Kaipara stream erosion project takes top tech prize

LiDAR technology can generate ultra-precise, 3D elevation maps of ground features. It’s helping to identify stream erosion hotspots in the Kaipara and better target mitigation and investment as part of wider restoration of the moana.

An estimated 700,000 tonnes of sediment are deposited into Kaipara Moana each year - about seven times pre-human settlement. The sediment is currently smothering the moana, affecting native sea grasses, shellfish and fish.

In a significant desktop research project, a team from WSP used LiDAR data from Auckland Council to analyse the profile of 24,000 stream banks in South Kaipara Moana - identifying sections that are eroding or likely to erode.

The team combined stream bank height and angle, and soil information to classify banks as unstable, at risk and stable.

A desktop portal allows easy access to the data-rich information and to view stream bank profiles. This gives the Council real-life context and helps them understand the potential for erosion, now and in the future.

Work is currently underway restoring the 94,000-hectare Kaipara Moana, in a co-governance arrangement between Kaipara Uri, Auckland Council (AC) and Northland Regional Council (NRC). The programme is co-funded by the Ministry for the Environment, AC, NRC and private landowners - with an operational team set up called the Kaipara Moana Remediation Maurikura.

Thanks to WSP’s LiDAR analysis over such a large area, the joint venture can now target stream reaches that are most in need of remediation in South Kaipara. Funding for riparian planting or other mitigations can then be better targeted.

Auckland Council Manager of Waterways Planning Scott Speed says by using LiDAR and the geospatial tools developed in the project, they're hoping to identify areas where sediment generated from stream erosion is highest.

"This will allow us to prioritise initial investment in these areas to maximise sediment reduction gains from waterways restoration initiatives like those funded through the KMR."