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Complete Streets: How Policy and Design Shape Urban Mobility

Posted on by Otak Staff

Communities thrive with greater connectivity. When this includes a multimodal approach that’s designed to accommodate users of all ages and abilities, it can be referred to as complete streets. The concept redefines the design of roadways to support a more holistic view of mobility, shifting from vehicle dominated corridors to spaces that serve everyone.

Complete streets are uniquely positioned to meet multiple goals at once. Increased public accessibility unlocks opportunities for economic growth, enhanced infrastructure, and improved public health. It not only promotes sustainability with active transportation and green infrastructure but also improvements for motorists with safety and traffic calming features.

Graphic introducing the topic of complete streets.

Comprehensive in nature, a complete streets policy can also be complex in its implementation. Each community has its own needs, constraints, and priorities, meaning complete streets must be thoughtfully tailored to their context.

In this blog, we’ll explore what complete streets are, the common elements that make them effective, and the process of creating policies leading to projects that bring them to life.

What Are Complete Streets?

Complete streets are an approach to planning, designing, building, operating, and maintaining streets that enable safe access for people of all ages and abilities. Rather than focusing primarily on vehicular traffic, this approach considers how all users interact within the transportation network to increase efficiency throughout.

At its core, complete streets emphasize multimodal transportation. This means integrating infrastructure for pedestrians, cyclists, transit users, and motorists while also adding improvements to infrastructure like stormwater management. The goal is to create streets that are not only functional but also inviting and efficient, improving both mobility and overall environment within a corridor.

Examples of Complete Streets Design Features

Complete streets incorporate a variety of design features that work together to improve access to businesses, essential services, and public spaces. This often leads to comprehensive improvements along a corridor impacting multiple aspects of public infrastructure.

Tualatin Moving Forward Transportation Bond

Aerial view of an intersection along the Boones Ferry Corridor.

Boones Ferry Corridor Improvements

A two-mile corridor is improved with practical, cost-effective solutions that enhance bike and pedestrian access.

Image of the completed redesign of the Martinazzi Avenue intersection as part of the Tualatin Moving Forward Bond Program.

Martinazzi & Sagert Intersection

Increased traffic capacity is combined with protected bike lanes and widened sidewalks as part of improved overall operations.

View of a pedestrian crosswalk and landscape as part of pedestrian safety improvements around Tualatin Elementary.

Tualatin School Pedestrian Improvements

Removal of barriers to students biking and walking to Tualatin Elementary also reduces roadway congestion in the area to improve safe routes to school.

The Sandalwood Swale from the adjacent sidewalk with signage describing the water quality facility.

Sandalwood Swale

To account for added impervious surfaces across the Tualatin Moving Forward Bond Program, a vegetated swale is designed to treat stormwater in the area with green infrastructure.

Roadways

Roadways can often be barriers to broader accessibility. While complete streets place less priority on a community’s vehicular traffic, improving roadways for their use is no less important. Taking a wider perspective, the design often seeks to reduce overreliance on cars, improving safety and traffic for everyone in the area.

Features such as wider shoulders, curb extensions, and roundabouts are commonly used to calm traffic and reduce speeds. These elements enhance safety for both drivers and pedestrians while maintaining efficient road diets. The result is a roadway that’s safer and more integrated with other modes of transportation, removing barriers for all.

Sidewalks, Bike Lanes, and Multiuse Paths

Active transportation infrastructure is a defining feature of complete streets. Sidewalks, bike lanes, and multiuse paths are designed to create safe and convenient options for people who walk, bike, or use growing forms of micromobility.

Municipal policies often guide these features, such as requiring sidewalks of a certain width along new developments. Increasingly, designers must also account for emerging transportation modes like e-bikes and e-scooters, as well as designated spaces for rideshare services that do not disrupt traffic flow. These improvements benefit local businesses by increasing accessibility and walkability. When people can reach shops and services without a car, it expands the customer base and enhances the overall experience of an area.

Accessibility is essential to this goal. Features like pedestrian bridges, median islands, and well-marked crosswalks with updated signals help ensure that streets are safe and usable for individuals of all abilities.

Laporte Avenue Multimodal Improvements

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A community’s multimodal goals are brought closer to reality with a transportation design that utilizes sustainable materials and preserves historic landmarks.

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Transit Stops and Bus Lanes

Public transit plays a vital role in complete streets. Integrating transit options such as bus rapid transit or light rail helps reduce congestion and provides reliable alternatives to driving.

Dedicated bus lanes can improve efficiency by allowing transit vehicles to bypass traffic, making service faster and more predictable. Equally important are the transit stops themselves. Comfortable, accessible, and well-designed waiting areas can significantly improve user experience and encourage more people to use mass transit. Providing adequate space for waiting passengers, along with amenities like seating and shelter, contributes to a more welcoming and functional system.

