The 3.8-kilometre Federal Falls walk was popular with walkers on Sunday as people used the trails for the first time in 13 months.

David Wade of Orange said he enjoyed a mix of running and walking the trail.

"I will do the Federal Falls one, it's not too long. The loop is good," he said.

Mr Wade said it was good to see the walks reopened, and he understood authorities wanted to ensure the trails were safe after being damaged in the fires.

"I've been on the Hopetoun Falls one before, it wasn't in the best condition the last time I went on it," he said.

Keen bushwalkers Mick and Kelly Jenkins came from Sydney to do the Federal Falls walk on Sunday.

They said they were unaware it was reopening.

"It's good timing. We didn't know it was closed," Mr Jenkins said.

The Orange Field Naturalist and Conservation Society has been surveying the flora on the mountain since the fires.

Life member Dr Colin Bower said the fires had removed 30 years of thick shrubs and undergrowth that had covered the mountain since the previous fires and revealed an astonishing display of flora that had been hidden for years.

"It's been pretty amazing really. There is a vast increase in the quantity of herbs, lilies and orchids, things like that," he said.

"The abundance of it is quite astonishing."

He said they saw the display last spring, and while it has now died back down through summer, he expected it would be an amazing sight in a few months.

"All the research indicates next spring will be as good as the last one," he said.

National Parks and Wildlife Service ranger Steve Woodham said the repairs had included removing and replacing around 300 burnt timber steps, several signs, and a bridge.

A helicopter was used to bring in supplies to remote access areas.

The walks have reopened just in time for the return of the Great Volcanic Mountain Challenge on March 31.

The fire damage forced organisers to cancel last year's event.

This year will see the regular 11-kilometre event from The Pinnacle picnic ground to the summit of Mount Canobolas, starting at 9am.

A new event, a five-kilometre family trail run, will depart at 9.30am and go to a plateau and return.