Willow poles to help prevent river erosion
Greater Wellington Regional Council has been working hard this planting season putting in around 15000 willows around the rivers of the Ruamahanga catchment of Wairarapa to help manage river erosion.
GWRC workers finished planting 2800 willow ‘poles’ in the Waiohine River last week. “We’ve been able to put in a lot more than usual this year. That’s down to good weather and less flood damage to repair,” says Robbie Graham, Field Supervisor. “Our planting season is restricted from July to September so there’s always a bit of a challenge to put in as many trees as we would like.”
The ability of willows to grow roots and leaves from a bare pole makes it relatively easy to plant successfully. Willow roots hold the bank together and the trees are very resilient.
“Alongside planting we also use a process called layering where we push over a few trees at the river edge of the stand of willows. These will re-grow and send up multiple new plants right where they are. In some areas we use machinery to get willow “poles” down into the damp ground. The 2m to 3m long willow poles will sprout in a very short time and send down roots,” says Graham.
GWRC uses different techniques to prevent land loss and river bank erosion along the 325km of Wairarapa waterways that GWRC manages in the Ruamahanga catchment; willow tree planting and layering, putting in rock groynes, gravel extraction and river alignment are all part of the tool box. This is essential in protecting our communities from flood hazard and ensuring infrastructure such as road-bridge footings and stop banks are maintained.