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7 Findings and Recommendations The Committee on Flood Control Alternatives in the American River Basin was charged to review technical and policy issues that arose from the Sacramento District's 1991 American River Watershed Investigation (ARWI) and, where possible, subsequent planning activities. The committee's task was to evaluate the scientific and engineering knowledge on which the selection of a flood hazard reduction strategy for the area will ultimately be based. The committee also endeavored to provide insights on public policies concerning flood hazard man- agement that are of concern to the nation. In line with that dual charge, the committee offers some thoughts specific to the USACE planning process as it was applied to the American River basin. The committee also comments more broadly on the nature of flood risk assessment and its application nationwide. The findings relate to (1) the identification and evaluation of alternatives in Sacramento District planning documents, (2) envi- ronmental issues in the upper American River basin, (3) risk methodology, (4) flood risk management behind levees, and (5) the implications of the American River example to resources planning and decisionmaking. The key issue in the planning process, and in this report, is how to reduce flood risk in the lower American River basin given a decisionmaking arena that includes significant scientific uncertainty and organized opposition to some of the possible risk reduction alternatives. This report discusses the uncertainties that confront floodplain managers and offers suggestions in many areas, includ- ing the need for additional research. But decisionmakers, agency officials, and interest groups reading this report should not use calls for additional research as an excuse for not taking action. 203

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204 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN It is time to select and implement flood risk reduction strategies for the American River basin. There are still areas where data and information are incomplete, particularly in our understanding of environmental impacts, but that should not forestall the decisionmaking process. Data collection and interpreta- tion can continue as the decisionmaking process proceeds. Adaptive manage- ment techniques can be used to select approaches that can be monitored, evalu- ated, and revised as implementation proceeds and additional information becomes available. It is important to understand that even if Sacramento achieves its stated goal of a "200-year level of protection," the city will still face a significant residual flood risk. The risk would be equal to a probability of flooding of 1 in 200 per year or about 22 percent over a 50-year period, essentially a 1 in 5 chance over 50 years. If flood risk in the city of Sacramento or Natomas is 1 in 100 per year, then the residual risk over 50 years is about 40 percent, or about the probability of getting "heads" with a single flip of coin. Moreover, estimation of the residual risk of flooding alone does not provide owners and occupants of facilities in the floodplain with a complete picture of the consequences and damages that are likely to result from flooding. Estimates of flood risk should be augmented by estimates of likely loss of life and property damages, which are affected by evacuation opportunities, warning times, and the likely depth and character of flooding. Such vulnerabilities can be communi- cated by realistic scenarios that illustrate how a flood event would look and what losses are likely to occur. Perhaps the worst thing that might be done is to create a false sense of security or to encourage people to think that any proposed project provides com- plete protection from flooding. Therefore, flood risk management needs to be an ongoing part of urban planning in the city of Sacramento, including in particular the Natomas area, to reduce residual vulnerability to disastrous flood losses. One element of such management is improved flood risk communication, which would give investors and residents in the area a better understanding of the risks and vulnerabilities they face. It is increasingly evident that the nation has entered an era when construction of new water projects will be rare. Budget constraints, environmental consider- ations, and organized interest groups all contribute to this situation. Because society is less willing to build new facilities, we must find ways to obtain more from existing facilities. We need to operate existing facilities more efficiently and to upgrade planning methods, system instrumentation, modeling capabilities, and other tools used to support operation. With better knowledge, we can make existing systems more efficient and more responsive to public needs without necessarily accepting greater risks. Such improvements would not preclude all new construction, but rather would reduce the need for new facilities. Despite this general admonition to strive for greater efficiency from existing systems, the committee cautions that reoperation of Folsom Dam and Reservoir

