geographic data, conduct flood hazard modeling, develop the DFIRMs and build the information system to support them. At the heart of this system is a Unisys ES7000 Orion 200 server running Microsoft Windows 2000 Datacenter Server and the Microsoft SQL Server 2000 database. The GIS software comes from ESRI of Redlands, Calif.
The system includes 10 terabytes of storage capacity. To map the entire state, Dorman said, another 10 terabytes to handle the inclusion of high-resolution orthographic maps on the site must be purchased.
Image Files versus Interactive Maps
Web site visitors can view PDF files of DFIRMs and interactive maps linked to the GIS database, which will be more current than the DFIRMs. Under federal regulations, each time a published DFIRM is updated, citizens have 90 days to review it and appeal any features they think are inaccurate, Dorman explained. That requirement makes it impractical to revise DFIRMs every time the database receives fresh information.
Dorman hopes regulations will change one day to make the digital maps the official DFIRMs.
"As changes occur in the development of the community, or in the characteristics of the stream or new roads, you need to update that as quickly as possible so people make good floodplain management decisions," he said.
Under agreements signed with local governments, North Carolina will use GIS data those governments have developed and offer its floodplain data to counties and municipalities. Beyond determining who needs to buy flood insurance, the data will support a host of other applications, such as wetlands, clean water management and preliminary design for road construction, Dorman said.
One rich source of data will be Mecklenburg County, which started working with FEMA on its own floodplain mapping modernization in 1998. Major floods in 1995 and 1997 spurred the county to become a CTP, said Bill Tingle, manager of Mecklenburg County Stormwater Planning. Because the FIRMs in place at the time were based on studies conducted in the late 1970s, some areas inundated by the floods weren't shown in the floodplain, he said.
Floodplain of the Future
Mecklenburg now has DFIRMs for the entire county, and has pushed the program a few steps beyond FEMA's original vision. The county's maps not only indicate the current floodplain, they also show how that plain will evolve in the next 20 to 30 years, based on planned development.
The county can also calculate a "100-year elevation," which refers to the height floodwaters will reach under conditions statistically likely to occur every 100 years.
"When somebody comes in for a building permit, if they're in any part of the floodplain, we look at that 100-year future flood elevation and say, 'Before you get your permit, you're going to have to show us you've built above that future 100-year elevation, so we won't have to worry about folks flooding in the future who build houses today,'" Tingle said.
The county offers this information on its Web site, and also provides elevation data for approximately 4,000 individual buildings in flood-prone areas. Prospective buyers, realtors, appraisers, insurance companies and mortgage lenders use this information, Tingle said.
Mecklenburg County is working with North Carolina on ways to incorporate the county's map data in the statewide project. Integration will be a challenge, since the state uses digital orthographs to develop its base maps, while Mecklenburg uses planametric maps, or line drawings.
"We haven't come up with a final solution for that," Tingle said.
Outside North Carolina, numerous state, regional and local organizations have also signed CTP agreements with FEMA. Alabama is developing the business plan for its floodplain modernization program, said Trey Glenn, director of the state's Office of Water Resources.
The program's benefits extend far beyond flood insurance problems, Glenn said. The map database will provide a fully integrated digital tool with the maps, models and delineations that state and local agencies can use for a wide variety of purposes, he said.
The Southwest Florida Water Management District is lining up consultants and funding to produce DFIRMs for its jurisdiction. The initiative dovetails with the district's other GIS activities, supporting its mission to manage the watershed, said Gordon McClung, engineering manager of the District's Resource Management Department.
"As we're doing what we do in our business, it makes good sense to coordinate with FEMA," McClung said.