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 land sits on low ground and would need fill for any redesign, to get it above the Potomac River flood plain.

From The Wall Street Journal • Dec. 13, 2025

He even ordered the Army Corps of Engineers to release millions of gallons into a flood plain and then weirdly claimed that he'd "invaded" Los Angeles and solved its water problem.

From Salon • Jun. 9, 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

"I live in Herefordshire. We live on a flood plain, so flooding has always been part of life there," he said.

From BBC • Jan. 9, 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