986, Sacramento had another brush with flood disaster as north- ern California was swept by vicious winter storms. Inflow from the upper Ameri- can River watershed poured into Folsom Reservoir faster than it could be re- leased through Folsom Dam's normal outlets. After the breaching of an upstream cofferdam released a surge of water into the reservoir, the dam operators opened five high-level spillways, gradually raising downstream flows to 130,000 cubic feet per second (cfs), well above the 115,000 cfs maximum release target for the levees along the lower American River. Extensive scouring occurred; Sacra- mento was spared a major disaster only by easing of storm conditions. Heavy rains in early 1995 reminded us again about the area's vulnerability. . . Vll
V111 PREFACE Since the 1986 near-catastrophe, flood planners at the local, regional, state, and federal levels have struggled to develop an acceptable and feasible set of measures to improve Sacramento's level of safety from American River floods. In an attempt to identify and evaluate the various available alternatives, in 1991 the Sacramento District of the U.S. Army Corps of Engineers (USAGE) prepared the American River Watershed Investigation (ARWI). The report examined a range of possible flood hazard reduction measures, but one in particular sparked controversy-possible construction of a "dry dam" upstream from Folsom. Plan- ners had hoped the dry dam option would be a compromise acceptable to every one. The dry dam concept, however, proved unacceptable to some stakeholders, who assailed both the 1991 ARWI and its accompanying environmental impact statement on many technical grounds. Meanwhile, some proponents of power, water supply, and irrigation continued to press for a multipurpose dam as was originally proposed and authorized for the Auburn site, but which was never built for a combination of technical and political reasons. The result has been a virtual impasse regarding agreement on what flood control project to propose to Con- gress. In 1992, Congress directed USACE to reevaluate the flood control options available for the American River basin (P.L. 102-396, Section 91594. Simulta- neously, Congress directed the Secretary of the Army to solicit the views of the National Academy of Engineering with respect to certain technical and policy issues. Pursuant to that mandate, the Water Science and Technology Board of the National Research Council established the Committee on Flood Control Alterna- tives in the American River Basin, which began work in October 1993. From the outset, this has been an unusual and challenging task for a National Research Council committee. The committee was originally called upon to re- view the 1991 ARWI, a report that was virtually moot by the time we came into existence. So we received many briefings and other informal input to enlarge and update our consideration of the American River flood dilemma. We paid particu- lar attention to the new risk and uncertainty methodology now used by USACE to evaluate proposed projects (see Chapter 41. Our task was further complicated by the fact that we were asked to report on our findings before release of the upcom- ing, revised Supplemental Information Report and Environmental Impact State- ment, meaning we had little written material upon which to base our analysis. As this is being written in March 1995, much is happening in the lower American River Basin relevant to both our study and USAGE's own reevalua- tion: · The 1992 act that launched these studies also directed the Sacramento District of the USACE and the Sacramento Area Flood Control Agency (SAFCA) to strengthen the Natomas levees, provided that ". . . such construction does not encourage the development of deep floodplains (within the Natomas Basin)."
