Land Use & Planning Terms#

Cascadia Subduction Zone#

A roughly 1,100-kilometer fault running offshore from northern California to Vancouver Island, where the Juan de Fuca tectonic plate dives beneath the North American plate. The CSZ is capable of producing magnitude 9.0+ megathrust earthquakes. The last full-rupture event occurred on January 26, 1700; USGS estimates a 10-15% probability of another magnitude 9 event in the next 50 years.

Why it matters: A CSZ earthquake would produce prolonged, violent shaking across the entire Puget Sound region and generate a tsunami along the Pacific coast. The Cascadia Rising exercises revealed that federal and state assistance could take days to reach affected areas, leading to revised preparedness guidance recommending two weeks of emergency supplies. The CSZ threat also drives building code updates, infrastructure investments (such as the SR 99 tunnel replacing the Alaskan Way Viaduct), and seismic retrofit programs for unreinforced masonry buildings.

Learn more: USGS Earthquake Probabilities | DNR: Earthquakes and Faults

Comprehensive Plan#

A city’s long-range plan for growth, land use, transportation, parks, and utilities. Required by Washington’s Growth Management Act. Seattle’s comp plan is updated on major cycles (most recently 2024) and guides zoning and investment decisions for 20+ years.

Why it matters: The comprehensive plan is the single most important policy document for Seattle’s future. It determines where growth goes, what gets built, and how the city invests. The 2024 update was a major battleground over density, equity, and neighborhood change.

See also: GMA, Zoning

Learn more: Seattle OPCD: One Seattle Plan | Seattle City Council: 2025 Comprehensive Plan

Concurrency#

A Growth Management Act requirement that infrastructure (roads, water, sewer, schools) must be adequate to serve new development at the time it’s built – or within a set timeframe. Development can be denied if infrastructure isn’t available.

Why it matters: Concurrency requirements can be used to block or delay housing projects if cities claim infrastructure is insufficient. Reform advocates argue concurrency has been weaponized to prevent density. The GMA has been updated to prevent concurrency from being used as a de facto growth moratorium.

See also: GMA, Comprehensive Plan

Learn more: MRSC: Concurrency | WA Commerce: Growth Management Act

Cumulative Impacts#

The combined effect of multiple environmental, health, and socioeconomic stressors on a community. Rather than assessing a single pollution source in isolation, cumulative impacts analysis considers how overlapping hazards — air pollution, contaminated land, proximity to highways, lack of green space, poverty, and poor housing quality — compound health outcomes in neighborhoods already under stress.

Why it matters: Cumulative impacts analysis explains why neighborhoods like Georgetown and South Park face dramatically worse health outcomes than the Seattle average, even though no single polluter may exceed its individual permit limits. A 2013 Cumulative Health Impacts Analysis of the Duwamish Valley found life expectancy 13 years shorter than Laurelhurst, double the youth asthma rate, and only 40 square feet of green space per resident versus 387 square feet citywide. Washington’s HEAL Act (2021) now requires state agencies to consider cumulative impacts in environmental justice assessments, and advocates are pushing for a cumulative air toxics law similar to Oregon’s.

See also: Environmental Racism, EIS, SEPA

Learn more: DRCC: Cumulative Health Impacts Analysis | The Urbanist: Washington State Needs a Cumulative Air Toxics Law

Displacement Risk Index#

A composite mapping tool created by Seattle’s Office of Planning and Community Development (OPCD) that forecasts which neighborhoods face elevated risk of displacing marginalized populations. The index combines five categories of indicators: socio-demographics, transportation qualities, neighborhood characteristics, housing market pressures, and civic engagement levels.

Why it matters: The Displacement Risk Index directly shapes Seattle’s zoning decisions. During the One Seattle Comprehensive Plan debates, the Harrell administration initially proposed using the index to justify lower-density zoning (triplexes instead of fourplexes) in “high displacement risk” areas like the Central District, Rainier Valley, and Lake City. This sparked controversy over whether limiting housing supply actually prevents displacement. The index was updated from its original 2016 version to a 2022 version with improved methodology and responds to House Bill 1220’s requirement that cities evaluate displacement risk and implement anti-displacement policies.