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FINDINGS AND RECOMMENDATIONS 205 cannot solve all the water problems faced in the American River basin. In the struggle to solve the myriad problems caused by too much or too little water in the Sacramento area, more may be asked of Folsom than it is able to deliver. The issue decisionmakers face is how best to determine and then implement an acceptable flood risk management program for the American River basin. Beyond all the complexities and subtleties, the ultimate question is whether the flood damage reduction offered through a combination of measures not including a new dam is acceptable, or whether a new upstream dam is necessary to reduce risk to a more acceptable level. The committee cannot answer that question, in part because detailed technical analyses comparing the current range of alterna- tives are still being developed (these analyses are expected in the Sacramento District's forthcoming supplemental information report, scheduled to be avail- able in the summer of 1995) and, importantly, because that judgment is beyond the committee's authority or appropriate role. The public should be forewarned that even when the technical analyses are available, there will be no simple technical answer. Scientists and engineers can and should provide careful analyses and interpret the information so it is avail- able to support decisionmakers, and they should be frank about uncertainties and risks. But the decision to be made should ultimately reflect more than technical factors; it should reflect economic considerations and value judgments pertaining to the appropriate use of natural resources, public monies, acceptable levels of risk, and willingness to accept constraints on land use. The final decision on these issues rests with the public and the political officials who represent them. IDENTIFICATION AND EVALUATION OF ALTERNATIVES Committee's Reaction to the 1991 and 1994 Reports The structural flood protection measures and alternatives described in the 1991 American River Watershed Investigation (USAGE, Sacramento District, 1991), as supplemented by the 1994 Alternatives Report (USAGE, Sacramento District, 1994a) are reasonably complete, although supporting analysis for the 1994 document remains to be seen. Alternative assumptions could have been selected, as discussed in Chapter 2, but the committee found no omissions or errors of a degree that should call the overall results into question. Planning Reoperation of Folsom Dam One concern identified soon after publication of the 1991 ARWI involved the operating policies assumed for analysis of flood control effectiveness of Folsom Dam. Since then, ongoing investigations of interim Folsom reoperation have been exploring a more dynamic allocation of Folsom storage capacity based on the level of storage in upstream reservoirs. The 1994 Alternatives Report

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206 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN assumed that the reoperation plan will be adopted as part of the without-project alternative. For alternatives that involve new low-level Folsom outlet works, the analysis should include modification of the Folsom operating policies to take full advantage of the new release capacity. Likewise, planning studies of a proposed dam at Auburn should investigate how to operate the dam to achieve the desired flood protection at Sacramento while minimizing environmental impacts. The committee was concerned by the fact that it was unable to evaluate how Folsom reoperation and other alternative reservoir operating policies were considered in the 1994 Alternatives Report. In particular, the committee could not identify or assess the assumptions made about the initial conditions in Folsom Reservoir and about the operation of Folsom Dam under the various alternatives considered. These concerns are expected to be addressed in upcoming documents, but resolu- tion of these questions should not slow the planning process. Recommendation In the American River planning studies, significant effort should continue to be devoted to development of effective but practical flood control operating policies that make full use of the storage and release capacities of Folsom and other reservoirs in the American River watershed so that the evaluation of alter- natives will reflect the level of flood control that the system realistically can achieve and actually should achieve. Levee Capacity and Long-term Channel Stability in the Lower American River Currently, there is disagreement among experts about the capabilities of the levees along the lower American River. The committee is concerned about uncertainties related to the proposed alternatives for repairing and enlarging the levees to permit conveyance of "objective releases" from Folsom Reservoir greater than 115,000 cfs. Development of channel and levee stability data should include an understanding of the basic alluvial stratigraphy of the lower American River because the stability of the underlying sediments is critical. Some model and data uncertainty is inevitable, and if that uncertainty about levee adequacy is unacceptable either to the public or decisionmakers, then flood risk reduction alternatives beyond levees such as building a dam at the Auburn site- may prove unavoidable. Recommendations Before the option of raising and enlarging the levees to permit convey- ance of 130,000, 145,000, or 180,000 cfs is included in the flood damage reduc- tion project, the Sacramento District, in concert with SAFCA and other local interests, should ensure that sufficient data and professional consensus concern