PREFACE IX · The city and county of Sacramento have completed a lengthy planning process to guide new development in Natomas and it largely disregards flood hazards. . The Bureau of Reclamation and the Sacramento District are developing a reoperation plan to make Folsom Dam more responsive to a developing flood situation. . SAFCA has established a Lower American River Task Force involving diverse stakeholders to develop a consensus plan for the redesign of the levees and banks along the lower American River. · SAFCA also is conducting research on the potential effects of occasional inundation on vegetation in the upper American River canyons. · The U.S. Environmental Protection Agency and the U.S. Fish and Wild- life Service are developing new water release requirements to improve water quality and anadromous fish habitat in the Sacramento River delta, which may affect the operation of Folsom Dam. · At the national level, a significant report on the 1993 Midwest floods Sharing the Challenge: Floodplain Management into the 21st Century, appeared during our study and we have considered its recommendations in this report where applicable. Meanwhile in January and March 1995, California experienced widespread flooding, which stimulated "rethinking" about the siting of new development in hazardous areas (see The New York Times, January 15, 1995~. Across the globe, winter floods in Holland forced precautionary evacuation of large areas behind dikes long thought to be safe, thus highlighting the costs and uncertainties of living behind flood barriers even when they do ultimately survive (see The New York Times, February 5, 1995~. Against this backdrop of ever-shifting political and scientific context, the committee sought to provide a useful and relevant report. We sought to address technical and policy issues both of immediate relevance to the American River basin and broader national significance. We were not charged, nor have we undertaken, to propose any particular solution for the lower American River flood problem. That is the responsibility of the political process. In particular, we take no position on whether or not Auburn dam should be built in any form. (We do strongly urge, however, that if a dry dam is built, it should have operable gates for both safety and environmental reasons.) The issue of Auburn dam has dominated the public debate on American River flood protection over the past decade to the possible detriment of giving fuller consideration to other approaches. We are pleased to note that certain recent initiatives, including but not limited to those listed above, are now in progress that do not depend on the resolution of the issue of whether Auburn dam should be built. I would personally like to thank my colleagues and fellow committee mem
x PREFACE hers for their cooperation, hard work, mutual respect, and enthusiasm. A more distinguished yet congenial group of professionals can scarcely be imagined. On behalf of the committee and the Water Science and Technology Board, I would like to express our appreciation to the fine officers and staff of the U. S. Army Corps of Engineers with whom we have interacted over the past 18 months. Our particular thanks are extended to Bob Childs, who served as the key liaison to the committee from the Sacramento District, plus Merritt Rice, Jaime Merino, Rick Johnson, and all the USACE staff who briefed us on issues and responded to our questions. We also appreciate the assistance we received from other liaisons to the committee, especially Tim Washburn, Sacramento Area Flood Control Agency; Ron Stork, Friends of the River; George Qualley, California Department of Water Resources; and Ray Barsh, California Reclamation Board. Special thanks should go also to Mary Beth Morris for her calm and efficient logistical support. Finally, we thank WSTB senior staff officer Chris Elfring for her expertise and good judgment in guiding us through the many rapids and shoals of this project. Rutherford H. Platt University of Massachusetts, Amherst
Contents SUMMARY INTRODUCTION The American River Basin, 13 The USACE Project Planning and Decisionmaking Process, 28 2 IDENTIFICATION AND EVALUATION OF ALTERNATIVES Selection of Project Alternatives, 33 Flood Risk Reduction from Alternative Plans, 50 Other Technical Issues: Flood Record and Geomorphology, 68 3 ENVIRONMENTAL ISSUES Treatment of Environmental Issues in the ARWI Report, 86 Assessing the Impacts of a Dry Dam, 91 Other Issues of Concern, 102 Conclusion, 112 13 32 85 4 RISK METHODOLOGY 114 Risk and Uncertainty: A Primer, 116 A Framework for Risk and Uncertainty Analyses, 120 Estimation of Flood Damage Incorporating Hydrologic Uncertainty, 125 Metrics for Project Performance Evaluation, 134 USACE Risk-Based Procedures, 136 USACE Use of Reliability in Project Planning, 149 Xl
. ~ X11 The 1994 Alternatives Report, 156 The Promise of Ecological Risk Assessment, 158 Conclusion, 161 FLOOD RISK MANAGEMENT BEHIND LEVEES The Flood Protection/Development Spiral, 164 The Natomas Basin, 166 Conclusion, 176 6 FLOOD RISK MANAGEMENT: IMPLICATIONS FOR THE AMERICAN RIVER AND THE UNITED STATES The American River Flood Risk Management Controversy: The Key Issues, 178 The Choice to Be Made: Acceptable Remaining Flood Risk, 183 Water Project Cost Sharing, 186 Communication of Flood Risk, 188 Improved Approaches to Flood Risk Management Planning, 192 The Water Policy and Management Context, 198 Conclusion, 200 7 FINDINGS AND RECOMMENDATIONS Identification and Evaluation of Alternatives, 205 Environmental Issues, 210 Risk Methodology, 211 Flood Risk Management Behind Levees, 213 Water Resources Planning and Decisionmaking, 215 Conclusion, 218 REFERENCES APPENDIXES A Biographical Sketches of Committee Members B Guide to Acronyms and Abbreviations CONTENTS 164 177 203 219 231 235
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