Watch: Dozens of people trapped on roofs in Hawke's Bay as Cyclone Gabrielle lashes region

Dozens of people are trapped on top of buildings in Hawke's Bay due to severe flooding from Cyclone Gabrielle. 

The cyclone has hit Hawke's Bay hard causing widespread damage, flooding and power outages. 

A Facebook live video shows a dozen people standing on their roofs while the flood waters lap at their feet. In the background, the tops of trees can be seen poking out of the water. The video is from somewhere in Hastings. 

There are reportedly more than 40 households trapped in Eskdale in Hawke's Bay because of the cyclone.

On Tuesday Transpower issued an emergency grid notice for Hawke's Bay warning people to prepare for extended power outages. 

Hawke's Bay Civil Defence has also urged people to stay away from rivers because heavy rain has caused them to overflow. 

Dozens of people are trapped on buildings in Hastings.
Dozens of people are trapped on buildings in Hastings. Photo credit: Newshub

It comes as the Government declares a National State of Emergency because of Cyclone Gabrielle. 

The Minister for Emergency Management, Kieran McAnulty, signed the declaration at 8.43am on Tuesday. 

The declaration will apply to the six regions that have already declared a local State of Emergency which are Northland, Auckland, Tairāwhiti, Bay of Plenty, Waikato, and Hawke's Bay.

This is only the third time in New Zealand's history that a National State of Emergency has been declared.

"This is an unprecedented weather event that is having major impacts across much of the North Island," McAnulty said.

"Since Sunday, NEMA have been in close contact with local civil defence emergency management (CDEM) teams of affected areas to assess the need of a declaration of a state of National Emergency.

"NEMA has been giving advice to myself and the Prime Minister on the need of a national State of Emergency based on the assessments of the local teams, and until now the advice has been that it was not necessary.

"NEMA met with the affected CDEM groups. Based on feedback from the groups and NEMA I consider that the criteria have now been met and a National State of Emergency would be beneficial."

McAnulty said Cyclone Gabrielle has caused widespread damage and the National State of Emergency will give emergency responders the support they need. 

"This declaration will enable the Government to support the affected regions, provide additional resources as they are needed, and help set the priorities across the country for the response.

"A National State of Emergency gives the National Controller legal authority to apply resources across the country in support of a national level response.

"This declaration gives us the ability to coordinate further resources for affected regions. I want to emphasise that the Government has already been surging support and resources to the regions for some days," he said.