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FINDINGS AND RECOMMENDATIONS 207 ing the structural stability of specific levees during flow conditions exceeding 115,000 cfs is developed to provide assurance that the levees can contain these higher flows. Although it should not slow the decisionmaking process, the Sacramento District, in concert with SAFCA and other local interests, should consider con- ducting additional work to better understand the long-term geomorphic response of the American River to mining impacts and Folsom Dam because these factors may influence long-term channel stability. Severity of the American River Flood Risk Flood risk for the American River is probably greater and more uncertain than indicated by the current estimates. High floods in the latter half of the American River flood series appear to be related to changes in the seasonal distribution of precipitation in the region. Recommendation USACE should assess the magnitude of uncertainty in the American River flood risk and damage estimates by performing a sensitivity analysis involving re-computation of the estimates using just the second half of the American River flood record, from 1950 to the present. Hydraulic Modeling of the Sacramento-American River System A better understanding of the complex flow behavior in the neighborhood of Fremont weir and Sacramento weir, Yolo Bypass, and the river junctions be- tween the Feather and Sacramento rivers and the Sacramento and American rivers is needed over the long-term to support water management decision-mak 1ng in the system. Recommendations . The Sacramento District should develop a two-dimensional unsteady flow model of the lower basin to support decisionmaking. The Sacramento District should investigate sediment movement and ac- cumulation at weirs, especially during high flows in key areas of the Sacramento and American river system. Design Considerations for a Dry Dam at Auburn If constructed without gates, a 425-foot-high dam at the Auburn site would be twice as high as any ungated dam that has been constructed by USACE.

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208 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN Operational gates are important for dam safety and for providing flexibility in the dam's operation, allowing operators to coordinate with Folsom and other flood control facilities and to minimize environmental impacts in the upper American River canyon by regulating drawdown. Recommendations If a dry dam is built at the Auburn site, it should incorporate operational gates to provide flexibility in the operation of the dam for dam safety consider- ations, to allow coordination with other facilities, and to minimize environmental impacts. Because of the size and possible impacts of a dam at the Auburn site, dam safety studies focused on possible seismic risk should be conducted, reviewed, revised, and acted on as necessary. Additional research is needed to better understand the potential impacts of inundation on canyon soils and slope stability, and how those impacts might be mitigated through design or operational considerations. Hydrologic Monitoring in the Watershed Soil moisture and snowpack water content affect flood risk in the basin, as does the storage level in reservoirs in the upper American River basin. Measure- ments of snowpack and streamflow levels are routinely made and used as input to a hydrologic forecasting system operated by the National Weather Service and the California Department of Water Resources that describes the hydrologic sta- tus of the basin and provides streamflow forecasts using current hydrologic con . . Tons. Telemetering of existing streamflow gages and provision of additional tele- metered streamflow gages for measuring inflows to Folsom Reservoir are needed to provide reasonable levels of real-time data for reservoir operations and Ameri- can River basin flood control management. There is also a need for a streamflow gage or improved definition of spillway outflow rating between Folsom and Nimbus dams to ensure accurate control of releases from Folsom. Recommendations Plans to expand the stream-gaging network in place in 1994 should con- sider installing telemetry in existing gages and providing additional telemetered streamflow gages at the Folsom Lake inlets to provide timely information on the movement of water toward Folsom and downstream toward Sacramento. Plans should also consider providing telemetered capability for accurate, real-time gag- ing of outflows from Folsom Reservoir. Gages should be strategically located at

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FINDINGS AND RECOMMENDATIONS . , .. ... . ~. 209 various elevations within the American River watershed and should be equipped with telemetering equipment to facilitate real-time operations. As part of watershed monitoring, the Bureau of Reclamation and USACE should coordinate with the National Weather Service, California Department of Water Resources, U.S. Geological Survey, and others as appropriate in efforts to consider how to use existing data and forecast products and how best to accom- plish installation of additional monitoring capacity. Folsom Operating Guidelines and Training Lapses or delays in Folsom flood operations can have adverse impacts on system performance, as was the case in the 1986 flood. Operators may be reluctant to rapidly increase or decrease American River discharges as will be required to ensure that high levels of flood risk reduction are achieved by Folsom Reservoir. Steps need to be taken to ensure that lapses in operation do not occur. Recommendation Stricter operating guidelines and operator training, using continuous in- teractive simulation of different storms, should be implemented to help system operators prepare for and deal with flood events. Maintaining Efficiency of Flood Control System Operation Population growth, increasing development, and other changes in the Ameri- can River watershed create a dynamic flood risk, and it is critical that system operating plans be revisited and revised periodically. For example, as discussed in Chapter 2, it was evident that during the 1986 flood existing operating rules did not adequately consider the existence of 100,000 acre-feet of storage behind the cofferdam upstream of Folsom, even though the dam was designed to breach in a 30-year flood event. Folsom Reservoir, despite its limitations, is the critical component in the flood control system for Sacramento. Consequently, it is essential that it be operated as efficiently as possible. Potential improvements are being considered in the ongoing development of the Folsom Flood Management Plan. But it is not clear how this ongoing effort considers Folsom reoperation, nor how it considers potential changes in the outlet capacity or storage capacity of the dam, or in the potential construction of upstream storage. It is essential that the operation plan for Folsom evolve in response to changes in the American River flood control system, technological improvements that facilitate reservoir operation, changes in political and economic demands on reservoir storage space, and potential changes in flood regime due to changes in climate and long-term watershed conditions. True efficiency of operations must include all steps from planning

