Cyclone Gabrielle: Council, Genesis Energy say opening of floodgates in river near Wairoa didn't lead to flooding

  • 23/02/2023
 Lake Waikaremoana.
Lake Waikaremoana. Photo credit: Getty Images

Genesis Energy and the local regional council have denied the opening of the floodgates played a part in the flooding in Wairoa during Cyclone Gabrielle. 

The cyclone devastated the town with floodwaters and high-speed winds, destroying infrastructure and leaving locals without basic essentials to survive.

The district became cut off following a river bursting its seams and taking out a number of homes, destroying roads and cutting off the country from reaching the township for days.

Conspiracy theories have been running rampant on social media that Genesis Energy opened the floodgates on the Waikaremoana Dam during the cyclone.

Genesis Energy told Newshub they acknowledge the tragic and catastrophic effects of Cyclone Gabrielle across the North Island and their "hearts go out to all those affected". 

"We understand in such trying times it is natural to look for answers as to how this situation could have occurred or if there are things we can do to prevent them happening again," a spokesperson for Genesis Energy said. 

"We believe there should always be a forum for these types of questions to be asked and we are open to sharing information and cooperating with any reviews."

However, interim chief executive Tracey Hickman said the company is concerned about misunderstanding or misinformation circulating regarding how they managed the water in the Lake Waikaremoana catchment area before and during the cyclone.

"It is just inaccurate to say the Waikaremoana Power Scheme was responsible for the flooding in Wairoa and surrounding areas," Hickman told Newshub. 

"Genesis operates the level of Lake Waikaremoana at 5.5m below the natural lake level which enables flood flows to be stored and not passed directly downstream."  

Hickman said in the days leading up to the cyclone, Genesis reduced the level of Lake Waikaremoana by six percent to mitigate the effect of inflows from rain. 

"During the cyclone, lake inflows peaked at 434 m3/s (cubic metres per second). Genesis released only 40 m3/s as required by our resource consents," Hickman said.

"This requirement exists to ensure dam and public safety and to avoid uncontrolled and potentially far greater volumes of water being released.

"These outflows contributed less than 1 percent to the water which ended up at Wairoa township. The rest of the floodwater came from streams and rivers below the power scheme's last point of control." 

Hickman said this is verified with independent river flow data from the Hawke's Bay Regional Council.

The council's General Manager Asset Management, Chris Dolley, said the discharge by Genesis at Lake Waikaremoana was very minor in the scale of flood flows.  

"At peak, the amount was less than 1 percent of the total flow at Wairoa River at the Railway Bridge," Dolley said.

"In terms of how the lake is operated during a major event such as Cyclone Gabrielle, the lake is able to buffer the outflow and store huge volumes of runoff, which reduces the peak flow in the major rivers compared to an uncontrolled outflow."