A few days ago, Brendon Harre wrote an article that looked into the future of Christchurch, and included proposing several options for rapid transit in Christchurch. The whole article hinged on the idea that Christchurch was currently shaped a bit like a “small apple’ (a compact circle), but that it was growing to the north and southwest, such that in a few years it will change to more closely resemble a “fat banana”.
People often talk about Christchurch being an “unconstrained” city, with an excess of flat land that it can just keep pushing into further and further with relative ease. If this is the case, then why should we go to a banana shape? Shouldn’t we instead just stay as an apple and gradually growing larger? I thought I’d look into this more.
First up, here’s a map showing the current urban area of Christchurch (grey), along with the key roads and railways.
Now I’m going to shade out the ocean, which obviously constrains us to the east and south.
The west is the direction that, on the surface, seems to have a lot of space to expand into. But firstly we have to think about the groundwater protection zone, which we really don’t want to contaminate.
And secondly, there is the airport and its massive noise restriction zone.
If we wanted to expand west we have to either shift the airport or relax our criteria for noise tolerance, and also relax our criteria for protecting our drinking water from contamination. I’m not an expert in either of these fields, but on the surface they seem like either very costly propositions, or very risky propositions with significant environmental and human health trade-offs. I’m not sure how likely electric planes are in the long-term – possibly that might change things? But if we’re just talking about the reasonably foreseeable future, then these two constraints together seem to form a pretty formidable barrier to any significant expansion to the west.
Finally, add in the Waimakariri River to the north and the marshy swampland areas to the northeast, which is at least expensive and risky to build on, if not completely impossible.
There are other constraints too, but these are the big ones. Even just with these, you can start to see a picture emerging that Christchurch actually is quite constrained. There really are only two directions we can expand into.
And I think you can start seeing where the “fat banana” terminology comes from.
The only alternative to the fat banana is to not grow outwardly at all. That is one option, albeit a pretty extreme one. I’m a fan of generally trying to grow up rather than out (allowing higher density housing and workplaces in our currently extremely low-density city). But Brendon has written previously about the market reasons for needing to simultaneously allow some growth outwards too (mainly to do with ensuring that city centre land prices are not inflating at such a high rate that they encourage land banking rather than development – articles here and here).
In conclusion, I think that Brendon chucking out the apple and replacing it with a banana in his recipe for Christchurch transport, is completely justified. It’s a significant shift in mindset from the idea of Christchurch as an unconstrained city, but one I think we collectively need to make.
Next post – I want to further poke around into Brendon’s second big assumption – that the existing railway tracks should be the foundation of any future transport network.