Which Australian city is sprawling the most?

Sat 3 December, 2016

For a while now, I’ve been tracking urban sprawl and consolidation in Melbourne, but some interesting recent research prompted me to compare Melbourne to the other large Australian cities.

My question for this post: How do Australian cities compare for growing out versus up? (by growth I’m talking about population)

Firstly, I need to define “outer” growth.

To do this, I’ve mapped the 2001, 2006, and 2011 ABS urban centre boundaries of each city. I’ve then looked at Statistical Area 3 regions within each Greater Capital City area that either saw substantial urban growth between 2001 and 2011, or were located on the fringe of the main urban area.

Here’s a map of Melbourne, with my designated “outer” areas shaded in a transparent blue:

The area in the middle is mostly shaded green – land considered by the ABS to be urban since at least 2001. There are a few yellow and orange areas (developed 2001-06 and 2006-11 respectively) that are not part the blue shaded “outer” area. The larger orange section visible in the south is mostly green wedge or industrial land, so does not represent growth of residential areas (maps for other cities below). The other yellow and orange areas are relatively small, and many have non-residential land uses.

I’ve done a similar process for Sydney, Perth, Adelaide, and the conurbation of South East Queensland (ie Brisbane, Gold Coast, and Sunshine Coast combined). See the end of this post for equivalent maps of these cities.

With an outer area defined for each city, I have calculated the annual population growth of these outer areas (based on 30 June estimates for each year), and compared it to growth of the city as a whole:

percentage-outer-city-population-growth

Perth comes out on top, with 81% of population growth in outer areas in 2015, with Sydney and Adelaide down at around 32%, while Melbourne and SEQ come in around 45-50%.

The SA3 population data goes back to 1991, which creates some interesting results in the early nineties (even though my defined “outer” areas are trying to measure growth from 2000 onwards). In Adelaide in 1993 the outer areas had “156%” of the city’s population growth – which actually means that the outer areas grew (by 4509 people) while the inner areas had population decline (by 1617 people). At the same time in Melbourne, “103%” of population growth occurred in the outer areas as there was a net reduction of 393 people in the inner areas of Melbourne. This reflects a previous trend for cities to grow mostly outwards until the mid 1990s, when urban densification took off. Indeed in another post, we saw the population-weighted density of Sydney, Melbourne, Adelaide and Brisbane bottom out in the mid 1990s:

SA3 cities pop weighted density time series 2

So is Perth the most sprawling large city in Australia? Well, yes in terms of percentage of population growth, but not in terms of absolute population growth in outer areas:

outer-city-population-growth

On my definitions of outer areas, Melbourne comes out top, with around 45,000 residents moving into growth areas in 2014-15. Perth almost matched Melbourne’s growth in 2012, but has fallen back since and in 2015 is closer to Sydney and SEQ. Adelaide just hasn’t seen a lot of population growth in recent decades.

Population growth in outer Sydney slowed dramatically between 2002 and 2006. The chart below shows there was also a slow down in non-outer areas, although it was a little less dramatic. Around this time Sydney also transitioned from around 50% of growth being in outer areas, down to around 30%.

Here is the annual population growth in the non-outer areas of each city:

nonouter-city-population-growth

Around 2007 there was an acceleration of population growth in non-outer areas in most cities (although there was a subsequent lull around 2010-2012).

A couple of things to note:

  • The outer areas will have some combination of urban growth and urban densification. My guess is that most population growth will be from urban sprawl, as urban consolidation is more likely to happen in the inner and middle suburbs. But my method doesn’t attempt to remove urban consolidation in outer areas.
  • You might be wondering about the inclusion of outer areas that are not experiencing urban growth. These areas are unlikely to have much population growth at all, so will have little impact on the calculations of percentage of growth in outer areas.

Finally, here are maps showing my defined “outer” areas of the other cities:

Sydney

sydney-cropped

I’ve used the full Greater Capital City area, which includes the Central Coast (Gosford / Wyong). This is arguably part of a conurbation with Newcastle but I’ve kept to the Greater Sydney boundary.  The large orange and yellow non-outer area to the west is mostly parkland or industrial, while the orange area to the south is mostly the Holsworth Military area which was defined as urban from 2011.

South East Queensland

seq-cropped

I’ve included all of Greater Brisbane, as well as the Gold Coast (as far as the border with NSW) and the Sunshine Coast. The conurbation population includes the established areas of the Gold Coast and Sunshine Coast as non-outer areas. The orange areas on the Sunshine Coast mostly contain National Parks and the airport, although it also includes the relatively new suburb of Peregian Springs, so not a perfect definition.

Perth

perth-cropped

The non-outer area is fairly well-defined as almost entirely urban in 2001. The entire of the City of Joondalup (on the northern coast, mostly surrounded by Wanneroo) counts as urban in 2001, although the suburb of Iluka in the north-western corner has developed more recently, so the calculation won’t be perfect.

