Nothing could have prepared the newly built Main North Line for the "exceptional" rainfall that led to its closure on Saturday, says KiwiRail.
It's been less than a month since crowds welcomed the first train to travel on the line between Picton and Christchurch following the Kaikoura earthquake.
KiwiRail says unusually heavy rain in September and the first half of October had caused 31 slips in the area, sending material onto the railway and road.
Acting chief executive David Gordon says the setback couldn’t have been avoided.
"It's just been appalling weather. Mother Nature's just played a hard game with us. The seaboard in Kaikoura is quite preponderous to slip. It will be with us before the quake and it'll be with us after the quake."
However, Mr Gordon is confident the work they are doing will help to mitigate poor weather conditions in the future.
"We’ll be putting it back better than it was. We're doing quite a bit in terms of moving the rail away from the base of the cliffs in a number of areas and dragging down loose debris. We're putting catch traps in place so if there is a slip, it gets caught before it gets on the line".
The aim is to have the line reopened by October 31, but Mr Gordon says "realistically we're not going to know until next Monday".
"We've got a lot of digger work to do, just to take debris away from the bottom. Set up the safety fences again to get ready for operation".
Truck drivers are hopeful the line will be back in working order by the end of the month, as newly running trains have shouldered some of the heavy freight burden placed on the alternate route after the November 11 earthquake.
They now face the added pressure of an upswing in freight volumes, with the Christmas period approaching.
"They're still vulnerable," Road Transport Forum chief executive Ken Shirley told 1 NEWS.
"They'll be stretched with the consumer demand.. but we shouldn't be too surprised about the closure. It's a small step back".
KiwiRail acknowledged many people may be disappointed by the closure, but committed to "getting it right" for New Zealand and those living along the coast.