Willows for flood mitigation – MCC field trip
Back in May, our Flood Risk Workshop in Tapawera opened up a catchment-wide conversation about flood risk, with input from science, council and landowners themselves. Dean Palmer of Hinetai Hops spoke that day about what he’d seen on his own land during the flood, and it struck a chord. People asked for exactly this: a chance to walk the land with him and see it firsthand.
That’s the model we work to at MCC — the community tells us what’s needed, and we help make it happen. So on 3 September — a still, sunny day, about as good as you could ask for in early spring — 24 of us gathered at Hinetai Hops, Tapawera: landowners, council staff, and a few from MPI, Boffa and Fish & Game.
We started in the carpark with a welcome and a plan for the day, then walked down to the first site together — the kind of easy, unhurried walk-and-talk where conversations start before anyone’s even reached the river.
Dean’s story: what years of floods have taught him
At Site 1, Dean talked us through years of trial and error — much of it hard-won — protecting his hop farm from flood debris. He was upfront that he’s no willow expert; this is simply what’s worked, and not worked, on his own ground.
Key lessons from Dean’s approach:
- Plant at an angle to the flow, not square-on. A straight wall of trees takes the full force of a flood and can blow out. Angled plantings let debris slide off rather than piling up.
- Keep the lines tight — gaps are the real risk. Water flowing through a planting is fine and expected — the angle allows for that. The problem is debris getting through a gap, and that’s what tears out fences and hop poles downstream. Overlapping rows so there’s no clear gap is the goal.
- It’s not just about the willows. Bare, grazed ground is what scours out in a flood. Dean destocked this land and let rank grass grow tall and dense, and that ground held together well. The one stretch that stayed grazed, or had disturbed ground from digger work, blew out twice. Grass cover matters as much as tree cover.
- Species and planting method matter for survival. Dean’s moved toward matsudana willow (ideally male), planted deep into the gravel with good backfilling — loose air pockets around roots cause them to dry out and fail. Poplars grew tall but can topple in floods; he’s kept later plantings lower.
- Multiple layers give redundancy. On vulnerable corners, Dean’s planted up to five layers of trees, so if one line fails there’s another behind it.
There was a good bit of back-and-forth and plenty of questions for Dean — people comparing notes on their own properties, asking about fire risk from the rank grass, root systems, and whether Dean’s approach would translate to their own stretch of river. That’s the value of standing on the actual ground: you can ask the follow-up question that a report never quite answers.
Council perspective: rules, mapping, and how engineers think about willows
Helen Forsey (TDC Catchment Advisor) walked us through the council’s role: which stretches of river are actively managed by TDC’s Rivers Team (where landowners should check in before planting to avoid duplicated cost), and how to get advice if you’re outside a managed zone.
A few things worth knowing:
- Willow plantings are modelled by engineers as increased channel roughness, not solid barriers — they only work if maintained, so debris doesn’t turn a planted line into a wall.
- Historic aerial maps show how much the river’s course has shifted over decades — useful context when thinking about your own risk.
- Where willow removal is being considered, a staged approach is recommended: establish natives first, then remove willows slowly.
Hinetai Hops field trip: what we learned
Nursery expertise: species, roots, and technique
Jacky Friedman and Eric Appleton (Appleton’s Nursery) shared decades of trial data on root structure and species selection:
- Root-anchoring differences between species and clones show up clearly even within a single growing season.
- Some poplar clones (e.g. Populus trichocarpa) are notably stronger-rooted and suited to erosion-risk sites; others prioritise fast growth.
- Planting tip: spray a ~1m circle with glyphosate before planting into rank grass — established grass roots release compounds that can suppress a new tree’s establishment. Once the tree’s established, use a grass-selective herbicide for ongoing weed control so you don’t harm the tree itself.
Lunch at Site 2: Dean’s plantings, up close
After Site 1, we loaded back into cars and drove along to Site 2 — past rows of hop poles standing tall against the willow lines, a reminder of exactly what all this planting is protecting. We stopped for a relaxed picnic lunch right among Dean’s rows and chevron plantings, an easy, informal stretch of the day where people wandered, asked Dean and Eric questions one-on-one, and swapped stories about their own places. Some of the best conversations of the day happened here — no formal talk, just people comparing notes over a sandwich, looking at trees that had clearly stood up to a real flood.
The bigger picture: a managed river at scale
David Arseneau (TDC) closed the day by showing us how the council’s planting programme has scaled — from around 5–6,000 poles a year to 50–60,000 — and outlined a 10–12 year vision to restore the river’s resilience to something closer to how it was before decades of neglect. It’s not a fast fix: as he put it, it took 30 years to get into this state, and recovery will be gradual too.
Key messages
- Right tree, right place — species and planting method need to suit the specific site, not a one-size-fits-all approach.
- Gaps, not water, are the enemy. Water flowing through a planting is fine and expected; debris getting through a gap is what causes damage.
- Ground cover matters as much as tree cover. Bare or grazed ground scours; rank grass and established vegetation hold the bank.
- This is a long game. Whether it’s a farmer’s own plantings or council’s river-wide programme, resilience is built over years, not one planting season.
- Peer-to-peer learning works. Hearing directly from another landowner who’s lived through it is often more useful than any technical briefing alone — and it’s exactly why MCC keeps bringing people back onto the land together.
Ngā mihi nui to Dean and the team at Hinetai Hops for hosting us, and to Helen, Jacky, Eric and David for such a generous and practical day.