A large landslide swept away a section of road between Wairoa and Gisborne on Tuesday night, cutting off about 1500 residents in the Hangaroa area.
Police said the section of Tiniroto Road between Rockhill Road and Parikanapa Road is impassable.
The section of road subsided several metres below its usual course on 3 October and the road seal has broken up.
Since Cyclone Gabrielle, locals have already been taking a long detour to get to Tiniroto and Hangaroa. Now they will have to drive even further.
Gisborne Mayor Rehette Stoltz said it was a huge blow for the small communities.
About 1500 Hangaroa residents in about 500 households have been affected by severe weather disruptions since January, when Cyclone Hale struck, then Cyclone Gabrielle hit in February.
"They have been using detours the whole year. This is just another cruel blow for that community," Stoltz said.
"I actually travelled that road on Tuesday to open a new bridge there and the community was so excited with recovery happening... so I know they will be very disappointed this morning."
The detours required would add "significant time" to the journey for people travelling from Tiniroto and Hangaroa to Gisborne, she said. Hampered access is of particular concern for emergency services.
Stoltz said council repair crews were on site on Wednesday morning, but it would not be a quick fix.
"It's a huge landslide. That's the same site where a landslide came down in 1985 and then during Cyclone Bola in 1988, there was a landslide there as well that actually caused the lake called Lake French," she said.
"If you take a look at those images, it will be a huge, huge job."
She said rain that lashed the area last weekend would have contributed to the slip. After nine major weather events in 18 months, local people's patience is wearing thin.
"We need to connect our communities, but we are coming up against this time after time.
"We just need a break for the soil to dry out, so that we can carry on with our recovery efforts."
Tiniroto Road resident Alex Campbell said the region had already been "tipped on its head access-wise" before last night's slip.
"Six bridges on the Hangaroa River, five of them are gone, so that just in itself created huge issues. We've got the main road through Tiniroto... that's been closed. They opened that up after the cyclone, it took a real battering as much from the river - got shaved off the face of the earth, a section of the road," Campbell said.
"They got that open and geo-techs have closed it based on the risk of rock-fall.
"That's been a real issue that the community has been battling with as it is.
"This has been a slam-dunk on top of all of that."
Residents were worried the road could be closed for a long period, he said.
Anyone travelling between Gisborne and Wairoa should use State Highway 2.
Local lines company Firstlight Network's acting operations manager, Linda Broughton, said the slip had taken down four spans of power lines, but no homes were without power.
However, the link between the Pehiri and Patutahi substations was lost, which compromised the back-up power for these areas.
The impassable road also meant repair crews would take longer to reach any other unplanned power outages.
She said the company was aiming to install a temporary line within the next 10 days, while working on a more robust long-term solution.