Mouth of Hawke’s Bay’s Esk River ‘became blocked’ by wood and debris during Cyclone Gabrielle

Craig Goodier (inset) appeared before a coroner's inquest into deaths associated with Cyclone Gabrielle, and gave evidence about flooding in the Esk Valley.

A mass of wood and debris probably blocked the mouth of the Esk River north of Napier during Cyclone Gabrielle, worsening deadly flooding in the valley upstream.

A blocked river mouth would also explain a change of direction in the river flow, pushing northwards towards North Shore Rd, where a little girl was washed away.

Coroner Erin Woolley is conducting an inquest into 19 deaths associated with the extreme weather conditions of January and February 2023 – the Auckland Anniversary Weekend floods and Cyclone Gabrielle.

Hearings are being held this week at the Hastings courthouse.

The inquest was told Hawke’s Bay Regional Council staff inspected the Esk River mouth just before 5.50pm on February 13, as the cyclone was bearing down on the North Island’s east coast, and found it was open and flowing.

However, the council’s principal engineer and hydrologist, Craig Goodier, said he had come to the view that the river mouth became blocked later that night.

“After Cyclone Gabrielle, I made site visits to the Esk Valley and inspected aerial photos, videos, and photos from the ground and from a helicopter flight,” Goodier told the hearing on Monday.

“I also heard from residents who were present during the flood,” he said.

“From this information that I gathered, I have formed the view that a log raft blockage at the mouth of the Esk River was likely a major contributor to the change in direction of flow of the Esk River from the expected outflow to the ocean,” he said.

Hawke's Bay Regional Council principal engineer Craig Goodier gives evidence at the Cyclone Gabrielle inquest in Hastings. Photo / Ric Stevens

“This change in flow direction of the river resulted in unpredictable conditions, which flooded houses,” Goodier said.

A photograph taken about 11.30am on February 14 shows the river mouth open again.

But it also shows a large dark patch off the shore which Goodier’s written evidence to the inquest identifies as the “raft of logs” which had likely blocked the river mouth earlier.

A photo of the Esk River mouth taken at 11.33am on Tuesday, February 14, 2023, during Cyclone Gabrielle. The photo was presented in evidence to the Cyclone Gabrielle inquest hearing in Hastings. Photo / Hawke's Bay Regional Council

Photographs also showed water had been pushed towards North Shore Rd, where 2-year-old Ivy Collins was lost in the flood.

Upstream in Esk Valley, Susane Caccioppoli, 56, was also swept away from a house she was looking after.

Goodier said that many trees in forested areas of the Esk catchment were blown over in the high winds of Cyclone Gabrielle, with the logs and wood ending up in the flood waters.

Photos, videos and observations also indicated there were many other items washing down the rivers in the floods, including “containers, vehicles [and] water tanks”.

“Such debris creates an unpredictable hazard during a flood,” Goodier said.

“The debris in the flood waters likely contributed to the blockage at the mouth of the Esk River,” he said.

“Blockages created by the debris cause increases in water levels upstream of the blockage, thus creating a worse flooding hazard in that immediate area.”

A comparison of water volumes in cubic metres per second at Waipunga Bridge on the Esk River during Cyclone Bola (1988), flooding in March 2018, and Cyclone Gabrielle (2023). The dotted part of the yellow Cyclone Gabrielle line represents estimated data after the monitoring equipment was washed away. The graph was presented in evidence to the Cyclone Gabrielle inquest in Hastings.

Goodier told the inquest that the volume of water flowing at the Waipunga Bridge on the Esk River during Cyclone Gabrielle has been estimated at more than 2175 cubic metres a second, at its peak.

This was more than double the peak of an extreme weather event in March 2018, which also caused flooding in Esk Valley, which was 1040 cubic metres a second at the same location.

It would also have exceeded a flood in April 1938, which covered the whole of the lower Esk Valley with silt.

That flood was estimated to have peaked at 2000 cubic metres a second at the Waipunga Bridge.

Wood and forestry slash at the Waipunga Bridge in the Esk Valley after Hawke's Bay was hit by Cyclone Gabrielle. Photo / Mike Scott

Ric Stevens spent many years working for the former New Zealand Press Association news agency, including as a political reporter at Parliament, before holding senior positions at various daily newspapers. He joined NZME’s Open Justice team in 2022 and is based in Hawke’s Bay.