flood plain

American  

Or floodplain

noun

1. a nearly flat plain along the course of a stream or river that is naturally subject to flooding.

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flood plain British  

noun

1. the flat area bordering a river, composed of sediment deposited during flooding

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Etymology

Origin of flood plain

First recorded in 1870–75

Example Sentences

The inquest has heard that the area is a designated flood plain, but did not have signage warning walkers that the water level might be high at the time Xielo entered the water.

From BBC • Feb. 3, 2026

At least part of it fell in the 100-year flood plain originally proposed by FEMA, a designation that would complicate building plans for the site.

From The Wall Street Journal • Oct. 19, 2025

It might be that in an era of what researchers are calling “mega rain” events, a flood plain should now be off-limits.

From Salon • Jul. 10, 2025

And an additional 777 miles of roadway would be in the new flood plain, nearly tripling the at-risk total to 1,212 miles of road.

From Los Angeles Times • Apr. 30, 2025

It was a miniature model of the Greasy Grass River, the hills to the east of the village site, and the flood plain where the village had stood.

From "In the Footsteps of Crazy Horse" by Joseph Marshall III