1. Rangitāiki-Tarawera Rivers Scheme & Rangitāiki Drainage Scheme

3. Scheme Assets Stopbanks Canal Systems Drains Floodgates Pump Stations
Riverbank Protection

5. Rangitāiki Tarawera Rivers Scheme Assets
Replacement Cost $77.3m (1 July 2014)

6. Community Outcomes

7. Typical Scheme Operational Activities
Drain Maintenance
Weed Cutter Boat
Digger desilting/weed clearing
Aquatic weed spraying
Grass carp
Culvert Replacements
Floodgate Maintenance
Bank Erosion Repairs
Pump Station O & M
River Maintenance
Willow layering/removal
Planting
Flood damage repairs
Stopbank Renewals

8. Significant Issues Climate change Residual risk to community
Affordability
Events greater than design
Levels of service
Population growth/decline
Geotechnical challenges

9. Environmental Considerations
Environmental Code of Practice Regional Plans Permitted Activities with conditions Resource Consents Weekly Notifications Retrofitting fish passages Promote drainage and flood protection works that minimise adverse effects

10. Implications of Climate Change
More frequent & intense rain events
& Sea level rise.
Combined with
Perched rivers
Land levels already low-lying [minus 1.5mRL at lowest]
Land shrinkage [already 6,000ha rely on pumping]

11. Geotechnical Issues Soil conditions very poor Historic seismic events
Perched rivers
Challenging to reinstate 100 year standard
Carried out huge amount of works but always risk of failures

12. Affordability/Debt

13. Rangitāiki Floodway Project
Major flood event in 2004
Main river channel lacks capacity
Floodway is key to getting 100 year protection reinstated
Capital works underway but met with many challenges

15. Same drawing as December AP workshop
Original scope of project
2. Extra works: toe-loading and pressure relief wicks
Note that estimate allowed for some geotech works (prob trenches) but not this large/specialist scope
3. In scope vs out-of-scope

16. Rangitāiki Floodway Stage 2b
Note the bridge ~ recycled beam from the Tauranga harbour bridge project
Saved approx 150k

17. Rangitāiki Floodway: Placing geotextile and rock in the ‘dry’ prior to joining up to canal. New stopbank in background

18. Other Operational Initiatives

19. Example – Whitebait spawning sites when undertaking erosion protection works

20. Tidal Flushing

21. Tidal Flushing – Fish Friendly Floodgates

22. Willow tree maintenance
This is one of the activities we have changed to make the operation more cost-effective, safer and faster. We used to have labour on the ground with chainsaws to layer the willow limbs. However this has always been tricky because the felling technique required is contrary to the standard scarfing practice that is mandatory with logging operations.

23. Toi Toi with willow Establishing
Completed works – rock toe strengthening benching ,willows and Native ToiToi planted December (2013)
Stable banks and alignment.
Sediment sealed.
Works to accommodate fluctuation.
Willow poles planted as groynes
Native Toi Toi planted between rows
Combination of hard engineering and soft engineering. Note: Willows have been mulched on opposite bank
Establishing

24. Working with Partners Variation in restoration planting Use mānuka - possible use for honey, mānuka oil Mechanical spade - efficiency
Fabricated a ‘spade’ on the mini digger to speed up planting of seedlings which makes the operation much quicker

25. Giant willow aphid Risks to willows.
Giant willow aphid attacks the trunks, sap leaks out, put trees under stress.
Attracts bees a health and safety issue for working around and amongst trees.