Who would solve a stormwater problem by cutting down large Kauri Trees

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May the forest be with you

I am afraid the answer is Auckland Council.

The evidence comes from recent incidents surrounding the property owned by Terry Chang in Hillcrest, North Shore.  Council has planned storm water work in the area.  They intend to enlarge the stream that runs down the back of Mr Chang’s property and this requires the removal of various trees including two large Kauri that Mr Chang is very fond of.

Mr Chang is vehemently opposed to what Council proposes and has been fighting a rearguard action to try and save the trees.  He recently sustained life-threatening injuries after falling into a storm water drain while protesting against work being performed on his section.  He is thankfully on the mend. I hope he recovers quickly.

The reason Council claims that the work is required is that a special housing area upstream will increase storm water run off.  The desire is to allow the storm water to rush through more quickly through a larger channel.  A more startling example of using industry grade engineering to solve a man made upsetting of natural balance you cannot imagine.

And why should Mr Chang’s Kauris be felled because of a problem upstream created by a large scale property development?  Shouldn’t the development be designed in such a way that it does not create the problem in the first place?  After all SHAs were meant to be constructed only in areas where there is sufficient infrastructure.

The basic premise, you have to fell a couple of large Kauri to address a storm water problem is odd. You see trees and reforestation present a much more durable solution to storm water problems.  They also improve amenity considerably as well as taking in carbon dioxide and contributing positively to global warming.

Dr Cate Macinnis-Ng, a senior lecturer in the school of biological sciences at the University of Auckland, explains the importance of Kauri in this video:

There is a world wide movement to rewilding countryside for their benefits which include superior handling of storm water. An example is Guardian columnist George Monbiot who has for some time urged reforestation of areas in the United Kingdom. He wrote recently about flooding in Cumbria where in these post global warming times flooding incidents that were meant to occur once in a hundred years were now occurring almost annually.

His conclusion about the best way to deal with flooding was this:

A rational policy would aim to prevent the flood from gathering in the first place. It would address the problem, literally and metaphorically, upstream. A study in mid-Wales suggests that rainwater’s infiltration rate into the soil is 67 times higher under trees than under sheep pasture. Rain that percolates into the soil is released more slowly than rain that flashes over the surface. But Cumbria’s hills are almost entirely treeless, and taxpayers, through the subsidy regime, pay farmers to keep them that way.

Rivers that have been dredged and canalised to protect farmland rush the water instead into the nearest town. Engineering works of this kind were removed a few years ago from the River Liza in Ennerdale. It was allowed to braid, meander and accumulate logs and stones. When the last great storm hit Cumbria, in 2009, the Liza remained clear and fordable the following day, while other rivers roared into furious spate. The Liza’s obstructions held the water back, filtered it and released it slowly. Had all the rivers of Cumbria been rewilded in this way, there might have been no floods, then or now.

So it will be a very sad day if these Kauri are felled for storm water purposes.  Because if you want to find a durable solution to stormwater problems while at the same time improving your amenity and greening your neighbourhood then Kauris are part of the solution, not the problem.

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