Five lives were lost and more than 3000 homes were damaged or destroyed in the Northern Rivers city on February 28 last year, when a month of record rain raised the Wilsons River to a record high of 14.4 metres.
The memorial on Tuesday will be preceded by a private ceremony to acknowledge the herculean effort of those involved in the "tinnie flotilla", who ferried hundreds of people from rooftops to safety.
The event kicks off three weeks of events in the city, including a music festival in the CBD this weekend and a celebrity cricket match on March 11.
Lismore mayor Steve Krieg says the one-year anniversary will be a tough day for the community.
"It is still so emotional," he told ABC TV on Tuesday.
"We have thousands of people living in temporary accommodation, they're paying mortgages on houses that are unliveable.
"The businesses they worked in were so badly affected as well.
"We hope that everyone rallies around each other and we'll get through today and look towards the future and rebuilding."
About 60 per cent of businesses have returned to the CBD, but the relocation of schools means hundreds of their customers have gone.
Ella Buckland, whose house was inundated with 1.5m of water, said when the crisis hit everyone was running on adrenaline.
"And then you had little wins, like the coffee shop coming back and everyone was really excited and supportive and kind, like cuddling people who you didn't know," she told AAP.
"Now everyone is just exhausted."
Harper Dalton said the emotions that rose up as the one-year anniversary approached reminded him how much trauma he and his friends had experienced.
"Most of us are flood-impacted, so having that type of community support is really helpful," he told AAP.
But Mr Dalton, who is still waiting to find out if the government will buy her home or offer money to raise it, thought she would be further down the recovery track.
"I really thought I'd have some indication of what I'll be offered by 12 months on from the worst flood in Australian history," he said.
"I'm pretty disappointed and feeling greater desperation as more time goes on, because it could technically flood next week or next month and nothing's changed."
National Emergency Management Minister Murray Watt, Premier Dominic Perrottet and Opposition Leader Chris Minns are expected to attend the memorial.
"For many, this event is still very raw, with the anniversary bringing into sharp focus what people have been through and what they're still going through," Mr Watt said.
Amid criticism for the speed of the home buyback, Mr Perrottet on Monday noted the mammoth task facing authorities and the community.
"It will be a long journey ahead,'' he said.
"It will be a challenge and we will stand with those communities, as we have over the last 12 months."
Mr Minns said it would be a tough day for residents impacted by the floods, but all of NSW was committed to continuing the rebuild of the Northern Rivers.
"One year on from the floods that devastated the Northern Rivers, we are reminded of your resilience, your courage, your community spirit, from the tinnie army, to the locals who put their own lives in danger to save others, to our emergency services'' he said.
The first home buyback offers were issued on February 21, with all 250 offers expected to be issued by April.
33°C