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Authorities have slammed the actions of drive-by "sightseers" who added to the woes of flood-ravaged residents on the West Coast.
Residents of Westport and surrounding areas face a big clean-up after floodwaters surged through about 16 dwellings and landslips blocked roads on Saturday.
Creeks and drains in the area failed to cope after 12 hours of continuous heavy rain. Million of litres of water had to be shifted.
Westport fire chief Pat O'Dea called it the worst flooding he had seen in his 60 years in the town.
While residents had pulled together to help mop up the town, some people had deliberately driven through the floodwaters and created "bow waves", which infuriated those already fighting back the water.
Buller civil defence manager Terry Archer said a fast-moving vehicle "sends out a wave and it slops over everything, pretty much in the same way a jet boat travels".
"It causes more damage and frustration when people are filling sandbags to keep the water out."
Mr O'Dea said drivers of larger vehicles had been the worst culprits.
"We had a few idiots driving around in 4WDs seeing how big the bow waves they could make. It puts the houses at more risk. But the police were pretty good at picking them up."
Some residents were so frustrated they used their cars to block off their streets.
Mr Archer said building inspectors had been through the 16 houses or sleepouts inundated by floodwaters to give advice. About six were considered to have been hit by "major inundation" of 100mm to 400mm.
"At that height it requires wall linings to be removed to allow insulation to be taken out and dried properly."
The Westport house used by the West Coast's Homebuilders Trust, a social service helping families, was one of the worst hit.
Trust member Peter Campbell said all the carpets had to be ripped up and furniture was soaked.
"We are really struggling to know at this stage what the damage is."
Blocked roads were open again yesterday, but residents were being urged to be careful of surface flooding.
The storm front that dropped the heavy rain in the Buller area has moved on to the lower North Island and is expected to bring more heavy rain.
The wild weather continued in Christchurch yesterday when a thunderstorm brought heavy rain and hail.
