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Archive for March, 2011

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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Spokane Street Viaduct Projects (Source: Seattle DOT)

In the wake of the Tohoku Earthquake in Japan, Seattle’s mayor and the Seattle Times’ Danny Westneat suggested closing the earthquake-damaged SR 99 Alaskan Way Viaduct sooner rather than later.  From Westneat’s column in the Times:

Living without one of our main north-south highways might finally bring the gridlock-apocalypse they’re always predicting.  What has hung up the viaduct project for a decade is that nobody knows. Some experts and studies say we can live without a waterfront highway. Others say as assertively that we can’t.

It is a counter-intuitive fact that several cities have removed urban freeways without signficant effects on auto traffic elsewhere, while improving the overall quality of life in the city.  I am on record in a previous post with my belief that freeways are detrimental to cities, and not precisely necessary. 

However, as we know from weekend closures of the Alaskan Way Viaduct, including the one this weekend, a level of gridlock occurs on surrounding freeways and on surface streets into downtown.  If the viaduct clousre were to extend beyond the weekend into weekdays, even worse disruption would occur.  A reasonable response for viaduct commuters  would be to switch to public transit.   For mobility to be maintained, transit must have prioritized, congestion-free routes to and from downtown.

If the Alaskan Way Viaduct were closed, as currently configured, West Seattle buses must access downtown through the lower West Seattle bridge and surface streets.  Several West Seattle buses (the 21, 22 and 56) always have, but construction projects related to the (unnecessary) widening of the Spokane Street Viaduct make those  routes so slow and inefficient, they barely qualify as transportation.  From 1st Ave. these routes turn onto S. Hanford St. across railroad tracks (frequently blocked by trains), and then across the lower West Seattle Bridge (frequently raised to allow ships passage).

It would be irresponsible to semi-permanently close the viaduct until these projects are in place:

  • Complete the new 1st Ave. on-ramp to the upper West Seattle bridge (scheduled for Fall 2011)
  • Provide a continuous transit lane, with signal priority from the 1st Ave. exit from the West Seattle Bridge to the 3rd Ave. transit spine in downtown Seattle.

If, and only if, these items are in place do I support immediately closing the Alaskan Way Viaduct.

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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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