Posts Tagged ‘census 2010’

In previous posts I have mapped the population density and household density of the City of Seattle.  The difference between the two maps is household size.  So I also created a map of average household size in the City of Seattle, based on the U.S. Census 2010 data, which I have guest-posted on the  Seattle’s Land Use Code blog.   Go read about it there, but I have included the map below for reference.

Data sources: U.S. Census Bureau, King County GIS, WSDOT


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It’s been a bit quiet over here at Build the City lately. I ran into trouble with an open-source GIS program, then got busy at work, and then took a two-week vacation to Europe. I will write some observations about the cities I visited in Europe (eventually), but today I saw an article in the Oregonian that caught my attention.

The census tract with the highest population density in the City of Portland shifted between the 2000 and 2010 censuses from NW 21st to the area around PSU.  What is notable is the population density cited for this census tract.  The article uses the strange metric of people/10,000 square feet, but when I do the math it comes out to around 27,000 people/square mile. 

For comparison, Seattle has two entire neighborhoods (Belltown and Capitol Hill) and five census tracts  that exceed this population density.  Seattle’s densest five census tracts are in Capitol Hill (45,000/sq. mi.), Belltown, the U_District and First Hill. 

This article about Portland is typical, because among the three big cities in the Pacific Northwest, Portland is by far the most spread out.   Below is a table that compares the city size and population density among four neighboring cities.

 Notice how the City of Portland takes up almost four times as much space as the cities of San Francisco or Vancouver, yet has a lower population.  Resulting in an average population density less than many suburbs.

Population density of northwest cities over the past 50 years (people/square mile)

Population density matters for Portland, because more people on a given block lead to more customers, which leads to more variety in local services, which leads to a convenient lifestyle on foot or on transit, which leads to building a city.  Portland has only a few neighborhoods where this dynamic has progressed, and therefore many residents find the need to use bicycles to reach daily destinations (2-mile radius).  Portland has the advantage of a consensus around progressive transportation, but it has a long uphill road to sufficiently populate its city.  The City of Portland could house 2,060,000 people at the City of Vancouver’s current density.

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I have created another map of Seattle’s population density, using units of gross households/acre.  This a measure of the built environment rather than of population, since household sizes can vary with time and between neighborhoods (maybe I’ll make a map of that also).  Net housing units/acre is a commonly used measure in land use planning and zoning, which excludes roadways and non-developable land from the area calculation.  This map is of gross density, incorporating all land, resulting in at least 40% lower density values.   

Only a few hotspots, such as Capitol Hill and Belltown, exhibit greater than 50 units/acre gross (red on the map).  At this level of household density most trips can be taken on foot or via mass transit.  The controversial state bill promoted by Futurewise would have mandated zoning average >50 units/acre net around high capacity transit stations.   A broader section of Seattle’s core has a continuous household density greater than 10 units/acre.  This level of households is associated with robust local bus transit combined with lots of trips via foot or bicycle.  In fact, the orange area on this map corresponds well with my personal experience of the zone in which you can catch a bus on a moment’s notice to go to the next neighborhood, without extensive pre-planning or OneBusAway use.  You are always within two blocks of a bus stop, and a bus is usually coming within a few minutes.

There is a wider swathe of Seattle with 5 to 10 units/acre gross, which generally represent the portions of the city with sidewalks.  While predominately single family homes, these neighborhoods were developed in an era of streetcars and small lots.  Unlike central and north Seattle, the south half of the city is rather inconsistently developed, with a patchwork of low, medium and highly developed areas.

Data sources: U.S. Census Bureau, King County GIS, WSDOT

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Next up in my series on the Census 2010 results is a population density map for the Seattle-Tacoma metropolitan area.  The GMA urban growth area (UGA) boundaries are shown for King and Snohomish counties (I’d love to also show the Pierce County growth boundaries, but alas, their data sharing policy is c. 1998).

A few points that jumped out at me from the map:

  • The Puget Sound region has succeeded at keeping higher population densities within the Urban Growth Boundaries (i.e. nothing but blue outside the lines).  There is still too much blue inside the lines, however, so we have room to grow.
  • Population in Snohomish County clusters around Highway 99 more than I-5, all the way up to Everett.  All the more reason to build North Link light rail along 99 instead of I-5, as I have argued earlier.
  • Our industrial areas are far too unpopulated.  The largest blue areas within the UGA are Paine Field/Everett Boeing Plant, the Duwamish and Green River industrial valleys, and the Port of Tacoma/Puyallup Nation.  This extreme form of monoculture land use is unsustainable, forcing people to live a minimum of several miles from their jobs and requiring duplication of retail services.  There are shops in the industrial areas only used during the day, and shops in the residential areas primarily used in the evenings; neither are very profitable.  Residential urban villages at a few locations in industrial areas would liven things up with minimal impact on industrial land availability.

