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Chapter 4: Flood Alerts and Warning Technology

What’s Your Number? Do you know the Flood Stage at the stream gage nearest to you?

The National Weather Service, in coordination with other agencies, has developed stream flow monitoring and as well as storm and flood forecasting that can help provide advance notice of predicted floods. The Advanced Hydrologic Prediction Service (AHPS)  shares detailed information about real-time and forecasted river and stream flows across the country. By visiting this website, or by signing up for flood alerts, people can get advance notice when waters begin to rise, giving extra time to take appropriate actions.

AHPS Flood Alerts for Riverine Flooding

The Advanced Hydrologic Prediction Service uses satellite feeds from river gages along the rivers and stream that are then fed into a computer model to show how high, and for how long, a rise on the river will occur. This can help predict a large rise in the river days before the water actually makes it to the mid and lower basin where the larger populations exist.

If a citizen is signed up to receive the service this can give as much as a day or two lead time to move belongings and take appropriate actions. In Easton, for example, the river flow may often be only a few feet. If you sign up to receive a flood alert, you can now expect to be notified when the river is predicted to reach Flood Stage, which is 22 feet.

The current river levels and flood stages of many points along the main stem of the Delaware can be found in the top right corner of the homepage, as well as at the AHPS site.

National Weather Service also provides weather alerts for other events, such as hurricanes or tropical storms that can also be helpful in planning for flooding.

Click here to see how to sign up for AHPS flood alerts.

Click here for more information about What’s Your Number? teaching materials.

AFWS Flood Alerts for Flash Flooding

The Automated Flood Warning System (AFWS) works quite differently from the AHPS system. Since flash floods can occur so quickly, the AFWS system monitors the weather conditions that show the potential to drop a lot of rain quickly. So people who sign up for this service can be alerted when the conditions that lead to a flash flood develop. In this way, they have the maximum amount of time to ready themselves, and possibly enact their evacuation plan, if they determine the impending situation warrants such action.

Details on how to use the AFWS system can be found here.

Discussion Question:

How would you use automated alerts to inform you of a flood? If you got such an alert that said water was one hour from your home, what would you do?

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This website was prepared by NNF under the award number NA09NWS4670005 from NOAA, U.S. Dept. of Commerce. The statements, findings, conditions and recommendations are those of the authors and do not necessarily reflect the view of NOAA or the U.S. Dept. of Commerce.