Authorities will dig a bypass channel to keep water away from the damaged wall of a Queensland dam after fears of a collapse sparked an evacuation order.

Residents of Talgai were evacuated on Friday after water began spewing from a large hole in the wall of the Bolzan Quarry Dam, on the Southern Downs, south-west of Brisbane.

An emergency was declared in the area after the property owner found water gushing from a 3.5-metre by 1.5-metre hole in the wall of the private dam.

O n Sunday night, residents were allowed to return to all but one of the evacuated properties.

Southern Downs Mayor Tracy Dobie said safety was the top priority as work began to shore up the dam.

“A bypass channel will be constructed around the southern edge of the dam wall to take the water away from the wall in a controlled manner,” she told ABC radio on Monday morning.

“That will be released down that valley, and that will contribute to the need for road closures, because there will be flooding.”

Roads in the area will be flooded as the water is emptied from the dam. Photo: ABC

Cr Dobie said engineers would start work on Monday to relieve pressure on the leaking dam wall. Some roads in the area would remain closed as water was released.

“There will be flooding across those roads,” she said.

“The water release will be controlled and that will be aimed at taking the pressure off the dam wall.

“Those who don’t need to be in the area shouldn’t be in the area.

“I ask residents or visitors not to go through those road-closed signs. There is still the emergency relating to the dam wall in case it gives way. The wall is unstable.”

-with AAP