People at the Lynnwood Community Transit Bus Rapid Transit Orange Line station.
Swift Bus Rapid Transit – Orange Line
A station and surrounding landscape as part of the Community Transit bus rapid transit green line.
Swift Bus Rapid Transit – Green Line

Stormwater Infrastructure

While it may not be the first thing that comes to mind with transportation, stormwater infrastructure can be one of the most important features. As with any roadway, complete streets must effectively manage water runoff, especially as these new developments can increase impervious surfaces, or change existing conditions.

These requirements can lead to opportunities to integrate green stormwater infrastructure solutions. A nature-based design approach may use features such as vegetated swales and rain gardens to not only manage water efficiently and with low impact, but also to enhance the environment of a corridor.

Gateway to Boulder (SH119)

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A complex multimodal design for adds roadway durability, green stormwater infrastructure, and a variety of park amenities for the growing communities outside Boulder, Colorado.

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Parks and Green Space

Complete streets often connect to parks, trails, and other recreational areas, expanding their reach and usefulness. By linking neighborhoods to regional trail systems, these projects can improve mobility across larger areas.

Green spaces add recreational value while also supporting environmental functions like stormwater management. Amenities such as bike racks, benches, and open spaces create new opportunities for alternative transportation and outdoor community activity.

Creating a Complete Streets Policy

Implementation of a complete streets design begins with a complete streets policy. This process, which can often take shape through comprehensive planning, establishes a framework for how streets will be planned and designed, ensuring consistency and alignment with community goals.

Because every community is different, policies must be flexible and context-sensitive, reflecting local priorities and conditions. There are several essential elements to that effort.

Lynnwood Comprehensive Plan

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A vision is set, based on extensive public engagement, with policy designed for two decades of community growth focused on multimodal development of a vibrant downtown core.

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Build a Team of Stakeholders

A successful complete streets initiative begins with assembling a diverse group of stakeholders. This often includes neighborhood organizations, government agencies, elected officials, public safety advocates, business groups, and design professionals.

Property owners are especially important to be involved, as they may be directly impacted by changes. Early collaboration helps identify concerns, build consensus, and create a shared vision for the project.

Align Regulation and Requirements

Regulations can play a significant role in shaping complete streets policies. Municipalities might require a minimum sidewalk width around redevelopment or have a Vision Zero policy directed at eliminating transportation related injury and deaths.

These requirements can not only guide design decisions but also be used to advance complete streets initiatives that enhance safety. Shifting responsibility toward system designers, such as engineers and policymakers, the focus moves to safe speeds, forgiving infrastructure, and equitable, data-driven actions, rather than relying solely on individual behavior.

Identify Deficiencies and Opportunities

From an engineering perspective, the design process begins with evaluating existing conditions. Identifying gaps, from missing sidewalks and inadequate transit stops to a lack of bike infrastructure, helps define priorities and opportunities for improvement.

Designers must also account for constraints like existing utilities, walls, and right-of-way limitations. Traffic data and modeling can inform decisions about lane configurations, including opportunities for road diets or additional capacity where needed.

McGilchrist Street Arterial Improvements

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A corridor analysis leads to a multi-phase design aimed at adding traffic calming and encouraging active transportation while also addressing several stream crossings to improve flooding and fish passage in the area.

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Community Engagement

Engaging the community is essential to creating successful complete streets. Public input helps identify desired features, anticipate how spaces will be used, and build support for the project.

Engagement can range from working with key stakeholders to broader public outreach efforts. Ultimately, incorporating community feedback ensures that the final design reflects the needs and values of the people it serves.

A Multidisciplinary Approach to Complete Streets and Vibrant Communities

Complete streets represent a shift toward safer, more connected, and sustainable transportation systems. They’re designed to safely accommodate pedestrians, cyclists, transit users, and motorists by integrating multimodal infrastructure, accessibility features, green spaces, and stormwater management. With thoughtful policies formed through a diverse set of stakeholders, these solutions are tailored to each meet the local needs of a community.

The approach ultimately helps foster neighborhoods where people of all abilities benefit from more vibrant, functional, and inviting environments for generations into the future.

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Stormwater and Transit Designs Earn ACEC WA 2026 Engineering Excellence Awards

Images of the Monroe Ave Stormwater Facility team and Swift Bus Rapid Transit team at the 2026 ACEC WA awards event.
The Monroe Ave Stormwater Facility team [right] and Swift Bus Rapid Transit team [left] at the 2026 ACEC WA awards event.
As major enhancements to their communities, two Otak projects were honored at the 2026 American Council of Engineering Companies (ACEC) WA awards ceremony for making a positive impact in distinctly different ways. The Monroe Avenue Stormwater Facility earned a Gold Award for its innovative application of techniques to deliver a unique piece of green stormwater infrastructure while the Swift Bus Rapid Transit Orange Line earned a Silver Award for its social, economic, and sustainable design.