Learn more: Seattle OPCD: Displacement Risk Indicators | The Urbanist: Seattle Releases Comprehensive Plan Less Ambitious Than Bellevue

Embodied Carbon#

The greenhouse gas emissions associated with manufacturing, transporting, and installing building materials — as distinct from the “operational” emissions produced by heating, cooling, and powering a building after construction. Concrete, steel, and aluminum are among the most carbon-intensive materials. Embodied carbon accounts for approximately 11% of global greenhouse gas emissions.

Why it matters: As buildings become more energy-efficient, the share of lifetime emissions attributable to materials grows. Washington passed the Buy Clean Buy Fair Act (HB 1282) in 2024, becoming the first state to require embodied carbon reporting for concrete, steel, and wood in state building projects. The law was informed by research from the University of Washington’s Carbon Leadership Forum. For Seattle urbanists, embodied carbon connects zoning and density debates to climate: denser construction that uses materials efficiently can reduce per-unit embodied carbon compared to low-density sprawl.

See also: BEPS, SEPA

Learn more: WA Commerce: Buy Clean Buy Fair | Carbon Leadership Forum: BCBF Signed Into Law

EIS (Environmental Impact Statement)#

A detailed study of a project’s or plan’s environmental effects, required under SEPA for major actions. Covers traffic, noise, shadow, displacement, and more.

Why it matters: EIS processes can add years and millions of dollars to projects. They’re an important environmental protection but also get used strategically to delay development or infrastructure. Understanding when an EIS is required helps you follow major project timelines.

See also: SEPA

Learn more: WA Ecology: Overview of SEPA

Environmental Racism#

The disproportionate siting of environmental hazards — polluting industries, highways, waste facilities, and contaminated land — in communities of color, and the systemic exclusion of those communities from environmental decision-making. In Seattle, environmental racism is inseparable from the history of redlining and racially restrictive covenants that confined communities of color to specific neighborhoods, which were then targeted for industrial zoning and highway construction.

Why it matters: The Duwamish Valley — Georgetown and South Park — is Seattle’s clearest example. The neighborhood is approximately 70% people of color, hosts a federal Superfund site, sits at the intersection of three freeways, and has life expectancy 13 years shorter than Laurelhurst. A 2023 UW study found that modern air pollution disparities in Seattle mirror the 1936 HOLC redlining maps. Understanding environmental racism connects seemingly separate policy areas — zoning, transportation, environmental regulation, and public health — and is the foundation of Seattle’s environmental justice programs including the Duwamish Valley Program and Environmental Justice Fund.

Learn more: Seattle.gov: Equity and Environment Initiative | The Urbanist: Community Development Counters Eco-Gentrification from Duwamish Valley Cleanup

Equitable Transit-Oriented Development (ETOD)#

A planning approach that combines transit-oriented development with explicit anti-displacement and community ownership strategies. Unlike conventional TOD, which focuses primarily on density near transit, ETOD prioritizes removing speculative pressures, banking land for community ownership early, and ensuring existing residents benefit from transit investments.

Why it matters: Seattle launched an ETOD initiative in response to displacement pressures that followed light rail expansion through the Rainier Valley. The City is leveraging a $1.75 million Federal Transit Administration grant to apply ETOD principles to the West Seattle and Ballard Link Extension corridors. ETOD represents a shift in how Seattle approaches station area planning – rather than letting the market determine who benefits from transit investments, ETOD seeks to proactively acquire land for affordable housing and community facilities before speculation drives up prices.

Learn more: Seattle OPCD: Equitable Transit Oriented Development | The Urbanist: State Must Pass Transit-Oriented Housing Rules Prioritizing Equity

Form-Based Code#

A zoning approach that regulates building form (height, setbacks, facade design) rather than use (residential, commercial, industrial). Emphasizes how buildings relate to streets and public spaces rather than what happens inside them.

Why it matters: Traditional use-based zoning separates housing from shops and offices, creating car-dependent sprawl. Form-based codes allow mixed uses while ensuring buildings create good streetscapes. Seattle hasn’t fully adopted form-based code, but elements appear in design guidelines and recent zoning reforms.

See also: Zoning, Design Review

Learn more: MRSC: Development Regulations and Zoning | Form-Based Codes Institute

GMA (Growth Management Act)#

Washington state law (1990) requiring urban areas to plan for growth, protect rural land, and provide infrastructure. Mandates comprehensive plans and urban growth boundaries.

Why it matters: The GMA is why Seattle has to plan for growth rather than sprawling indefinitely. It’s the legal framework behind comprehensive plans, urban growth boundaries, and concurrency requirements. Recent GMA updates have pushed cities toward more housing production.

