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Remote Sensing for Coastal Management
Updating State Flood Insurance Rate MapsIn 1998, Hurricane Floyd, a Category II storm, brought devastating flooding to coastal and inland North Carolina. The state was unable to adequately prepare for and manage the extensive flooding because many of North Carolina's flood maps were outdated. In response, North Carolina initiated a statewide floodplain mapping effort using LIDAR (Light Detection And Ranging) data as its source for accurate and detailed elevation data. The Project: North Carolina Flood Mapping Project
Managers in North Carolina were unable to adequately plan for and manage the flooding brought by Hurricane Floyd because a large proportion of the state's Flood Insurance Rate Maps (FIRMs) were old and outdated. Although the Federal Emergency Management Agency (FEMA) updates FIRMs for the nation on an annual basis, they have very limited funds and resources. On average, FEMA is able to update the FIRM for one of North Carolina's 100 counties each year. Managers in North Carolina rely heavily on FIRMs for designating and managing flood-prone areas, regulating construction, and setting flood insurance requirements. The impact of Hurricane Floyd illustrated the need for comprehensive flood planning in North Carolina - lives were lost, thousands of citizens were evacuated, and millions of dollars of damage were caused to homes and buildings, many of which were uninsured or underinsured. In response, North Carolina became the first state to become a Cooperating Technical State with FEMA. The partnership gave the state ownership of the FIRMs and the power to update and maintain their maps. FEMA, the state of North Carolina, and other federal partners are working together to fund this ongoing project.
Deriving FIRMS with LIDAR dataFlooding is influenced by the topography of the land. Seemingly small changes to the landscape can significantly alter how and where dangerous flooding will occur. To develop forecast models that realistically predict where and how much water will be moving across a landscape, managers need accurate elevation data and they need it quickly. The state of North Carolina contracted the acquisition of elevation data gathered using Light Detection And Ranging (LIDAR) to help update and develop new Digital FIRMs (DFIRMs). DFIRMs are static maps used to show areas that are likely to flood based on the elevation of the water and land.Elevation data from LIDAR can be collected over large areas and processed relatively quickly, can be very accurate (on the order of centimeters), and unlike other methods of developing elevation, does not require daylight for acquisition. LIDAR elevation data are being used to map the results of complex flood-prediction models with data about soil and land cover type, rainfall, and historic flooding. The ResultNorth Carolina is using the new DFIRMs to reduce the long-term impacts of flooding. Managers are reevaluating current flood insurance requirements to ensure that owners of at-risk homes are aware of the need for flood insurance. The maps are also used for planning; state and local planners are making informed decisions about siting new developments, updating or retrofitting existing features, and determining if certain types of development (roads, developments, forest clearings) may increase the risk of flooding in nearby areas.One of the unique aspects of this project is that the information is being made available to the public via the Internet. The public can access easy-to-view maps that highlight flood boundaries and flood zones. The data are being displayed on USGS Digital Orthophoto Quadrangles (DOQs) so users can see where their home or business is located relative to the anticipated flood areas. For More Information
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