City continues to crumble
Slips are becoming a regular Wellington feature, thanks to rain, crumbly rock and ongoing fallout from the November 2016 quake.
Two slips in recent days – one on Happy Valley Rd, pictured, and another that shut down the Johnsonville train line – had a sense of deja-vu for city folk.
Last year, the capital experienced 1000 slips, which cost ratepayers about $1.5 million to clear.
Wellington City Council figures show there were 77 slips in June this year – the same as in June 2016, though June 2017 had 82.
But looking at year-to-date figures and 2016, when there were 168, pales in comparison. By this time in 2017, Wellington had 279 slips and there have been 230, so far, in 2018.
The council figures only include roading slips, so those on private land were not counted.
Victoria University erosion expert and senior lecturer Kevin Norton last year said while quakes were part of the problem, the main trigger was rain – especially when there was a lot of it.
Wellington was already sitting on a foundation of fractured bedrock that fractured a little more with each quake.
‘‘One of the problems in Wellington is you have steep hills and you need to have roads, and the only way to build roads is to cut into the hillside. That pretty much means you’re going to have slips coming down on to the road.’’
Niwa data shows that June in Wellington had 128mm of rain, compared to the 104mm that fell in June 2017. Total rainfall in Wellington this year was 720mm compared to the average of 565mm.
Council spokesman Richard MacLean said the fact ‘‘landslide season’’ always fell in winter suggested that rain was the major cause but ‘‘we can never be 100 per cent certain that earthquakes are not a factor’’.