Coastal Services Center

In 1999, Hurricane Floyd caught many inland North Carolina residents off guard when it dropped massive amounts of rain, causing significant loss of life, property damage, and environmental pollution. Since then, an extensive partnership of state, federal, and academic coastal resource managers and scientists has been working on a project designed to help improve forecasts of coastal and inland flooding.

This summer, components of the experimental forecast system were tested in North Carolina during Tropical Storm Hanna—and passed.

“This is very encouraging, and a long time coming,” says Jack Thigpen, North Carolina Sea Grant Extension director.

The Coastal and Inland Flooding Observation and Warning project, or CI-FLOW, still faces an extensive assessment period leading up to a “real-time example run of the system,” but project partners are hopeful that the system may be ready in North Carolina in time for the 2009 hurricane season, says Suzanne Van Cooten, the National Oceanic and Atmospheric Administration (NOAA) National Sea Grant weather and climate extension specialist.

CI-FLOW information could aid emergency managers during hazardous weather events, enable coastal planners to make better-informed decisions about locating infrastructure, and potentially provide resource managers with the capability to monitor water quality, impacting decision-making on everything from drinking water to fish habitat. Researchers would also have additional data on estuaries.

Once initial testing is complete, system capacities may be demonstrated in regional test sites for three to five years before being available to augment national storm forecasts, Thigpen says.

Combining Measurements

In February 2000, the North Carolina and South Carolina Sea Grant programs, several NOAA agencies, and other partners began work on the CI-FLOW project.

The goal of CI-FLOW, Thigpen says, is to “develop a method by which we can accurately measure water levels and potentially water quality in a coastal river basin, and predict what the water level will be in the future.”

“In the past,” says Thigpen, “we’ve done a good job with the measurements that we have in predicting rainfall and floodwaters coming down the river and storm surge coming in from the sound and ocean,” but CI-FLOW is the first attempt at combining all three of these components.

“It’s something that’s not been done and needs to be done,” says Van Cooten. “When you have a tropical land-falling system, it’s not the coastal storm surge that kills the most people, because existing forecast predictions are being used to urge people to evacuate.” The majority of people are killed by inland flooding.

She adds, “Currently, water level predictions that combine both storm surge and inland water level information are not available” to emergency managers in coastal watersheds. “These are the people who are responsible for evacuating people and getting first responders back in after a flood event. This will also help planners know that where they put a shelter is actually safe.”

NOAA partners in the development of CI-FLOW include the National Severe Storms Laboratory, National Sea Grant College Program, National Weather Service Weather Forecast Offices of North and South Carolina, National Weather Service Hydrology Laboratory, National Weather Service Southeast River Forecast Center, NOAA in the Carolinas, NOAA’s Southeast and Caribbean Regional Team, and the Coastal Services Center. Other partners include the University of Oklahoma, North Carolina State University, University of North Carolina at Chapel Hill, and Texas Sea Grant.

Testing, Testing

The system is now being tested in the Tar-Pamlico and Neuse River basins in North Carolina—the area where Hurricane Floyd claimed 51 lives and caused six million dollars in losses to businesses and agriculture.

CI-FLOW uses information from a variety of sources, including existing North Carolina stream flow gauges, weather monitoring information, and rainfall estimates produced by the National Severe Storms Laboratory. CI-FLOW predictions are compared to historical data to determine accuracy.

When Tropical Storm Hanna hit the North Carolina coast on September 6, components of the project underwent their first critical test, says Van Cooten.

The system forecast storm surge of one to three feet, and a research facility reported a three-foot storm surge on the eastern end of Albemarle Sound. It also accurately forecast how the surge would affect inland regions.

Predicting Water Quality

Eventually, the system will also factor in land use and soil permeability to help determine the amount of rainwater expected to run off the land surface into a river. This not only affects flooding estimates, but also may help predict post-storm water quality.

Using this information could be particularly important for communities that use a river as a water source, Thigpen says.

“If you have a big slug of water coming down the river that has a high level of contamination,” he says, water resource managers “would be able to cut off their drinking water intake supply before that arrived and keep it shut until it passed by so that they wouldn’t run the risk of having that contaminated water in their system.”

This information would be beneficial in the event of a toxic spill upstream and may help track saltwater intrusion resulting from sea level rise, as well as nutrient levels and the resulting impact on environmental resources, such as fish and their spawning habitats.

National Framework

Although the tests during Tropical Storm Hanna were “very encouraging,” Van Cooten says the complete CI-FLOW system will undergo an extensive assessment by researchers and forecasters in December and a full test-case in April 2009 to ensure “we are on the right track.”

When testing is complete in North Carolina, plans are to begin regional testing of CI-FLOW in South Carolina and Texas, and possibly additional areas, says Thigpen. “Once we’ve got things lined up, this can expand to other parts of the country.”

He adds, “The main thing is to help NOAA and state partners provide more accurate information to the public. CI-FLOW could help do this on a wide range of topics.”

For more information, point your browser to www.nssl.noaa.gov/projects/ciflow/. You may also contact Jack Thigpen at (919) 515-3012, or jack_thigpen@ncsu.edu, or Suzanne Van Cooten at (405) 325-6320, or suzanne.van.cooten@noaa.gov.