As an organization committed to advancing the industry, ACEC holds the annual awards to recognize engineering firms for projects that demonstrate an exceptional degree of innovation, complexity, achievement, and value. A closer look at these two projects, adding to a list of award-winning work, and their impact on surrounding communities can be found below.

Monroe Avenue Stormwater Facility – Gold Award: Uniqueness and/or Innovative Application of New or Existing Techniques

The Monroe Avenue Stormwater Treatment and Infiltration Facility represents a breakthrough in urban stormwater management and a model for engineering innovation solving long-standing environmental, flooding, and community space challenges within highly developed basins.

Located in the 260-acre Renton Highlands watershed, the project replaced an outdated infiltration pit with a facility designed to manage 100-year storm events, improve water quality, and deliver lasting public benefits. Among its most innovative elements is a multi-layered sediment and pollutant removal ‘treatment train’ engineered to preserve the infiltration capacity of the native soils. Altogether, the project will reduce flooding and improve water quality in the City of Renton for generations to come.

Swift Bus Rapid Transit, Orange Line – Silver Award: Social, Economic, and Sustainable Design

Adding to the state’s first rapid transit system of its kind, the Swift BRT Orange Line is an 11-mile connection between multiple communities in Snohomish County. This expansion of public transportation enhances accessibility for the region’s residents to a variety of vital services as well as economic and social opportunities.

Two Otak Projects Recognized at ACEC OR 2026 Awards

Group photos of the Upper Kellogg Creek and 1st and Strand project teams at the 2026 ACEC awards.
The Upper Kellogg Creek project team [left] and 1st and Strand project team [right] at the 2026 ACEC OR awards.
Multidisciplinary, multi-phase expertise was recognized at this year’s ACEC Oregon awards, with two Otak projects earning honors from the American Council of Engineering Companies Oregon Chapter. Work to reduce flooding by adding green stormwater infrastructure in a unique neighborhood setting was highlighted with a Small Project Award for the Upper Kellogg Creek Capital Improvements, while an Honor Award for the design and planning around 1st and Strand showcased upgrades aimed at growing the downtown waterfront of St. Helens, Washington.

As an organization committed to advancing the industry, ACEC holds the annual awards to recognize engineering firms for projects that demonstrate an exceptional degree of innovation, complexity, achievement, and value. A closer look at these two projects, adding to a list of award-winning work, and their impact on surrounding communities can be found below.

Upper Kellogg Stormwater Management & Capital Improvements – Small Project Award

With a unique application of green stormwater infrastructure in a residential neighborhood setting, work on Upper Kellogg Creek addressed chronic flooding for the surrounding community while also enhancing its natural habitat. Initial capital improvement planning led to a design that connects a restored stream with an updated roadway stormwater system to eliminate the frequency of flooding issues during storm events.

1st and Strand: St. Helens Waterfront – Honor Award

Transforming an old mill site into a walkable, multimodal public space that sets up the downtown St. Helens waterfront for future growth was the basis of a planning effort and subsequent transportation design for the area. A new multiuse path and roundabout along with the added ability to close off a portion of the street for festivals reduces congestion in the area, supporting public use and continued economic growth.

DJC Top 250 List Includes Six Otak Experts in Highlighting Industry Professionals

Graphic introducing the 2025 DJC Oregon Top 250 List.

In celebrating innovators, leaders, and change makers shaping the built environment, the Daily Journal of Commerce (DJC) Oregon Chapter included six Otak experts as part of their annual Top 250 list.

The recognition includes representatives from a variety of groups from across our multidisciplinary expertise and complements a list of award-winning work. Selected solely by the DJC editorial staff, the honor recognizes leaders whose work improving communities in the region stands out for impact, integrity and influence. More information about this year’s members—along with a glimpse into one instance where each has made their mark—can be found below.

 

Kristen Ballou, PE – Senior Civil EngineerHeadshot of Kristen Ballou.

Kristen Ballou, who is also a past recipient of the Women of Vision honor, has been designing increased connectivity for communities at Otak for more than two decades. Her efforts to improve transportation infrastructure have placed a priority on enhancing accessibility, multi-modal features, and an overarching increase in livability.

