Flood Risk Management and the American River Basin -- Copyright -- Preface -- Contents -- Summary -- THE COMMITTEE'S CHARGE -- THREE PREMISES -- Alleviation of Sacramento's Flood Risk is Critical -- National Flood Policies Urge Multiple Adjustments to Hazard -- Technical Assessment Includes Policy Judgments -- IDENTIFICATION AND EVALUATION OF ALTERNATIVES -- ENVIRONMENTAL ISSUES -- RISK METHODOLOGY -- FLOOD RISK MANAGEMENT BEHIND LEVEES -- WATER RESOURCES PLANNING AND DECISION MAKING -- FINDINGS AND RECOMMENDATIONS -- THE ROLE OF SCIENCE IN THE DECISION MAKING PROCESS -- 1 Introduction -- THE AMERICAN RIVER BASIN -- Physical Setting -- Historical Context of the Flood Control Controversy -- The Scale of Decision making and Externalities -- Competing Strategies of Flood Response -- Intergovernmental Cooperation and Cost Sharing -- Scientific Uncertainty -- Folsom and Auburn Dams -- THE USACE PROJECT PLANNING AND DECISION MAKING PROCESS -- 2 Identification and Evaluation of Alternatives -- SELECTION OF PROJECT ALTERNATIVES -- Flood Control Measures -- Flood Control Alternative Plans -- Criticisms of the 1991 Measures and Alternatives -- Issues of Importance in the 1991 and 1994 Alternative Plans -- Folsom Reservoir -- Folsom Reoperation -- Flood Forecasting and Flood Control Effectiveness -- Folsom Operation During Flood Events -- Recommendations on Folsom Operations -- Gated Auburn Dam -- Offstream Flood Control Storage on Deer Creek -- Nonstructural Measures -- FLOOD RISK REDUCTION FROM ALTERNATIVE PLANS -- Development of Inflow Design Hydrographs for Unregulated Conditions -- Estimation of the Probabilities of Unregulated Flood Volumes -- Construction of Inflow Design Hydrographs-Unregulated Conditions -- Development of Design Hydrographs Below Folsom -- Accounting for Effects of Folsom Dam -- Accounting for Effects of Auburn Alternatives.

Accounting for Downstream Inflows -- Hydraulic Modeling -- Assumptions About Confluence of American and Sacramento Rivers -- Hydraulic Models -- Geotechnical Analysis -- The 1991 ARWI Analysis -- Subsequent Investigations -- Recent Work -- OTHER TECHNICAL ISSUES: FLOOD RECORD AND GEOMORPHOLOGY -- American River Flood Record -- Geomorphology of the Lower American River -- Historical Channel Changes -- Mining Sediment -- Bank and Lateral Stability -- Channel Lowering and Enlargement -- Vertical Incision -- Channel Enlargement -- Channel Changes at Streamflow Gages -- Fair Oaks Gage near Old Bridge -- Fair Oaks Gage at Hazel Avenue -- Geomorphic Conclusion -- 3 Environmental Issues -- TREATMENT OF ENVIRONMENTAL ISSUES IN THE ARWI REPORT -- Overview of NEPA and CEQA -- Environmental Information Deficiencies in the 1991 ARWI -- Project Alternatives Assessment in the 1991 ARWI -- Limitations of the Environmental Impact Assessment Approach to Project Planning -- ASSESSING THE IMPACTS OF A DRY DAM -- Canyon Slope Stability -- Physical Mechanisms of Slope Failure -- Past Hillslope Failures -- Long-term Hillslope Stability -- Plant Communities -- Estimating Plant Inundation Impacts -- Experimental Research and Data Collection from Sites with Similar Plant Communities -- Projecting Indirect or Longer-term Impacts -- Directions for Future Research -- OTHER ISSUES OF CONCERN -- Impacts on the Lower American River Plant Community -- Geomorphological Influences on Flood Control -- Recreation Conflicts -- Impacts on Fish and Wildlife Resources -- Projecting Ecosystem Responses in Impact Assessments -- CONCLUSION -- 4 Risk Methodology -- RISK AND UNCERTAINTY: A PRIMER -- Uncertainties, Safety Factors, and the Meaning of Level of Protection -- Definitions for Risk and Uncertainty -- A Distinction Between Risk and Uncertainty -- Sources of Uncertainty.

