Visualising the changing density of Australian cities

Mon 1 October, 2012

Following on from my last post on Melbourne density, I thought it would be worth creating animations of the change in population density in other large Australian cities.

Below are animated maps showing density using estimated annual population on the ABS Statistical Area Level 2 (SA2) geography for the period 1991 to 2011. You’ll need to click on them to see the animation (and you may have to wait a little if you have a slow connection).

I’ve used SA2 geography because it is the smallest geography for which I can get good time series data. Please note that some SA2s with substantial residential populations will still show up with low average density because they contain large parks and/or industrial areas, or are on the urban fringe and so only partially populated (the non-urban areas bringing down the average density).

Sydney

You can see the growth out to the north-west and south-west, the rapid population growth in the CBD and to the south of the CBD, and general densification of the inner suburbs.

Perth

Perth is a little less dramatic, but you can see strong growth to the far north in the late 2000s, populating of the CBD area, and increasing density in the inner northern suburbs. Many of the middle suburbs show very little change. A lot of Perth’s growth areas don’t seem to show up, probably due to low average densities of fringe SA2s that include non-urban areas.

Brisbane

You can see rapid population growth all over Brisbane, particularly in the CBD are inner suburbs.

Melbourne

In case you missed my last post, here is the map for Melbourne.

I had a bit of a look at Adelaide, but the changes between 1991 and 2011 were not very pronounced due to slow population growth. The process of creating these maps is fairly labour intensive so sorry Adelaide, no map for you (unless I get lots of requests).

I hope this is of interest.

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A first look at 2011 Melbourne residential density, and how it has changed

Fri 21 September, 2012

With the gradual release of 2011 census data, I thought it would be worth looking at some transport related themes. I’ll start with residential density (for my look at 2006 density, see an earlier post). This post looks at 2011 density, and how density has changed over the years.

The big issue with residential density is how you measure it. In showing it graphically, I prefer to use the smallest available geographic areas, as that can remove tracts of land that are not used for residential purposes (such as parks, creeks, wide road reservations etc).

At the time of posting, 2011 census population data was only available at “Statistical Area Level 1” (SA1). In 2013, population figures for the smallest ABS geographic unit – mesh blocks – will be available for a fine grain look at density.

However, land use descriptions for mesh blocks were available at the time of posting. I have used the indicated land use of each block to mask out land where you would not expect people to live – including land that is classed as parkland, industrial, water, or transport.

So the map below shows the residential density of Melbourne for SA1s, after stripping out non-residential land. The densities will be higher than if you simply looked at straight SA1 density, but I think they will be a better representation (although not as good as what can be drawn when 2011 mesh block population figures are available). You’ll want to click on the map to zoom in.

The map doesn’t show areas with less than 5 persons per hectare (otherwise there would be a sea of red in rural areas). Many of the red areas on the urban fringe are larger SA1s which will be fully residential in future but were only partially populated at the time of the census. However some are just low density semi-rural areas.

Note that the older middle and outer eastern suburbs are much less dense than the newer growth areas to Melbourne’s north and north-west.

How has density changed between 2006 and 2011?

I think the most interesting comparison will be between 2006 and 2011 mesh block density maps. We will be able to see in detail where densification has occurred, and it will be particularly interesting to look at activity centres.

The smallest unchanged geography level with time series data available is at Statistical Area Level 2 (SA2) – which generally contain one large suburb or a couple of smaller suburbs. Data is available for all years 1991 to 2011 (estimates for June 30, based on census results).

The following map shows the change in estimated density from 2006 to 2011 (using full SA2 land parcels, including any non-residential land). This could equally be considered density of population growth. Unfortunately urban growth in pockets of larger SA2s are less likely to show up as the impacts are washed across the entire SA2, but it gives some idea.

