Holidaymakers and locals have told how they they were forced to frantically flee and watch on helplessly as flash flooding in coastal Victoria washed away cars, caravans and other belongings.

Clean-up efforts are under way after torrential rain brought havoc along the Great Ocean Road on Thursday, with the Wye, Kennett and Cumberland rivers quickly swollen by an inland downpour.

Huge amounts of water were carried downstream, swamping campgrounds and picking up objects in its way.

“We went outside and could see the river had broken its banks and was quickly moving up the street,” Victorian holidaymaker Alex Kelly told the ABC.

She and her family had been staying at the Wye River caravan park, and were among hundreds of campers who had to evacuate in the rain. She said they watched cars being swept into the ocean and smashed on rocks in the churning waters.

“It was pretty intense but everyone really looked after each other.”

Another witness, musician Mike Brady, told the Herald Sun that the sky turned pitch black just before the storm.

“It created like a wall of water – a raging torrent came down our little creek, and then it just opened up … I’ve never seen anything like it in my lifetime,” he said.

Blindsided bystanders documented the rapid water rise, with videos showing powerful currents washing cars into the ocean.

More than 170 millimetres of rain fell in the area in over just six hours, and the SES was inundated with calls for assistance. One man had to be winched to safety from a roof at Cumberland River.

Victorian authorities said up to 300 people were displaced on Thursday night, and put up in campsites or local homes.

“We’ve been fortunate there’s only one injury reported – a young child airlifted out of the flash flood zone and they’ve been taken to hospital,” Emergency Management Commissioner Tim Wiebusch said on Friday.

“Otherwise, at this stage, we’ve been fortunate with very minor injuries and importantly, Victoria Police are saying there are no missing persons.”

He offered no further details about the age or condition of the child.

While the water shopped just short of the Kellys’ caravan, others were not so fortunate.

Caravan hire owner Mel Strom and her husband were counting their losses after discovering one of their vans half-submerged in floodwaters on the news. They salvaged what they could overnight after driving from Geelong.

“It was absolute carnage,” she said on Friday, describing the scene at a Wye River caravan park.

“The flood took everything. There were cars, there were eskies, there were surfboards – you name it.”

After the tourist route was closed to non-emergency traffic on Thursday, those returning on Friday were met with muddied roads and debris from mangled cars and caravans mixed with fallen trees strewn across the landscape.

Campgrounds at Lorne, Cumberland and Wye River remain closed as emergency crews assess safety.

“There is a risk of floodwater, electrocution, and biological hazards,” Surf Coast Shire Mayor Libby Stapleton said.

“It may be some time before people can actually get back in there.”

About 200 people visited a local emergency relief centre in Lorne, with a few sheltering overnight.

“A lot of people are filtering in this morning to have breakfast and get some reassurance and find out what’s next,” Stapleton said.

Another 40 people stayed at the Lorne Surf Life Saving Club.

“We’re really fortunate that everybody’s safe,” Stapleton said.

“We know that hundreds of people have been impacted, whether they’ve lost cars or caravans or personal property has been damaged.”

Cars were swept up in the floodwaters.

­Federal Emergency Management Minister Kristy McBain said the scenes were “extraordinary and terrifying”.

She said the downpour was the highest for any 24-hour period in the area since site records began in the early 2000s.

“It’s obviously still a pretty dangerous situation,” she told ABC Radio National on Friday morning.

The Victorian State Emergency Service described the intensity of the rainfall as “off the charts”.

“The previous totals down there for a whole day total was 123mm,” spokesman Alistair Drayton said on Thursday.

The area is a popular tourist spot, with hundreds of holiday-makers visiting at this time of year.

The Great Ocean Road is open from Torquay to Lorne, but still closed south of Lorne to Skenes Creek, with the space between Lorne and Apollo Bay to be off limits for some time.

Elsewhere in Victoria, ongoing windy conditions threaten to complicate efforts for fire crews sill tackling nearly a dozen bushfires, after last week’s strong winds and  high temperatures sparked blazes that burned more than 410,000 hectares and destroyed almost 900 structures.

While widespread rain is forecast for the coming days, meteorologist Angus Hines said it was more likely the fire-affected regions would get just single-digit rainfall totals.

“In fact, gusty winds could cause those fires to flare up once again,” he said.

Elsewhere, emergency warnings were issued for dangerous surf and storms in Wollongong, Batemans Bay, Kiama, Ulladulla, Bulli and Port Kembla in NSW on Friday.

“Beach conditions in these areas could be dangerous and people should stay well away from the surf and surf exposed areas,” the weather bureau said.

“Damaging surf conditions are expected to ease during Saturday evening.”

The state SES said severe thunderstorms were likely to produce large hailstones, damaging winds and heavy rainfall that may lead to flash flooding later on Friday.

–with AAP