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Three types of flood warnings: what’s the difference?

There are three different types of flooding: areal flooding, river flooding, and flash flooding
There are three different types of flooding: areal flooding, river flooding, and flash flooding(NWS)
Published: Jul. 29, 2021 at 3:14 PM EDT|Updated: Jul. 29, 2021 at 3:18 PM EDT
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(WHSV) - Since its the middle of summer where thunderstorms and heavy rain commonly happen, its a good time to look at what each type of flood warning means.

Areal Flood Warning

Areal flood warnings are the least concerning of the three types of flood warnings. Areal flood warning in our area are usually issued when an area gradually picks up 1 to 2 inches of rain. It’s a warning that indicates the potential for standing puddles of water on a roadway. Creeks and streams are also typically stressed in this occasion, as they may slowly grow out of their banks. An areal flood warning typically is issued when storms have decent movement and drop heavy rain in the process.

A large amount of water covering a roadway
A large amount of water covering a roadway(NWS)

River Flood Warning

River flood warnings are issued when a river is predicted to at least reach flood stage. In this instance, it typically takes several rounds of heavy rain over a few days or even weeks to potentially trigger these warnings. It can also happen when streams and rivers flow into another river and a more heavier, prolonged rain is present. River flood warnings can last for extended amounts of time as it can take a while for a river to flood or to recede after flooding. If the river is in a significant flood stage, it can cause major damage to low lying areas as rivers flood into these areas.

Significant flooding along the Red River
Significant flooding along the Red River(NOAA)

Flash Flood Warning

Flash flooding occurs when a large amount of rain comes down in a very short time period. Water has to find a place to go in these situations and danger can escalate quickly under these circumstances. Flash flooding is more likely in hilly areas as water flows downhill. The problem is that water at higher elevations often merges and then gets collected at the bottom of a hill. A perfect example of serious flash flooding was back in August 2020 when heavy rain flooded Staunton. With flash flooding, storms produce rainfall rates of several inches a hour and have little movement.

In August of 2020, the city of Staunton suffered from two different floods.
In August of 2020, the city of Staunton suffered from two different floods.(Terry Vosbein)

If flash flooding is significant enough, a “Flash Flood Emergency” may be issued. With a flash flood emergency, flash flooding is extreme, deadly, and can cause catastrophic damage. These emergencies are rarely issued.

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