Here's What To Expect When Eight Floodgates Open On The Mansfield Dam

Oct 17, 2018

Update: The LCRA now says it will not open eight floodgates on Thursday, Oct. 18, but may in the coming days. 

It’s never happened before, but the Lower Colorado River Authority will likely open eight floodgates on the Mansfield Dam above Lake Austin by noon Thursday.

So, what can you expect if you live in Austin?

Flooding On Some Streets

When eight gates are open, 50,000 cubic feet of water per second will flow from the dam.

That will cause some streets to flood, says Karl McArthur with Austin’s Watershed Protection Department.

RELATED | Lake Travis Has Taken On More Water In One Week Than Austin Uses In Four Years

“We would definitely have to close Cesar Chavez in the vicinity of Lamar Crossing,” he said. “At Longhorn Dam we would have flow over the emergency spillway. The emergency spillway is Pleasant Valley Road, so we’d have to close Pleasant Valley road there.”

(You'll able to find a list of road closures at ATXfloods.)

A group of people check out the water level at Lady Bird Lake near the Hike and Bike Trail.
Credit Jorge Sanhueza-Lyon / KUT

Flooding In Some Parks

Expect serious flooding on parks along the lake, McArthur said.

With eight flood gates open, he says, you can expect to see something like that photo of the statue of Stevie Ray Vaughan at Auditorium Shores with water up to his waist. That’s why the Hike and Bike Trail is closed.

Minimal Structural Damage, Probably

One thing McArthur doesn’t expect the opening of all gates to cause is flooding of many structures along the river in Austin. Of course, that could change if weather forecasts do.

Correction: An earlier version of this post said the dam had eight floodgates total. It has 24. Eight would be the most ever opened simultaneously.