Boones Ferry CorridorAerial view of an intersection along the Boones Ferry Corridor.
In leading work across projects stemming from the Tualatin Moving Forward bond program, Kristen Ballou was instrumental in finding the efficient multi-modal enhancements that now span the Boones Ferry Corridor. Learn more about the complete approach that overcame challenging site constraints to create a safer environment for the community.

 

Casey McKenna, AIA – Business Unit Leader of ArchitectureHeadshot of Casey McKenna.

With 28 years of experience, Casey McKenna specializes in mixed used, housing, and hospitality projects contributing to Otak’s multidisciplinary work by delivering complex architectural solutions. In developing the growing architecture team, he emphasizes the importance of trust and communication as an essential component to encouraging creative and innovative approaches. Casey’s commitment to his community extends beyond the office, where he is an active member of a local youth football organization.

The Byway at Wood VillageStreet view of part of The Byway and its tower feature.
A common thread among Casey McKenna’s work is an approach to design that aims to incorporate themes from the surrounding area. Learn more about The Byway at Wood Village, a mixed-use development that seamlessly integrates with its place near the base of Mount Hood.

 

Sarah Oaks – Director of Project Management and Construction ManagementHeadshot of Sarah Oaks.

Bridging the gap between project development and public trust, Sarah Oaks has been leading complex capital improvement projects at Otak for nearly a decade. Her wide range of work has been particularly impactful for communities in guiding public safety infrastructure projects and school bonds programs to maximize their value. Sarah is also a past recipient of the Women of Vision Honor and is an active supporter of the Architecture Construction Engineering (ACE) Mentor Program, invested in advancing the future of the industry.

Tigard-Tualatin School District Bond ProgramA classroom within one of the improved facilities from the Tigard-Tualatin School Bond Program.
With a combination of technology, safety, and seismic improvements, Sarah Oaks guided a $350 Million bond for the Tigard-Tualatin School District to maximize the community’s investment in its future. Learn more about the project and how it added and expanded its facilities while also supporting net-zero energy goals.

 

Amanda Owings, PE – Business Unit Leader of Transportation and InfrastructureHeadshot of Amanda Owings.

Dedicated to enhancing community mobility through impactful infrastructure projects, Amanda Owings stands out as a leader within Otak’s multidisciplinary team. Her expertise in transportation is matched by her ability to foster collaboration among the various disciplines to find the best possible solutions. Amanda is a Women of Vision honoree and an active member of the APWA Oregon chapter.

McGilchrist Street Arterial ImprovementsAerial view of an intersection along the Boones Ferry Corridor.
A vital connection for the community of Salem, Oregon, Amanda Owings led efforts to not only improve the major arterial of McGilchrist Street but also the infrastructure and natural habitat it intersects. Learn more about the design of this roadway and its variety of impacts from traffic and flooding to fish passage.

 

Margaret Steinhilber – Senior Project ArchitectHeadshot of Margaret Steinhilber.

Margaret Steinhilber is a leader not only within the Otak architecture group, but also in the firm’s broader efforts to support more sustainable development. She is a WELL Accredited Professional and member of the Green Otak (GO) Committee, bringing together experts across disciplines to collaborate on best practices and internal processes that add resilience in communities. Aside from her design work, Margaret is also a Women of Vision honoree and an active participant in mentoring students as well as volunteering with Lift UP to deliver food to those in need.

Cascade Administrative BuildingView of stadium seating in casino road adaptive reuse project.
The adaptive reuse of 70,000 square-feet within an existing two-story concrete tilt panel building became the new headquarters for Community Transit. Margaret Steinhilber’s design work emphasized employee amenities and an expanded space for a modern work environment. Learn more about the project and  upgrades to several other Community Transit facilities.

 

Saretta Tillmaand – Project ArchitectHeadshot of Saretta Tillmaand.

Saretta Tillmaand is a leader on both architecture projects and the development of future architecture professionals, as a primary stakeholder in the Otak internship program. Saretta’s extensive career in design is matched by her involvement with community service, volunteering for a variety of organizations and connecting colleagues with opportunities to do the same. A previous Women of Vison honoree, her team-focused approach aims to expand opportunities for hands-on experience, maximizing potential for professional growth.

South Cooper MountainView of one of the buildings at Amity Orchards.
Contributing to collective goals around addressing affordable housing within the architecture group, Saretta Tillmaand was vital to the development of South Cooper Mountain. The project included Amity Orchards, three multi-family buildings that add 164 affordable housing units. Learn more about the project and how it is integrated with the surrounding community.

