Levees at Columbia Lakes in Brazoria County have been breached, according to the official Brazoria County website.

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FLASH FLOOD WARNING western Brazoria county until 5:45 PM. Brazos levee at Columbia Lakes has breached. All residents urged to evacuate now pic.twitter.com/7MZRyL3M3x — FOX26Houston (@Fox26Houston) August 29, 2017

"Get out now," the alert reads.

Portions of Brazoria County, due south of Houston, had been under a mandatory evacuation notice since Sunday.