State Highway 50 Waipawa River was the first Resilient River Communities project to be completed. The Kānoa – REDU recovery fund committed 64% of project costs, 30% co-funded from Waka Kotahi and the remaining 6% co-funded through the Regional Council.
Erosion along the Waipawa riverbank upstream of State Highway 50 has been gradually deteriorating over the last 10 years. Previously the Regional Council had managed this erosion with small scale engineering works and planting but with limited success. The aim of this project was to minimise the risk of erosion through a combination of engineered design and re-direction of the river to deter the water from the banks.
The design solution incorporates a balance of river ‘calming’ methods and channel realignment to deter the water away from the banks. The works include a combination of large-scale earthworks to realign the meandering braid, allowing for greater capacity by deepening and widening the bed, and armouring of the riverbanks.
We used akmons (large precast concrete blocks linked with steel cables) which were partially buried and positioned on the left bank, upstream of the bridge to deflect the flow of water back into the design channel. In addition, a lattice of steel rail irons woven together by steel cable formed groynes on left and right banks to capture debris and build up transported gravels minimising the risk of erosion to the banks. Planting of willows and indigenous trees give the groynes and embankment stability through their deep root structures.
We collaborated with Te Wai Mauri Kaitiaki Rangers to assist with strategic planting on the awa. The Kaitiaki Rangers, all employed through local hapū Ngāti Parau, are based out of Waiohiki Marae with a focus on riparian planting and environmental restoration. During this project, Hawke’s Bay Regional Council invested in upskilling and training with the Kaitiaki Rangers to plant willow poles, slot trees and plant native species at the Waipawa River SH50 site. In total, over 4,700 willows and 1,000 native plants were established on the banks of the river.
As part of the works, HBRC engaged an ecologist to undertake an assessment before, during and after the completion of the project to understand and improve environmental outcomes. This stretch of river is ecologically sensitive as it has one of the most densely populated areas of banded dotterels in Hawke’s Bay. After the works were completed, we confirmed an increase in banded dotterel breeding areas.
The project was completed in August 2021. Watch the video here.
