Video has emerged showing the bloated Llano River overrunning a bridge in Kingsland, about 65 miles northwest of Austin.
The National Weather Service says the river hit near-record levels at 12.5 meters, which is 5.5 metres above major flood stage.
A flash flood warning is in effect, and forecasters describe it as a “very dangerous situation.”
Four people were washed away last week when the river overran an RV park in Junction, Texas.
Three bodies have now been recovered.
Evacuations are underway in the cities of Kingsland and Marble Falls, both northwest of Austin.