Horizons Regional Council river management staff will start the removal of bamboo plants in Kowhai Park on Thursday to help protect the park's stopbanks.

The bamboo has grown between the Matarawa Stream and the Kowhai Park stopbanks for a number of years. The bamboo growth is now becoming an issue for the integrity of the stopbanks said Horizons' senior engineer officer Jeremy Cumming.

Mr Cumming said Horizons "understands the balance between providing open space park environments with trees and shrubs and providing flood protection in the same place".

"However, we need to remove large areas of bamboo because it has an invasive rooting system," said Mr Cumming.


"We have taken into account the area is one of the largest inanga spawning sites, and will work with Whanganui District Council to provide new plantings, specifically grasses, to ensure their habitat continues to thrive.

"Bamboo grows what are known as rhizomes, which are stems running underground horizontally. They strike new roots out of their nodes, down into the soil and up to the surface.

"The rhizomes generally grow quite close to the surface (2-3 feet) but once they die they leave a hollow tube in the soil structure which can cause problems for the stopbank during a flood event."

Horizons councillor Nicola Patrick says many people don't realise the damage that bamboo can cause to the stopbanks.

"The potential for piping of water through dead rhizomes is a serious risk which we must mitigate to keep the integrity of the banks," she said.