 

Public Introduced to a Daylighted Stream that Supports Habitat and Community Growth

Project stakeholders during the ribbon cutting ceremony for the restored Miller Creek.
Otak project lead, Russ Gaston (far right), during the Miller Creek Restoration ribbon cutting ceremony

A collaborative effort between multiple municipalities and a multidisciplinary Otak team reached a significant milestone last week with a ribbon cutting ceremony at Miller Creek. Stakeholders from Port of Seattle, the Cities of Burien, and SeaTac, gathered alongside project leads to celebrate the completion of 1.4-acres of restored floodplain designed to enhance habitat for endangered salmon and reduce flooding for the surrounding community.

The project is just one piece of the Northeast Redevelopment Area (NERA) where master planning set a vision for economic development near the growing regional airport. In addition to the green stormwater infrastructure and environmental enhancements, the design also opened the area to greater public recreation with access to the regional trail system.

About the Miller Creek Restoration

To support redevelopment of a 162-acre subarea near the expanding SeaTac International Airport, the restoration of Miller Creek improved stormwater capacity, natural habitat, and public use. By daylighting 900 linear feet of a stream that previously flowed through a failing pipe system, the project also adds protection for private property and downstream wetlands from runoff. The restored stream will now also provide important natural habitat for endangered salmon and other aquatic species by bringing it to the surface and removing other barriers to fish passage. These efforts contribute to broader efforts to restore the Puget Sound Watershed.

One of several stakeholders speaking during the ribbon cutting event of Miller Creek.
One of several stakeholders speaking during the ribbon cutting event for the restored Miller Creek.
People walking along the Miller Creek Trail.
People walking along the Miller Creek Trail on a guided tour during its ribbon cutting event.
Developed plan, permitted, and oversaw construction
Graphic with information on this green stormwater infrastructure and it’s place in the natural hydrologic process.

Multimodal Connectivity for an Iconic Colorado City Recognized at 2025 ACEC CO Engineering Excellence Awards

Graphic introducing the 2025 ACEC CO Engineering Excellence Awards with pictures from the event.
Upper Left Image: Kevin Dooley (Left) and Jake Warren (Right) at the 2025 ACEC CO Engineering Excellence Awards

A creative approach to challenging mountain terrain was recognized at the 2025 American Council of Engineering Companies (ACEC) of Colorado event with an Honor Award for the Maroon Creek Trail. The transportation design behind this multimodal path is transformative for the City of Aspen, adding community connectivity while using low impact methods in this environmentally sensitive corridor.

For more than 65 years, the annual ACEC CO Engineering Excellence Awards (EEA) have been highlighting projects that demonstrate an exceptional degree of innovation, complexity, achievement, and value. Learn more about how the Maroon Creek trail met these criteria to enhance mobility, safety, and environmental stewardship in this iconic Rocky Mountain setting.

About the Maroon Creek Multiuse Trail

The Maroon Creek Multiuse Trail provides a safe, non-motorized, and clearly-defined connection throughout the City of Aspen. Integrating with the city’s 22 miles of existing trails, it provides year-round access between the city’s neighborhoods, schools, and downtown core. This includes priority locations such the Aspen Recreation Center transit hub, Aspen Highlands Ski Area, and Maroon Bells Scenic Area. By encouraging walking and biking over vehicle use, this asset supports local climate goals while also reducing traffic congestion.

The trail has become a visible symbol of engineering’s role in promoting active transportation and environmental stewardship. As part of an extensive public engagement, the final design gave careful consideration of adjacent properties while giving priority to community input and ensuring fiscal responsibility. With steep slopes, limited right-of-way, sensitive wetlands, and proximity to a major waterway, the Maroon Creek Trail design addressed a variety of complex challenges. A combination of technical ingenuity and stakeholder collaboration successfully navigated these constraints, including extensive hydrologic modeling and specialized materials to accommodate seasonal freeze-thaw cycles and avalanche-prone areas. A careful balance of roadway separation and physical barriers were part of a creative approach to setting trail alignment in narrow settings.

Otak stakeholders with broader members of the Maroon Creek Trail project team.
Otak stakeholders with broader members of the Maroon Creek Trail project team
Graphic showing a map of the Maroon Creek Trail project area.
Graphic showing a map of the Maroon Creek Trail project area
Image of the Maroon Creek Trail during construction.
The Maroon Creek Trail during construction
View of a pedestrian bridge and one finished portion of the Maroon Creek Trail.
View of a pedestrian bridge and one finished portion of the Maroon Creek Trail

Two Otak ‘Project of the Year’ Awards at APWA OR 2025 Fall Conference

Image introducing the 2025 APWA OR Project of the Year Awards.

The 2025 American Public Works Association (APWA) OR Fall Conference included two presentations by Otak experts and two more award-winning projects for the firm. Project of the Year honors highlighted the transportation design of 1st and Strand and the environmental design for the Springwater Wetland Restoration.

