The Hawke's Bay Regional Council hopes the Clive River will soon be back to normal after a seasonal "haircut" left the stream clogged with a delta of grass islands.

But paddleboarder and long-time river user and shore-dweller Glenn Abel is not easily convinced, saying that the council, like a good barber, should still be cleaning up afterwards.

While the council says most of the grass sweeps out to sea, Abel, Australia-born but resident of New Zealand 45 years and of Clive about 14 years since building in Delta Mews, says it should be netted or removed by other means to protect what he says is one of Hawke's Bay's great natural treasures.

Grass floating along the Clive River has been giving local watercraft grief. Photo / Paul Taylor
Grass floating along the Clive River has been giving local watercraft grief. Photo / Paul Taylor

"Some does (get washed out to sea), a lot doesn't and it drops and rots," he says. "In any case it's still pollution. This river is beautiful and it should be like the Avon River in Christchurch, and treated that way."

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The weed-drift and the rafts of grass heading towards the river mouth are the result of regular weed-cutting upstream to reduce the risk of flooding, and "in most cases" it floats out to sea, council senior engineering officer waterways Dave Paku said.

"The growing weed displaces water which results in higher retained water levels, and water flow slows dramatically," he says.

"If a storm event comes along there's a high risk of this weed getting ripped off and blocking culverts, bridges and screens at pump stations, resulting in severe flooding and damage."

Paku says the council has trialled the feasibility of capturing and removing cut weed — "as recently as last year".

"But it is still costly and limited, and it's also a risk to fish life as they hide in the collected weed and get caught," he says.

The weed in the Clive River is cut four times a year, while grass cut on the tributaries, including the Karamu Stream also float towards the river mouth.

That's been greater this summer because of optimum growing conditions of heat, moisture and nutrients.

"The weed growth is abundant," he says.

"It may be a short-term nuisance for some craft as rafts of weed float downstream. It's similar to a haircut in that weed continues to grow in the summer."

Havelock North man Geoff Russell was on the river trialling what he says will eventually be a solar-powered scale model paddle boat. Photo / Paul Taylor
Havelock North man Geoff Russell was on the river trialling what he says will eventually be a solar-powered scale model paddle boat. Photo / Paul Taylor

Havelock North man Geoff Russell, who was on the river on Tuesday trialling what he says will eventually be a solar-powered scale model paddle boat, believes costs of the extensive and continual maintenance of a slow-moving river with continuing weed-growth issues may be prohibitive and the weed may be "one of those things you've just got to live with."

"They do it in Christchurch with the Avon River," he said. "But you might need the greater population to afford to pay for it."

He conceded while the paddle wheels of his craft would ride over the submerged weed, it would be different for the faster boats with propellers behind them.

The current clearing project ends this week, and the final cut for the summer will be at the end of next month.