Working together to slow the flow

It’s not possible to stop flood waters, but it is possible to slow them down.

This was a key takeaway for attendees at two ‘Slowing the Floodwave’ interactive workshops held at Okaramio Hall and Miller’s Rest in Rai Valley in June attended by farmers, landowners and rural professionals.

Run as part of the Nature Based Solutions (NBS) project, led by the Marlborough District Council with funding from the Ministry for the Environment, the workshops were focussed on modelling how possible solutions can be applied in steep catchments prone to flooding. Twenty-one projects across fifteen regions were chosen to be part of the project and, in Marlborough, Te Hoiere/Pelorus catchment was selected as the study area.

Matt Oliver, Marlborough District Council Senior Environmental Scientist – Land, said the purpose of the workshops was to inform the catchment community about the NBS project, share the modelling results and seek feedback from stakeholders about workable solutions. Project-lead Jon Tunnicliffe from the University of Auckland delivered the presentation.

The workshops focused on the results from computer modelling, which highlighted practical options to slow and temporarily store water during adverse weather events.

“Nature-based flood management can reduce flood peaks and erosion. The workshops provided a good opportunity to understand how some solutions suggested might work in specific catchments and to share the key messages and outcomes from the project,” Mr Oliver said. “Nature-based solutions can have a more significant impact on smaller, more regular floods rather than on the more extreme events, but they can help to build resilience within a catchment for when the big ones arrive.

“Slowing floodwaters does not always require heavy engineering. Small, strategic interventions over time, such as riparian and headwater planting or structures to reduce peak flow, can make a significant cumulative impact. It is all about measures to slow, store and delay - and everyone can contribute to that.”

The workshops provided a chance to share valuable research results, including data gathered from twenty water sensors located throughout the Te Hoiere and Kaituna catchments. These sensors capture real-time data during actual flood events, forming a reliable foundation for building accurate flood models, Mr Oliver said.

“Using these models, Jon and the University of Auckland team explored how implementing nature-based solutions could affect water flow during flood conditions. We have tried to illustrate this work to landowners and farmers to help them visualise potential outcomes on their own properties and collectively, on downstream flood levels.”

A final report and update to the Marlborough District Council website is expected later in July.

For more information on the Nature-Based Solutions project, go to: https://arcg.is/0rLOH00.

Photos below:

• Members of the NBS team from left to right, Council’s Anne Bruce, Heather Collins (Heather Collins Consulting), Jon Tunnicliffe (Associate Professor- Fluvial geomorphology-University of Auckland), Council Senior Environmental Scientist Matt Oliver and Council Hydrologist Charlotte Tomlinson
• Modelling results were shared from the Nature Based Solutions project at recent workshops
• Te Hoiere/Pelorus catchment is the study area for the NBS project