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New inland & coastal flood prediction system passes first test

By George Olsen


New inland & coastal flood prediction system passes first test

New Bern, NC – INTRO - Tropical Storm Hanna provided an opportunity to test out a new project designed to better improve forecasts of coastal and inland flooding. George Olsen has more.

While hurricane forecasting remains an inexact science, most would say it has certainly improved over the years. A new project the Coastal and Inland Flooding Observation and Warning program, or CI-FLOW now tries to make similar advances in more accurately predicting the when, where and how much of flood threats.

01:01 In the past we've done a good job with the measurements that we have in predicting rainfall and flood waters coming down the river and storm surge, but CI-Flow is the first attempt at combining all those models so we can get accurate and timely information about any spot along the river, what the water level will be.

Jack Thigpen is an extension director for N-C Sea Grant. The system is currently being tested in the Tar-Pamlico and Neuse River basins. CI-FLOW utilizes information from a variety of sources including stream flow gauges and rainfall estimates provided by NOAA's National Severe Storms Laboratory. As that information comes in, it's compared to historical data run by CI-FLOW to forecast inland and coastal flooding.

16:38 The models use algorithms and equations, very complex computerized models that are based on historical data. In the past when these conditions existed and this type of you had so much rain for so long, this is how much the river came up, that's what they do combine millions of pieces of information from past events and project into the future if you have a certain situation in the future, what will the result be.

Tropical Storm Hanna was the project's first test, and initial indications are it works as advertised. The system forecast storm surge of one-to-three feet, and a research facility at Duck reported three-foot storm surge on the eastern end of Albemarle Sound. It also accurately forecast how the surge would affect inland regions as well.

13:57 We have some measurement gages in the Pamlico River that shows the water level and how it fluctuates, how it comes up and down based on the wind driven energy coming in from the storm and we have a model based on historical information, how much we would expect it to rise based on the wind direction, velocity and how long the wind has been blowing and these also compared favorably, so we were glad to see the actual measurements we had and what our models predicted were very similar.

The system also factors in the amount of rain water expected to run off the land surface into the river based on land use and soil permeability, which not only affects flooding estimates but another factor of CI-FLOW still in an experimental phase predicting water quality which could help communities avoid problems after the storm has passed.

10:43 People in communities that use the river as a water source, if you have a big slug of water coming down the river that has a high level of contamination, you would want to cut off your drinking water intake supply before that arrived and keep it shut until it passed by so that you wouldn't run the risk of having that contaminated water in your system.

Those post-storm predictions may be CI-FLOWs big advantage. Thigpen says CI-FLOW is meant to act as an additional tool to tweak storm forecasts that he says are already good from the National Weather Service offices. But as CI-FLOW is refined, predictions for what might happen post-storm at any time at any spot along the rivers should be enhanced, much to the advantage of public safety officials.

18:47 Having to spot information along the river, you really don't have much accuracy, say, what is it going to be doing in 12 hours 10 miles down the stream, but with the models projecting this, we will be able to provide the information and they'll be able to pass it on to emergency managers and community officials and that type of thing to plan for storm events.

Jack Thigpen is an extension director with N-C Sea Grant. I'm George Olsen.