The map shows several SA2s with reduced population density, mostly outer established suburbs:

  • Mill Park – South -1.4 persons/ha
  • Mill Park – North -0.6 persons/ha
  • Bundoora West -0.5 persons/ha
  • Kings Park -1.5 persons/ha
  • Keilor Downs -0.8 persons/ha
  • Wheelers Hill -0.7 persons/ha
  • Toorak -0.4 persons/ha
  • Hoppers Crossing South -0.9 persons/ha
  • Rowville Central -0.5 persons/ha
  • Clarinda – Oakleigh South -0.5 persons/ha

There are increases in many areas, particularly:

  • the Melbourne CBD and immediate north
  • many of the inner suburbs
  • the outer growth areas, particularly to the west, north and south-east.
  • Ormond – Glen Huntly, up 4.4 persons per hectare (not sure what the story is there!)

How has density changed between 1991 and 2011?

Here is an animation showing how Melbourne’s density has changed between 1991 and 2011. You’ll need to click on this to see the animation and more detail.

Note in particular:

  • The CBD and Southbank area going from very sparse to very dense population.
  • The significant densification of Port Melbourne.
  • The significant densification of the inner northern suburbs, particularly in the late 2000s.
  • Some large SA2s in the growth areas don’t show up as becoming more dense as they are very large parcels of land with urbanisation only occurring in a small section. This is especially the case for Wyndham and Whittlesea.

So what was Melbourne’s “urban” density in 2011?

That all depends how you define “urban” Melbourne! The table below shows some calculations based on different criteria for including land. The more restrictive criteria will give an answer that is more of a “residential” than “urban” density.

The different geographies are confusing, so I have produced a map below to try to help.

When more census data is available I will aim to update this list (eg to include density of the Melbourne urban locality).

Geography Area 
(km2)
Population Density 
(pop/ha)
Areas on map
“Greater Melbourne” Greater Capital City Statistical Area 9990.5 3,999,982 4.0 white + yellow + green + red
SA1s, within Greater Melbourne, with population density >= 1 person/ha 2211.4 3,903,450 17.7 yellow + green + red
SA1s less non-residential land, within Greater Melbourne, with population density >= 1 person/ha 2295.2* 3,906,680 17.0 yellow + green
SA1s less non-residential land, within Melbourne Statistical Division, with population density > 1 person/ha 2199.7 3,862,387 17.6 yellow + green within purple boundary
SA1s less non-residential land, within Greater Melbourne, with population density >= 5 person/ha 1740.1 3,787,610 21.8 green

*This area is actually larger than the row above, because more SA1s meet the criteria. Confused? It’s because I’ve cut out the non-residential land from each SA1, which increases the average density of what remains meaning more SA1s meet the criteria. The residential land area of the extra SA1s was slightly more than the non-residential land that was cut out. On the map below there are some yellow and green areas that do not have red “underneath”. The red areas you see on the map below are non-residential land in SA1s.

I’ve calculated the average density of “Greater Melbourne” in the first row for completeness, but this is a bit meaningless as the vast majority of land in “Greater Melbourne” is non-urban land (the white area in the map below).

Here is a map showing the various land areas used in the calculations above (note green and yellow areas overlay most red areas):

I’ll aim to post more about 2011 density when ABS release more census data (including population figures for mesh blocks and ‘urban centres and localities’)


What does Melbourne’s urban density look like? (2006)

Sat 2 April, 2011

Transport planners love to talk about urban density, but what does Melbourne’s urban density actually look like? Google for a Melbourne urban density map and you won’t find much.

The ABS publication Melbourne.. A Social Atlas has a density map (see pages 12-13) at the Census Collection District (CCD) level, but only has five colour graduations so subtleties are quickly lost.

So I’ve decided to draw one myself.

Arguably the best source of data for housing density is the ABS’s experimental mesh blocks, which are smaller than Census Collection Districts (CCD). Mesh blocks are designed to have more uniform land use, which gets around the problem of a CCD which might contain a mix of residential, parkland and commercial land use showing up as low density. But I’ll come back to this.

So here is a 2006 population density map of Melbourne at the mesh block level:

(I’m using people per square km, which is 100 times larger than people per hectare if you need to convert).

