Seattle’s planning system nowadays is characterized by a high number of (informal) visions and strategies approved by politics as well as regular plan updates under broad community participation. The element of mandatory plans became more important because the Washington State Growth Management Act passed in 1990 demands comprehensive land use plans that anticipate growth and impact for a 20-year horizon and are updated regularly (King County 2013, see Figure 13.2).
Today, around 3.4 million people live in the Seattle metropolitan area (U.S. Census Bureau 2010). The population density stands at 2866 people/km2, and the share of parks and open space is 14%. For the larger central Puget Sound region, growth to five million people by the year 2040 is forecasted (Department of Planning and Development n.d.). Further challenges the city faces are storm-water management, salmon recovery, and carbon emission reduction.