Most houses in central Westport are under water up to window-level.
The Herald surveyed the damage from the air this afternoon and images and video taken show the extent of the weekend's flooding.
Murky brown floodwater covers many properties, entire streets are submerged and paddocks are awash.
Civil Defence, emergency services, Defence Force and council staff are staff are working around the clock to help residents.
Many had to be evacuated and waiting at community centres for news about when they can go home.
For some, the wait will be long.
The Buller District Council said today it appreciated the cooperation and patience of locals.
"We know you are keen to get home, however, due to the risk of floodwater contamination and the potential for electrical hazards, we advise you to stay where you are.
"Emergency Service personnel are out in affected areas this morning and we will update you as soon as possible."
Westport mayor Jamie Cleine said the "massive quantity of water" gushing out of the Buller Gorge breached a river into the township.
"Last night was awful... this morning although the rain stopped, the water was about the same as it was when I left at midnight last night."
It was hard to see the people in his district struggling.
"It's upsetting. people take a lot of pride in their property," he said.
"It's the uncertainty it creates, we don't have all the answers people are looking for... the people aspect, it's really hard on everybody."
He said recovery was now in full swing.
Cleine urged people to be patient and work with the council as they made plans to get them back into their homes.
"Approximately half of the town was evacuated. We're waiting on the rapid assessment teams to report back on the extent of the damage," he said.
"But it will be hundreds of houses; a significant number of households."
Cleine said plans would be in place in the next few hours in terms of where residents could turn for help from insurance companies, Work and Income New Zealand and other agencies.
He said the priority was to assess houses and make sure people in welfare centres had what they needed.
Barely any rental properties were available in the area so finding displaced people a home was also critical.
"We're getting a handle on what the scale of that will be," Cleine said.
Herald visual journalist George Heard has been in Westport for the past 24 hours recording the damage and aftermath.
He said from the air the full extent of the carnage is patently clear.
"You can see farmland completely flooded, water up to the roofs of utes in paddocks, farmers out in tractors trying to feed stock with water lapping around," he said.
"Whole blocks of houses are completely under water.
"The floodwater reeks, there's a lot of rubbish floating about - including toilet paper - and a lot of wood: firewood, bark, it's everywhere.
"This is something some in the town are describing as a one-in-100-year event: the coast has had its floods but they say this is unprecedented."
Heard said in the lesser affected areas people were out in the streets trying to clean up.
Heard said the feeling in Westport was "quite resilient".
The devastation was real and raw and residents were in shock and gutted about the damage to their homes.
"But they're all banding together, no one is extremely distraught - it's just that old West Coast attitude of get it done, get it cleaned up."
Moments ago more NZDF troops arrived to help with cordons and accessing hard-to-reach houses.
Yesterday 14 personnel from Burnham Military Camp were sent and another 10 arrived today.
A Royal New Zealand Air Force NH90 helicopter landed in Westport just before 1pm to assist in the region.
Water boil notices remain in place for the district.
FOR FULL INFORMATION ABOUT THE BULLER DISTRICT COUNCIL INSTRUCTIONS AND ADVICE CLICK HERE.
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