Awatarariki Stream and Lagoon Works
The debris detention structure will allow debris floods to pass through and continue into the fan where an improved channel will be required to convey this flow. This channel will be a “balanced cut to fill” type channel constructed along the existing stream channel that may be realigned and straightened to improve the stream gradient (made slightly steeper) and thus reduce the sediment deposition potential in the stream.
This will include measures to limit sediment delivered further downstream in the lagoons during higher flows. These large sediment traps will enable this sediment to be captured and contained for removal at a later safe period after the event.
The project works to mitigate the effects of a similar event to that of 2005 in the future include:
- Deepening of the Awatarariki Stream downstream of Moore's Bridge with associated strengthening of the stream banks and bunds to increase capacity for debris floods
- Excavation and filling parts of the Te Awa o Te Atua Lagoon at the outlet of the Awatarariki Stream to create sediment basins into which sediment can be deposited in a controlled fashion during debris flows and floods
- Works associated with the restoration of the lagoon and surrounding environs
- Deposition of excavated material around the lagoon environs to form bunds and raised areas
- Construction of a drainage swale at Clem Elliott Drive.
Ready access will be required for maintenance and debris removal and management in the Awatarariki Stream and Lagoon.
Resource consent has been granted and works have been completed.