Safe to return home: slow release of Mangahauini dam alleviated threat

LAKE MANGAHAUINI: The lake formed by a huge slip in Mangahauini Gorge that caused extensive damage to the highway between Tokomaru Bay and Te Puia Springs is estimated to contain around 400,000 cubic metres of water, silt and trees. Experts are to return to the site this week for a detailed assessment and to look at ways to further alleviate the risk of the dam giving way and water rushing down Mangahuini River and into Tokomaru Bay. Picture supplied

Tokomaru Bay residents evacuated on Thursday night from areas around the Mangahauini River catchment were allowed to return to their homes on Saturday afternoon.

More than 60 homes in the river catchment and in Tokomaru Bay township were evacuated as a precaution because of the risks a huge debris dam on the river might give way.

The residents remained out of their homes until Saturday afternoon. They were accommodated at local marae or with whānau in safe areas.

An assessment was made of the debris dam by engineers and scientists on Saturday morning and it was considered safe for whānau to return.

“A slow release of the dam alleviated the immediate threat,” Tairāwhiti Civil Defence said in a statement on Saturday afternoon.

Tokomaru Bay civil defence spokesperson Lillian Te Hau-Ward said the evacuated residents got the “all-clear” to return to their homes at 1.30pm Saturday.

“With the rain on Friday night the water in the dam found a natural pathway through.

‘We held a community meeting at 4pm on Saturday and showed footage that we had gathered over the past week up the Mangahauini and out to Hikuwai Bridge, which was sobering for our whānau,” she said.

Her Tokomaru Bay team had the day off yesterday although checkpoints remained in operation at the base of Busby's Hill.

“Our team were back in action this morning to be ready to respond to the next heavy rainfall event expected today.”

Tairāwhiti Civil Defence said experts would return to the Mangahauini dam site this week to do a detailed assessment and look at options to further alleviate the risk.

Mangahauini Gorge has been blocked by a major slip, damming the river and forming a temporary lake.

It is estimated to be holding about 400,000 cubic metres of water, silt and trees.

There were concerns that if the dam gave way the water build-up would go “fast and hard” down the river and into the township.

Gisborne Mayor Rehette Stoltz and Gisborne District Council director of community lifelines David Wilson accompanied the experts who visited the debris dam site on Saturday morning.