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210 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN through execution, and some long-term mechanism for reviewing operating plans and their implementation is essential. Recommendations The operating plan for Folsom Reservoir should be periodically evaluated and revised as necessary, especially as added experience is gained from extreme events. The evaluation and improvement of flood control operating rules for res- ervoirs such as Folsom should consider contemporary technological capabilities in precipitation and runoff forecasting, remote sensing of rainfall, rainfall-runoff simulation, and real-time monitoring of precipitation, upstream reservoir storage, soil moisture, snowpack, and streamflows. In the future, such capabilities may help operators increase readiness, including temporary encroachment on the con- servation and power pool when a major rainfall event is almost certain to occur. ENVIRONMENTAL ISSUES Knowledge of Ecosystem Tolerance and Slope Stability Knowledge of flood tolerances of upland California native plants is limited, and the extent of impacts on Auburn canyon plant communities from a dry dam cannot yet be projected reliably. It can be stated with certainty, however, that even temporary inundation will yield a variety of impacts from submersion, landslides, erosion, and other physical changes that will affect the canyon envi- ronment. The nature and extent of impacts cannot be quantified reliably because of the absence of field data on the impacts of periodic inundation on evergreen, physiologically active upland plant communities. Recommendation As long as a dam at the Auburn site remains a proposed or selected alternative, field and laboratory research should continue to better understand the variables affecting the area's plant communities, especially slope stability given fluctuating water levels. Improving Resource Management Traditional environmental impact assessments fail to evaluate flood risk management alternatives in an ecosystem context because they use a species- oriented framework. This approach has limited usefulness.

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FINDINGS AND RECOMMENDATIONS Recommendations . 211 Environmental impacts should be characterized within the context of the regional significance of the resources involved. Potential scenarios for shifts to different ecosystems or ecotypes and the positive or negative consequences asso- ciated with these shifts should be described in environmental impact documents. Adaptive management, an approach that includes careful monitoring and opportunities to alter management strategies based on that monitoring, should be incorporated into the American River planning process to allow decisionmakers to proceed with planning while retaining management flexibility. This approach will enhance the mitigation of environmental impacts, even as research to gather new information continues. Reservoir Operations to Minimize Environmental Impacts The operating policy for Folsom Dam and a dry Auburn dam, if it were built, would affect the frequency and depth of inundation in the canyon and the rates of drawdown and related impacts. Given the uncertainty of effects in the canyon, a dry dam should be operated jointly with other measures to minimize the fre- quency of impoundment. A dry dam should not be a first defense against large floods, but rather it should be used to contain peak flows from extreme events. Recommendation Should any alternative that includes a dam at the Auburn site be consid- ered or pursued as a flood risk reduction measure, then the gate design and operating policies should provide options to control the depth and frequency of inundation, allowing operators to reduce plant mortality while keeping draw- down rates low to reduce environmental impacts from landslides. RISK METHODOLOGY Risk and Uncertainty Planning Methodologies The new USACE flood risk and uncertainty analysis procedures are an inno- vative and timely development that should improve national flood protection planning. The committee sees significant merit in the USACE efforts to better recognize uncertainty in its planning efforts. As time passes, the USACE risk and uncertainty procedures will undoubtedly improve. However, the committee is concerned about the formulation of key steps in the current guidelines and the particular approaches taken to apply the guidelines in the American River plan- n~ng process. In particular, the treatment of hydrologic uncertainties, and other potential

