UF coastal engineer: FEMA should update flooding prediction methods

January 29, 2009

GAINESVILLE, Fla. — Loss of life and destroyed property could be avoided if the Federal Emergency Management Agency replaced current flood maps with ones containing high-resolution land surface elevation area — and if the agency used up-to-date modeling techniques.

So says a new FEMA-commissioned report from the National Academy of Sciences/National Research Council. Peter Sheng, a University of Florida professor of coastal engineering, was one of the chief scientific contributors to the report published late last week.

“We’re calling for new maps, and we’re also calling for FEMA to update their technology,” Sheng said. “Their current methodology is getting very old.”

FEMA uses flood maps to set flood insurance rates, regulate development and inform those who live in the “100-year” floodplain of potential hazards. FEMA’s Map Modernization Program of 2003 to 2008 resulted in digital flood maps for 92 percent of the continental U.S. population. Most live in areas that had outdated or no maps.

However, after a $1 billion investment, only 21 percent of the population has maps that meet all of FEMA’s data quality standards, the National Research Council said

For this reason, FEMA and the National Oceanic and Atmospheric Administration asked the research council to examine the factors that affect flood map accuracy. FEMA also sought to assess the costs and benefits of producing more accurate maps and find ways to improve mapping and management of flood-related data.

In response, the research council committee, the NAS Committee on FEMA Flood Mapping Accuracy, collected and analyzed information on selected streams in test states of Florida and North Carolina and on the economic costs and benefits of creating new digital flood maps in North Carolina.

The committee’s report concludes that the costs for improving flood maps — including analyzing flood-related data and updating regulations — would be outweighed by benefits.

These include not only more accurate flood maps, which would help reduce loss of life, property, and businesses, but also more efficient planning and response for emergency services and preservation of natural functions of floodplains.

Sheng said the 13 committee members spent two years researching the material that went into the report’s conclusions. His responsibility, he said, was to produce the section on coastal flood mapping. He concluded that FEMA, which continues to use flood modeling methods rooted in 1970s-era research, needs to modernize.

“Academics have developed new models and new technologies that lead to more accurate predictions,” he said, adding that the agency currently uses a simple, one-dimensional model to forecast wave action combined with storm surge. “We are recommending that they start doing a two-dimensional surge-wave model,” he said.

He said the updated models will not necessarily cause flood zones to grow or shrink, but rather that predictions will be more accurate.

“The uncertainty comes from the topological data and the way you do modeling, and we are trying to remove the uncertainties,” he said. “In some places, the projected flood levels could go higher, while in other places, they might go lower.”

Sheng is a veteran researcher in the field of flood and storm surge research and modeling. Among other efforts, he heads a Florida Sea Grant-sponsored project to test a new storm surge modeling system in Florida. He is leading experiments on storm surge and inundation models for National Oceanic and Atmospheric Administration, and co-developing a regional storm surge forecasting system for NOAA and the Office of Naval Research.