North East Catchment Management Authority has contracted Alluvium Consulting to look into the cause of the flood and build a case for government funding to address the problem.

Many from Tarrawingee strongly believe the Great Alpine Road bridge over Hodgsons Creek is too low, so when the creek floods, debris causes a log-jam and makes the flooding worse.

But Alluvium director Ross Hardie said this was only a minor problem in December.

"In this region, it was a most extraordinary event. We were most unlikely to see it in our lives," he told a public meeting on this week.

"We've estimated it to be in the order of about a one in 2000 year event.

"The chance of it occurring in any year, in your creek system, is 0.05 per cent.

"It's a really rare event, highly unlikely to occur - but you got it."

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Flooding seriously damaged homes, properties and the historic Tarrawingee pub.

"You had 400m3/s coming down Hodgsons Creek, but the creek system only has capacity to discharge around 50m3/s - 350m3/s of water was breaking out of Hodgsons Creek well upstream of town," Mr Hardie said.

Some at the meeting called his verdict on the cause of the flooding "rubbish".

Resident Doug Ellis said 700 metres of debris had to be taken away from the creek after the flood.

"This bridge here is totally inadequate and too low so it's going to collect debris, whereas if it was higher it wouldn't collect so much," he said.

"On the morning of the flood, I could see the water banking up and subsequently flooding people's houses."

Hodgsons Creek had a series of rock structures installed to prevent the creek from getting deeper and wider, and causing issues for structures like bridges.

Mr Hardie said 14 of these structures were damaged in December's flood.

"If we don't get them repaired, we won't hold this creek together," he said.

His research will be used as part of NECMA's proposal for government funding.

Regional Roads Victoria planning manager Rebecca Steer said the bridge at Tarrawingee would continue to be inspected before forecast flooding in the future.

"What we've learnt from Ross's work is that the role the bridge played, in an event of that nature, wasn't significant, but what we can do in the more common events is make sure we're on top of that debris management," she said.

Wangaratta Council infrastructure manager Marcus Goonan said the damage bill from the flood was expected to be about $4 million, but "the goalposts seem to shift" on the frustrating method of claiming damage compensation from the Victorian government.

"We heard back last week that all of our claims have been rejected ... We're hurriedly going back and pushing those claims back through the process and changing some of the things," he said.

"It's not a matter of 'we won't get the funding' it's just there's a process to be followed."