Anger is mounting in the northern NSW city with scores of businesses preparing to take class action against authorities for mishandling the flood. Local volunteers have quit the State Emergency Service in disgust after continuing to be verbally attacked for following orders and forcing shopkeepers to evacuate.

The State Emergency Service ordered the Lismore CBD to be evacuated 12 hours before a levee wall was overtopped early on March 31 preventing the removal of stock and equipment.

Beth Trevan, a local business woman and co-author of the Lismore Citizens' Review into the disaster, said she had watched every flood since 1940 and the CBD had never been so badly damaged.

"The SES sidelined local SES knowledge in preference to Tweed Richmond HQ or the State HQ in Wollongong and it has cost this town millions, not to mention the ongoing personal pain and worry," she said.

The NSW government estimates at least 68 per cent of businesses in the Lismore CBD suffered damage. Combined total damage of infrastructure and agriculture in the area was just under $40 million.

Only 2 per cent of businesses had flood cover. Insurance companies have been tough on stormwater versus floodwater assessments, rejecting most applications.

Two reports revealed the chaos as the flood approached.

The SES commissioned former assistant police commissioner Dave Owens to review its flood response and he made 36 recommendations on streamlining bureaucracy, more protocols and more finance.

He also provided a snapshot of the confusion at the SES Richmond Tweed Region HQ and the SES HQ in Wollongong with evacuation orders issued prematurely, senior officers unsure of who was in charge, problems with staff shortages and inexperience and long lapses between receiving Bureau of Meteorology information and the issue of warnings and alerts.

SES Commissioner Mark Smethurst admitted mistakes had been made in the authority's response.

"Clearly, the order that did go out should have given people time to get out of the Lismore CBD by the overtopping of the levee," Commissioner Smethurst said.

"That was missing and that was an error, it's in the Owens report. We've said it was a mistake and we need more detail."

A Lismore Citizens' Review said the SES needed to be reformed to allow locals to lead the response rather than distant salaried officers.

"The lack of timely warning, coupled with the premature evacuation order, led to unprecedented and avoidable costs to those who obeyed them," the review said.

"Sidelining the Lismore City SES in critical decision-making deprived the community of local knowledge so vital within a constantly changing community.

"No centralised organisation can pretend to match the years of experience and memory which have served the Lismore community so well in the past.

"The flood warnings issued by the Bureau of Meteorology underestimated the situation and were not upgraded in a timeframe reflecting the evolving emergency conditions."

Lismore mayor Isaac Smith said he was confident 90 per cent of the closed businesses would reopen.