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212 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN sources of uncertainty, in the new USACE risk methodology inflates the esti- mated risk of flooding and the estimates of flood damages that might be avoided by a project. This upward bias is a concern if the methodology is adopted nationwide because it could distort the economic evaluation of projects. (The committee did not have the resources to determine or evaluate the actual distor- tion for the American River study.) Recommendations USACE needs to develop a consistent scientific methodology and an effective vocabulary for description of residual flood risks and uncertainties to technical and public audiences. To avoid the problem of bias described above, and to simplify the analysis so that it can be more easily understood, the primary descriptions of the expected economic damages and the probability of flooding should be based on traditional estimates of the flood-flow frequency relations and other factors that contribute to flood risk and damage, such as those given in Bulletin FIB, without the expected probability or other uncertainty adjustments. Best estimates of expected annual damages and the risk of flooding should be supplemented by descriptions of the uncertainty or the possible errors in such performance criteria due to hydrologic, hydraulic, and economic uncertainties. Uncertainty and its impact can be described by a standard error or percentiles of the distribution of system performance criteria due to uncertainty, or the prob- ability that the net economic benefits might turn out to be less than zero. This would be consistent with the requirement in the USACE risk and uncertainty procedures that "the estimate of NED (National Economic Development) ben- efits will be reported both as a single expected value and on a probabilistic basis . . . for each planning alternative." It is the committee's understanding the American River study will not address economic uncertainties. Estimates of expected damages and economic benefits associated with dif- ferent projects, and the probability of flooding at different locations, are likely to be the primary criteria describing flood risk and economic impacts. It will often be useful to calculate other indices of system performance and the reliability of different components of the river channel and levee system. The committee questions in general the value of the system "reliability" index adopted by the USACE and employed in the American River study. It seems to be an awkward combination of traditional and new concepts that would easily be misunderstood. Ecological Risk Assessment Ecological risk assessment is not yet sufficiently developed to provide much useful guidance for evaluation of flood control alternatives in the American River

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FINDINGS AND RECOMMENDATIONS 213 planning effort at this time. However, it does provide a new approach to help us think about environmental impacts and select questions for investigation; it will be increasingly important in helping planners broaden the context examined in future planning activities. Recommendation USACE should follow the rapidly evolving potential of ecological risk assessment and adopt this approach as it develops to improve the decisionmaking process. FLOOD RISK MANAGEMENT BEHIND LEVEES Federal Participation in Flood Damage Reduction Projects for the American River Development within the levees of the Natomas Basin faces chronic flood risk. Improvements in the existing flood protection system including the reop- eration of Folsom Dam and levee expansion are in progress or foreseeable. Other measures that might contribute to flood hazard reduction, such as construction of a dry flood storage dam at Auburn, are hypothetical and speculative at this writ- ing. Environmental, fiscal, and political factors are likely to continue to delay or even eliminate that option from consideration. The future level of reliable flood protection therefore is difficult if not impossible to assess in light of both hydro- logic and sociopolitical uncertainty. Those who propose to permit new development in the Natomas basin should not assume that federal flood control projects on the American River will elimi- nate flood risk or that the only flood risk is from the American River. Additional hazards are presented by the Sacramento River and by limited internal drainage capabilities. In addition, flood risk will continue for the already developed parts of the city. The committee does not sanction the development of Natomas, but in acknowledgment of the development pressures and in recognition of extensive existing development, the committee recommends that future federal participa- tion in flood damage reduction projects for the American River be conditioned upon the following: Recommendations Congress should explicitly determine whether flood control projects on the American River warrant federal involvement based on the presence of wide- spread national benefits from flood protection or on a limited ability of the community to provide its own flood protection. If a federal interest in flood protection works in the American River basin