Learn more: MRSC: Growth Management Act Basics | Sightline: Seattle, a Model for Low-Sprawl Urban Growth

Landmark District#

A geographically defined area designated by the Seattle City Council to protect the architectural character and historic integrity of a neighborhood. Each of Seattle’s eight landmark districts has its own review board or committee and set of design guidelines. Any exterior changes to buildings within a district require a Certificate of Approval from the review board. Seattle’s eight districts are Pioneer Square (1970), Pike Place Market (1971), International District (1973), Ballard Avenue (1976), Columbia City (1978), Harvard-Belmont (1980), Fort Lawton (1988), and Sand Point (2011).

Why it matters: Landmark districts regulate what can be changed in some of Seattle’s most historically significant neighborhoods. The Certificate of Approval process adds a layer of review beyond standard building permits, which can affect project timelines and costs. Properties within designated landmark districts are exempt from SHB 1576’s owner-consent requirement, meaning the districts themselves remain protected even as the state limits new individual landmark designations.

See also: Zoning, SDCI, Unreinforced Masonry (URM)

Learn more: Seattle DON: Historic Districts | The Urbanist: Legislature Wants to Rein In Historic Landmarking

MUP (Master Use Permit)#

Seattle’s combined land use permit that bundles zoning approvals, environmental review, and design review into a single application. Required for most new construction and major alterations.

Why it matters: The MUP process is where most development projects get approved (or denied). Understanding MUP timelines and requirements helps advocates track projects in their neighborhoods. MUP decisions can be appealed, making them a key intervention point for both supporters and opponents of development.

See also: Design Review, SEPA

Learn more: Seattle SDCI: Land Use Division | Seattle SDCI: How to Get a Permit

Liquefaction#

A phenomenon in which water-saturated, loosely packed soil loses its strength during earthquake shaking and behaves like a liquid. Buildings, roads, and utilities on liquefied ground can sink, tilt, or collapse. About 15% of Seattle’s total land area is prone to liquefaction, primarily in areas built on artificial fill over former tideflats and estuaries.

Why it matters: Seattle’s most vulnerable liquefaction zones – SODO, Georgetown, Pioneer Square, Interbay, and portions of Rainier Valley – contain critical transportation corridors (I-5, SR 99), rail and marine terminals, and Boeing Field. During the 2001 Nisqually earthquake, SODO experienced pervasive liquefaction including sand boils and ground cracking. SDCI updated Seattle’s liquefaction-prone area map in 2023, and the Growth Management Act requires cities to identify and regulate development in geologically hazardous areas including liquefaction zones.

Learn more: Seattle OEM: Earthquake Hazards | DNR: Geologic Hazard Maps

Middle Housing Model Ordinance#

A state-created zoning code developed by the Washington Department of Commerce that automatically supersedes local regulations if cities fail to comply with HB 1110’s middle housing requirements by their deadline. The model ordinance establishes development standards for duplexes through sixplexes, townhouses, courtyard apartments, cottage housing, and stacked flats.

Why it matters: The model ordinance acts as a “default” code that creates a floor for housing capacity statewide. For Seattle, the compliance deadline was June 30, 2025. If the city hadn’t adopted compliant regulations, Commerce’s model code would have automatically taken effect – and housing advocates noted it was actually more generous than Seattle’s initial proposals. The final 2024 model code allows buildings roughly 80% larger than what Seattle proposed, with more flexible setbacks, lot coverage, and floor area ratios. This dynamic – where the state’s backstop code is more permissive than local proposals – has reshaped negotiations between cities and housing advocates.

See also: HB 1110, Missing Middle Housing, GMA

Learn more: WA Commerce: Planning for Middle Housing | The Urbanist: State Improves Model Code to Promote Middle Housing

Neighborhood Centers#

A new land use designation in Seattle’s One Seattle Plan, applied to approximately 30 locations where existing small commercial districts provide anchors for surrounding residential areas. Neighborhood Centers receive modest zoning increases extending about 800 feet (1-3 blocks) from commercial cores.

Why it matters: Neighborhood Centers represent a shift from concentrating all growth in urban villages. They’re intended to bring small-scale density and walkable amenities to more neighborhoods. The designation has been contentious, with debates over which areas should be included and how much density to allow.