In addition to the accolades, a panel with water resources team leader Phil Kenyon focused on strategies that streamline collaboration between operations and engineering on projects while civil engineer team leader Keith Buisman shared an in-depth look at the design behind the award-winning 1st and Strand project. These sessions were followed by a wine tasting event where all proceeds went toward supporting the APWA Oregon Scholastic Foundation, advancing education opportunities in the industry.

Altogether, this year’s event followed a theme of “Public Works Unmasked.” It placed an emphasis on the details behind the work and ideas that were shared across the event’s activities. A closer look at the two Project of the Year winners can be found below.  

Graphic showing the 1st and Strand project team and project site after winning APWA OR Project of the Year.About 1st and Strand – Project of the Year (Transportation Category: $5 million – $25 million)

Situated along the downtown waterfront, work at 1st and Strand set up the City of St. Helens for continued growth. An initial planning effort was  followed by a transportation design that clearly defines this downtown core, both with infrastructure for growing business in the area and enhancing its use for the community.

Adjacent to City Hall and other public buildings, the streetscape design allows the area to host public events without disrupting traffic. The enhancements improve congestion, parking, and pedestrian access while also extending utilities that create shovel-ready sites for future development.

 

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Graphic showing the Springwater Wetlands project team and project site after winning APWA OR Project of the Year.About the Springwater Wetlands Restoration – Project of the Year (Environmental Category: $5 million – $25 million)

 
A reconnected floodplain was designed to improve flooding for the City of Portland with the restored Springwater Wetlands. This extensive example of green stormwater infrastructure in an urban environment also adds a natural area for natural habitat and public access with connection a regional trail system.
 
The project was informed by complex hydraulic modeling and environmental science to account for historic flooding events. Data from those studies were also used in designing public access amenities and several other community-focused features found throughout the site.
 
 
 
 
 
 
 
 
 
 
 

A Guide to Green Stormwater Infrastructure and the Growing Benefits of Nature-Based Solutions

Posted on by Otak Staff

As urban environments and their infrastructure expand, so do the amount of impervious surface they create. Where rainwater would otherwise naturally find its way into the soil, those surfaces make it so that it is now prevented and diverted by hardened and water-resistant surfaces such as roadways, parking lots, and rooftops. Stormwater planning addresses this issue.

Infographic with features and benefits of green stormwater infrastructure (GSI).

Traditionally, “gray infrastructure” like sewer systems is designed with a single purpose: move water from one place to another as quickly as possible. Over time this approach has led to increasing issues with flooding, erosion, and pollution to local waterways. In response, green stormwater infrastructure (GSI) has risen in popularity to better manage stormwater by utilizing the natural functions of soil and plants.

In this blog we’ll discuss how, by blending nature-based solutions into infrastructure, communities find multiple benefits. Green stormwater infrastructure not only improves the immediate management of runoff but also the long-term resilience of their design.

Read on, or skip ahead:

What is Green Stormwater Infrastructure?

Green stormwater infrastructure (GSI) refers to systems that utilize the inherent qualities of nature-based solutions to improve the management and treatment runoff. Unlike gray infrastructure that consists of only man-made materials such as concrete or steel and is engineered solely to move water, GSI incorporates features that better slow, retain, and filter stormwater through natural processes.

Often involving planting vegetation, reconnecting natural water systems, or using permeable materials, green stormwater infrastructure is designed to replicate the natural hydrological processes by enabling infiltration below ground and evapotranspiration above. This approach treats rainwater as the resource it is rather than as waste while improving flooding, water quality, and a variety of other community benefits that come with a greener environment.

Benefits of Green Infrastructure and Nature-Based Solutions

The advantages of green stormwater infrastructure extend across environmental, social, and economic factors. Aside from obvious benefits to community flooding and natural habitat, this approach is also often more cost effective.

Niver Creek Tributary M

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After development caused downstream degradation that posed a public safety risk, Niver Creek Tributary M was restored to stabilize the natural system and reconnect its floodplain to retain stormwater. Take a closer look at how flood mitigation was accomplished leveraging nature-based solutions while also creating a new public space for the community.

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Adding green features, sometimes through the comprehensive planning process, to urban environments also can have wide-ranging positive effects on both quality of life as well as property values for a community where present. In fact, research has shown that properties near green stormwater features can increase in value by around 11%, reflecting the demand for communities that integrate green spaces into daily life.

Below is a quick overview of some of the primary benefits of green stormwater infrastructure for a community.

Flood Control and Water Quality

One of the most pressing challenges in stormwater management is flooding. Gray infrastructure often only shifts the problem from one place to another, channeling water away until systems overflow. By contrast, green infrastructure captures rainfall close to where it falls or diverts it to an area designed to naturally hold and absorb. The natural process of infiltration helps remove pollutants while slowly releasing runoff into groundwater. This reduces the burden on sewers, minimizes the risk of downstream flooding, and prevents the high percentage of pollution caused by untreated runoff entering rivers and lakes.

