Puget Sound Mapping Project - Washington State Department of Commerce

Growth rates slowed markedly during the recession and only recently started to match pre-recession rates. King County has captured almost half of the region’s new housing units between 2000 and 2017.  Snohomish and Pierce County have also seen high levels of growth. Within the region’s rural areas, growth has clustered within a few miles of the urban growth boundaries.

Increasing populations and development typically results in loss of vegetation and increased impervious surfaces (pavement and buildings). Increases in impervious surfaces reduces the amount of water that is naturally absorbed into the ground and reduces the amount of ground water available for drinking.  Impervious surfaces also increases run-off of contaminants like fertilizers and pesticides to rivers, lakes and the ocean, reducing the amount and quality of water that is available for people, aquatic life, and wildlife. Threats to water quality challenge our best efforts to reduce impacts of urbanization.

One of the Puget Sound Partnership’s Vital Sign recovery targets for 2020 is to focus at least 85% of regional growth within urban areas (and to protect rural areas by limiting rural development less than 15% of the overall total). As of 2017, the region is meeting this goal, with less than 10% of growth occurring in rural areas over the past few years.  However, recently, as growth continues to increase, development is starting to shift to rural areas, and some counties are experiencing rural development rates at or above the Puget Sound Target. Go here for line graph.

Dept. of Ecology’s Watershed Characterization Project designated approximately 3,000 “Watershed Characterization Assessment Units” (AUs) throughout the Puget Sound and evaluated these areas for their value for restoration and protection. Overall, our mapping indicates that these AUs saw the creation of 430,316 new housing units between 2000 and 2017; or an increase of just over 26%. Areas of high housing growth outside of urban growth boundaries are broadly associated with coastal plains near cities, within the valleys of the Cascade Mountains and near freeways, highways or major roadways. A map of growth within Ecology’s AUs shows a broad depiction of growth patterns.

In 2017, our region-wide mapping analysis indicates that most housing development within urban growth areas, has occurred primarily in Intensive Urban (12,748 units) and Urban Character Residential (6,276 units) land use categories.  In rural areas, the Rural Character Residential (1,589 units) land use category has experienced the most growth. Other land use categories accounted for 463 new units. Mixed Use and Commercial Area growth rates are increasing with 2017 rates exceeding the annual average rate from 2000-2017. In addition, Low Density Urban Residential (1.1-3 Units/Acre) areas also saw higher rates in 2017 than the long-term average annual rate. Click here to see a graph on the amount of growth happening in rural areas.

Most of the region’s urban growth is occurring in Seattle, Bellevue, Everett and Tacoma and their proportion of regional growth appears to be increasing. In addition, large master planned communities such as the Issaquah Highland, Snoqualmie Ridge and Redmond Ridge show intensive new housing growth. In the southern portions of the region, Joint Base Lewis-McChord (JBLM), Frederickson and Puyallup are experiencing the heaviest housing production. Mill Creek, Alderwood, Marysville, and Lake Stevens are more recent heavy growth counterparts on the northern end of the region. Whatcom, Skagit, Kitsap, and Thurston counties are also showing strong yearly increases in both rural and urban areas. In other counties, such as Clallam, Island, Jefferson, Mason, and San Juan, rural development is occurring at a rate similar to (or higher than) urban development levels.

One of the Puget Sound Partnership’s Vital Sign recovery targets for 2020 is to focus at least 85% of regional growth within urban areas (and to protect rural areas by limiting rural development less than 15% of the overall total). As of 2017, the region is meeting this goal, with less than 10% of growth occurring in rural areas over the past few years.  However, recently, as growth continues to increase, development is starting to shift to rural areas, and some counties are experiencing rural development at rates at or above the Puget Sound Target. Go here for line graph.

An Excel table of housing estimates for each polygon provides the ability to summarize statistics by years, or groups of years, by a number of geographic boundaries. These boundaries include city/county name, urban/rural status, watershed analysis, and land use subcategory.

Within the table, the abbreviation “HU” indicates housing units as identified by the Washington State Office of Financial Management Small Area Population Estimates.

“HU_2000” indicates the number of housing units located within the polygon in 2000.  “HU_2001” indicates the number of housing units in 2001, and so on. Columns that contain fields listed as “NEW” mean the number of new units constructed between indicated dates, for example, “NEW_00_10” means units constructed between 2000 and 2010.  Similarly, columns headed by the abbreviation “PCT” means the percentage increase in the number of units over that period.  While the full name of the field does not show on the web display, it will be fully visible by maximizing column width after download.

Base units (those existing pre-2000) can be calculated by dividing the net new units by percentage change – for example if 1,500 new units occurred between 2000 and 2010 and the percentage change was 66.67 percent then the base units would be 2,250 (1,500/.6667 = 2,250).

“FID” represents the attribute table ID number.  “MASTER_CAT” and “SUB_CAT” correspond to the master and sub land-use category designations for that polygon while “SUB_CAT_1” shows polygons with active land uses (minus water, rights-of-way, undesignated, etc.).  The column entitled “URB” indicates the polygons location within a Growth Management Act designated urban area.  The “CITY_NM” column indicates the city, if applicable, and “NAME” provides the information on the county in which the polygon is located. “AUPolyID” provides the WRIA Watershed Characterization Project Assessment Unit number in which the Polygon is located.  The “LUCodeID” and “SubCID” fields correspond to polygon identification numbers contained in the attribute table for the housing unit map layers.