Some 56 homes were flattened, dozens more buildings were damaged and hundreds of residents and visitors were displaced when the blaze swamped the picturesque coastal village on March 18, 2018.

A coronial inquiry on Monday heard the blaze, that did an estimated $63.5 million in damage, began in an electrical easement about seven kilometres northwest of the town before strong winds quickly fanned it over a 100-metre wide stretch of the Bega River.

"Shortly after the fire jumped the river, the town of Tathra - to use the words of an RFS volunteer - was under siege from embers falling from the sky," counsel assisting Adam Casselden SC said in his opening address.

"The fact no one lost their life in the fire was remarkable, given the ferocity of the fire, and the spread and indiscriminate nature of its attack."

Coroner Elaine Truscott will hear from 36 witnesses as she examines the management of the electrical easement, the wider management of forest fuel loads and the adequacy of the firefighting and evacuations.

The court is expected to hear strong winds, an abundance of dry fuel and the fire's genesis being partway up a hill meant it swiftly became intense and forced local fire crews to a reactive strategy.

Every RFS brigade in the area was either battling the Tathra blaze or one-of-six other fires nearby, Mr Casselden said.

"Due to the number of incidents, there was little opportunity to develop a comprehensive strategy," he said.

The fire likely started in the six seconds between a sensitive earth fault being detected along the two 11,000-volt transmission lines at Reedy Swamp at 12.19pm and the power automatically being shut off.

But Mr Casselden said experts were divided about how precisely that fault came about.

Arborist Marcus Lodge is expected to say three trees that fell into the easement on the day of the fire had been dead for years and were likely significantly weakened by termite infestation or other decay.

But, like another arborist due to appear at the hearing, he can't conclusively say which tree fall sparked the blaze.

Mr Casselden anticipated electrical engineer Trevor Blackburn to say one tree fell into a power pole and maintained contact for "tens of seconds", generating burning embers that set the bushfire in motion.

But bushfire risk management consultant Paul de Mar is expected to pin the blame on a different tree snapping a line that would have electrified the ground, igniting vegetation.

State-owned energy supplier Essential Energy last assessed the trees beside the easement for defects in December 2016.

A remote survey of vegetation encroachment was conducted in December 2017 but results weren't received until nine days after the fire.

No lightning strikes were recorded in the area that could have caused the fire, Mr Casselman said.

Australian Associated Press