October 2, 1998 - A new mapping method developed by the United States Geological Survey can produce updated flood inundation maps with greater detail at a much lower cost than traditional hand-drawn flood maps.

The new, streamlined method uses geographic information system (GIS) computer programs that can include digital map information such as the location of roads and buildings.

"Many of the aging flood maps were based on now-outdated flood flow estimates, as well as on paper maps that lack sufficient detail," said Joseph L. Jones, USGS hydrologist and lead developer of the new system.

"With our new digital method, we can cut map-updating costs by up to 80 percent over the traditional methods while producing maps with improved accuracy and much greater detail. We can quickly update maps as new flood probability estimates and high-accuracy elevation data become available."

Most of the detailed flood maps produced for the National Flood Insurance Program in the 1970's and 1980's now need updating. Since the original maps were drawn, more flood level data have accumulated, which can significantly change calculations of flood estimates. The new USGS method is a quick, affordable way to include the new data and calculations while also providing greater detail and more flexible analysis capabilities.

The report detailing the new method, "Updating flood maps efficiently--Building on existing hydraulic information and modern elevation data with a GIS," by Joseph L. Jones, Tana L. Haluska, Alex K. Williamson, and Martha L. Erwin, is published as U.S. Geological Survey Open-File Report 98-200. The report can be viewed on the World Wide Web at this URL:

As the nation's largest water, earth, and biological science and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial, scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to sound economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources. Contact Joseph L. Jones, Hydrologist, (253) 428-3600, ext 2684 (253) 428-3614 fax , e-mail: jljones@usgs.gov.