You’ll need to click to zoom in, and you might want to then zoom in again with your favourite image viewer to see the detail.

Some observations:

  • Many areas on the very fringe show as low density, but this might be because that area was under development at the time of the census, and only some people had moved in.
  • Everyone talks about low density sprawl on the fringe, but even back in 2006 there was evidence of higher density development in the outer suburbs. Have a look at the Craigieburn area in the north or around Narre Warren and you will see many patches of green. New blocks on the urban fringe are now actually quite small in places compared to those in the middle suburbs. Two storey townhouses are actually not uncommon in new estates.
  • In the north-west (around Delahey/Sydenham), you can see a north-south divide where there is higher density on the eastern side. This corresponds with the municipal boundary between Brimbank and Melton. Presumably they’ve had different urban development policies.
  • The biggest clumps of density are in the inner city, particularly Carlton and Carlton North, Fitzroy, St Kilda, Richmond, and Kensington (the western side of which enjoys a 5½ days per week route 404 bus service).
  • Looking at the Central Activities Districts (CADs), there are clumps of density near the Dandenong and Box Hill CADs. But nothing to speak of inside Ringwood, Frankston, or Broadmeadows CADs (in 2006).
  • Other curious pockets of density in the suburbs include west of Highpoint Shopping Centre, Sunshine, Glenhuntly/Carnegie, and Glen Iris.
  • The lowest density suburbs in Melbourne are found in the middle and outer eastern suburbs (particularly Upwey/Belgrave), and in the north-east around well off areas such as Eltham, Toorak and Eaglemont. North west Reservoir seems to be a problem area – high socio-economic disadvantage and low density (not to mention a bus route that runs 5½ days a week).
  • Interesting to see relatively higher densities south of the Dandenong rail line.

For comparison purposes, I’ve also created a version based on larger Census Collection Districts (CCDs):

(note: this map doesn’t show anything outside the Melbourne SD)

What’s the difference you ask? You cannot see a great deal of difference, though the CCD map makes Melbourne look a little less dense.

But if you zoom in you can spot differences in some areas where a CCD is part residential, part not. Here’s an example in the Black Rock/Beaumaris area:

The CCD map on the left shows a few darker red blocks next to the whitespace, but that low density is not visible in the mesh blocks on the right, because the mesh blocks split the parkland and houses. You can also see that the CCDs run to the shoreline, while the beach area has been split into separate mesh blocks.

The advantage of the mesh block map is that it pretty much shows housing density, as most pieces of land that are not residential have been removed (including suburban parks).

But the advantage of CCD density is that it includes local parkland, which is a measure of open space within and immediately surrounding residential areas.

A better way of looking at the density equation is a cumulative distribution chart, as created by Fedor Manin on his blog We Alone on Earth (also referenced on Human Transit).Rather than having to worry about whether low density areas on the fringe are “urban” or not, you can just look at density by population share, and the fringe areas will quickly tail out anyway. On this basis the problems of using an administrative boundary of a city (which often contains a large areas of rural land) largely go away, but then you don’t get a single number.

I’ve lined up all mesh blocks and CCDs in the Melbourne SD in order of density, and created a cumulative profile of density for each.

You can see a big difference between CCDs and mesh blocks (note the X axis is logarithmic). On a mesh block basis, about half of Melbourne’s population lives at a density of greater than 3200/km2, whereas on a CCD basis, only 30% of Melbourne’s population lives at a density greater than 3200/km2. Take note anyone doing a comparison between cities!

Here’s a chart on the same data showing a population distribution across densities, using mesh blocks and CCDs:

You can see the most common density for mesh blocks is slightly higher than for CCDs. The peak for mesh blocks is between 2818-3162 people/km2 on my intervals. That’s an funny sounding interval because I’ve used logarithmic intervals (if you use even intervals of 100 people/km2, the peak is between 2900 and 3300 people/km2)

So what is the average density of Melbourne?

