Public Release: 

Boulder researchers reassess national flood damage estimates

University of Colorado at Boulder

The researchers, from the University of Colorado's Cooperative Institute for Research in Environmental Sciences, or CIRES, and the National Center for Atmospheric Research, have compiled state and basin damage information as well as new and improved national damage estimates to provide a more accurate look at flood costs in the United States.

The new data set shows that from 1955 to 1999, Pennsylvania, with flood damages approaching $12 billion, and California with flood damages estimated at nearly $11 billion, lead the nation in total flood damages.

"The data indicate that California's large damage is the sum of many damaging floods, whereas the damages suffered in Pennsylvania resulted from a few major events," said Roger Pielke Jr., director of the Center for Science and Technology Policy Research at CIRES. "But if you consider population, North Dakotans have suffered most per capita economic losses due to flooding.

"Despite programs intended to control the growing costs of such hazards, flooding cost the United States approximately $50 billion in damages during the 1990s alone," he said.

But there is no consensus on why costs continue to spiral, he said. Potential reasons for the increase include climate change, increasing population and failed policies.

"Decision makers need to understand the roles that climate, population growth and development, and policy play in determining flood damage trends," Pielke said.

The report, "Flood Damage in the United States, 1926-2000, A Reanalysis of National Weather Service Estimates" was co-authored by Pielke, Mary Downton of the Environmental and Societal Impacts Group of the National Center for Atmospheric Research and J. Zoe Barnard Miller of NCAR and CU-Boulder. The report was sponsored by the National Oceanic and Atmospheric Administration's Office of Global Programs.

Downton said policy is being made without adequate information.

"Unfortunately, available records are inadequate for policy evaluation, scientific analysis and disaster mitigation," she said. "There are no uniform guidelines for estimating flood losses, no central clearinghouse to collect, evaluate and report flood damage, and the data that do exist are rough approximations that have been reported in lots of different ways.

"Also, most damage estimates focus on national totals, but scientists need data at river basin or community-scale levels to make sense of flood causes and effects," she said. "The National Research Council has stressed the importance of a comprehensive and consistent database because sound flood policy-making depends on having a continuous time series of damage estimates. Reliable loss data are critical for cost-effective hazard mitigation and planning for future disaster response."

The new report is posted at

In addition, data from the report are available online in the Extreme Weather Sourcebook, which provides a ranking of flood damages by state and easy-to-read graphs of each state's damage due to floods, hurricanes and tornadoes at


Annette Varani, (303) 492-5952
Anatta, (303) 497-8604 (NCAR)
Aug. 5, 2002

Editors: State-by-state flood damage estimates are available on the Internet at Click on "Floods."

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