The main road between Blenheim and Nelson could be closed for months.
Initial assessments show parts of State Highway 6 have been completely wiped out and communities still cut off are relying on air support for fresh food and water.
Many of Marlborough's roads have mountains of mud blocking both directions. Queen Charlotte Drive is undrivable until contractors can dig their way through.
From a bird's eye view, the devastation is immense.
Hillsides have slipped away, homes destroyed and some roads on State Highway 6 just don't exist anymore.
Marlborough Civil Defence controller Richard McNamara told Newshub that the roads need a complete renovation.
"Just isn't covered in debris, the road is broken. Right down to the foundation."
Waka Kotahi road managers and geotechnical teams have been assessing the extent of the damage from the air.
"I've lived here in Marlborough all my life, actually grew up in Marlborough sounds so to see it first-hand was pretty disheartening. Pretty sad for me," Waka Kotahi Marlborough roads network manager Lucan Orchard said.
State Highway 6 - the main route between Blenheim and Nelson - remains impassible with no timeframe on when it could reopen.
Marlborough Mayor John Leggett thinks it will take far longer than expected.
"Oh, I think weeks could be a little bit too conservative, longer than that."
A trip that would normally take an hour and a half is now a 534-kilometre drive of at least seven hours - not including the inevitable delays on State Highway 6, between Brightwater and Murchison.
Contractors are working around the clock to open the alternative route through State Highway 63 as soon as they can.
"That's the one we can have the most impact on in a short amount of time, we're still thinking over the weekend," McNamara said.
River levels in Marlborough have dropped, revealing just how much debris and slash has washed down the Wairau River.
There's still a lot of mahi to do in low-lying townships where some streets are swamped.
Others are in desperate need of drinking water. Marlborough Helicopters has been ferrying precious food for every man and their dog to those stranded in the Sounds.
"At the moment we've got whānau who are isolated at Durville Island," iwi liason EOC Marlborough District's Joshua Joseph told Newshub.
For many communities, air support is the only connection to the outside world.
"The damage is pretty extensive and I don't think we would have got a gauge as to how much damage there is if we didn't get up and see it from a height," Emergency Management Minister Kieran McAnulty told Newshub.
But with a break in the weather, the clean-up is underway.
