Do we Really want to Swap our Small Apple for a Fat Banana?

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.

10 thoughts on “Do we Really want to Swap our Small Apple for a Fat Banana?

  1. A good explanation (although I think you mean Waimak River, not Rakaia?). You could also argue that the Port Hills provide a bit of a constraint to the south too; while you can build up them a bit, at some point you hit the limit of existing reserves and concerns about sightlines along ridges.

    The “banana” model does assume that growth is contiguous, i.e. that we don’t just ‘jump’ over the constraints and build other nodes further out. This already happens in a few spots (e.g. West Melton) but is not terribly efficient from a transport or utility services perspective.


    1. Good spot, have corrected the river. Yea i guess you can get sombre development out west that way but im not sure it could ever get that big due to the water protection zone, and the need for a transport connection.


    2. West Melton is just south of the aquifer recharge area and north-west of the airport noise contour. A train line spur could be run out from Hornby to West Melton. This could create a new satellite town next to West Melton (East Melton?).
      There would also be an opportunity for another satellite town around Weedons with rail configured to connect to it.


      1. If East Melton was built it would just widen the fat banana. The stylised banana shape would still be apparent.
        What would undermine the fat banana analogy would be if a second western bridge was built over the Waimak and a township was built on the north side of the river.

        This could still be a TOD town connected by a light rail spoke. It could be an extension of a light rail route that connected the city centre to the uni and the airport.

        In that case the banana model would become the spoke model.

        That would only be necessary if the city was growing really big. Say if it doubled in size.


  2. Re: “The only alternative to the fat banana is to not grow outwardly at all”.

    I am a fan of cities growing upwards too. I have written about plenty of ideas that would facilitate this and will continue to be an advocate for this type of city building. But I am also a pragmatist. I know since the earthquakes 75% of house building in Greater Christchurch has been in greenfield locations i.e. outward growth. None of this has been supported by rapid transit services in advance of growth.

    So the city has doubled down on automobile dependency -which causes congestion for inner city areas -which discourages inner city areas building upwards. Yet if we stopped all greenfield development then the restriction in supply would lead to land banking, rent increases and rapid house price inflation.

    I believe supporting transit oriented development in the fat banana is the best compromise solution. It can lower automobile dependence and provide new high quality transit corridors through existing urban areas. Over time this will support the city building upwards too.


    1. As long as you accept that this pragmatism is necessary simply because Council and Government fail to engage with the public on the topic, and fail to look at more radical options that have far better outcomes.

      The pragmatism is not from a substantive or technical position. It’s only from a political position. And this is because there has been no government-led discussion or engagement. Imagine what we could do if we took a leaf out of China’s book, and set up Public Exhibition Halls of Urban Planning, so that the public could really understand their city.

      Christchurch has plenty of wide streets and at-grade carparks and even red-zones that can accommodate temporary housing in the form of caravans and tiny houses until the intensification starts kicking in. Rental for spaces can easily cover portable amenities. And it has plenty of intensification opportunities.

      There’s nothing logical at all in continuing with greenfields development when the very challenge that brownfields development provides is the trigger to start planning properly.


      1. hmm.. interesting way of looking at it. I do think you’re right in that there are currently big challenges to doing brownfields developments that we need to fix. The UDA will hopefully help in a handful of places. But I think we need far more than just that – we need to take away all the unnecessary barriers to intensification generally. Either something like hyperlocalism, or completely chucking out the RMA in our urban areas and bringing in some other planning law that’s is more fit for purpose.


      2. Yes, I don’t want to be one more critic of the RMA, but in terms of urban form, I think it’s either not suitable, or it’s been misapplied. Need to read more on the subject. If I was King of Tartary, I’d:

        Choose some urban forms that provide the necessary level of green infrastructure, intensity of housing, transport amenity, resource efficiency, carbon footprint and liveability. Launch into a discussion with the public about these forms, the need for the intensification levels, and inviting ideas for other forms to consider. Then each suburb gets to vote on which of several it would prefer. For each chosen form, a set of regulations would be developed that would allow site-by-site development towards that form. Or, if the form prevents site-by-site development, a protocol for entire blocks to masterplan a development would be developed (similar to what Brendon has proposed except more straight forward because there would already be a suburb-wide mandate).

        People could then sell and buy into the type of suburb they’d prefer to live in, so even if they didn’t like the chosen form for their suburb, they’d probably have plenty of time to move to a place with a form they’d prefer. (Although I’m a bit worried there could be a First Past the Post type problem with this…)

        The motivation for home owners to develop would be that only if you develop up to the required intensity will the caravans and tiny houses be removed from your local streets and places. 🙂


      3. I like the idea of suburbs getting to vote on their planning rules. Currently Councils use consultation to gauge public opinion, but this doesn’t work as it always gets hijacked by small numbers of vocal people who have heaps of time on their hands. Normal people living busy lives are not represented through the consultation process.


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