What is an areal flood? Here’s what it means if you see an ‘Areal Flood Advisory’

SALT LAKE CITY ( ABC4 ) — On Sunday evening, the National Weather Service issued a flood advisory for some areas in Salt Lake and Utah counties, expected to be in effect until 8 p.m.

Some residents received notifications that an ‘Areal Flood Advisory’ was in place for their part of town. So, what is an areal flood advisory?

For starters, the word “areal” is defined by Merriam-Webster as meaning “of, relating to, or involving an area.”

While the word almost looks (and sounds) like “ aerial ,” “areal” doesn’t apply to the air when it comes to a warning from the National Weather Service.

Instead, the NWS said that “an Areal Flood Warning is issued for highflow, overflow or inundation of a defined area, or when creeks and non-mainstem rivers are expected to flood or remain in flood after 6 hours and there is a threat to life or property and possible evacuations.”

When an area is “inundated,” the National Oceanic and Atmospheric Administration and NWS said that means an area that is normally dry ground is flooded after a storm.

ABC4’s Chief Meteorologist Alana Brophy explained the areal flood advisories in Utah, and said the following:

Areal flood advisories have popped up following strong thunderstorms that ushered in heavy rain throughout the state. We see an advisory like this when gradual flooding is expected in low lying areas, creeks and streams in the boundaries of the advisory. Advisories like this can only be issued by the National Weather Service, and when issued, there’s high confidence the area will see rising waters.”

Alana Brophy

For Sunday’s alert , the NWS said, “Urban and small stream flooding caused by excessive rainfall is expected,” along with minor flooding in areas with poor drainage.

The following areas are expected to see flooding, according to the NWS:

• Alpine
• American Fork
• Bluffdale
• Camp Williams
• Cedar Fort
• Cottonwood Heights
• Draper
• Eagle Mountain
• Granite
• Holladay
• Lehi
• Lindon
• Little Cottonwood Canyon
• Little Cottonwood Creek Valley
• Pleasant Grove
• Riverton
• Sandy
• South Jordan
• Utah Lake
• Vineyard

Is an areal flood different from a flash flood?

The short answer is yes. The difference between an areal flood and a flash flood essentially comes down to the timeframe of the flooding.

“A Flash Flood Warning is issued for flooding that normally occurs within six hours of heavy or intense rainfall,” the NWS explained online — and flash flooding can develop rapidly and threaten “life and/or property.”

An Areal Flood Warning, on the other hand, would be issued when the flooding occurs more gradually — or, as the NWS explained, “usually from prolonged and persistent moderate to heavy rainfall.”

Areal flooding usually happens more than six hours after rain begins to fall, and results in a gradual buildup of water in low-lying areas, the NWS said. Areal flooding can still threaten life and property, despite building up over a longer period of time than a flash flood.

Low-lying and flood-prone areas, as well as areas near small creeks or streams, often see gradual areal flooding, the NWS said.

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