Ashley Rakahuri flood protection scheme | An update on tree felling
We understand that the Ashley Rakahuri Regional Park area where trees were felled recently was valued by locals. Here, we explain why the trees had to be removed, and highlight future development initiatives for the area.
Ashley River flood protection scheme
Some people thought that the felling was done to plant native trees. In fact, this small area (less than 0.1% of the total catchment) forms a critical part of the Ashley River flood protection scheme and won’t be replanted.
It’s worth noting that the majority of the felled trees were in very poor health and were rotten in the middle making them unstable and a hazard to park users. Engineers estimate that 50% were very rotten and an additional 25% in a significant state of decay.
Trees felled in floodway
The recent felling removed trees between the primary and secondary stop banks that acts as a floodway if the primary stop bank fails.
Any trees in this area would slow the water flow and increase the water depth through this critical zone. Modelling of flood flows by river engineers indicated that with the trees in place, overflows of the secondary stop bank into Rangiora were likely.
Homes, businesses and public assets such as roads, railways, pipelines, water supply intakes, power and telephone lines have all benefitted from the river control system since the primary stop banks were first installed in the 1930s.
Waimakariri District: a history of flooding
The Ashley Rakahuri River starts with headwaters in the Puketeraki Range, northwest of Rangiora. This river is relatively steep compared with other braided rivers in New Zealand and moves a substantial amount of sediment.
It also has a long history of flooding.
The last time a major breakout occurred here was 1953. The water broke out on the southern side of the river next to the Rangiora traffic bridge, in an area now known as ‘Break Bank’. The waters flowed through Rangiora and out towards Kaiapoi, Woodend and Waikuku, causing large amounts of damage and forcing many people to abandon their homes.
River engineering and protection works have since managed to prevent any major breakouts, although the river came close in 1986 and in 2002.
Ashley Rakahuri Regional Park: a destination for recreation
One of the key goals of the Ashley Rakahuri Regional Park Management Plan released in 2016 is to maintain and extend recreational opportunities. The park still has lots of great options for leisure activities including the Rakahuri Trail; an easy shared walking and mountain bike track running from Groyne 1, behind the racecourse, downstream to East Belt. Shorter mountain bike tracks can be found in the pine forest downstream from East Belt.
Another track is the Mike Kean Walkway; a 0.9km easy track from the Ashley Picnic Ground, east of the State Highway 1 road bridge, to the car park at the rail bridge. There are lots of great spots for picnics too at Ashley, Rail Bridge, Groyne 1, Waikuku Beach and elsewhere in the park.
Future plans for the Ashley Rakahuri
The Ashley Rakahuri area has been earmarked for future funding. Projects will be undertaken to increase native biodiversity and mahinga kai, with a focus on a number of outcomes including native planting, habitat restoration, invasive pest control and community engagement. If you would like to keep up to date with what’s happening in the parks, please sign up to our newsletter.
- Learn more about Ashley Rakahuri Regional Park.
- Check out a map of the primary/secondary stop banks and further information on the flood protection scheme.
- Download the Ashley River Floodplain investigation - 2016 update (PDF File, 10.47MB). This document identifies this area as a critical area for the scheme and recommends vegetation be kept to a minimum (Section 3.4.6).
- Download the Ashley Rakahuri Regional Park Longterm Management Plan July 2016 (PDF File, 1.67MB).