Tairāwhiti Civil Defence declared a state of emergency after the deluge forced evacuations and trapped people in floodwaters in the Tolaga Bay and Tokomaru Bay areas.
Emergency Management Minister and East Coast MP Kiritapu Allan said 150 people had been evacuated and 750 homes were without power, and the Hikuwai River had risen rapidly to more than 12 metres.
A person was rescued from their car trapped in a river at Tokomaru Bay, where MetService said 308mm of rain had fallen overnight, and rescue efforts were under way to free two people trapped by the water north of Tologa Bay.
Gisborne Civil Defence manager Ben Green said the rainfall was a lot heavier and had come in sooner than expected. "I'd almost describe it as biblical," he said.
Gisborne mayor Rehette Stoltz told Morning Report authorities have urged residents to stay home if possible with the region expecting "way more rain" later today.
"As it's now daylight we can start and reach out and see the extent of the damage but a lot of our coastal communities are affected and they're cut off from us now because State Highway 35 is closed," Stoltz said.
She said those small communities knew exactly what to do after they were put through a similar flooding scenario in June last year.
Tolaga Bay Civil Defence officer Nori Parata says the situation there is dire, with a major river running higher than it did during Cyclone Bola in 1988.
Parata said seven families were evacuated to higher ground early this morning.
She said there are others who are safe but trapped by floodwaters.
"We are concerned we have a healthy respect for what's going on here, the Hikuwai river about an hour ago was at 12.8 metres in (Cyclone) Bola it reached 12.2 so that alone gives you an indicator of how serious things are here."
Parata said the Uawa River was expected to reach high tide at about 11am.
State Highway 35 from Gisborne around East Cape to Ōpōtiki is closed because of flooding, slips and washouts.
"We are aware that there's huge parts of State Highway 35 that are under water and not just surface flooding you can't see markers on the side of the road or the tops of fences.
"There's a number of slips all the way along and we have power lines down at Waihau Bay Beach Road so yeah it's pretty dire here at the moment."
She said the community was well-drilled and many of the worst affected people were in contact with Civil Defense.
Ruatoria resident John Logan had to scoop up his family in a tractor as floodwaters rose rapidly into their house. The whānau from Makarika Valley in Ruatoria near the flooded Mata River had water up to their thighs inside the home.
Tairāwhiti Civil Defence ordered the evacuation of residents in the Mangatuna area north of Gisborne, because the Hikuwai River is at a very high level and more rain is expected.
Tolaga Bay Civil Defence has been set up and anyone in immediate danger of flooding should move to higher ground, civil defence says.
