In the last 30 years, inland flooding has been responsible for more than half the deaths associated with tropical cyclones in the United States (Rappaport, 2000). More than 60 percent of the nation's population lives in coastal states from Maine to Texas, Hawaii, and Puerto Rico. This demographic, combined with the increased inhabitation of flood-prone coastal regions, reveals a significant and rising vulnerability to hurricanes and associated inland flooding. The potential impact and severity of inland flooding was realized in eastern North Carolina in 1999 with the record flooding associated with Hurricane Floyd. Fifty-six people died and over 4,000 homes and businesses were destroyed. A request for assistance by the governor of North Carolina brought about opportunities provided by both federal and state initiatives to build partnerships and accelerate implementation of improved flood forecasting and mapping for water management and emergency response.

One such initiative exemplifies the successes of these partnerships. Through the Advanced Hydrologic Prediction Services (AHPS) program, NOAA’s National Weather Service (NWS) and Coastal Services Center, in a partnership with the State of North Carolina, and the United States Geological Survey (USGS) has implemented a flood forecast mapping capability for the Tar River in eastern North Carolina. The goal of this pilot project was to provide customers with visually oriented and easily accessed flood forecast products. Data used included remotely sensed raster data in the form of LIDAR-derived digital elevation models (DEMs) and digital orthophotography, traditional geographic information system (GIS) vector data layers, as well as in situ measurements of streamflow, precipitation, and engineering data. Use of partnered data was the key to developing hydraulic models to accurately predict flood water surface elevations and map these elevations via high-resolution DEMs. This project relied on the data provided by North Carolina through the Cooperating Technical State partnership with the Federal Emergency Management Agency (FEMA) National Flood Insurance Program. Outreach meetings with state and local officials, before and after the project, provided valuable feedback for designing graphical products that conveyed risk in an easy-to-understand manner. Such meetings have helped to identify a strong desire from various user groups for these new types of products and information in other parts of the nation as well.

FEMA currently has a map modernization initiative to update flood maps for the nation to digital format and increase public awareness of the importance of the maps. As part of this initiative, critical detailed elevation data is being collected by states and local governments to meet the production requirements for new flood mapping. Improved flood insurance study (FIS) techniques, coupled with better elevation data, result in more accurate digital flood insurance rate maps (DFIRMs). The same data can be used by the NWS to improve flood forecasting modeling and mapping capability. River cross-sections and elevation data, for example, are needed to produce both flood insurance rate maps, and flood forecast maps. To identify and convey varying degrees of risk and vulnerability, the NWS is now producing experimental graphical depictions of flood categories. If both NWS warning categories and the FEMA 100-year flood stage are combined into one product, the resulting graphic or map can then be used to clearly illustrate the relationships between the FEMA 100-year flood and the NWS flood warning categories. This is an example of leveraging federal and state resources to enable the producers of national flood risk information to more cost-effectively develop products that convey risk for not only planning, management, and mitigation purposes, but also for forecasting purposes.

Collaboration and data sharing between partners with missions to reduce economic and societal impacts from future events is just the beginning of effectively conveying flood risk to customers and partners. The future of conveying risk in an all-hazards approach lies in building strong alliances that result in interoperable data systems. These systems provide the backbone of a global observation data network which cuts across the traditional sub-disciplines of the geosciences as well as societal impacts. A framework built on Web services that links observations and forecasts, metadata, and infrastructure is needed to meet multiple needs including environmental and emergency management as well as the larger homeland security challenge.

References

Rappaport, E. N., 2000: Loss of life in the United States associated with recent Atlantic tropical cyclones. Bull. Amer. Meteor. Soc., 81, 2065-2073