Michmutters

Residents living upstream from Lismore say faults in the rain and river gauge network deprived them of potentially life-saving data as a catastrophic flood hit the New South Wales Northern Rivers in February.

There are 27 rainfall and 19 stream level gauges in the Wilsons River catchment that provide data to the Bureau of Meteorology to help predict flood heights and develop forecasts.

Residents also monitor the data directly via the bureau’s website.

When the February flood hit, one rain gauge was already broken and a further two rain gauges and six stream gauges stopped transmitting data during the event.

ABC’s 7.30 can reveal that crucial equipment failed because it was poorly located, while key rainfall data was missed or distorted due to a lack of maintenance.

The revelations follow the release of a NSW parliamentary report examining the flood response, which found information from the Bureau of Meteorology was “incorrect and out of date”, and called for the bureau to review its rain data infrastructure to ensure rain and flood gauges were appropriately placed, maintained and updated.

Local resident Annie Kia says the failures of the gauge network caused “much distress” among her upstream neighbours, who were among the first to witness the scale of the disaster firsthand.

“The upstream people knew that a catastrophe was hurtling toward Lismore in the night, and felt very frustrated that they could not get their message across,” she said.

‘People downstream really need to know’

Nan Nicholson’s property is nestled in the hinterland north of the town, flanked by two creeks that feed into the Wilsons River catchment.

“If it’s torrential rain up above, we know that Lismore is going to really cop it,” she said.

As a low pressure system moved south on the night of February 27, she was keeping a close eye on the local rain and stream gauge data, which she and her neighbors rely on for real-time information to decide when to evacuate.

The stream gauge said the nearby creek was “steady.”

However, that was in stark contrast to what was unfolding in her backyard: The creek was rapidly closing in on her home, and the hammering rain showed no signs of easing.

She could see the flood was shaping up to be far worse than initial predictions of a peak around the 2017 height of 11.59 meters.

“You could watch it within the minute rising very, very rapidly, so I just didn’t believe [the data]and that really filled me with dread,” she said.

“I thought, ‘People downstream really, really need to know this, and they’re not getting that information’.”

Ms Nicholson and her husband made a narrow escape in the night.

By the time they left, the nearby river gauge was not transmitting any data at all.

The rain gauge failed a short time later.

“Because of our knowledge of the area, we felt prepared to some degree, but it would have helped a great deal to know that that river gauge … was telling the truth,” she said.

“It’s a basic government responsibility to deliver us the data that we need to make decisions about our survival.”

‘Whole network needs to be reassessed’

Duncan Dey is a flood hydrologist and Byron Shire councilor who used to install and maintain rain and stream gauges.

I have identified key flaws in the gauging station near Ms Nicholson’s property.

He said a shed housing equipment that sends data to the weather bureau should have been located on higher ground.

“We know that the shed went underwater, and I’m stunned, actually, because it went underwater by three or four meters, which means that it was wrongly located in the first place,” he said.

“The whole network needs to be reassessed for whether the machinery shed is high enough above the flood levels.”

Mr Dey said he was also “shocked” to see a tree overhanging the top of the rain gauge.

“So it’s not actually measuring the right amount of rain. It’s completely non-standard,” he said.

“We now have computer modeling that works really well on taking rainfall, putting it into a catchment and working out what happens downstream — the modeling is fantastic, but it only works if you’ve got good data.”

A BOM spokesperson said the outages did not impact the bureau’s forecasts and warnings during the February flood, and that redundancy has been built into the observation system.

However, the bureau is reviewing its infrastructure across the catchment.

Council requests more gauges

The state gauge network is jointly managed by local, state and federal governments, along with some private agencies.

Lismore City Council owns the gauges that malfunctioned in February.

General manager John Walker said all but two of the gauges have been fixed, with parts on order from overseas, while one was broken prior to the flood because a technician could not get access to the site due to ground conditions.

Mr Walker said all existing gauges were located above the 1974 flood levels and the equipment that had been repaired has been relocated to higher ground, above the 2022 flood height.

He said the gauges were maintained every three months, or more often if a fault occurs.

The council’s request for more gauges, he said, was being assessed by the NSW Planning and Environment Department, after it was initially rejected in February.

A spokesperson for the department said it was awaiting completion of the council’s flood plain management plan before it could review the funding application.

Resident Annie Kia is among many — including local councils and MPs — calling for a single agency to own and maintain the gauge network.

“It’s clear to me that the system is not fit for purpose,” she said.

“We need to have some government system that manages these creek and rain gauges, and it seems to me it would be better if it was one agency — as long as it’s one, competent agency.”

Watch this story on 7.30 on ABC TV and ABC iview.