Adelaide

adelaide-cropped

The two large orange areas in the non-outer area are non-residential, so there will be little fringe growth outside the blue area.


Are Melbourne’s suburbs full of quarter acre blocks?

Sun 22 May, 2016

A lot has been said about the great Australian dream of moving to the suburbs and living on a quarter acre block. But is Melbourne suburbia actually full of quarter acre blocks? Where are they to be found? Are they disappearing? This post delves into block sizes in Melbourne.

Where are the quarter acre blocks?

A quarter-acre translates to 1011.7 square metres in modern units, but for the purposes of this post I’ll allow some leeway and count any block between 900 and 1100 square metres. For this post I’ve also filtered out blocks in planning zones that cannot include dwellings (eg industrial areas), but that does mean I’ve included blocks in mixed use zones, commercial zones, etc. So not every block counted is residential. Also some larger blocks might contain multiple small dwellings but not actually be subdivided (eg a block of flats).

First up, here is a map of Melbourne showing the prevalence of quarter acre blocks. It looks like there are lots of them, but because the blocks are so small, the total area occupied by quarter-acre blocks is significantly over-represented on this large scale map.

Melbourne quarter acre block map

There are larger concentrations in the outer north-east and outer-east, but very few blocks in the current growth areas to the west, north and south-east.

Here are the top 20 suburbs for numbers of quarter-acre blocks:

Mooroolbark 1625
Rye 1545
Ferntree Gully 1504
Boronia 1471
Croydon 1437
Mount Martha 1430
Eltham 1229
Mount Eliza 1125
Werribee 1054
Sunbury 1035
Lilydale 996
Mornington 982
Reservoir 978
Balwyn North 936
Berwick 898
Upwey 897
Pakenham 772
Langwarrin 767
Kilsyth 732
Greensborough 724

There are almost 78,000 quarter-acre blocks within Melbourne’s Urban Growth Boundary, which sounds like a lot, but is only 3.75% of the 1.8 million blocks in my dataset.

So what are typical block sizes in Melbourne?

For this analysis I’m considering blocks within land use zones that can include dwellings, that are also within the urban growth boundary. But I’ve excluded blocks of less than 40 square metres on the assumption these are unlikely to contain dwellings.

Here’s the frequency distribution of block sizes in Melbourne:

The most common block size is 640-660 square metres, and 34.5% of blocks are between 520 and 740 square metres. The median is 540-560 square metres. 180-200 is the most common smaller block size, and there is a small spike in block sizes of 1000-1020 square metres, which includes the quarter-acre block. But quarter-acre blocks are certainly very uncommon.

I’ve calculated the median block sizes for all suburbs within Melbourne’s Urban Growth Boundary.

The inner city has median block sizes under 300 square metres, and 300-500 is typical in the inner northern and western suburbs. Block sizes are larger in the middle and outer eastern suburbs, older suburbs in the south-east, and blocks along the Mornington Peninsula. But the more recent growth areas to the west, north and south-east see median block sizes of between 400 and 500 square metres (purple), reflecting higher dwelling densities encouraged by current planning policy for growth areas. Quarter-acre blocks are the median only in places like Upwey, Belgrave and Portsea.

Inner city Carlton has the lowest median of 100-120 square metres, followed by Cremorne, North Melbourne, South Melbourne at 120-140 square metres, and then Abbotsford, Fitzroy North, Port Melbourne, Richmond, West Melbourne at 140-160 square metres. Urbanised suburbs at the other end of the scale include Park Orchards at 3020, Selby at 1440, and Warrandyte at 1260.

There are two interesting outliers in the central city: Southbank (in yellow) has a median block size of 980 square metres, and Docklands (in blue) has a median of 660 square metres. Both have been redeveloped in recent decades with many medium to high-rise apartment towers on those larger blocks.

Beyond these medians, there is a lot of variation within suburbs. Let’s go for a wander around the city.

Mooroolbark has the highest count of quarter-acre blocks and a median size of 840 square metres. As well as larger blocks, you can see a lot of further subdivision, particularly close to the train line (thin black line).

You may have noticed in the suburb map above a black coloured suburb in the middle south-eastern suburbs. That suburb is Clayton, and here is how it looks:

While blocks of 700-800 square metres were probably typical in the original subdivision, further subdivided blocks now outnumber the larger blocks, with a median of 260 square metres. Clayton of course is home to a major Monash University campus, and I suspect a lot of the smaller blocks house students.

A bit further down the line in Noble Park you can see extensive further subdivision near the rail line, surrounded by almost uniform blocks of 500-600 square metres:

Heading further south, Cranbourne is an interesting mix. The inner core (old town) has larger blocks but lots of further subdivision. This is surrounded by many blocks of around 700-800 square metres, but the most recent development has much smaller bocks, most less than 500. It’s a bit like tree rings, with each ring of incremental urban growth reflecting the preferred new block size of the time.