What is Melbourne? Should we include satellite urban areas around the city? For example, is Sunbury part of Melbourne? It is within the Melbourne SD (Statistical District) but not within the Melbourne “Urban Centre” as defined by ABS. Do you want to include non-residential areas (urban density), or not? (residential density)

Here are six very different measures of the urban density of Melbourne, including some measures that have minimum density threshold to restrict the calculation to “residential” areas. The maps above use 1000 people/km2 as a threshold for colouring, and this appears to include all “residential” areas, except for some very large block estates.

Geography Area (km2) Population Density (pop/km2)
Mesh blocks within all Urban Centres/Localities within Melbourne SD 2,357 3,506,207 1,488
“Melbourne” Urban Centre 2,153 3,368,069 1,564
CCDs within Melbourne SD, with population density > 100 people/km2 2,151 3,514,658 1,634
Meshblocks within Melbourne SD, with population density > 100 people/km2 1,566 3,511,982 2,242
Meshblocks within “Melbourne” Urban Centre, with population density > 100 people/km2 1,350 3,358,317 2,487
Meshblocks within Melbourne SD, with population density > 1000 people/km2 1,084 3,316,516 3,060

You can quickly see why trying to calculate an average density is a fraught exercise! Though the first two are trying to measure “urban density”, while the later are attempting to measure “residential density” (and note the threshold for residential density makes a big difference).

A density profile chart (as above) is clearly a good way to get around the defined area problem. But you still need to be consistent in the land parcel size you use when comparing cities. Not easy when comparing cities with different statistics agencies.

Land use map of Melbourne

Before I finish up, the other beauty of the mesh block data is that it contains a land use classification for each mesh block.

So it is really easy to produce a land use map of Melbourne (and Geelong for good measure):

What are those two black blobs I hear you ask? Essendon and Moorabbin Airports. Tullamarine and Avalon airports are actually classified agricultural.

And you will see residential areas stretching a fair way east of Frankston, and north of Craigieburn – though these are not actually developed. So it’s not perfect.

In fact, according to the data, there is a mesh block in Melbourne with 358 people living in an area of 420 square metres (852,700 people/km2). That’s 1.17 square metres of land space per person. Really? No, what appears to have happened is that almost every resident of the Burnside Retirement Village was registered to one tiny parcel of land. I suppose that’s census data for you!


Urban density and public transport mode share

Sat 16 January, 2010

Are all the statistics we see about urban density and transport reliable?

In in most recent book Transport for Suburbia (and his paper to ATRF 2009), Paul Mees highlights mis-use of urban densities figures by some researchers – the trouble being inconsistent determination of what exactly is the urban area of a city when you calculate density (= population/area).

To redress the issue of data quality, Paul has used calculations based on the actual urbanised area for Australia, US, Canadian and English cities (looking at entire greater metropolitan areas). He’s used figures based on urbanised areas as opposed to a statistical district, municipal council area, or other arbitrary administrative boundary which could contain large areas of non-urbanised land.

The calculations define urbanised areas using the following criteria:

  • US and Canadian cities: minimum 400 per square km,
  • Australian cities: minimum 200 per square km (meaning Australian cities might be slightly understated)
  • English cities: detailed mapping, likely to lead to slighty higher density figures.

So the calculations are not perfectly aligned, but they are more comparable than density calculations that use simple administrative boundaries. And they are also certainly consistent within each country.

He publishes tables of this data, talks about the relationships between them, but for some reason fails to plot the results on a chart. So I’ve decided to chart them (if you are after the data tables consult the ATRF paper above and/or the book).

The table of data is quite interesting in that it debunks some myths about the densities of various cities. Los Angeles is the highest density city in the entire table (the Freakonomics blog has a good series on Los Angeles Transportation: Facts and Fiction that is worth reading).

Firstly, car mode share in journey to work:

Is there a relationship between urban density and car mode share on journey to work? What do correlation coefficients say (closer to 1 and -1 means stronger) – something Mees didn’t calculate:

  • Australia: -0.74
  • Canada: -0.58
  • US: -0.46
  • England: -0.68

That suggests a relationship does exist, but it isn’t particularly strong. In reality, every city has unique characteristics and other attributes will explain the differences (the quality of services and infrastructure of alternative modes would certainly have a lot to do with it).

