As floods decimated Lismore, the town mayor stood beside a highway - which became a river bank - and watched soldiers of the 41st Royal NSW Regiment pull people from boats and take them to safety.

While rapidly-rising flood waters caught residents by surprise, Mayor Steve Krieg had a front-row-seat to the regiment's first response on March 1, as they assisted 200 civilian boats with 4000 rescues.

"This was everyone from aged-care residents to a six-month-old baby," Mr Krieg said.

"I spoke to a mum who was standing on the handrail of her stairs and clinging to her gutter with her children, trying to get rescued.

"41 RNSWR came through, picked them up and took them to safety. Those are images that will live with me forever."

About half the town's 30,000 residents live more than 10 metres above sea level, but many were forced onto roofs when waters reached a record-breaking 14.37 metres.

Army Reservists from 41 RNSWR mobilised, pulling people from homes into emergency boats and to higher ground.

Nine days later, Mr Krieg visited 41 RNSWR's Lismore depot to commend the efforts of their soldiers.

"The town of Lismore did everything right for a flood event, but this event was bigger than a flood - it broke all records," Mr Krieg said.

"We needed help and it is such a blessing to see so many Defence Force personnel here.

"Their actions literally kept Australian citizens alive. I just can't say thank you enough, 41 RNSWR are amazing."

The Commander of Operation Flood Assist Joint Task Force, Major-General David Thomae, surveyed the devastation with Mr Krieg from an Army helicopter and spoke with 41 RNSWR soldiers.

Commanding Officer 41 RNSWR Lieutenant-Colonel Susanna Fernandez - who is also a helicopter pilot - had to choose between saving a rescue helicopter and saving her car. She saved the helicopter.

"The more I talk to soldiers, the more stories I hear that are unbelievable - you couldn't write this as a movie script," Major-General Thomae said.

"They've literally ripped iron off roofs to rescue people from cavities.

"We had Army helicopters rescuing people, and nine days on they've only just started to slow down, because we have had communities within 20 kilometres of here, which became completely isolated."