Flood warning systems were compromised by the failure of a repeater station.
Flood warning systems were compromised by the failure of a repeater station.
Two independent reviews have found the failure of backup power supplies at a repeater station knocked out telemetry from dozens of rainfall and water level meters during Cyclone Gabrielle.
The Mt Kahuranaki repeater, which relays information to Hawke’s Bay Regional Council (HBRC) headquarters in Napier, failed at about12.30am on February 14.
The independent reviews were commissioned by the HBRC.
Independent reviewer Graeme Horrell found 42 of Hawke’s Bay’s 84 rainfall sites failed to send data during the cyclone. Thirty-eight of those 42 were as a result of the loss of power at the Kahuranaki repeater.
Twelve of Hawke’s Bay’s 32 water level sites also transmitted no data during the early hours of the cyclone. Ten of the 12 were, again, as a result of the loss of power at Kahuranaki.
The performance of flood warning systems during February’s weather event has been a talking point, with the loss of telemetry assumed to be a result of the sheer volume of water.
Horrell’s review says no rainfall sites suffered sensor problems, while eight of the 32 water level sites had their sensors damaged by the flood.
The HBRC cyclone recovery committee will discuss Horrell’s review on Wednesday and that of David Walker, who looked at why the Kahuranaki repeater failed, as part of its own Cyclone Gabrielle telemetry review.
Walker’s review found that, once the mains power supply was lost at 12.30am, the backup mains supply generator - which is operated by Chorus - broke a shaft. Back-up batteries were then tried.
“Battery back-up should have kept the radios going for several days, but the batteries were old and needed replacing,’’ Walker wrote.
The HBRC cyclone recovery committee telemetry review agenda adds that those batteries “were drained in a very short time”.
A smaller generator was flown on site to Kahuranaki, near Havelock North, on February 15 “but was unable to power HBRC equipment”.
Mains power was finally restored to the repeater station on February 18.
Links Rd residents being rescued during Cyclone Gabrielle.
The HBRC owned and operated the repeater station until 2011, when it was sold. It was leasing equipment and a site from communications service provider Vital at the time of the cyclone.
“With over 50 per cent of the telemetered sites failing to provide live data throughout the Cyclone Gabrielle event due to the Kahuranaki repeater malfunction, consideration should be given to the practice of contracting out components of the telemetry system, as this was the only component of the flood warning system not under direct control of HBRC staff,’’ Horrell wrote.
Horrell also included a recommendation from former Horizons Regional Council manager Jeff Watson who, as a result of the Manawatū River flood of 2004, said commercial communications providers should not be used for hydrological purposes and that more power at repeater stations was a basic requirement.
