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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
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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.
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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
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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
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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
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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.
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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
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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)."
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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
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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
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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
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. ~
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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Me American R~er Basin
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