Stopbanks can easily be weakened.
Farmers are being cautioned to keep grazing stock off stopbanks in winter or face liability for any damage - as they provide flooding protection for thousands of people in the Bay.
The Bay of Plenty Regional Council said it was aware of several landowners who may be causing damage but no enforcement action was being taken.
"There are some landowners who may be financially liable depending on the extent of the damage. Council has not yet determined the level of this damage," it said in a written statement.
Council principal works engineer Tony Dunlop said wetter soil conditions, combined with heavy animals, can weaken and damage stopbanks.
Grazing was allowed by cattle at certain times of the year but should be kept to a minimum in winter, he said.
"During winter it is commonsense to keep cattle off the stopbanks as much as possible to prevent the pugging and damage they can cause. Most farmers and lifestyle block owners know this and take care of our community assets.
"Good grass cover on a stopbank helps protect the soil structure underneath, so pugging is not just a surface problem. It can cause much greater issues; one weak area can have a disastrous effect on surrounding properties and stopbanks. All it takes is one breached section of stopbank to flood thousands of hectares of farmland."
It was an offence to damage stopbanks, and landowners can be held liable for any damage.
"The stopbanks are designed to protect property, production and the safety of everyone in our community. So we need to reinforce the importance of looking after our stopbanks to anyone who may be grazing stock," Mr Dunlop said.
"We will keep an eye on our stopbanks to ensure farmers are doing the right thing. There is too much at stake to risk flood damage to the properties and surrounding communities."
Council manages and maintains 352km of stopbanks, protecting many millions of dollars' worth of land and property.
A council spokesperson said the costs involved in managing and maintaining stopbanks covered a range of activities and did not relate solely to damage costs. "Any financial charges to landowners as a result of damages are incorporated into wider council stopbank management cost."
Federated Farmers Bay of Plenty provincial president Rick Powdrell said there had been more dialogue between the council and farmers regarding stopbanks, which was good.
However, he said there were several factors to consider.
"It is important that stopbanks are grazed when the conditions are right to keep down the weeds and control grass growth. But it is also important when it's wet to make sure stock are not on them causing damage and weakening the integrity of the stopbank."
Mr Powdrell said in the wake of an adverse event like a flood or extreme weather the safest place for stock on low farmland was the stopbank.
"Then the conversations between farmers and council is even more important as we want to look after the welfare of the animals and protect the stopbank. So it becomes more of a juggling act at that time."