River Maintenance on the Tapuata and Mangatera Streams

Horizons Regional Council is looking to undertake river management works on the Tapuata and Mangatera streams, from their confluence by Weber Road to Edward Street and upstream of Riverdale Road.  

What work are we doing?

The work will consist of vegetation maintenance. Much of this will involve mulching and removing willow trees from the bed and banks of the river using a mechanical digger and personnel with chainsaws.

The work will be undertaken either from the bed of the river or on the banks. It is envisioned that the digger and personnel will enter the river at the entry points marked on the map and work their way upstream to the exit points.

This work is planned to be undertaken from 13/01/20 to 28/02/20. All works will be undertaken on weekdays (i.e. no weekend work) between the hours of 7:30am to 5pm.

Why are we doing the work? 

Willow trees have a strong root system and are very effective at stabilising banks to prevent erosion and loss of land during flooding. However, if left unchecked, they have a tendency to congest the bed of the river, through:

  • Sediment accumulation on their roots and build-up of the banks;
  • Catching and trapping woody debris and creating dams;
  • Falling into the active flow and creating dams; and
  • Taking root in the active flowing bed of the stream. 

This reduces the carrying capacity of the stream, making it more prone to flooding. Congestion can also create conditions for excessive erosion upstream and downstream.

For these reasons it’s important for us to carry out vegetation maintenance activities to control willow growth and prevent them from contributing to congestion and flooding.

What else?

During the works, there will be some further erosion and discolouration of the stream as the bed widens in response to the clearing activities. This will pass fairly quickly and river water clarity should return to normal within 24 hours.

If you have any questions, please feel free to contact:

James Feary
Area Engineer – Horizons Regional Council

06 952 2989, 0212277174
james.feary@horizons.govt.nz

 

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