not account for geographic and hydrologic differences at different locations and may thus have provided different levels of flood protection in different localities. Procedures for calculating the economic benefits conferred by levee freeboard were also questioned.

The Corps felt that development and application of risk analysis techniques held great promise in addressing these issues, as these techniques aim to quantify and explicitly incorporate uncertainties in hydrologic, hydraulic, and geotechnical parameters into levee design analysis. It was envisioned that proper application of risk analysis could replace the need for a standard 3 feet of freeboard.

Risk analysis also became part of a federal levee certification procedure jointly conducted by the Corps and the Federal Emergency Management Agency (FEMA). Within the National Flood Insurance Program, FEMA identifies areas subject to varying degrees of flood risk on flood insurance rate maps. One of these areas is the Special Flood Hazard Area (SFHA), defined as the area that is inundated by a flood having a 1 percent chance of being equaled or exceeded in any given year (the 1% flood). Property within a Special Flood Hazard Area is subject to mandatory flood insurance purchase requirements and may be subject to local land use regulations, as well.

Floodplain property can avoid the Special Flood Hazard Area designation, and the mandatory flood insurance requirements that attend it, if it is protected by a levee certified to provide protection against the 1% flood. The Corps of Engineers is responsible for certifying levees as meeting this safety standard. As levee certification could exempt a community from flood insurance purchase requirements (and possible exemptions from local land use requirements), this certification procedure has great local economic and public policy significance.

The historical standard for levee certification had been that levees must provide protection to the average stage (height) of the 1% flood, plus 3 feet of freeboard. With the Corps's adoption of risk analysis techniques in the early 1990s, the freeboard standard for levee certification was abandoned in favor of the new risk analysis standard.

The public, however, was not entirely comfortable with the replacement of a time-tested standard by relatively new techniques. These issues came to a head in a Corps flood damage reduction project planning study in Portage, Wisconsin in the early 1990s. The Corps study recommended a levee of elevation 798.3 feet for the city of Portage. But this recommended levee (the “National Economic Development” levee project alternative) would not have been high enough to be certified as providing protection from the 1% flood. Because the calculations for

Front Matter (R1-R14)

Executive Summary (1-11)

The Corps and U.S. Flood Damage Reduction Planning, Policies, and Programs (12-28)

Decision Making and Communication Issues (29-39)

Risk Analysis Concepts and Terms (40-50)

Risk Analysis Techniques (51-70)

Case Studies (71-113)

Evaluation and Proposed Improvements (114-138)

Levee Certification (139-158)

Conclusions and Recommendations (159-167)

References (168-174)

Appendix A: Glossary (175-180)

Appendix B: Corps-FEMA Levee Certification Documentation (181-192)

Appendix C: Economic and Environmental Principles for Water Related Land Resources Implementation Studies (193-195)

Appendix D: Functions and Random Variables (196-198)

Appendix E: Biographical Information (199-202)