Waitangi Stream Remediation & Erosion Protection

The Project

During 2017 – 2019, we were engaged by Bay of Plenty Regional Council (BOPRC) to develop a design solution to remediate and prevent further erosion of a section of Waitangi Stream. Waitangi Stream connects Lake Ōkareka to Lake Tarawera in Rotorua. Our team carried out the geotechnical investigations required to build a ground model, which in turn informed the design. Two key elements of this project included:

Raising the riverbed by rockfill, reducing sedimentation and helping to prevent further erosion of the riverbed
Regrading the stream banks and placement of gabion baskets. This helped prevent further erosion of the banks.

We also assisted BOPRC with construction review and site inspection and monitoring while the design was being built. The construction methodology had to be carefully thought through to prevent sediment-laden water discharging to the stream and into Lake Tarawera, especially during trout spawning season. The stream had to be diverted in a bypass pipe under the new stream bed while construction work was carried out.

Key Aspects:

Gabion wall design
Slope stability analysis of the stream banks
Construction review and site monitoring for issue of PS4

This project was undertaken in association with a number of other contractors, including Mappro – their summary and further pics can be found here.