Council reviewing tree management

Horizons Regional Council is looking at its management of willow trees and reviewing its practices in the aftermath of damage caused by Cyclone Gabrielle.

The cyclone hit the North Island last month, causing havoc across the east coast. Tararua was hit hard by flooding, but rivers on the western side of the Ruahine Range also had high flows and parts of Manawatū flooded.

While covering the cyclone, Stuff has spoken to multiple people across the region concerned about the effects of Horizons spraying trees as part of its tree management scheme, which they say leads to trees going into waterways during floods and causing damage.

The cyclone caused logs to be washed into rivers and many ended up on beaches. Logs were also caught under bridges across the region and strewn along river banks.

Ā kitio Beach was covered with logs after the flood, as was the Manawatū Estuary at the mouth of the Manawatū River at Foxton Beach.

It’s believed a bridge over the Manawatū River on Rakaiatai Rd north of Dannevirke was destroyed by a build up of dead trees that had been swept down the river.

Horizons’ group manager of catchment operations Jon Roygard said the council managed willow trees planted for flood protection, which protected river banks from erosion, as well as willows planted by other people.

‘‘Management is undertaken to maintain willows at a state that makes them most effective for flood protection and a range of methods is used to do this, including mulching and spraying.

‘‘Cyclone Gabrielle was a weather event of a size that was beyond the scale our plantings can handle. We know we’ve lost a number of plantings in some places, including ones that have withstood other floods, which isn’t surprising considering the size of the event.’’

The council’s river management staff discussed the management of willows and decided to review its practices post-recovery to take into account what had been learnt from the cyclone.

‘‘We’re aware of debris in the Tararua district and we have been working with the district council at specific locations to clear debris, broadly in the district clearing of debris from river systems is a priority for us.

‘‘The other main priority across the region is assessing in detail the damage from Cyclone Gabrielle and other events and determining the repairs that are required to provide flood protection to our communities.’’

Spraying and mulching is a management method for willows where the trees are causing blockages, congestion in channels or establishing in places on the riverbank that is impacting river flow.

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Spraying is intended to kill the trees and council staff often go back to spray sites to remove the dead trees if access was possible.