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NC Statewide Flood Mapping Program
The State of North Carolina, the Federal Emergency Management Agency (FEMA), and numerous other Federal, State, and local agencies have entered into a Cooperating Technical State (CTS) agreement, whereby the State will assume primary ownership of and responsibility for the National Flood Insurance Program (NFIP) Flood Insurance Rate Maps (FIRMs) for all North Carolina communities. This project will include conducting flood hazard analyses and producing updated, digital FIRMs.
North Carolina's Flood Mapping Program
North Carolina is the first state to enter into a CTS partnership with FEMA. North Carolina's interest in updating its flood maps is understandable. The State faces extreme hazard and consequence from hurricanes and flooding. Since 1989, there have been 14 federally declared disasters in North Carolina. The updated digital FIRMs produced through this CTS project will help to protect the lives and property of North Carolina citizens, and contribute to their general well being. In August 2000, the North Carolina General Assembly allocated $23 million to the flood mapping project. FEMA has contributed an additional $5.3 million toward the project, as well as in-kind contributions of engineering, mapping, and program management services through its Mapping Coordination Contract with Dewberry & Davis LLC, a private architectural and engineering firm.
Based on the General Assembly's directive, work has begun on Phase I, which includes the 6 eastern river basins (Cape Fear, Lumber, Neuse, Pasquotank, Tar-Pamlico, and White Oak). These were the basins most impacted by Hurricane Floyd. They account for approximately one-half of the state, affecting 57 counties (in whole or in part) and approximately 21,200 linear miles of streams and rivers. Studies will be completed for the Lumber, White Oak, and Tar-Pamlico River Basins by August 2001 and for the other three basins by August 2002. Phase II, which includes 5 basins in central North Carolina, will be initiated in 2001, and Phase III, which includes the final 6 basins in western North Carolina will be initiated in 2002. The goal is to have the entire State remapped by the end of 2005.
Process for Scoping Flood Hazard Mapping Needs
The development of updated digital FIRMs for the 6 eastern basins began with a comprehensive 'scoping' phase. The scoping process entailed researching and inventorying all available elevation, flood hazard, and digital base map data that may be useful for preparing updated digital FIRMs. Existing flood hazard data (for example, flood elevation profiles, floodplain boundaries, floodways, and coastal hazard zones) on effective FIRMs are assessed for adequacy. Where the existing flood hazard data are inadequate, the most appropriate technical method to develop up-to-date flood hazard data is determined and a priority level established. Face-to-face meetings were conducted with counties and communities to determine needs for updated FIRMs. Data that need to be developed or acquired — such as digital base maps, field surveys of stream channels, hydraulic structures, and coastal transects — are identified. The proposed scales and paneling scheme for digital FIRM production are determined. Finally, a schedule for completion of updated flood hazard data and digital FIRM production is developed. The results of this scoping research and coordination are consolidated and synthesized to produce "Basin Plans" tailored to the needs of all the counties and communities within the basin.
Currently, the state and FEMA have met with more than 250 communities in the 6 eastern river basins individually for initial scoping. Final Scoping Meetings to present the Draft Basin Plans have been held for the White Oak, Lumber, and Tar-Pamlico River Basins. The Final Scoping Meetings for the Cape Fear, Neuse, and Pasquotank River Basins will be completed this spring. All impacted counties and communities are invited and provided a final opportunity for input.
Production of Flood Hazard Mapping
Following scoping, the map production phase will begin. Production of digital FIRMs involves overlaying topography and flood data on a base map. Digital Orthophoto Quarter-Quadrangles (DOQs) produced in partnership by the State of North Carolina and the U.S. Geological Survey will be used as the primary base map, unless there is a locally produced base map that is more current or accurate than the DOQs.
The North Carolina CTS project will entail the acquisition of high-resolution topographic data and development of accurate Digital Elevation Models (DEMs). Using the basin plans developed during the scoping phase and the DEMs being developed, work on updated engineering analyses and floodplain mapping will begin. The updated flood hazard data and floodplain mapping will be used to produce seamless digital FIRM coverage statewide. Digital FIRMs will be produced on a countywide basis, whereby the county and its incorporated municipalities are shown on the same set of maps. The vertical reference for elevation data on the FIRMs will be the North American Vertical Datum of 1988 (NAVD 88). The North Carolina Geodetic Survey will work with communities and counties to implement the use of NAVD 88.
The preliminary countywide digital FIRMs will be issued to each county and its communities for review and comment. The State will hold a meeting in each county subsequent to the issuance of its preliminary digital FIRM to present the maps. After the meeting, a statutory 90-day appeal period will be provided. During this appeal period, the impacted county, communities, and/or citizens will have the opportunity to comment on the maps and submit scientific or technical data refuting or contesting the results of the preliminary digital FIRM.
In addition to production of digital FIRMs, the North Carolina flood mapping project also includes implementation of a state-of-the-art, dynamic Information Technology (IT) infrastructure to analyze, maintain, and archive maps and associated flood hazard data. This system will also present and distribute the mapping data (DEMs, engineering analyses and models, base maps, digital FIRMs, study reports) and associated documents to the public via the Internet. Finally, the project plan includes the eventual development of a real-time flood forecasting and inundation mapping capability.
Organization of the CTS Flood Mapping Program
The North Carolina Office of State Budget, Planning and Management (OSBPM) will oversee and manage the program in close coordination with the North Carolina Division of Emergency Management. The North Carolina Geodetic Survey, a component of OSBPM, will be involved in the acquisition of topographic data and development of DEMs. The North Carolina Center for Geographic Information and Analysis, also a component of OSBPM, will be involved in the development and acquisition of digital base maps, production of digital FIRMs, and implementation and operation of the digital IT system.
A cornerstone of the project is the State of North Carolina CTS Committee. The Committee will be responsible for strategic planning; providing input regarding data and products; facilitating multi-level government coordination; providing technical and programmatic expertise and advice; and reviewing and concurring on Mapping Activity Statement Agreements. The CTS Committee is comprised of stakeholders from more than twenty Federal, State, County, and local government agencies, as well as several North Carolina professional associations and the academic community.
The State of North Carolina has selected two private firms to conduct the work: Greenhorne & O'Mara and Watershed Concepts. Their work will include two major components: (1) conducting hazard analyses and producing updated, digital FIRMs and (2) designing and implementing the IT Infrastructure for the Statewide mapping program.
ncfloodmaps.com
To keep informed about the State's program and the latest developments, you can visit www.ncfloodmaps.com, a public website providing: |