The area around Berwick also has a wide variety of block sizes, depending on the timing of development:

Here is the Frankston area:

Again significant further subdivision in central Frankston, a variety of block sizes in different parts of Langwarrin, and lots of large blocks in Frankston South and Mount Eliza (in some of the pink areas most blocks are over 2500 square metres).

In the middle northern suburbs you can see suburbs from an era when new block sizes were relatively large, and they’ve since had extensive subdivision. Here is Pascoe Vale:

Here is Reservoir. You can see smaller blocks in the surrounding suburbs:

The large block area to the west of the train line was apparently developed around the 1960s.

And to the west St Albans is another suburb with larger blocks being subdivided:

And further east there is a lot of further subdivision in Boronia and Bayswater, particularly near the rail stations:

The north-west corner of Templestowe has not too many larger blocks yet to be subdivided. But to the south-east you can see areas with blocks larger than 1200 square metres (light pink).

The area around Eltham has many large blocks, including many larger than quarter-acres. There has been quite a bit of subdivision around the rail stations however.

Another area with many large blocks is around Upwey/Belgrave:

A significant proportion of blocks are larger than a quarter-acre, with a median of 1060 in Belgrave, 1120 in Upwey, 1000 in Tecoma, and 980 in Upper Ferntree Gully.

If you want a quarter-acre block relatively close to the city, then Balwyn North has quite a few (many with swimming pools). Good luck saving a deposit for those.

But if a quarter-acre block isn’t big enough and you can afford the real estate, then you might want to try Canterbury or Deepdene, also relatively close to the city:

Or of course Toorak with plenty of very large blocks even closer to the city (although many will contain apartment buildings).

Essendon also has some larger blocks, including some quarter-acres:

There has been plenty of further subdivision, but there is also a stripe of green that is mostly in tact (a restrictive covenant applied perhaps?). You can also see the recent Valley Lake development in purple in Niddrie.

Most of the growth areas have small blocks, but here are some exceptions in eastern Doreen:

So there is plenty of variation in block sizes across Melbourne, but not that many quarter-acre blocks. Perhaps we should talk more about the one-seventh-acre block.

Data acknowledgement

This analysis was made possible with data available from data.vic.gov.au under a creative commons license. The data is Copyright © The State of Victoria, Department of Environment, Land, Water & Planning 2016.

I have used November 2015 property boundary data and May 2016 planning zones (sorry, not quite aligned, but this post has been a while in the making and the differences are unlikely to be significant).


Are Australian cities becoming denser?

Tue 5 November, 2013

[Updated and fully revised June 2015 with June 2014 population data and 2011 density calculations using square kilometre grid population data. First published November 2013]

While Australian cities have been growing outwards with new suburbia, they have also been getting denser in established areas, and the new areas on the fringe are often more dense than growth areas used to be (see last post). So what’s the net effect – are Australian cities getting more or less dense?

This post also explores measures of population-weighted density for Australian cities large and small over time. It also tries to resolve some of the issues in the calculation methodology by using square kilometre geometry, looks at longer term trends for Australian cities, and then compares multiple density measures for Melbourne over time.

Measuring density

Under the traditional measure of density, you’d simply divide the population of a city by the metropolitan area’s area (in hectares). As the boundary of the metropolitan areas seldom change, the average density would simply increase in line with population with this measure. But that density value would also be way below the density at which the average resident lives because of the inclusion of vast swaths of unpopulated land within “metropolitan areas”, and so be not very meaningful.

Enter population-weighted density (which I’ve looked at previously here and here). Population-weighted density takes a weighted average of the density of all parcels of land that make up a city, with each parcel weighted by its population. One way to think about it is the residential density in which the “average resident” lives.

So the large low-density parcels of rural land outside the urbanised area but inside the “metropolitan area” count very little in the weighted average because of their small population relative to the urbanised areas. This means population-weighted density goes a long way to overcoming having to worry about the boundaries of the “urban area” of a city. Indeed, in a previous post I found that removing low density parcels of land had very little impact on calculations of population-weighted density for Australian cities. However, the size of the parcels of land used in a population-weighted density calculation will have an impact, as we will see shortly.

Calculations of population-weighted density can answer the question about whether the “average density” of a city has been increasing or decreasing. But as we will see below, using geographic regions put together by statisticians based on historical boundaries is not always a fair way to compare different cities.

Population-weighted density of Australian cities over time

Firstly, here is a look at population-weighted density of the five largest Australian cities (as defined by ABS Significant Urban Areas), measured at SA2 level (the smallest geography for which there exists a good consistent set of time-series estimates). SA2s roughly equate to suburbs.

SA2 pop weighted density large cities time series

According to this data, most cities bottomed out in density in the mid 1990s. Sydney, Melbourne and Perth have shown the fastest rates of densification in the last three years.