Air Quality and Heat Mitigation

Urban areas with large amounts of pavement experience the “urban heat island effect,” where temperatures rise due to absorbed and reflected heat. Higher temperatures also worsen air quality by increasing smog levels, posing risks to human health. It’s no secret that vegetation naturally converts CO2 into oxygen, which has a direct impact on improving air quality and reducing greenhouse gases. Drawing on these inherent characteristics, green infrastructure features help counter the urban heat island effect by reducing the amount of reflected heat by shading surfaces, filtering pollutants, and cooling the air through evapotranspiration.

Improved Natural Habitat

Even small green features can have a large impact on natural habitat. Projects that restore streams, reconnect wetlands, or replace outdated culverts not only manage stormwater more effectively but also improve fish passage (along with that of other aquatic organisms) and natural habitat for a variety of species. At the same time small additions of vegetation and tree cover provide homes for birds, insects, and small mammals. Together, these systems contribute to biodiversity and improve the resilience of communities.

Resource and Energy Savings

Green infrastructure also saves resources and lowers energy costs. For instance, green roofs insulate buildings, reducing heating and cooling expenses by up to 12%, while also lasting twice as long (20 versus 40 years on average) as conventional roofs. Permeable pavements help water reach soil and infiltrate. Altogether, these systems reduce embodied carbon footprints, extend infrastructure lifespans, and minimize long-term maintenance burdens.

Green Infrastructure Examples

Green infrastructure takes many forms that are tailored to the site and community needs. Below are some common examples of nature-based solutions in action:

Rain Garden

Aerial view of the NE 40th Water Quality Facility, designed to capture polluted stormwater runoff from a highway.
NE 40th Water Quality Facility

Rain gardens are shallow depressions planted with vegetation designed to capture runoff from nearby impervious surfaces. They filter pollutants, recharge groundwater, and provide habitat for wildlife such as birds and pollinators.

Green Roof

Block 49/Gray’s Landing

In an urban environment, rooftops are one of the most prevalent impervious surfaces. A green roof transforms that surface of a building into a living landscape. By covering rooftops with soil and vegetation, green roofs capture rainfall, reduce heat, and extend roof lifespans. They also insulate buildings, lowering energy demands.

Porous Pavement

View of drainage along the North Creek Trail and adjacent wetlands.
North Creek Trail

Unlike traditional asphalt or concrete, porous pavement allows stormwater to seep through the surface into the soil below. This reduces runoff volumes, lessens strain on stormwater systems, and reduces quantities of pollutants that reach the stormwater system.

Reconnected Wetlands & Floodplains

Aerial view of the Foster Floodplain Natural Area.
Foster Floodplain Natural Area

Many historical wetlands and floodplains have been cut off by development over time. Restoring these natural features allows them to serve their natural purpose during heavy rains, pooling and filtering water while slowly releasing it back into the water table.

Bioswales & Biofiltration

Vegetation starting to grow in at the Sandalwood Swale.
Sandalwood Swale

Bioswales (or biofiltration swales) are shallow, vegetated channels that collect runoff along roadways or developments. When planted with native plants, swales not only filter stormwater but also enhance the character of streetscapes and support biodiversity.

A Complete Approach to Green Infrastructure

As communities continue to grow and climate conditions become more unpredictable, stormwater management is an increasingly critical challenge. Green stormwater infrastructure offers a proven, cost-effective way to address flooding, improve water quality, and create healthier, more resilient communities. Implementation of this approach is a multidisciplinary process that draws on the expertise of planning, landscape architecture, water resources engineering, and environmental sciences to maximize its value.

By harnessing natural processes, these systems move beyond the limitations of gray infrastructure, blending engineering with ecology to deliver wide-ranging benefits. From improved air quality and habitat creation to reduced energy costs and enhanced property values, GSI demonstrates how infrastructure can serve people, nature, and the economy at once.

See More Green Infrastructure Work

A Community Gathers to Celebrate a Green Solution to Urban Flooding


A reconnected historical floodplain, designed to alleviate costly issues for a community that’s prone to flooding, was officially introduced to the public at the Springwater Wetlands grand opening. Members of the community gathered alongside local leaders for a celebration of the project’s completion, along with a birdwatching walk through the area that now serves as a public open space and a restored natural habitat for a variety of native species.

