Heavy rainfall threatens East Auckland homes with land collapse gallery video

TARANNUM SHAIKH/stuff.co.nz

Robert McCallum has grave concerns for his property at Liston Crescent.

When heavy rain falls, residents of Howick's Liston and Luplau Crescents anxiously look through their windows to see how much of their backyard has washed away. 

The properties on these streets back onto Liston Stream, which runs from Paparoa Road to Howick Beach. 

Following a significant downpour in April, as a result of Cyclones Debbie and Cook, the stream was subject to a landslip which took down a retaining wall and blocked an access track.

Robert McCallum with Liston Stream behind him.
TARANNUM SHAIKH / FAIRFAX NZ

Robert McCallum with Liston Stream behind him.

While residents on the upper part of the stream, on Liston Crescent, are worried about their properties slipping away, dwellers on the lower section of the urban waterway, on Luplau Crescent, face flooding threats from the gushing stream.

Robert McCallum, a resident of Liston Crescent, says he first noticed erosion on the retaining wall behind his property around 18 months ago. 

A group of residents including McCallum contacted Watercare and Healthy Waters for help.

Trees fell over and pipes were exposed after a landslip.
SUPPLIED

Trees fell over and pipes were exposed after a landslip.

McCallum says it's been a battle ever since to have the stream's banks stabilised and strengthened. 

"The first 15 months were just frustrating, trying to deal with the large organisation and getting them to understand that actually there was a problem.

"You feel like you're not being listened to and you're having to make a point."

This video, by a resident shows the heavy flow of water at Liston Stream.

Some residents, including McCallum, also filed claims with the Earthquake Commission (EQC) for property damage.

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"We've received a geotech report from Tonkin and Taylor on behalf of EQC which put our houses at imminent risk of a slip within the next six months," he says.

He has yet to hear back about what resolution EQC will come to.

Damage at the Liston Stream, with the collapsed retaining wall lying on the left.
SUPPLIED

Damage at the Liston Stream, with the collapsed retaining wall lying on the left.

Waterways planning team manager Nick Vigar says he first became aware of the problem in November last year when a stream bank collapsed at the lower end.

"The residents were keen to see something done rapidly because it's pretty distressing seeing your back stream bank fall away."

He says because of the complexity of the matter, Healthy Waters and Watercare needed time to assess the problem.

"It takes a certain amount of time to understand the problem and design around it and the costs.

"When there's significant costs involved we can't just suddenly leap in and do something off the cuff."

McCallum says the Tasman Tempest storm in March caused a further section of the bank and retaining wall to collapse, heightening the residents' concerns.

Five days later another large section of the slope washed away "leaving dwellings at risk".

Vigar says the erosion downstream also became much worse.

"That was a pretty significant event that caused a lot of damage. At that point we put everything on an emergency works list."

McCallum believes an increase in the number of dwellings in the area and increasing stormwater drainage are causes of the significant erosion.

"We're not the only ones affected of course, the people further down are. It's a really big issue in terms of the whole area."

Vigar says erosion is becoming a common trend around Auckland because more infill housing results in more impervious area during rain.

"You get much more run-off and higher flows more frequently, which causes erosion.

"[It] also causes flooding, causing the stream to spill out of its banks much more frequently, and we get multiple issues of property flooding and erosion.

"It's not something that's suddenly happened, but I think it more or less got to a point where once the erosion starts, it actually gets worse quite quickly."

Vigar is working with Watercare to find a solution for the distressed residents.

"We decided that Watercare would stay in charge of the upper part of the stream, around Liston Crescent, so they're repairing the retaining wall and the erosion present." 

Watercare spokesperson Ramari Young confirms this, saying the cost of the repairs will be split between it and Healthy Waters.

The repair work is expected to take about five weeks to complete.

Vigar says the work will take place in two parts and Watercare will return in summer for more restoration. 

"Currently the scope of the work is to stabilise the streambanks."

McCallum says the fast-tracking of the work looks promising, much to his relief.

"Since March it's been an emotional roller coaster. Every time it rains through the night you wake up and think 'I wonder how much more has disappeared'.

"It's a deep concern, alarming and depressing when you're sitting and watching bits of the section vanish and being almost unable to do anything about it."

Vigar sympathises with the residents' concerns.

"It's pretty traumatic to see that outside of your house. It's really a torrent," he says.

"It's distressing to see your property erode into the stream and be worried about your house.

"I know that things haven't progressed as fast as the residents would like them to have, but they've been pretty patient."

Watercare is due to start an emergency rebuild of the retaining wall at Liston Stream later this month.

 - Stuff

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