What about smaller Australian cities? (120,000+ residents in 2014):

SA2 pop weighted density smaller cities time series

Darwin comes out as the third most dense city in Australia on this measure, with Perth rising quickly in recent years to be equal to Brisbane. Most cities have shown densification in recent times, with the exceptions being Geelong, Hobart, and Townsville.

However, we need to sanity test these values. Old-school suburban areas of Australian cities typically have a density of around 15 persons per hectare, so the values for Geelong, Newcastle, Darwin, Townsville, and Hobart all seem a bit too low for anyone who has visited them. I’d suggest the results may well be an artefact of the arbitrary geographic boundaries used – and this effect would be greater for smaller cities because they would have more SA2s on the interface between urban and rural areas (indeed all of those cities are less than 210,000 in population).

For reference, here are the June 2014 populations of all the above cities:

Australian cities population 2014

The following map shows Hobart, with meshblock boundaries in black (very small blocks indicate urban areas), SA2s in pink, and the Significant Urban Area (SUA) boundary in green.  You can see that many of the SA2s within the Hobart SAU have pockets of dense urban settlement, together with large areas that are non-urban – ie SA2s on the urban/rural interface. The density of these pockets will be washed out because of the size of the SA2s.

Hobart SUA image

 

 

Reducing the impact of arbitrary geographic boundaries

As we saw above, the population-weighted density results for smaller cities were very low, and probably not reflective of the actual typical densities, which might be caused by arbitrary geographic boundaries.

Thankfully ABS have followed Europe and released of a square kilometre grid density for Australia which ensures that geographic zones are all the same size. While it is still somewhat arbitrary where exactly this grid falls on any given city, it is arguably less arbitrary than geographic zones that follow traditional notions of area boundaries.

Using that data, I’ve been able to calculate population weighted density for the larger cities of Australia. The following chart shows those values compared to values calculated on SA2 geography:

pop weighted density 2011 grid and SA2 australian cities

You’ll see that the five smaller cities (Newcastle, Hobart, Geelong, Townsville and Cairns) that had very low results at SA2 level get more realistic values on the kilometre grid.

You’ll notice that most cities (except big Melbourne and Sydney) are in the 15 to 18 persons per hectare range, which is around typical Australian suburban density.

While the Hobart figure is higher using the grid geography, it’s still quite low (indeed the lowest of all the cities). You’ll notice on the map above that urban Hobart hugs the quite wide and windy Derwent River, and as such a larger portion of Hobart’s grid squares are likely to contain both urban and water portions – with the water portions washing out the density (pardon the pun!). While most other cities also have some coastline, much more of Hobart’s urban settlement is near to a coastline.

But stepping back, every city has urban/rural and/or urban/water boundaries and the boundary has to be drawn somewhere. So smaller cities are always going to have a higher proportion of their land parcels being on the interface – and this is even more the case if you are using larger parcel sizes. There is also the issue of what “satellite” urban settlements to include within a city which ultimately becomes arbitrary at some point. Perhaps there is some way of adjusting for this interface effect depending on the size of the city, but I’m not going to attempt to resolve it in this post.

International comparisons of population-weighted density

So now that I have calculated population weighted density of Australian cities using a kilometre grid – I invite other analysts to do the same calculations for other cities of the world – and then we might have a much fairer comparison of city densities (although still not perfect).

Changes in density of larger Australian cities since 1981

We can also calculate population-weighted density back to 1981 using the larger SA3 geography. An SA3 is roughly similar to a local government area (in Melbourne at least), so getting quite large and including more non-urban land. Also, as Significant Urban Areas are defined only at the SA2 level, I need to resort to Greater Capital City Statistical Areas for the next chart:

SA3 cities pop weighted density time series 2

This shows that most cities were getting less dense in the 1980s (Melbourne quite dramatically), with the notable exception of Perth. I expect these trends could be related to changes in housing/planning policy over time. This calculation has Adelaide ahead of the other smaller cities – which is different ordering to the SA2 calculations above.

When measured at SA2 level, the four smaller cities had almost the same density in 2011, but at SA3 level, there is more separating them. My guess is that the arbitrary nature of geographic boundaries is having an impact here. Also, the share of SA3s in a city that are on the urban/rural interface is likely to be higher, which again will have more impact for smaller cities. Indeed the trend for the ACT at SA3 level is very different to Canberra at SA2 level.

Melbourne’s population-weighted density over time

I’ve taken a more detailed look at my home city Melbourne, using all available ABS population figures for the geographic units ranging from mesh blocks to SA3s inside “Greater Melbourne” (as defined in 2011) or inside the Melbourne Significant Urban Area (SUA, where marked), to produce the following chart:

Melb pop weighted density time series 2

Note: I’ve calculated population-weighted density at the SA2 level for both the Greater Capital City Statistical Area (ie “Greater Melbourne”, which includes Bacchus Marsh, Gisborne and Wallan) and the Melbourne Significant Urban Area (slightly smaller), which yield slightly different values.