Looking at some outliers:

  • London has the highest density and lowest car mode share. It compares so favourably to all other English cities in car mode share, despite being only slightly more dense than Brighton/Worthing/Littlehampton (one combined urban area).
  • Canadian cities with the lowest car mode share are Toronto (highest density) and Victoria (second lowest density).

What about public transport mode share for journey to work?

This chart shows relationships stronger in some countries than others. Indeed the correlation coefficients are:

  • Australia: 0.79
  • Canada: 0.87
  • US: 0.42
  • England: 0.58

So much stronger relationships in Canada and Australia. Again there is a lot at work (particularly the quality and quantity of available public transport, which is one of Paul’s points).

In terms of outliers:

  • London is off the chart at 45.9% public transport.
  • Brisbane is perhaps an outlier for Australia – low density but pretty much the same rate of public transport use as Melbourne.
  • Los Angeles – which actually has the highest density of all the US cities but still relatively low public transport use.
  • The city with the highest PT mode share in the US is New York, even though it isn’t the most dense city in the US (there is lots of sprawl outside Manhattan).

The following walking chart might seem to suggest a strong relationship when you look at all cities, but remember that the density measurements aren’t quite the same, so it’s not fully conclusive. However, English cities still tend to have higher densities, particularly as many have green belts to prevent sprawl.

There is actually a negative correlation between density and walking (and cycling) for Australia and Canada. However I wouldn’t read too much into that as the sample size if small and there are lots of unique factors affecting each city.

But if you reckon there should be a positive correlation between walking and density, the outliers are:

  • Victoria (Canada) – low density but high walking mode share.
  • San Francisco and Los Angeles have low walking share.
  • Hobart – highest walking share in Australia, despite low density (and a big river dividing it in two).
  • Toronto – Canada’s most dense walking city, but least walking mode share
  • London – highest density but lowest walking share (9.2%)

Same again for cycling:

It looks like almost no one cycles in the US, despite having more favourable climate than Canada. Again higher cycling rates in the UK.

Cycling outliers:

  • Victoria (Canada) – high walking and cycling mode share
  • Kingston upon Hull (UK) 11% – off the chart’s scale (Mees suggests a large university may be the cause)
  • Canberra – which has a good network of bike paths (but still only 2.5% cycling mode share)
  • Sydney – with just 0.7% cycling – hilly terrain not helping.

What if you add up all the sustainable transport modes (PT, walking and cycling)? In theory, density should help all sustainable transport modes.

The correlations are:

  • Australia: 0.77
  • Canada: 0.62
  • US: 0.44
  • England: 0.70

The English result is actually stronger than PT (0.58), walking (0.32) and cycling (0.02). Do people respond to density using different, but sustainable modes?

Can public transport be effective in low density cities?

Paul’s main argument is that low transport density isn’t a barrier to successful public transport, and that it is easier to change public transport provision in a city, than it is to change urban densities (not that increasing urban densities isn’t a worthy goal).

Certainly urban density makes it easier to make public transport successful, but I’d agree that it is possible to make public transport work a lot better in low density environments.

Indeed, in Melbourne, relatively high quality SmartBus routes (that run every 15 minutes for most of the day on weekdays, very good by suburban Melbourne standards!) have been trialled in the outer suburbs, and the patronage response has been much stronger than typical elasticities (the subject of another post).

More generally, in Melbourne over the last three years we’ve seen a very strong correlation between growth in service provision (26% more kms) and growth in patronage (29%) – more than any other potential driver of patronage (again, topic for another post).

Comparable cities for population and density

Finally, by plotting population and density, you can see which cities are most similar – at least in these two respects (I’ve only looked at cities under 7 million and UK cities are off the density scale). I’ve labelled Australian cities and nearby equivalents. Note: the US and Canadian data is year 2000, while Australia is 2006.