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Published: 2007-05-29 00:00:00

Environment Waikato and Environment Bay of Plenty are hoping to make flood gates in tidal areas more ecologically friendly using a bit of Kiwi ingenuity.

Environment Waikato has been supporting Environment Bay of Plenty and NIWA to develop a mechanism that could be retrofitted to flood gates to allow tides to flow through them.

The technology would be the first of its kind in New Zealand.

“International models are really expensive, so the aim is to produce one for a fraction of the price,” Environment Waikato river and catchment services environmental manager David Speirs said.

Mr Speirs said three prototypes had been developed by Environment Bay of Plenty and Kelly Hughes of Opotiki company Advanced Traffic Supplies. They are currently being tested at NIWA’s Ruakura research facility in Hamilton. Environment Waikato has assisted by providing funding and technical support.

“One prototype is working very well but now needs to be field tested to make sure it can operate in a real drainage situation,” Mr Speirs said.

The working prototype will be showcased at a workshop at Environment Waikato’s Hamilton office on May 30, which has attracted interest from other regional and district councils from all over New Zealand.

“This is an opportunity to bring the trial and the technology to the attention of other councils,” River and Catchment Services Committee chair Andra Neeley said.

“It’s early days yet, but hopefully we might be able to leverage some national funding collectively to develop a commercially viable mechanism. It’s also an opportunity to find out how widespread the issue of tidal blockages is.”

Flood gates help to keep land dry enough to live and farm on, but also prevent tidal water flowing into drainage areas, drying up plant and animal habitat.

“If we could install this technology in enough streams we could restore some of these habitats to a more natural condition, without compromising the flood protection and drainage services they provide,” Mr Speirs said.

“This would result in big biodiversity improvements. It would also allow migrating fish into some areas they can’t currently access, and create new spawning areas for inanga and other whitebait species. It would be a good way of offsetting some of the negative environmental impacts flood control schemes have had.”

Mr Speirs said allowing tidal water into drains in a controlled way could also benefit farmers by helping to flush water out and by killing fresh water plants that sometimes caused blockages.

Cr Neeley said it was important to note the device was being engineered to ensure the essential flood and drainage management functioning of the flood gates would not be compromised.

“These floodgates would still close at a set water level.”

The prototype on display tomorrow has taken more than a year to develop. The next step will be field testing it and it is hoped this will begin within the next couple of months.