All of the time series data suggests 1994 was the turning point in Melbourne where the population-weighted density started increasing (not that 1994 was a particularly momentous year – the population-weighted density increased by a whopping 0.0559 persons per hectare in the year to June 1995 (measured at SA2 level for Greater Melbourne)).

You’ll also note that the density values are very different when measured on different geographic units. That’s because larger units include more of a mix of residential and non-residential land. The highest density values are calculated using mesh blocks (MB), which often separate out even small pockets of non-residential land (eg local parks). Indeed 25% of mesh blocks in Australia had zero population, while only 2% of SA1s had zero population (at the 2011 census). At the other end of the scale, SA3s are roughly the size of local councils and include parklands, employment land, rural land, airports, freeways, etc which dilutes their average density.

In the case of SA2 and SA3 units, the same geographic areas have been used in the data for all years. On the other hand, Census Collector Districts (CD) often changed between each five-yearly census, but I am assuming the guidelines for their creation would not have changed significantly.

Now why is a transport blog so interested in density again? There is a suggested relationship between (potential) public transport efficiency and urban density – ie there will be more potential customers per route kilometre in a denser area. In reality longer distance public transport services are going to be mostly serving the larger urban blob that is a city – and these vehicles need to pass large parklands, industrial areas, water bodies, etc to connect urban origins and destinations. The relevant density measure to consider for such services might best be based on larger geographic areas – eg SA3. Buses are more likely to be serving only urbanised areas, and so are perhaps more dependent on residential density – best calculated on a smaller geographic scale, probably km grid (somewhere between SA1 and SA2).

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Comparing the residential densities of Australian cities (2011)

Fri 19 October, 2012

I’ve looked at Melbourne residential density in detail, so what about other Australian cities?  Is population weighted density a useful measure? Does population weighted density help explain differences in public transport mode shares?

For this exercise, I’ve looked at 2011 census data at the Statistical Area Level 1 (SA1) geography (currently the smallest geography for which population data is available) for Greater Capital City Statistical Areas (which include large tracts of rural hinterland). I’ve sometimes applied an arbitrary threshold of 3 persons per hectare to define urban residential areas.

Measures of overall density

Population weighted density is a weighted average of the density of all the parcels of land in the city, with the population of each parcel of land providing the weighting. This provides a figure indicative of the residential density of the “average person”, although that’s still a little abstract. A city where a large proportion of people live in dense areas will have a much higher weighted population density than average population density.

Average density is simply the total population divided by the area of the city (or if you like, the average density weighted by the areas of each parcel of land). In calculating average residential density (which I’m doing in this post), the area would only include residential areas (I’ve arbitrarily used a threshold of SA1s with at least 3 persons per hectare).

Another measure is urban density, which considers all the land that makes up the urban city, including non-residential areas, but excluding the rural land that makes up large parts of most metropolitan areas when defined by administrative boundaries. I have not attempted to measure ‘urban’ density in this post.

Firstly here’s a table of data for the six largest Australian cities with three different measures of 2011 residential density:

Greater Capital City Statistical Area Pop Pop (>3/ha) Area, square km (>3/ha) Pop-weighted density, persons/ ha (all SA1s) Pop-weighted density, persons/ ha (SA1s >3/ha) Average residential density, persons/ ha (SA1s >3/ha)
Greater Sydney 4391578 4225278 1530 50.2 52.1 27.6
Greater Melbourne 3999924 3832366 1812 31.8 33.1 21.1
Greater Brisbane 2066134 1866794 1127 22.6 24.8 16.6
Greater Perth 1728567 1639849 963 21.6 22.7 17.0
Greater Adelaide 1225136 1161668 644 21.2 22.3 18.0
Australian Capital Territory 356563 350917 221 20.5 20.8 15.9

You’ll notice that Melbourne has a lower population than Sydney, but the total land area above 3 persons/ha is much larger.

Here are those densities in chart form:

You can see Sydney has around double the population weighted density of most other cities, but its average density is only about 60% higher. These figures show Sydney has a very different density pattern compared other Australian cities.

You can also see very little difference in weighted density whether you exclude low density land parcels or not (the blue and red bars). The density is brought down only slightly by the relatively small number of people living in very low density areas (below 3 persons/ha) within the statistical geography. Thus weighted average density is a good way to get around arguments about the boundary of the “urban” area. But then we are only measuring residential density here – and the large unoccupied spaces between residents of a city are very important when it comes to transport issues.

Can you compare population weighted density of Australian cities with international cities? Yes, but only if the parcels of land used are of a similar size and created in a similar fashion. The more fine-grained the geography (ie smaller the parcels of land), the more non-residential pockets of land will be excluded from the calculation. Anyone doing an international comparison should compare how the ABS create their geography at SA1 level with approaches of other statistical agencies. And please comment below if you get a set of comparable figures.

