A controversial no-mow policy for some of Christchurch's riverbanks is being revised because of complaints from residents.

Photo: RNZ / Conan Young

The city council stopped mowing sections of the Avon and Heathcote banks at the end of 2016 in an effort to encourage whitebait spawning.

The plan had the backing of several community groups, including the Ōpāwaho Heathcote River Network and the Christchurch-West Melton Zone Committee.

However, the no-mow trial was not universally popular.

A council report said one resident took matters into their own hands by mowing the riverbank in front of their house.

At the same location a sign about the trial was thrown into the river.

Some whitebait spawning habitats were also accidentally mown during the trial by council contractors.

"There was some uncertainty amongst contractors as to exactly where the trial was being undertaken and when it ended," the report read.

Council land drainage manager Keith Davison said staff would now cut back excess grass during winter, but leave enough length before the next whitebait spawning season.

"By allowing minimal grass mowing in these areas we hope to able to better balance the ecological benefits of having longer vegetation with community expectations for tidy-looking river banks," he said.