Learn more: Seattle OPCD: One Seattle Plan | The Urbanist: Op-Ed on Neighborhood Centers

Pedestrian Zone (P-zone)#

A zoning overlay applied to Neighborhood Commercial (NC) zones that designates an area as “an intensely retail and pedestrian-oriented shopping district where non-auto modes of transportation to and within the district are strongly favored.” Pedestrian zones prohibit drive-through lanes, restrict parking to behind buildings or within structures, and discourage driveways crossing sidewalks on principal pedestrian streets. Seattle had 33 P-zones before a 2015 expansion (Ordinance 124770) added or expanded the designation in 42 neighborhoods, bringing the total to roughly 73.

Why it matters: P-zones are the city’s strongest zoning tool for maintaining walkable commercial character. They directly shape what new development looks like at street level — ensuring that buildings front the sidewalk with active uses rather than parking lots or blank walls. When a neighborhood’s commercial area has a P-zone designation, auto-oriented businesses like drive-throughs and gas stations are prohibited, and new construction must create a pedestrian-friendly streetscape. Understanding P-zone designations helps advocates evaluate whether proposed developments are compatible with their neighborhood’s commercial character.

See also: Neighborhood Centers, Zoning, Form-Based Code

Learn more: Seattle OPCD: Pedestrian Retail Areas | The Urbanist: A Big Revision: Seattle’s Pedestrian-Oriented Commercial Districts

PSRC (Puget Sound Regional Council)#

The federally designated Metropolitan Planning Organization (MPO) for the four-county central Puget Sound region (King, Snohomish, Pierce, and Kitsap counties). PSRC coordinates regional growth planning through VISION 2050, allocates approximately $300 million per year in federal transportation funding, and adopts the Regional Transportation Plan. PSRC has more than 100 member entities including counties, cities, tribal nations, transit agencies, and port districts.

Why it matters: PSRC shapes where growth goes in the region through VISION 2050’s growth targets, which every city’s comprehensive plan must accommodate. Its control over federal transportation dollars gives it significant influence over which projects get built. For urbanists, PSRC’s planning processes – especially the Regional Transportation Plan updates and federal funding competitions – are key intervention points for advocating for transit, bike, and pedestrian investments.

Learn more: PSRC | The Urbanist: Vision 2050 Has Passed

Regrade#

A large-scale earthmoving project that lowers or levels terrain by cutting away hillsides, typically using hydraulic hoses, steam shovels, or conveyor systems. Between the 1890s and 1930s, Seattle carried out roughly 60 regrades that moved more than 50 million short tons of earth. The largest was the Denny Regrade (1897-1930), which lowered Denny Hill by over 100 feet across 62 city blocks. Other major regrades included Jackson Street (85-foot cut) and Dearborn Street (112-foot cut). The excavated material was used to fill tideflats, extend the waterfront, and build Harbor Island.

Why it matters: The regrades created much of the flat, buildable land that forms Seattle’s modern downtown, Belltown, SoDo, and the Chinatown-International District. They also created land built on fill that is now prone to liquefaction during earthquakes — a direct concern for seismic retrofit planning and new construction in Pioneer Square, SoDo, and Interbay. Understanding the regrades explains why Seattle’s topography abruptly changes between neighborhoods and why certain areas face elevated seismic risk.

See also: Liquefaction, Landmark District

Learn more: HistoryLink: Denny Regrade | The Urbanist: Seattle’s Long-Forgotten Hill

Regional Centers / Urban Centers#

The new hierarchy of growth centers in Seattle’s One Seattle Plan. Regional Centers (Downtown, Northgate, University District, etc.) are the most intensive growth areas. Urban Centers are the next tier, including places like the Central District, Fremont, and Columbia City. These replace the old “urban center” and “hub urban village” designations.

Why it matters: The center hierarchy determines where the most growth goes and what zoning is allowed. Regional Centers will see the tallest buildings and most intensive development. Understanding which tier your neighborhood falls into helps predict future changes and advocacy opportunities.

Learn more: Seattle OPCD: One Seattle Plan | The Urbanist: Seattle Releases Comprehensive Plan

SDCI (Seattle Department of Construction and Inspections)#

The city agency that issues building permits, enforces codes, and administers design review. Formerly called DPD (Department of Planning and Development) until a 2016 reorganization.

Why it matters: SDCI is the agency you’ll interact with for any building project, from ADUs to apartment towers. Understanding SDCI’s processes, timelines, and decision-making helps navigate the permit system. Their online permit portal lets you track projects in your neighborhood.