Density by distance from the CBD

The differences in density can be seen a little more clearly when you look at weighted average density by distance from the city centre:

(note: I’ve chopped the vertical scale at 100 persons/ha so parts of central Sydney, Melbourne and Brisbane are off the scale).

For Perth, Adelaide, Brisbane and Canberra (ACT) you can see a weighted average density in the mid to low 20s for large areas of the city, indicating large tracts of what you might describe as traditional Australian suburbia. In Canberra this kicks in at just 2 km from the CBD, and in Adelaide it kicks in 3 km from the city.

In Melbourne the weighted average density doesn’t get below 30 until 9 kms from the CBD indicating a larger denser inner area, and in Sydney it doesn’t drop below 30 until you are 39 km from the CBD!

Distribution of population at different densities

Here’s a frequency distribution of densities in the cities:

I’m using an interval of 1 person/ha, and the figures are rounded down to form the values on the X axis (ie: the value you see at 20 persons/ha is the proportion of the population living between 20 and 21 persons/ha).

You can see Sydney has the flattest distribution of all – indicating it has the widest range of densities of any city. Melbourne is not far behind, whereas Canberra has a lot of people living in areas between 12 and 24 persons/ha.

Note that many cities have a significant proportion of the population living at rural densities (0 to 1 person per hectare), particularly Greater Brisbane.

Another way to look at this data is a cumulative frequency distribution:

You can read off the median densities for the cities: Sydney 33, Melbourne 28, Brisbane 22, Perth 22, Adelaide 22, Canberra 19.

You can also see that 30% of people in Sydney live in densities of 44 persons/ha or more – compared to only 12% of Melburnians, 5% of Brisbanites, and less than 2% of people in the other cities.

If 15-30 persons per hectare is what you define as suburbia, then that’s 26% of Sydney, 37% of Melbourne, 44% of Brisbane, 55% of Perth, 57% of Canberra and 62% of Adelaide.

Spatial distribution of density

For the purest view of density you cannot get past a map. The following maps show a simple density calculation at the SA1 geography.

Update 22 Oct 2012: maps now include railway lines using OpenStreetMap data provided by Maps Without Borders. The data is licensed under Creative Commons Attribution-ShareAlike 2.0, copyright OpenStreetMap and contributors.

Sydney

You can see vast areas of darker green (40+/ha), particularly between Sydney Harbour and Botany Bay. There are also quite a few green areas in the western suburbs, while the northern north shore has the lowest density. There are many concentrations of density around the passenger rail lines.

Melbourne (and Geelong)

You can see areas of dark green around the inner city, with large tracts of yellow and green in the suburbs (25-35 persons/ha). There are however areas of moderate green (30-40) in some of the newer outer growth areas to the west and north, reflecting recent planning. There’s a not a strong relationship to train lines, but this might reflect higher densities equally attracted to tram lines (not shown on the map).

Note this map is slightly different to that in a recent post where I masked out non-residential mesh blocks.

Brisbane

You can see dark green patches around the river/CBD, but then mostly medium to low densities in the suburbs. There’s very little evidence of higher densities in fringe growth areas. There are some denser areas around railway lines (note the map does not show Brisbane’s busway network).

Perth

You can see green patches around the city, but also in some fringe growth areas where new planning controls are presumably forcing up densities. There are however vast tracts of orange (15-25 persons/ha), and little evidence of higher density around the rail lines (note: a lot of the lines are freight only and the north-south passenger line has very broad station spacing and limited walking catchment as most of it is within a freeway median).

Adelaide

Adelaide some inner city blocks of high density, but once you get outside the green belt surrounding the city blocks, you fairly quickly head into suburban densities. There are only a few pockets of high density in the middle and outer suburbs, and very little relationship evident between density and the rail lines.

Canberra (and Queanbeyan)

Canberra has vast areas at low density, and only a few pockets with dark green. There are however green patches on the fringes (particularly in the far north and far south), perhaps again reflecting planning policies forcing up densities.

Sydney is really quite a different city compared to the rest of Australia, with a much larger share of the population living in high density residential areas (more than I had expected). Melbourne has a much lower population weighted density (still quite a few people living in high density areas, but much less so than Sydney), followed by four cities that aren’t that different when it comes to density: Brisbane, Perth, Adelaide and Canberra.

What about density and public transport use?

Here’s a comparison of density (measured as both average and population weighted) and the most recent estimate of public transport mode share of motorised passenger kms for Australian cities:

Population weighted density certainly shows a stronger relationship with public transport use than average density (r-squared of 0.89 versus 0.82 on a linear regression).

