Bees do it, so the Dunedin City Council is, too. The DCC is harnessing the power of the hexagon to repair a small section of Taieri Mouth Road and protect the adjacent beach.
Tried and tested in North Island coastal and river erosion situations, the New Zealand-made, hexagonal, fibre-reinforced concrete modules are being used by the DCC for the first time for erosion control. They will be used on the seaward side of the Taieri Mouth Road about one kilometre northeast of the intersection with Dicksons Road.
A short section of the road is down to one lane after being damaged in the October 2024 rain event. The modules will act as physical barriers to beach erosion, protection for the road and as containers that support ecological habitats, with plantings of native species planned.
DCC Transport Capital Delivery Team Leader, Kieran Trainor, says, “The natural sand dunes next to Taieri Mouth Road face continual erosion especially during strong swells.
“We are keenly aware of the need to adopt updated engineering solutions for road dropouts and slips adjacent to coastal areas. Instead of using a typical rock buttress approach to reinstate the road, we have decided to use the modules, laid to reinstate the two-way road, the road shoulder and support the adjacent dunes. The modules are more expensive than a rock buttress, but they are more cost effective because they will last longer, with the added benefit of supporting plantings.
“The hexagonal geometry provides the ability to interlock the modules, shaping the structure to soften and absorb wave energy rather than reflecting it, preventing secondary erosion.
“Because they are a hexagonal block, they achieve a strong, efficient structure maximising in-fill and load distribution. Bees figured that out long ago for their hives.
“It’s gratifying that this project can protect both the road and the coastline.”
The $450,000 project is due to take place between early October and mid-December. Preparing the site for the modules and their installation will cost some $400,000, with the balance used for culvert repair.
