River survey provides understanding of flood risk

What lies beneath the surface of Southland’s rivers is no longer much of a mystery.

Environment Southland has recently completed a project using innovative survey and modelling techniques for the Ōreti and Aparima rivers, as well as the New River Estuary. This project aims to enhance understanding of these river environments and to support the development of flood risk scenarios.

The bathymetric LiDAR (Light Detection and Ranging) survey uses sensors loaded on small helicopters to map the contours of the riverbeds. This survey enables the creation of 3D pictures of the depth, shape and key features of the river.

Environment Southland’s integrated catchment management general manager Lucy Hicks said the survey and modelling of these two rivers and the New River Estuary provides us with a rich dataset.

“This advanced mapping enhances our understanding of flood risk, sedimentation and erosion, as well as river habitat and ecological condition.

“The Bathymetric LiDAR can enable us to improve the management of our ageing flood defences, like our flood banks, and ensure that we have solid information on where and when we invest in these improvements to our flood infrastructure,” she said.

“The modelling will also help us understand gravel movement and support our ongoing work to manage gravel in our rivers.”

The next phase of the project will include additional surveying using multibeam sonar and traditional surveying for ground control.

“It’s great to be able to adopt the use of this new technology to complement traditional methods in flood risk mitigation. By combining the methods, this project puts us in a better position to understand, manage and lessen flood risks for our communities and the critical infrastructure we all rely on,” Lucy Hicks said.

Once complete, the data will be publicly available on the Land Information New Zealand and Environment Southland websites.