'Smart' maps could thwart rising waters Harford system is part of U.S. effort to predict flooding

August 01, 1993|By Phyllis Brill | Phyllis Brill,Staff Writer

Harford County has received $50,000 from the federal government to re-examine the county's flood plains and create computerized maps that could help keep homes and property from being inundated.

The digitized maps, which will record the county's flood plains in detail, are a critical part of the National Flood Insurance Program, which insures flood-prone communities across the country.

As the Midwest seeks to dry out from the heavy rains and disastrous flooding of recent weeks, flood plain managers are focused on the future -- talking of prevention and looking closely at low-lying areas that could invite similar problems.

In Harford County, the flood plain maps are just another layer to be added to a sophisticated computer system that can draw on a video screen a picture of the county -- locating roads, buildings, vegetation, storm drains, property lines and even swimming pools -- in a matter of minutes.

With the additional funding, local planners and engineers can now integrate into their mapping system the latest surveys of low-lying, flood-prone land.

When viewed in conjunction with other information, the flood plain drawings will be among the most accurate that national flood insurance managers have, says Patricia Bernhardt, a Harford County environmental planner.

In fact, it was the quality of Harford's Geographic Information System that convinced the Federal Emergency Management Agency (FEMA) to enter into an agreement with the county, which took effect in June.

Rather than hire a private contractor to map Harford, as FEMA is doing with most other jurisdictions in its insurance program, it chose to use the county's expertise in a broad plan to update federal flood plain maps throughout the country.

"They have gone to the trouble to develop a wonderful base map," said Cynthia Pollnow, a program analyst with the National Flood Insurance Program, noting that the county's computerized maps include almost everything needed to gauge land use -- from roads to streams to town boundaries.

"It took a lot of time to create a good, accurate base map, and they showed they could provide what was needed for smart flood plain management," she said.

Ms. Bernhardt said Harford's baseline map was created from aerial photos of every part of the county shot in 1990 from 6,000 feet.

4 "They are accurate to within 2 1/2 feet," she said.

Digitizing the flood plain maps means employing a standardized computer format that can be used throughout the country. It also means that the maps, now on paper, can be stored on computer disks and used and distributed more efficiently.

The federal maps will be used by the National Flood Insurance Program to determine the vulnerability of specific properties to flooding and to assess which of them needs insurance coverage and how much.

There are 800 buildings in the flood plains of unincorporated Harford County, says Ms. Bernhardt, but only 439 of them are now covered by flood insurance. Another 114 policies have been written in the towns of Bel Air, Aberdeen and Havre de Grace. But hundreds of uninsured households also are in flood-prone areas.

"The ultimate goal is to keep people out of the flood plains," she says. "And remapping is the first step in prevention."

The more accurate the maps, the greater the likelihood that zoning regulations, permits and construction will be in keeping with the lay of the land.

Even bankers -- who have to rule on whether to provide financing for builders and homeowners -- and real estate agents will benefit from the information on improved maps, says Ms. Bernhardt.

Many of Harford County's earlier flood plain maps, recorded on paper and based on aerial photos from the 1970s and unsophisticated surveys, haven't been revised since 1983.

The county's population has grown rapidly since then, increasing about 36 percent from 146,000 in 1980 to 198,000 in June of this year.

Population growth and land development force wetlands and flood plains to shift, and the land's potential to change, says Ms. Bernhardt.

The National Flood Insurance Program is entering the third year of a projected 10-year program to digitize its flood plain maps.

Ms. Pollnow said that by the end of the program FEMA expects to have at least 50 percent of the maps digitized, representing 95 percent of the flood insurance policy base.

Harford's role in the project, which lasts a year, is a cooperative venture involving three county departments: Planning and Zoning, Public Works and Geographic Information System. The $50,000 will cover staff time, some equipment and software, surveying, and training in use of the GIS operation.

"If we hired another contractor, the map might not be as detailed in the area the county is most concerned about, or as usable," said Martin Frengs, a civil engineer with Region III of the Federal Emergency Management Agency.

"We think we'll get a product that's more useful to FEMA and the county, and in the long run it probably will cost us less," he said.

"The thing about GIS is that you are not just replacing a flat map, but you're attaching data to it. You're adding information to geography and combining the two. It becomes a 'smart map.' "

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