See also: Design Review, MUP

Learn more: Seattle SDCI | Seattle SDCI: Permit Portal

SEPA (State Environmental Policy Act)#

Washington’s environmental review law. Requires government agencies to evaluate environmental impacts before approving projects, plans, or permits.

Why it matters: SEPA review is a common step in development and planning that can significantly affect timelines. It’s also a tool that community members can use to raise concerns about projects. Knowing what SEPA covers helps you participate meaningfully in public comment periods.

Urban Growth Boundary (UGB)#

A line on the map separating urban areas (where growth is directed) from rural areas (which are preserved). King County’s UGB limits sprawl and concentrates development.

Why it matters: The UGB directs growth into urban areas rather than allowing outward sprawl. It directly shapes the density debates within city limits. A Sightline Institute analysis found that between 2000 and 2020 the Seattle metro added roughly one million residents with a larger share of that growth occurring as urban infill than any other large U.S. metro – evidence that Washington’s UGB framework is working as intended.

See also: GMA, Comprehensive Plan

Learn more: King County: Urban Growth Capacity Report | MRSC: Growth Management Act Basics

Urban Village#

Seattle’s planning designation for neighborhood centers that are targeted for growth. Includes hubs like Capitol Hill, the U-District, and Ballard, as well as smaller “residential urban villages.” Created in the 1994 comprehensive plan.

Why it matters: Urban villages have been the framework for where Seattle directs growth for 30 years. A Sightline Institute analysis found that this approach helped Seattle achieve the highest rate of urban population growth among large U.S. metros from 2000 to 2020, with neighborhoods like South Lake Union quintupling in population through infill rather than sprawl. The 2024 comp plan update is shifting away from this model toward more distributed growth, which is a significant conceptual change.

See also: Comprehensive Plan

Learn more: Seattle OPCD: One Seattle Plan | Seattle 2035 Comprehensive Plan

Urban Heat Island#

The phenomenon where urban areas experience significantly higher temperatures than surrounding rural or less-developed areas due to the concentration of heat-absorbing surfaces — buildings, roads, parking lots, and rooftops — combined with reduced tree canopy and vegetation. In Seattle, heat mapping data shows that formerly redlined neighborhoods with less tree canopy and more impervious surfaces are consistently the hottest areas of the city.

Why it matters: A 2020 Seattle/King County heat mapping study documented large temperature disparities across the city: 54% of Seattle residents live in areas that are at least 8°F warmer than surrounding areas. During the June 2021 heat dome, when temperatures reached 108°F in Seattle, heat-related deaths were concentrated in older buildings without air conditioning in the city’s hottest neighborhoods. Urban heat island data now guides the city’s tree planting priorities and cooling infrastructure investments. Understanding the urban heat island effect connects climate adaptation, tree canopy, environmental justice, and public health.

Learn more: Seattle Trees: Urban Heat | Axios Seattle: Heat Islands

Unreinforced Masonry (URM)#

A building constructed of brick, stone, or concrete block without steel reinforcement or structural connections between walls, floors, and roof. Most URMs in Seattle were built before 1945. During earthquakes, URM walls can separate from floor and roof structures and collapse outward. Seattle has approximately 1,100 identified URMs housing over 22,000 people.

Why it matters: URMs are the most dangerous building type in earthquakes and the focus of Seattle’s most significant seismic safety policy debate. The city adopted a voluntary retrofit code in November 2024 and plans to adopt a mandatory retrofit ordinance with compliance timelines of 7-13 years. Pioneer Square and the Chinatown-International District contain a concentration of URMs, many housing affordable units and small businesses. The retrofit program intersects with historic preservation, affordable housing, and equitable development – retrofitting these buildings is essential for preserving both lives and neighborhood character.

See also: Cascadia Subduction Zone, Liquefaction, SDCI

Learn more: Seattle SDCI: URM Buildings | ASAP! Coalition

Zoning#

Government rules that dictate what can be built where – building height, density, use (residential, commercial, industrial), setbacks, lot coverage, etc.

Why it matters: Zoning is the fundamental tool that shapes what Seattle looks like. Almost every land use debate comes down to zoning. If you understand zoning basics, you can follow most development controversies.

See also: FAR, Upzoning, Comprehensive Plan

Learn more: Seattle SDCI: Codes | Seattle Interactive Maps (includes zoning layers)

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