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.

---

flood plain British  

noun

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

---

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

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

"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