Click here for the full-size pdf of the map.

Data sources: U.S. Census Bureau, King County GIS, Washington State Department of Transportation and Snohomish County GIS

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Below is a map of the population density of King County (the home of Seattle) based on the recently released Census 2010 data.  The map is drawn at the level of Census Block Groups (smaller than census tracts).

A few comments:

  • The three suburban areas most consistently populated are the 99 corridor in SW King County, the Soos Creek Plateau east of Kent in SE King County, and the Bellevue/Crossroads/Redmond area of the Eastside. 
  • The only population hotspots outside of Seattle are in the Crossroads area of Bellevue.
  • The population dead-zones in King County are the Green/Duwamish River industrial area, Sea-Tac airport, and the Bridle Trail area between Bellevue and Kirkland.
  • King County has lots of room to accept new people.  There is no reason develop virgin forest or farmland on the urban fringe, until this map has a lot more yellow.

Sources: U.S. Census Bureau, King County GIS, WSDOT

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I have finally learned enough GIS to create maps from the recently released Census 2010 data.  Below is a map of the population density of the City of Seattle.  The map is drawn at the level of Census Block Groups (smaller than census tracts).  The five most densely populated census block groups in Seattle are:

1. 80.01 Group 5 (Belltown): 110,810 ppl/sq. mi.
2. 80.01 Group 4 (Belltown): 67,489 ppl/sq. mi.
3. 74.02 Group 3 (Capitol Hill): 65,855 ppl/sq. mi.
4. 53.01 Group 1 (U District): 64,672 ppl/sq. mi.
5. 53.02 Group 1 (U District): 61,854 ppl/sq. mi.

Sources: U.S. Census Bureau, King County GIS, WSDOT

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How methods shift perception of population growth

The Seattle Times recently reported on 2010 census data by tabulating the “fastest growing” cities in Washington State and writing a feature about Snoqualmie, on the top of the list at 396% growth since 2000. As with many media outlets, they ranked areas based on percentage growth, not absolute numbers of people.  In the table below are the 10 fastest growing cities, ranked on percentage growth as printed in the Seattle Times.

10 Fastest Growing Washington Cities Ranked by Percent Growth

Footnote: Percentages based on initial 2000 census data. Seattle Time table based on adjusted 2000 census data.

Note that most of these towns are rather small.  It is easy to grow by 200% if you start out at a population of 2,000.  You may not have heard of many of these towns. But if you looked them up on a map, you would see that most of these towns are on the urban fringes of the Seattle-Tacoma metro area. The takeaway could easily be that urban sprawl and small town living are very popular.  Policies such as growth management have failed, and most people have chosen with their feet to move to the exurbs.

But what if we ranked “fastest growing” cities by the number of people that moved in?  In the table below the top 10 cities in Washington state for 2000 to 2010 population increase are listed.

10 Fastest Growing Washington Cities Ranked by Total Growth

This list is very different from the first list.  The three cities that appear in both lists are highlighted.  Larger cities may add a lot of new residents, but their percentage growth is less than small towns because they started from a larger base.  Yet, one more modification is needed to accurately compare growth between cities.  Some of the cities in this list, such as Marysville, increased in population mostly due to annexations of adjacent previously populated areas.  Washington State keeps records of populations of annexed areas, so I subtracted these populations from the population increase reported in the 2010 Census.  In the table below the 10 fastest growing cities in Washington State are ranked based on population increase, excluding annexations.

10 Fastest Growing Washington Cities Ranked by Total Growth, Annexations Excluded

Now the list of the fastest growing cities is similar to a list of the largest cities in the state.  Only one city, Issaquah, an outer Seattle suburb, remains from the original list.  The City of Seattle tops the list as fastest growing.  Tacoma is notably absent, but large cities in other parts of the state grew strongly.  Two of the three tri-cities are listed, Kennewick and Pasco.  So are Spokane and Vancouver, the Portland metro’s second city.  In the Seattle metro area, the fastest growing suburbs are established (and affordable) middle-ring suburbs such as Renton, Kent and Auburn.  The takeaway from this list is different from the first list: most people moved to large towns and suburbs; and the most of all moved to Seattle, the fastest growing city in the state.

Please keep in mind, when developing stats, do you want to calculate magnitude of growth, or magnitude of growth compared to the initial base?  If the former, look at absolute numbers not percentages.

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