A FRAMEWORK FOR RISK AND UNCERTAINTY ANALYSES -- Including Uncertainty in the Analysis -- Describing Uncertainty -- ESTIMATION OF FLOOD DAMAGE INCORPORATING HYDROLOGIC UNCERTAINTY -- An Example to Consider the Estimation of Flood Damages -- Analysis Without Hydrologic Uncertainty -- Analysis Incorporating Hydrologic Uncertainty -- Explanation of Bias -- The Bayesian Viewpoint -- Recommendation -- METRICS FOR PROJECT PERFORMANCE EVALUATION -- USACE RISK-BASED PROCEDURES -- The New Methodology -- Description of Risk and Uncertainty in the New Methodology -- Hydrologic Risk -- Hydrologic Uncertainty -- Flood Stage Uncertainty -- Levee Performance Variability -- Flood Damage Uncertainty -- Using the USACE Risk-Based Analysis Framework for the American River -- American River Risk-based Simulation Analysis -- Discharge-Frequency Relationship (Hydrologic Variability) -- Hydrologic Uncertainty -- Reservoir Operation -- Stage-discharge -- Hydraulic Uncertainty -- Levee Performance -- Stage-Damage Relationship -- Stage-Damage Uncertainty -- Organization of the American River Study Analysis -- USACE USE OF RELIABILITY IN PROJECT PLANNING -- USACE Guidelines for Use of a Reliability Index -- Application of Reliability Indices in the ARWI -- THE 1994 ALTERNATIVES REPORT -- THE PROMISE OF ECOLOGICAL RISK ASSESSMENT -- Development of the Paradigm -- Ecological Risk Assessment and the American River -- CONCLUSION -- 5 Flood Risk Management Behind Levees -- THE FLOOD PROTECTION/DEVELOPMENT SPIRAL -- THE NATOMAS BASIN -- The Setting -- Natomas Flood Hazard -- NFIP Status of Natomas -- CONCLUSION -- 6 Flood Risk Management: Implications for the American River and the United States -- THE AMERICAN RIVER FLOOD RISK MANAGEMENT CONTROVERSY: THE KEY ISSUES -- THE CHOICE TO BE MADE:ACCEPTABLE REMAINING FLOOD RISK -- WATER PROJECT COST SHARING -- COMMUNICATION OF FLOOD RISK.

IMPROVED APPROACHES TO FLOOD RISK MANAGEMENT PLANNING -- THE WATER POLICY AND MANAGEMENT CONTEXT -- CONCLUSION -- 7 Findings and Recommendations -- IDENTIFICATION AND EVALUATION OF ALTERNATIVES -- Committee's Reaction to the 1991 and 1994 Reports -- Planning Reoperation of Folsom Dam -- Recommendation -- Levee Capacity and Long-term Channel Stability in the Lower American River -- Recommendations -- Severity of the American River Flood Risk -- Recommendation -- Hydraulic Modeling of the Sacramento-American River System -- Recommendations -- Design Considerations for a Dry Dam at Auburn -- Recommendations -- Hydrologic Monitoring in the Watershed -- Recommendations -- Folsom Operating Guidelines and Training -- Recommendation -- Maintaining Efficiency of Flood Control System Operation -- Recommendations -- ENVIRONMENTAL ISSUES -- Knowledge of Ecosystem Tolerance and Slope Stability -- Recommendation -- Improving Resource Management -- Recommendations -- Reservoir Operations to Minimize Environmental Impacts -- Recommendation -- RISK METHODOLOGY -- Risk and Uncertainty Planning Methodologies -- Recommendations -- Ecological Risk Assessment -- Recommendation -- FLOOD RISK MANAGEMENT BEHIND LEVEES -- Federal Participation in Flood Damage Reduction Projects for the American River -- Recommendations -- Reforming National Flood Risk Management Policy -- Recommendations -- WATER RESOURCES PLANNING AND DECISION MAKING -- Risk Communication for the American River -- Recommendations -- Risk Communication in Federal Programs -- Recommendations -- Improving USACE Risk and Uncertainty Assessment and Risk Communication -- Recommendation -- Planning for the American River -- Recommendations -- The American River as Part of a Larger California Water System -- Recommendation -- Reforms in Federal Planning -- Recommendation -- CONCLUSION -- References.

APPENDIX A Biographical Sketches of Committee Members -- APPENDIX B Guide to Acronyms and Abbreviations.