Loud rumble not a quake but a roadway collapsing into a stream

Part of Riverdale Rd, above the bridge is down to one lane after a washout Friday night took away a large chunk of the road. Photographer: Christine McKay.

When Margie Delaney was woken by a loud rumble on Friday night she braced for an earthquake.

The quake didn't arrive, but on Saturday morning the cause of the noise was revealed. Part of Riverdale Rd, up from the bridge on the town side of the road collapsed into the Mangatera Stream.

"The noise scared the crap out of me," Mrs Delaney said.

Known as Swing Bridge Hill by locals, the collapse of this part of the road has been a foregone conclusion for a while, her husband Tim said.

"I'm worried when the remnants of Cyclone Debbie arrive as predicted we are going to get a soaking and more of the road could go."

And on Saturday, from the Delaney's back yard, the rumble of debris continuing to fall down into the stream was unsettling, with the occasional loud thump as a larger chunk of the bank dropped.

Riverdale Rd is a very busy road, with school buses, stock trucks and other traffic using it as the close-to-town access for Maunga and Tipapakuku Rds.

"That's a blind corner where the collapse has occurred and with no temporary lights controlling the slip zone, it's an accident waiting to happen," Mr Delaney said.
"It's a real worry."

With more than 44mm of rain falling during last week's torrential downpour and the Mangatera Stream roaring, Mr Delaney said he believed rubbish clogging the stream and the amount of water flowing could have had something to do with the road collapse.

"The sound of the stream roaring in the heavy rain was incredible," Mrs Delaney said.
And the worst may not be over, with a large crack in the remaining road.

"At least another metre could go yet," contractor and district councillor Ernie Christison said. "This could be going to get worse rather than better."

On Saturday afternoon Horizons Regional Council staff were checking the stream and arranging for clearing of the debris. The problems with this section of the road have been ongoing, with a smaller washout a few years ago.

And approximately 20 years ago the bridge was blocked by debris, during a storm, with the water lapping at the bridge.

Raj Suppiah, council chief financial officer, said the council would go to the New Zealand Transport Agency (NZTA) to seek additional funding for the repairs.

"This is quite a significant slip," he said.

Council chief executive Blair King said the repair work could easily run into six figures.
"It's the practicality of rebuilding a vertical drop," he said.

Council's Alliance roading team will apply to NZTA for flood-damage funding but in the meantime, a digger was yesterday carrying out some remedial work before the predicted heavy rain was due to hit the district today.

Mr King said the Alliance's application to NZTA could also be altered if there is "a fair bit of damage from the storm".

Council sees the Riverdale Rd as a vital transport link, but Mr King said it would be down to NZTA to decide whether to leave the road as single lane or restore it to a two-lane.