Stream Restoration
Lucas Creek Project for North Shore City Council.
Lucas Creek was a stream restoration project for the North Shore City Council. It was an innovative project that runs for about 1km through the Hooton Reserve near the Albany stadium. Several new to New Zealand systems were used on this project in conjunction with RST and John McCullah a bio-engineering expert from the USA. With John's help RST were able to install low impact systems to restore the stream and stop the on-going erosion issues that the council had with the stream.
The systems used were stream widening and bank shaping, rock riffles, rock vanes, lunkers, woody debris structures, and Living MSE walls. A new approach was taken to enable us to work and do the installations in a live stream rather than install a stream diversion. This meant that the project was completed in record time and with a lower cost than would traditionally be expected.
The system used was to have flexible construction plans which meant a new approach of "designing on the go." Effectively the plans were drawn as the areas to be rehabilitated were cleared which meant there was no problems with making structures fit the surrounding ground conditions.
Stream widening and shaping took place along the length of the stream. This meant that we doubled the width of the stream bed and reshaped the banks to give a better slope angle and more flood plain areas. A pre-washed GAP 20 aggregate was put over any new earthworks on the bed to stop any sediment movement. The new area of bed was cut just above water line in the live stream.
Rock riffles are specially constructed rapid structures that create habitat within the stream bed and dissipate energy as well as stopping any down cutting. Large boulders are specifically placed and then tied in the locking rocks.
Rock vanes are used to direct flow and in the case of Lucas Creek we used one to redirect the stream flow more evenly under the bridge.
Living Walls are an MSE structure that was used on the steeper areas of the bank where flow could cause problems. The walls are tied in using a geo-grid.
Lunkers are a wooden retaining wall structure that are installed with an excavator. These ones used the kanuka trees that had to be removed from the bank for construction reasons. They create habitat both above and below water and make the stream have a natural look to it.
Root wads are tree stumps that are placed into the bank and are used instead of rock structures. They are great for creating habitat.
Cross Vane
Woody debris structures are used for flow direction and are placed in the stream or the bank using an excavator. They also help to create natural structures in the stream.
Using these systems has meant a lower cost to the Council for the in stream works and a more natural finish.
Woody Debris in stream
Re-Direct Flow