The nation’s newest lake, Rototaupua, which was formed last year when a slip moved during Cyclone Hale and blocked the Waiorongomai River near Ruatoria, is set to disappear in a few months.
Tikapa Beach resident and conservationist Graeme Atkins has been one of the few people to visit the new lake and named it Rototaupua which means “temporary lake”.
During the March 2022 storm event in Tairāwhiti, a landslide occurred in the upper Waiorongomai Valley partially blocking the Waiorongomai River, inland from Ruatoria.
On January 12, 2023, Gisborne District Council became aware a lake had formed as a result of further landslide movement during Cyclone Hale, when a forest manager for Summit Forests reported the landslide dam to Tairāwhiti Emergency Management Office (TEMO).
The GDC was alerted to the lake’s formation and immediately took action to assess the risks it posed to downstream infrastructure and residents.
“I had the honour of being the first to stand on its shore and with that, the privilege of naming it,” Atkins said.
He said there is no chance of driving there due to the numerous slips and dropouts, and hundreds of fallen pines, so it’s a 20km walk one way to the lake.
“When we first visited it in Easter last year, the dam wall was actively eroding, forming a deep, ever-widening outlet,” Atkins said.
“From those observations, we guessed the lake wasn’t going to be a permanent feature. Hence the very apt name.”
Analysis of the valley using the remote-sensing technology LiDAR revealed it had been partially blocked before Cyclone Hale, indicating the initial landslide failure occurred during a severe storm in March 2022.
GDC principal scientist Dr Murry Cave has continued to monitor the area and new high-resolution aerial imagery was used to map it in November 2023.
“This shows that the lake behind the landslide dam is gradually diminishing in size, and it’s anticipated that the lake will have fully drained by the end of winter.”
Cave said that while it would be nice if the Tairāwhiti region had a new permanent lake, it is expected that the lake will have completely gone within the next few months.
