Images of this 50m long slip in Matakatia appeared on TV following the storm in the wake of Cyclone Debbie early last month.
Below it sits the house of Graham Midgley. Along with several of his neighbours, Graham was evacuated during the storm, returning after he was given the all clear by Civil Defence five nights later.
Almost a month after the slip happened, he is still removing mud and debris by the truckload. Trees that were carried down the hill on a tide of brown water ended up on top of his rainwater tank.
He is also still waiting to hear from Auckland Council: advice he received from a geotechnical engineer was that the slip was caused by stormwater flowing from properties on Whangaparaoa Road down onto a strip of Council land above his property, which became sodden and gave way.
As a retired farmer, Graham says he knows the land. He recently spoke with the Hibiscus & Bays Local Board in an attempt to get Council’s attention. “The stormwater system is not coping and I would like it properly assessed and dealt with,” he says. “The land along the edge of the Council reserve strip is sodden and slumping and the engineer told me that the next bit is ‘ready to go’,” Graham said. “I’m afraid another big slip could take my home with it.”
It’s a risk that Council’s head of operational management and maintenance, Agnes McCormack, says is low.
“A council geotechnical specialist visited the Matakatia Parade slip on Good Friday and determined that it occurred across the boundary of the public reserve and privately-owned land and should significant rainfall happen again, further smaller slips may occur but that the risk to life or the main house is low,” she says. “Steep slopes such as this are naturally only marginally stable.”
“It is unlikely a faulty stormwater pipe contributed to this landslide. There is a stormwater collection system in the reserve behind Matakatia Parade and it appears to be functioning, based on a visual inspection. Overland flow is likely to have occurred during the rainfall from the reserve as the rainfall event was larger than most stormwater systems are designed for.”
Council will monitor the site and provide advice on addressing the issue, long-term. “In general the most effective way to stabilise this style of slip is with slope regrading and planting. Council is scoping these works on the reserve, and will recommend that the landowner undertakes similar work on their land.”