If you believe that higher population density will lead to higher public transport use (for a given level of public transport service), then you would expect Sydney to be well placed to have a higher public transport mode share. Which indeed it does, but does it have the same level of public transport supply as other cities, and are all other factors equal? That’s a very difficult question to answer.

You could measure public transport service kilometres per capita, but different modes have different speeds, stopping frequencies and capacities, public transport supply will vary greatly across the city, and some cities might have more effective service network designs that others.

If all cities had the same levels of public transport supply and all other things were equal, you might expect a straight line relationship (or perhaps an exponential relationship). But Brisbane and Melbourne (and to a small extent Perth) seem to be bucking what otherwise might be a linear pattern. Are these cities doing much better with quality and quantity of public transport supply? Or is it something else about those cities?

Car ownership rates do vary between Australian cities, but this might be more a product of public transport viability for particular residents:

Also, we know that car ownership doesn’t have a strong relationship with car use.

When working population census data comes out I would like to look at the distribution of employment within cities. We know that public transport use is highest for journeys to work in the CBD (as it usually competes strongly against the car), so the proportion of a city’s jobs that are in the CBD is likely to impact the public transport mode share (at least for journeys to work). Moreover, a higher average employment density in general might be easier to serve with competitive public transport, and thus lead to a higher public transport mode share. It will hopefully also be possible to calculate weighted density of employment (at least at the SA2 level).

Finally, I’d like thank Alan Davies (The Urbanist) for inspiring this post.

Other posts about density:


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.


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’)


Melbourne urban sprawl and consolidation

Wed 4 April, 2012

[Last updated April 2016 with revised June 2015 population estimates. First posted April 2010]

How much is Melbourne sprawling, and how much is urban consolidation happening?

This post sheds some light by looking at ABS population data and dwelling approval data.

Note that this analysis uses local government areas (LGAs) within the Melbourne Statistical Division (although with all of the Shire of Yarra Ranges), rather than the new Greater Melbourne Statistical Area.  ABS now publish annual population estimates at an SA2 level (essentially suburb level). I’ve had a look at this data and the trends are very similar to the results for LGAs, so I am continuing with LGAs for now in this post.

Population growth

The first chart shows net annual population growth by regions of Melbourne. “outer-growth” refers to the designated growth LGAs on the fringe of Melbourne, namely Wyndham, Melton, Hume, Whittlesea, Casey and Cardinia (see the end of this post for definitions of regions and note that the areas have different sizes and starting populations).

As you can see, Melbourne’s population growth accelerated in the years up to 2008-09, slowed down dramatically for a couple of years but has since bounced back to strong growth. The big slump in growth in 2010 and 2011 was largely a reduction in urban consolidation in established areas, while the outer-growth areas continued strongly.

There were an estimated net 89,856 new residents in 2014/15, an average of 1728 per week (annual growth rate of 2.1%).

The following chart shows how the growth was spread across Melbourne:

In 2009-10 there was a significant shift in the balance of growth towards the outer suburban designated growth areas as population growth in established areas slowed dramatically. However we appear to have reverted to the previous pattern, and now 47% of population growth is in the outer growth areas.

The following chart compares the estimated actual share of population growth in the outer-growth areas with the 2008, 2012 and 2014 Victorian Government’s “Victoria In Future” population projections (which DTPLI stresses are not targets or predictions).

Apart from 2010-11, the share of population growth in the outer suburbs has been significantly below all projections, mostly because established area population growth has been much higher than projected. The 2008 projection was for the share of population growth in the outer-growth areas to decline slowly over time, the VIF 2012 projection was for the share to be steady around 55% for the next 15 years, while the new VIF 2014 forecast is for an increasing share in the outer growth areas, peaking in 2028. The 2015 estimated actual is closer to the VIF 2014 projection.

Note:

  • these figures don’t include Mitchell which is now partly within the Melbourne Urban Growth Boundary.
  • not all greenfields sites are in “outer growth” LGAs – smaller greenfields developments occur in established LGAs (eg Keysborough in Greater Dandenong).

If you’d like a more detailed idea about where changes in density is occurring see my posts showing changes in Melbourne density over time and a comparison of 2006 and 2011 at meshblock level.

Population growth compared to projections

The following chart shows the variations between the VIF 2008, 2012, and 2014, and estimated actual population for Melbourne:

The 2015 estimated result is remarkably close to the VIF 2014 projection – out by only 1085 people or 0.024%!

The next charts shows the VIF2008 projected population growth 2007 to 2015, compared to the estimated actuals:

Actual population growth in the inner and middle suburbs was more than double the 2008 projections, growth in the centre and outer regions was above projections, whilst population growth in outer-growth areas was slightly less than projected. That’s a lot of urban infill that was not accurately foreseen in the 2008 projections (the VIF 2004 projections foresaw even less of the urban consolidation in established areas).

