Moncton city council has voted unanimously to accept responsibility for 300 metres along the Petitcodiac River and cover any future costs due to erosion.

The New Brunswick government had requested a signed indemnity from the city. Otherwise, it was going to start placing large rocks, known as rip-rap, along the riverbank next to Bore Park as of midnight on Tuesday.

The provincial government is worried about erosion from the tidal bore destroying lands and infrastructure. It had offered $430,000 worth of rocks to stem the erosion.

But council had rejected the offer, ignoring the provincial government, two engineering firms and its own own experts and deciding to let the river run free.

Council based its decision on an engineer hired by the environmental group Riverkeeper, who said fears of erosion and high costs are exaggerated.

Now the city will have to pay for any damage or maintenance.

Those costs include damage to the nearby walking trails and boardwalk. There could also be higher insurance costs and expenses totalling hundreds of thousands of dollars to protect the archaeological sites that are appearing as the river continues to erode the banks.

The river has pushed the banks of Bore Park back 20 metres in the last two years. Engineers have warned if it erodes another two feet, the park's lookout could fall into the river.

The river has eroded much faster than predicted since the causeway gates were opened in April 2010.