Police are cracking down on car owners who dump their unwanted vehicles in the Waimakariri riverbed.
Vehicles dumped in the Baynons Rd area have either been set on fire by their owners or left for others to vandalise and torch.
Sergeant Mike Brooklands, of Kaiapoi, said police contacted an owner who towed his vehicle to the riverbed recently and set it on fire. He was likely to face charges.
Another car dumped in the same area two weeks ago was attacked by vandals who were arrested on unrelated matters as they drove away.
The wreck was later torched by others, setting scrub on fire and prompting a callout by the Kaiapoi Volunteer Fire Brigade.
Sergeant Brooklands said the area had been a popular dumping spot for stolen cars a year or so ago, but he couldn't understand the mentality of owners abandoning their unwanted cars in the riverbed.
"If they took them to a scrap metal yard, they might get $50 for them," he said.
Owners would be prosecuted if they were able to be traced.
Environment Canterbury parks and forests team leader David Owen said the wrecks were "an eyesore and a significant pollution problem for the river".
The costs of removing the wrecks would be charged to owners who could be traced. Wrecks with no value or whose owners couldn't be located "go to the crusher''.