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214 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN is established, project construction should be delayed until SAFCA, working with FEMA and private insurers, has a program to require new development at Natomas and in the city to purchase flood insurance at actuarially sound rates for the residual flood risk appropriate to the alternative selected. SAFCA should implement a flood hazard mitigation plan that includes flood risk communication, flood warning systems, evacuation plans to reduce loss of life, highway and other infrastructure designs to facilitate evacuation, and floodproofing and elevation requirements wherever cost effective. The public should be informed of the inherent flood risks pertaining to the Natomas Basin despite the levee system. Reforming National Flood Risk Management Policy A recent report, Sharing the Challenge (IFMRC, 1994), suggested that the standard project flood (defined as the "most significant flood event" expected to occur) be adopted as the basis for planning a comprehensive flood risk manage- ment program. To obtain maximum benefits, a comprehensive flood risk man- agement strategy should consider nonstructural flood damage reduction measures together with structural measures, especially as applicable in currently undevel- oped areas such as the Natomas Basin. These measures should include appropri- ate floodplain zoning, floodproofing, education, and, when feasible, relocation. A comprehensive program would ensure that people who locate in hazardous areas bear, to the extent practicable, the costs of that location decision by paying a substantial share for flood water control works, by accepting restrictions on development in flood prone areas (foregone development value), and by paying adequate insurance premiums against the residual flood risk after structural and nonstructural measures have been implemented. Recommendations . USACE, FEMA, and other relevant federal agencies should adopt an agreement governing federal participation in structural and nonstructural flood risk management efforts to require that benefiting local communities have a program requiring new development to purchase flood insurance at actuarially sound rates for residual flood risk. Existing development should also purchase residual risk insurance. The federal government, possibly working with private insurers, should develop provisions for sharing the cost of flood insurance premi- ums and flood damage reduction measures with communities and individuals who implement structural and nonstructural flood damage reduction measures. Congress should reform the cost-sharing requirements in the 1986 Water Resources Development Act to increase the nonfederal cost share above currently authorized levels. Exemptions to the cost share requirement could be made if it is

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FINDINGS AND RECOMMENDATIONS 215 demonstrated that flood control benefits are widespread, or that the benefiting communities have limited ability to pay for otherwise justified flood protection, or that communities have committed to flood mitigation programs assigned a high rating in the National Flood Insurance Program's community rating system, thereby exceeding minimum federal criteria for floodplain management. Congress should define all cost-sharing requirements as a percentage of total project costs. Under special conditions when the local sponsor can demon- strate both that noncash contributions (e.g., lands, easements, and rights of way) are necessary for the project and that they will be undertaken, such contributions should be allowed to offset nonfederal cost responsibilities. WATER RESOURCES PLANNING AND DECISIONMAKING Risk Communication for the American River The Sacramento District continues to use the term "level of protection" in its presentations and publications and has not developed good explanations of its new risk and uncertainty procedures and of the results from their application in the American River. However, sound risk communication is of central impor- tance to effective risk management. Recommendations The Sacramento District should cease using "level of protection" and act with SAFCA and other local leaders to build and publicize realistic scenarios to describe the consequences of a levee being overtopped or breached, with the goal of educating the public about the risk and increasing preparedness. Description of the vulnerability of the Sacramento and Natomas areas to storm events that overtop or breach the levee system should clearly address the extreme depth of flooding possible, the transportation difficulties that will be faced, and the prob- lems recovering from flooding in a closed basin. As the change-over in terminology occurs, and "level of protection" con- tinues to be used, the Sacramento District and SAFCA should interpret the con- cept of 100-year "level of protection" in ways that more clearly articulate the risks in terms with meaning to the public. For example, using the old terminol- ogy, a 100-year "level of protection" includes a 40 percent chance of at least one catastrophic flood event in the next 50 years. Thus the probability of at least one catastrophic flood within the lifetime of most residents is roughly equal to the probability of flipping a coin and getting heads. Similarly, the Sacramento Dis- trict and SAFCA should interpret the flood risk on the American River with a 200-year "level of protection" as a 22 percent chance over the next 50 years that flood waters will overtop the levees and inundate the Sacramento area.

