What do whitebait, stoneflies, and streambank slip rates have in common? They are all part of a scientific investigation now under way in Karanema Havelock North.
By counting native fish and aquatic insects, and measuring everything from streambed sediment to water flow, a team of engineers, scientists and ecologists is building a detailed picture of the health of the five key tributaries of the Te Karamū Stream: Herehere, Mangarau, Te Kahika, School, and Karituwhenua.
Led by WSP for Hastings District Council, this project is gathering vital ecological and erosion data to guide the long-term care and restoration of these streams following the damage caused by Cyclone Gabrielle.
“Cyclone Gabrielle caused extensive damage throughout the stream systems,” said Council Havelock North streams/dams programme manager, Darren de Klerk.
“We want to raise awareness, mitigate further erosion, and work collaboratively with landowners to address issues before they become bigger problems.”
The fieldwork includes cutting-edge ecological DNA (eDNA) sampling to detect which species are present in each stream, including native fish like inanga (whitebait), shortfin eels, and redfin bullies, as well as invasive species such as mosquito fish (gambusia).
Macroinvertebrate sampling – counting aquatic insects such as mayflies and stoneflies – is also under way. These tiny creatures are powerful indicators of water quality and pollution, giving scientists insight into how well the ecosystem is functioning.
WSP senior ecologist, Alex Reid said each species tells the team something different about the health of the stream.
“When we look at their presence or absence, and in what numbers, we get a clearer idea of what’s happening below the surface.”
Measurements are also being taken of streambank condition, bed material, width, depth, and flow – all factors that influence how suitable the streams are as spawning and feeding habitats for native species.
As well as assessing current erosion risks, the study will also draw comparisons with historical data, giving the Council a valuable long-term view of how these natural systems are changing.
It’s part of a wider Council effort to manage stormwater and protect the environment in the wake of Cyclone Gabrielle, with findings from this project feeding into a full catchment management plan set for completion in 2026.
Hastings Mayor, Sandra Hazlehurst said Council had been working on a significant programme of work across the streams and dams network since Cyclone Gabrielle
“This study will further help our understanding of how the system works, and how we can manage and mitigate risks, as well as how we continue to collaborate and work with the many landowners whose properties the streams traverse through,” said Mayor Hazlehurst.
