Gilbert F. White National Flood Policy Forum (2004)

Reducing Flood Losses: Is the 1 percent Chance Flood Standard Sufficient?

The first assembly of the forum tackled the question of the sufficiency of the 1 percent annual chance flood standard, which is the basis for most flood loss reduction programs today, here and abroad. Probability-based flood standards— including the 1 percent chance frequency—underlie most floodplain management programs at all levels of government today. So any improvements to the standard or its use will require the full participation of all stakeholders in flood loss reduction programs in the United States. For its inaugural assembly of the Gilbert F. White National Flood Policy Forum, it is hard to imagine that the ASFPM Foundation could have selected a topic more complex or more universally applicable than the question of the sufficiency of that fundamental premise of the nation’s floodplain management programs. What role has the 1 percent standard played in shaping the face of floodplain management as we know it today? How can we improve upon the results we are seeing? Is there a better way?

It is essential that these difficult questions be tackled, particularly when, as in this case, little expert discussion of the issue has taken place even though decades have passed since the standard was instituted. Further, because use of the 1 percent standard is so widespread, it will take concentrated effort by all the players—at all levels of government and the private sector—to move successfully toward any shifts in thinking, policy or legislation that may be needed.

As a way of approaching an analysis of the sufficiency of the 1 percent standard, in this report we adopted a science-based policy analysis forwarded by Gilbert White and his two perennial colleagues, Robert W. Kates and Ian Burton, in a recent issue of Environmental Hazards. With regard to the apparent failure of hazards management to reduce losses worldwide, they asked:

Is the knowledge still insufficient, sufficient but not used, used but ineffectively, used but with an unanticipated lag in taking effect, or used with positive results that have simply been overwhelmed by increased vulnerability due to population growth, economic expansion or other factors? (White et al., 2001)

Their five questions are a thoughtful and useful way of breaking down an analysis of the 1 percent flood standard—or any standard. In this report, the discussion of the forum participants on these issues and others is summarized. We hope practitioners, policymakers, researchers and others involved in floodplain management today find it useful and illuminating.

Download the Final Forum Report (pdf, 783 KB)

Download Background Issues Papers (pdf, 2.77 MB)

Download MS Power Point Presentation 2005 (pps, 1 MB)