A NSW parliamentary committee is looking into the official response to the flood catastrophe of February and April that struck primarily in the Northern Rivers region.
At least 10 people died in the weather crisis that forced thousands of residents to flee their homes and left many towns in the region severely damaged.
Federal and state authorities have faced criticism over their handling of the emergency, including on response times, preparedness and recovery.
On Monday, Byron Shire Council mayor Michael Lyon told the inquiry the floods revealed an "inability to deal" with a housing crisis which existed before the crisis.
"We've put planning proposals (in on) tiny homes, caps on short-term letting, we've been attempting this for several years, we haven't been able to get those through," Mr Lyon told the inquiry, sitting in Ballina.
"What that meant was that the exacerbation caused by the floods, and that existing crisis, left us really exposed and it's made things so much harder in the aftermath of the floods.
"If you fail to plan then the plan is to fail and I think that's what we saw in a number of areas as the result of this devastation."
He also hit out at the NSW Department of Communities and Justice (DCJ), saying the agency failed at times, especially on setting up evacuation centres.
He pointed to one evacuation centre in the town of Mullumbimby having to be "informally stood up" as DCJ "didn't really make the effort to get in there".
"That left residents stranded with nowhere to go," he said.
Telstra was also in Mr Lyon's firing line for what he said was a telecommunication network that remained down for weeks during and after the floods.
He said the telco giant had serious questions to answer over the way its network was designed and whether its privatisation contributed to its performance.
"I'm interested to know how that can be improved so that we are ... more resilient for the future," he said.
Ballina Shire Council mayor Sharon Cadwallader, in her evidence, said residents knew the area faced a flood risk, but "mitigation money" had been inadequate.
Ms Cadwallader also cited communication problems during the crisis which left the area isolated, labelling what happened as "totally inadequate" .
The situation was so dire, she said, "runners" had to go between evacuation centres and people had to cross the border to Queensland to get messages out.
The upper house inquiry continues.
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