The VIF2014 projections for 2014-15 are much closer to the estimated actuals:

The next chart shows estimated actual annual population growth by region to 2014, along with VIF2014 projections for upcoming years:

Growth in dwellings

Two readily available dwelling-based datasets are dwelling approvals (data available to a fine geography level) and dwelling completions (unfortunately these area estimates available at state level only). There will always be a time lag between approval and completion, and many approved dwellings don’t end up getting built. The ratio of dwelling completions to dwelling approvals in Victoria for the last 15 years is 92%. Comparing the two datasets for whole of Victoria, I found a 12 month offset provides the strongest correlation between approvals and completions:

dwelling approvals versus completions

Further complicating the analysis, the RBA has estimated that around 15% of dwelling approvals replace demolished dwellings, and around 8% are second homes or holiday homes.

There isn’t a strong correlation between Melbourne dwelling approvals and Melbourne population growth either, but for the purposes of this post I’ll look at dwelling building approvals because that is the only data I can get in any geographic detail.

The following chart shows a recent acceleration in dwelling approvals across Melbourne, with 55,303 new dwellings approved in 2014/15, more than double the 2007 figure.

Of particular interest are the recent surges in approvals in central, inner and middle Melbourne. The number of dwelling approvals in “inner” Melbourne almost match the outer growth areas in number. If these dwellings actually get built and occupied, then perhaps we will see a surge in population growth in established areas.

Comparing dwelling and population growth

The following chart shows the ratio of population growth to dwelling approvals, which provides indicators of average household size. In 2008-09, there was one new dwelling approved for every 3.2 new residents, but this dropped to around one new dwelling for every 1.7-1.8 new residents in 2009-10 and 2010-11, thanks to a surge of dwelling approvals combined with slower population growth. From 2012 to 2014 population growth picked up relative to dwelling approvals, but the surge in dwelling approvals in 2015 has sent it down to 1.6.

The chart also shows the VIF 2008 projection of average household size (of occupied dwellings), the forecast ratio of population growth to dwelling growth, and the average household size based on census data for 2006 and 2011. The forecast was for slowly declining average household size (following a recent trend). The census-derived average household size in 2011 was 2.445 persons, essentially unchanged since 2006.

Curiously, the ratio of new residents to dwelling approvals was only 1.5 in the early parts of the decade, much lower than average household sizes. Does this reflect small dwelling sizes approved in those years, or maybe a large number of dwelling demolitions?

Measuring progress against the Melbourne 2030 urban consolidation target

Melbourne doesn’t have population targets for different regions, but there was a target for dwellings growth in the (now defunct) Melbourne 2030 strategy. It stated the aim to:

reduce the overall proportion of new dwellings in greenfield sites from the current figure of 38 per cent to 22 per cent by 2030

The greenfield sites in Melbourne 2030 were mostly (but not entirely) located in the designated growth areas. As “greenfields” dwelling approval data isn’t readily available, I have used dwelling approvals in the designated outer growth LGAs as a proxy (the stated figure of 38% appears to match the data for these LGAs)

The dashed red line is a straight line interpolation of the Melbourne 2030 target for greenfields dwelling share. The outer growth LGA’s share of dwelling approvals had been higher than the target until the end of 2012, but has fluctuated a fair bit.

The 2012 Victoria in Future projections had around 48% of net new dwellings in Melbourne occurring in the outer-growth areas between 2011 and 2026, far higher than the old Melbourne 2030 target of 22%.

Now the 2014 Victoria in Future projections (released with the final version of Plan Melbourne) have around 45% of dwelling growth occurring in the outer growth areas between 2011 and 2031. The Plan Melbourne share of dwelling growth in the outer growth areas to the year 2051 is 39%, which suggests more urban consolidation between 2031 and 2051.

In reality, we seem to be tracking much closer to the original Melbourne 2030 target.

(Note: The outer-growth LGAs’ share early in the 2000s was much lower. This may reflect urban growth that was still occurring in areas I have classified as “outer” as opposed to “outer-growth” before the Melbourne 2030 plan was released in 2002.)

Appendix: Definitions of regions

I have allocated local government areas to regions as follows:

Centre = Melbourne, Yarra, Port Phillip

Inner = Hobsons Bay, Maribyrnong, Moonee Valley, Moreland, Darebin, Banyule, Boroondara, Stonnington, Glen Eira, Bayside

Middle = Brimbank, Manningham, Whitehorse, Monash, Kingston, Greater Dandenong (all but one in the east)

Outer = Nillumbik, Maroondah, Yarra Ranges, Knox, Frankston, Mornington Peninsular (all in the east and south-east)

Outer growth = Wyndham, Melton, Hume, Whittlesea, Casey, Cardinia

Here is a map of Melbourne with the regions shaded (dotted white area indicates within the 2006 urban growth boundary, sorry the colours don’t match exactly).

Here is a reference map for those unfamiliar with Melbourne LGAs. You’ll need to click to enlarge so you can read the text.