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216 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN Risk Communication in Federal Programs USACE, as an agency, has great national influence in flood management planning. Its new risk and uncertainty assessment procedures should contribute to understanding the likelihood and consequences of flood events under different risk management alternatives. The traditional term "level of protection" may mislead the public and is not consistent with the analytical outcomes expected from the new USACE procedures. Recommendations USACE should select a technically sound risk communication vocabulary and approach to communicating flood risk likelihood and consequences and use it consistently in all reports and presentations. USACE should work with FEMA, as well as other agencies, the states, and private insurers, to develop a standardized vocabulary that adequately con- veys risk and vulnerability from flooding. Improving USACE Risk and Uncertainty Assessment and Risk Communication Several of the findings and recommendations listed above address the com- mittee's concerns with the USACE approach to risk and uncertainty analysis and risk communication, as these were described to the committee. The risk and uncertainty procedures are clearly new and still under development. In fact, the American River is one of the first applications, and almost surely the most com- plex yet attempted. Some committee members questioned whether the methodol- ogy was sufficiently well developed to be adopted as the basis of the evaluation of such an important and controversial project. On the other hand, there is a tradition in USACE and among engineers to work out the details of analysis methodologies as they are being implemented. Recommendation USACE should convene an intra-agency workshop that would include invited outside experts familiar with risk communication issues and risk and uncertainty procedures related to water resources projects. The purpose of the workshop would be to review the concerns expressed by this committee and others pertaining to the new USACE approach to risk and uncertainty analysis, as well as the USACE approach to the communication of those results to technical and general audiences. The workshop should develop guidelines that have broad support among risk analysis experts within and outside USACE.

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FINDINGS AND RECOMMENDATIONS 217 Planning for the American River Failure by SAFCA and the Sacramento District to incorporate a wide range of purposes and institutional adjustments into plan formulation and to open the American River planning process to multiple interests was a barrier to reaching agreement on a flood risk management alternative. Recommendations Flood risk management decisions for the American River are influenced by the larger context of California water management, including several recent environmental rulings, and can be addressed properly only within that context. As a result, the state of California should not expect the flood control controversy on the American River to be resolved solely under the Sacramento District's leadership. The state needs to increase its participation in, and resources dedi- cated to, basin-wide water resources planning. State leadership is critical to build a consensus on technical and institutional strategies to manage competing water demands. If no agreement is reached on an acceptable approach to flood risk man- agement in the near future, the Sacramento District and SAFCA should expand the consensus-building efforts of the Lower American River Task Force. This expanded effort should address the full array of purposes that were originally part of the study authorization, including water supply and allied purposes. It should also work to identify institutional agreements that can be employed to address these purposes. In this effort, the Sacramento District and SAFCA might request the leadership and assistance of the state of California's Resources Agency. The American River as Part of a Larger California Water System The proposed shift in release patterns from Folsom Reservoir related to reoperation to reflect upstream storage levels may affect seasonal releases into the Sacramento River and the delta system. Changes in releases have implica- tions that go beyond the American River basin. Likewise, the Central Valley Project Improvement Act (P.L. 102-575, Title 34) and the federal-state water quality standards announced in December 1994 for the San Francisco/Sacra- mento-San Joaquin delta estuary may affect Folsom operations and water release requirements. Recommendation Development of flood control operating guidelines for the American River needs to recognize the wider impacts of reoperation of storage facilities in the

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218 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN American River basin, including revised downstream water quality and habitat requirements. Reforms in Federal Planning Plan formulation demands the creation of the widest possible range of engi- neering and institutional alternatives so that agreements can be reached among multiple decisionmakers. Recommendation USACE should issue guidance to its districts stressing the requirement to maintain a broad view of water resource planning purposes and address those multiple purposes throughout the planning process, including both the develop- ment and evaluation of institutional as well as engineering measures. Especially when contentious disagreements are involved, USACE should advise its districts to facilitate but not dominate local decisionmaking. CONCLUSION This committee was charged to evaluate the scientific and engineering knowl- edge on which the selection of a flood hazard reduction strategy for the lower American River will ultimately be based, and to provide insights where possible on public policies concerning flood hazard management in the Unites States. To these ends, the committee has presented more than 20 findings and associated recommendations. These are offered in a spirit of constructive criticism and to encourage the continued progress in reducing the American River basin's flood risk and in the evolution of the nation's understanding of flood risk management. The committee reiterates its concern that nothing stated in this report should be used as an excuse for delaying action in the American River basin. It is time to select and implement appropriate flood risk reduction strategies.