Horizons to continue investigating ‘room for the river’ approach to river management

Integrated Catchment Committee chair Cr Peter Wells says Horizons was granted $300,000 from the Ministry for the Environment, through Nature Based Solutions for Resilience Planning, to conduct a feasibility study looking at if management practices such as channel symmetry, alignment and confinement were still relevant, and to further explore the concept of mobility corridors for the Ōroua and Pohangina rivers.

“This allowed us to conduct a study looking at how nature-based solutions, commonly known as the ‘room for the river’ approach, could be applied to the Ōroua and Pohangina rivers,” says Cr Wells.

This approach is being successfully delivered in the Rangitīkei River catchment, says Cr Wells.

“At a recent Integrated Catchment Committee meeting, members received the investigation report and resolved to release the report, noting further work would be required to inform any next steps to implement this approach.

“We know landowners in this area have been impacted heavily by flooding in recent years – not just by Cyclone Gabrielle, but many other events too – and further engagement with them will be required before implementing anything from the report.

“This report is one component of the work. There is also important economic analysis and work on social implications to consider, with input from impacted landowners also required.

“Council has committed to invest further into physical works in the catchment as a priority, with Council voting this year to dedicate additional resources to the Pohangina-Ōroua Scheme. We are also working with a new landowner sub-committee to guide works.

“At this stage, there is no further work planned on the Pohangina-Ōroua ‘room for the river’ approach while Council and landowners focus on the physical works required.”

Horizons group manager catchment operations Dr Jon Roygard says the ’room for the river’ approach comes from a flood management strategy where natural river floodplains were allowed to move and shape over time.

“Various parts of New Zealand are investigating the approach and some are implementing it,” says Dr Roygard.

“Implementation is quite unique for each catchment. 

“The strategy allows rivers space, increasing their capacity for safely handling higher flow rates, and has seen success in providing better resilience planning for flood events overseas.

“The ‘room for the river’ concept looks at historic channel positions, geology, river processes, community and cultural values, and existing infrastructure within the floodplains to develop a river management envelope containing lines, and channel and buffer zones.

“Inside the envelope, lines are drawn to give the river space to move, and minimal works are undertaken to increase management efficiency. Outside the lines, the river can be more intensively managed, for example, by using hard engineering to protect key infrastructure.

“This strikes a balance between allowing space for the river to move, while still allowing for investment into hard engineering to protect people, property, businesses and infrastructure.

“River management lines can be a useful tool for managing rivers holistically and sustainably. They can be created, interpreted and implemented in slightly different ways, but are commonly used to outline areas alongside the river where the channel is likely to move laterally, so it is easier to make decisions about how to respond to erosion.”

This approach is river-specific, says Dr Roygard. 

“The science is only one aspect, and it is important to consider the economic components and the community view.

“Essentially, each river would require its own river management lines report because it depends on the river system, how it behaves and what we are trying to achieve through river management.”

“It is important to understand that the ‘room for the river’ approach is not Horizons drawing lines to secure land and enforce them.

“Rather, this is a way to understand where multiple data sources say the river may end up travelling in a flood to provide guidance around how we manage the scheme into the future.

“It is not designed for us to stop people using land, but to help people to do so in a way that is sustainable.”

Cr Wells says the Integrated Catchment Committee also resolved to continue the nature-based solutions approach for the Lower Rangitīkei River, and continue exploring the high-level scientific analysis for the Mangatainoka River catchment.

“While the development of options for river management lines informed by the ‘room for the river’ approach will proceed, this doesn’t stop any of the river management work already planned across the region.

“This options development will help to inform any further work required to improve the community's resilience to flood events.”

It will take a few years for the science report for the Mangatainoka catchment to be ready, says Cr Wells.

“In the meantime, the focus remains on completing repairs and maintenance work within the catchment. This work is underway at an accelerated scale following Council prioritising work and approving additional staffing and funding for this over June and July,” says Cr Wells

To read more about the nature-based solutions investigation for the Pohangina and Ōroua rivers, see https://www.horizons.govt.nz/your-council/projects/nature-based-solutions-investigation-oroua-and-pohangina-rivers.