Discussions at the event focused on the project’s goals to both reduce insurance costs for the community and better connect its members with nature, while also improving urban wildlife habitat. The project’s proximity along the Springwater Corridor Trail makes it easily accessible to the public, encouraging greater community engagement. The restoration for this portion of the Johnson Creek Watershed follows earlier work at the adjacent Foster Floodplain Natural Area. Together, both projects add to continued improvements for the City of Portland’s green stormwater infrastructure.

About the Springwater Wetlands Restoration

Working closely with the City of Portland and Bureau of Environmental Services (BES), work on the Springwater Wetlands reconnects and restores the Johnson Creek floodplain to address persistent flooding with green stormwater infrastructure. The project relied on extensive hydraulic modeling to properly map the area in planning for 10-to-100-year flood events and to return the floodplain to its more natural state. A multiuse trail through the new natural habitat complements the existing trail network and opens it up further for public use and wildlife viewing.

A crowd and cameras gathered at the grand opening of Springwater Wetlands
A gathering of the community and media at the grand opening of Springwater Wetlands
A sign with information about the restored Springwater Wetlands on display during its grand opening event.
Information about the restored Springwater Wetlands on display during its grand opening event
View of part of the retention area as part of the restored Springwater Wetlands.
Part of the restored Springwater Wetlands and stormwater retention area
People gathered at the restored Springwater Wetlands during its grand opening event.
People gathered at the restored Springwater Wetlands during its grand opening event

Ribbon Cutting Introduces Final Phase of a Rail to Trail Connection in Redmond

The ribbon cutting ceremony at the Redmond Central Connector Trail.
After more than a decade of multiple phases, the complete Redmond Central Connector Trail that transforms an abandoned rail corridor into a multimodal regional connection was officially introduced to the public. State, local, and project leaders joined the broader community to speak to the importance of the completed project that unifies downtown Redmond and its neighboring urban areas with the natural setting of Sammamish Valley.

 

“This trail not only connects Redmond to our neighbors in Sammamish, Kirkland, and Woodinville—it also connects us to many of the things that make Redmond special, including the natural beauty of the Sammamish Valley, parks, gathering places, public art, transit, local businesses, and the energy of Downtown.”

– Angela Birney, Redmond Mayor

 

The completion of this 1.6-mile segment follows two earlier phases that added 2.3 miles of trail extending from downtown between 2013 and 2017. In addition to several business districts, the project also completes a linkage to the 42-mile Eastrail trail network as well as provides access to Sound Transit stations for direct access to the Bellevue and Seattle area (including SeaTac Airport). This final phase also just so happens to pass directly in front of Otak’s Redmond office. Its proximity not only provided our team as stakeholders with quick access and a first-hand view of progress, but will now benefit them as members of the community with alternate commute options. Several staff members made their way to the event by bike or on foot to join the celebration that also included remarks from project manager Nico Vanderhorst.

 

“One of the key aspects of this project has always been about making connections… it had been difficult to get to downtown without a car and adding these alternatives for regional connectivity is very powerful.”

– Nico Vanderhorst, Project Manager

 

About the Redmond Central Connector Trail

This rail to trail project transformed a rail corridor, originally constructed in 1889, into a multiuse connection between downtown Redmond and the surrounding area. Completed across three phases, the transportation design process started with planning efforts that set a vision for the trail. Ahead of phase three, initial work was completed to add fish passable culverts, create a subbase for the trail, and strategically place utilities for Puget Sound Energy in anticipation of completing this new transportation asset.

 

“One of the technical challenges we solved was how to retain stormwater runoff. What we did was turn the east shoulder of the corridor into a collection and flow control facility avoiding very expensive piping and a retention pond for which there was no available space.”

– Touta Phensgsavath, Project Engineer

 

Navigating the Sammamish Valley, the trail accentuates the area’s natural surroundings, including a vegetated stormwater control facility to safely treat runoff and a retrofitted historic bridge with lookouts over the Sammamish River. Accessibility and safety were central to the project throughout its design. The final phase of work added crossings at numerous intersections with features like variable paving materials, defined concrete scoring patterns, urban amenities, signalized crossings with improved pedestrian push buttons, and uniquely designed roadway barriers. Together these features established a visual consistency as part of maximizing the overall user experience.

Cyclists using the Redmond Central Connector Trail during its ribbon cutting event
Members of the Otak team using the Redmond Central Connector Trail
Otak project team leads at the Redmond Central Connector ribbon cutting.
Left to Right: Nico Vanderhorst (Project Manager), Touta Phensgsavath (Project Engineer)
View of signage and a map from the Redmond Central Connector ribbon cutting.
A map and signage on display during the Redmond Central Connector ribbon cutting event
Otak team members gathered at the Redmond Central Connector Trail ribbon cutting.
Otak team members gathered at the Redmond Central Connector Trail ribbon cutting