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

That designation involves even more restrictions than the 100-year flood plain, generally prohibiting new construction and significant renovations to existing buildings.

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

The flood plain is defined as areas that have at least a 1% chance of flooding each year, which is considered to be “high risk,” according to the Federal Emergency Management Agency.

From Los Angeles Times • Apr. 30, 2025

Water voles now roam the network of channels, streams, and ponds the beavers use to navigate the flood plain.

From BBC • Feb. 28, 2025

Near the far edge of the flood plain I find Alice’s footsteps in a stretch of muddy sand.

From "On the Far Side of the Mountain" by Jean Craighead George