flood-warningNOAA’s National Weather Service

In the United States, weather watches and warnings are most often generated through the National Weather Service (NWS) which is a subsidiary of the National Oceanic & Atmospheric Administration (NOAA).

NWS provides local and regional forecasts as well as emergency alerts for severe storms, hurricanes, tornadoes, floods, extreme heat, winter storms, fire, tsunamis, and even solar flares. With 122 Weather Forecast Offices and thirteen River Forecast Centers, the NWS is a useful resource in all jurisdictions within the United States.

Flood watches and warnings are issued for both large-scale gradual river flooding and rapid flash flooding. Both can be issued on a county-by-county basis or for specific rivers or for points along a river.

NWS warnings allow first responders to implement pre-planned responses, including evacuation, placement of flood defenses, initiation of road closures, and pre-deployment of search and rescue resources.

Flood Watch

Issued by NWS to inform the public and cooperating agencies that current and developing conditions are such that there is a threat of flooding but the occurrence is neither certain nor imminent. Timeframe for the onset of river flooding is 12-48 hours; for flash flooding, within six hours.

Flood Warning

Issued by NWS to inform the public and cooperating agencies of flooding that is imminent or already occurring along larger streams in which there is a serious threat to life or property. A flood warning will usually contain river stage (level) forecasts as follows:

Minor Flooding: minimal or no property damage, but possibly some public threat.

Moderate Flooding: some inundation of structures and roads near stream. Some evacuations of people and/or transfer of property to higher elevations.

Major Flooding: extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.

Record Flooding: flooding which equals or exceeds the highest stage or discharge at a given site during the period of record keeping.

Source: NOAA’s NWS website: www.nws.noaa.gov

Local Flood Warning Systems

Local Flood Warning Systems (LFWS) can be part of a community’s preparedness to handle floods. Many areas of the country already have a system in place.

The NWS has information available to help jurisdictions with the complex process involved in determining whether a LFWS could contribute to a community’s attempts to mitigate flooding. Other federal and state agencies have also instituted programs for helping communities identity and solve local flood problems.

LFWS generally “sell themselves” but often it is only after a disastrous flood strikes a community. A “Local Flood Warning System Handbook” is available at www.nws.noaa.gov/oh/docs/alf\vs¬≠handbook/handbook.pdf.

The Flood Information & Notification System (F.I.N.S.)

There are some excellent examples of systems already in place that link flood-related early warning systems directly to the Emergency Services. The Flood Information & Notification System (F.I.N.S.) in operation in Charlotte, North Carolina is a particularly good example.

F.I.N.S. is not intended to be a public warning system. It only notifies emergency responders. The National Weather Service continues to provide flood watches and flood warnings to the news media and public.

F.I.N.S. is a partnership between the City of Charlotte, Mecklenburg County, and the U.S. Geological Survey. This government agency continually monitors rainfall and stream depth levels. Emergency responders are notified when there is a potential or actual problem.

There are three levels for F.I.N.S. notification:
ALERT:

When rainfall is intense or streams rise rapidly. The F.I.N.S. system automatically sends the alert via pager, cell phone, and e-mail to emergency responders and Storm Water Services staff.

INVESTIGATE:

If the situation gets worse, emergency personnel must personally visit the location of heavy rainfall or flooding. They may barricade streets or take other action as needed.

EMERGENCY:

The highest level. Additional precautions may be necessary such as evacuating residents near the high-water areas.

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