Breach highlights value of wetlands
Unauthorised excavation of a blocked stream adjoining a protected wetland has landed a Mahanga resident with an enforcement action.
The Mahanga wetland is situated near Mahia. It covers about six hectares of land, almost the size of six international rugby fields, and is home to several vulnerable species like bittern, fernbird, inanga (whitebait) among others.
Hawke's Bay Regional Council's regulation team responded to the non-compliant activity which took place during the first week of July.
“The actual action was on the mouth of the Hine Rauiri stream that had blocked up and swelled. One of the residents organised an excavation to open up the mouth and let it flow out,” said Nathan Heath, northern area manager for Hawke's Bay Regional Council (HBRC).
“The mouth was already a bit open but he further extended it and made it worse,” he said.
Mr Heath was familiar with the many issues the wetland faced and the unpopular opinion some in the community had about it.
Most rivers and streams on the East Coast of the North Island had a tendency to “swell up” due to deposits like sand over time, he said. The Hine Rauiri stream was no exception.
“The mouth of the stream is probably 100m away from the outlet and the drain behind it collects. So if we open the outlet, more water flows in and affects the wetland.
“Once the water level rises on the wetlands, the drain fills up and may lead to overflow into residential properties,” Mr Heath said.
The overflow, however, was not just restricted to the properties but also a “paper road” called Happy Jacks Road that intersects with the stream. An overflow would potentially make it unusable and limit access for the local residents.
“We don't really have a concrete method to solve it at the moment as there are conflicted outcomes but we are investigating options for design and location.”
The council was getting a recommendation from ecologists and internal engineers from Hawke's Bay for technical advice, he said.
One of the options being discussed would include placing a weir — a small wall-like barrier — that would help retain a significant amount of water in the wetlands.
“We are well aware of the Mahanga community's concerns about the flooding of property from the wetland and we are working with Wairoa District Council and the Department of Conservation locally to try to resolve this.”
HBRC policy and regulation manager Katrina Brunton said residents should not take matters into their own hands.
The Department of Conservation (DoC) had an interest in protecting the wetland values of the Mahanga wetland, said the department's East Coast operations manager Chris Visser. DoC would continue to work with the local councils to support an engineering solution to management of the water level of the wetland.
The only other breach was reported last year in April when the wetland was drained by a digger during Covid-19 at Alert Level 4.
Wetland sites have been decimated nationally, with only 2 percent of original wetlands now remaining in Hawke's Bay. The regional council is calling on the local community| to help.