UPDATED 9.52PM: Civil Defence are describing the flooding in Whanganui as a "one in 100 year event."

Homes and business have been inundated, after the city's river burst its banks last night.

Hundreds of people in Whanganui are spending the night in evacuation centres or with friends and family.

The Whanganui District Council is not expecting anymore flooding, but is still waiting for water to recede from flooded homes.

Whanganui Residents are waiting for clearance to return home.

But St John's Trudy Taylor says it may be days before that comes.

"If it was just surrounded by water, or [water] threatening [the home] and they've evacuated, they may be allowed back in. However, if there's water gone through the houose they definitely will not be allowed back in yet."

Volunteers have been working around the clock providing food and support to those who may not be able to return home tonight.

Fire station officer Gary Wilson said the river has doubled in width, and nearby streets are now part of it.

"The stop banks on the east side were extended this year, and I think people felt more safe, but it didn't work out."

"It's just sodden, absolutely sodden, and the river is roaring out of it at the moment."

PHOTOS: Intense flooding hits Whanganui

NZME's Hits announcer Darryl Mallett is in the city this morning.

"It's actually scary. There is only one word for it. Lights are out, power is out, the water is lapping at shops."

Stopbanks on Anzac Parade have been breached, and hundreds of homes have been evacuated.

AUDIO: Civil Defence Emergency Manager Kevin Ross in Whanganui

One big slip came down at Durie Hill, threatening a woman's home.

Darryl Mallett said told Newstalk ZB, "[I] was there at one o'clock this morning, when the Army was in there waking up an elderly lady who refused to believe her house was right on the edge of a massive slip that came down the hill."

AUDIO: Darryl Mallett on the ground in Whanganui

ROAD CLOSURES ACROSS THE REGION

Emergency managers say the Whanganui River is likely to continue rising in the urban area, but the Matarawa has peaked.

Whanganui east is still cut off from the rest of Whanganui.

Mayor Annette Main says the three bridges across the river in that area are still closed by floodwaters.

The Mangawhero River is being assessed, and it's possible a slip has dammed the river.

Two welfare centres are operating, but Ross says most people who've had to evacuate are staying with family and friends.

Even once the water has gone, Ross admits a lot of people won't be able to go home until Monday at the earliest, and more likely Tuesday.

States of Emergency

There are states of emergency in both Whanganui and the Rangitikei District.

The state of emergency declarations made for the area gives the Civil Defence Controller the authority to order people to evacuate if necessary.

The Army joined firefighter to rescue people from the isolated village of Koitiata, where there are 140 homes.

Rangitikei Mayor Andy Watson has warned he expects more evacuations in the region by the end of today as people headed back to their houses and realised their home is a mess.

He reports a helicopter flyover with civil defence late this morning revealed much of the coast near Turakina beach was blocked off from State Highway 3 by flooding.

The mayor adds they do not have access other than by air to Turakina beach so they have got to find some kind of way to get rid of a massive amounts of water.

Watson estimates there are about 100 people at the beach who were currently unable to leave.

Meanwhile, he says six to 10 people in Whangaehu had been isolated by floodwaters and it is too dangerous to retrieve them, even by helicopter, at the moment.

A welfare centre is operating at the Memorial Hall in Marton, with the help of Red Cross, and a helicopter is being sent into Waitotara Valley today, to respond to pleas for help from locals.

Engineers have acknowledged they're concerned about the safety of the Waitotara Bridge.

All 60 homes in the small township were evacuated last night and it's not known when people will be able to go back.

Civil Defence controller David Lean said engineers are now checking the integrity of the Waitotara Bridge, after a buildup of pressure from a shed which had been washed away.

"Together with a large tree that was with the water coming down the river in great masses, very close to the top of the bridge."

Red Cross say their focus in Whanganui is now on supporting the most vulnerable.

Emergency Management Officer Graeme Langford admits people respond differently to trauma but he's hopeful the community will pull together.

He acknowledges it will be traumatic for all involved when they've left with nothing - but resilience and preparation will get them through.

He adds their long term plan now is to assist councils with civil defence centre staffing.

Palmerston North

Palmerston North residents are now free to wash, flush, and clean.

A notice to conserve water following floods in the city has been lifted.

Sewerage systems were overloaded during the floods, so residents were asked not to use water to relieve pressure.

The Palmerston North City Council is warning residents to treat anything that was covered in floodwater as contaminated.

Whanganui residents are also being warned to stay away from a favourite local park.

The local council warns Kowhai Park is dangerous and people need to stay out.

The manhole covers were lifted to lessen the impact of spilling stormwater and sewage on nearby properties.

Mayor Annette Main says people need to avoid the temptation of sloshing about in the water.

"Please obey all of the instructions to stay out of Kowhai park. It's one of our favourite places and it will be up and going again once we've cleaned up after this flood, but for the time being please just stay clear."

About 200 people have had to abandon their homes because of the floods.

In addition to that, Kevin Ross said "we have a number of houses that are affected by subsidence and slippage as well, so there are a number of structural things we have to address."

Calls are being made to isolated farmers throughout the lower North Island.

Government on standby

The Civil Defence Minister will visit flooded Whanganui this afternoon.

The Ministry of Civil Defence has activated its national crisis centre in Wellington, in response to the flooding affecting Whanganui, Rangitikei and Taranaki.

She's also pledging Government help with the cost of recovery.

The Ministry of Civil Defence says around 600 people spent the night away from their homes.

There are power outages across the region, and people are being asked to check on their neighbours.

Many roads are also impassable.

The focus is shifting from response to recovery, and officials are preparing to begin assessing businesses and homes for flood damage.

Wanganui District Council Spokeswoman Cass Alexander said the Council will be looking to work with the Ministry of Social Development to support residents.

"So we'll definitely be looking at how people are doing and making sure they've got everything they need."

Army support

It's not quite the training weekend that Army reservists from Wellington had in mind.

Thirty soldiers are on the streets of Whanganui, manning the cordons in the flood-stricken city.

Major Jono Meldrum says twenty reservists were in Whanganui this weekend on a training exercise, when they were reassigned to help Civil Defence.

He's full of praise for their response.

"They've spent in effect 24 hours straight standing in the rain and wind supporting the people of Whanganui and Civil Defence. It's quite humbling when you see that."

Power outages

Most Powerco customers in Whanganui have their power back after repairs to a flood-damaged substation.

The substation flood, and a large slip that brought down power lines and poles, cut supply to parts of the city.

Powerco Acting Network Operations Manager Dean Stevenson says there are still several other pockets within Whanganui, Rangitikei and Taranaki without power.

Crews will fix damaged sections of the network as soon as roads are cleared.

There were 6,000 customers without power this morning due to fallen trees and debris on power lines and flooded out stations.