Symbiosis with Stormwater|UW MLA 2024 Capstone Project

SYMBIOSIS WITH STORMWATER Creating Resilient and Regenerative Hydrology in North Seattle

Water serves as the connecting element between Licton Springs Park, Green Lake and Ravenna Park in North Seattle. This historic hydrology facilitates the construction of a 'Sponge City' to enhance stormwater management, addressing the challenges posed by frequent rainfall and extreme climate events such as floods and droughts. This design vision aims to create a resilient and regenerative hydrology that also fosters community sharing, provides ecological services, and promotes environmental sustainability.

Lu He Master of Landscape Architecture University of Washington

Advisor: Julie M. Johnson

UW MLA CAPSTONE STUDIO 2024

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BACKGROUND Long-term Rainfall Climate in Seattle An extreme storm for Seattle, WA is a 48-hour rainfall total greater than 0.7 inches. Historically, about 15.2" of rain (or the equivalent in snow) fell over about 12 storms each year. By 2050, about 18.3" of rain are projected over about 15 storms each year. The annual precipitation in Seattle, WA is projected to increase from about 35.4" to about 38.0".1

Data from March 2024

Thornton Creek Licton Springs Park

Green Lake

Ravenna Park

Union Bay

Residents of Seattle, are particularly vulnerable to the impacts of precipitation, high temperatures, and drought. The region experiences abundant rainfall in the winter, followed by drought and heat in the summer.

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https://climatecheck.com/washington/seattle

In addition to Thornton Creek, North Seattle also has another potential watershed, it's Licton Springs Park - Green Lake Ravenna Park - Union Bay. Strengthening the stormwater management in this watershed will help enhance Seattle's resilience to weather changes and frequent rainfall.

Aerial View: google maps

SITE ANALYSIS Preparing for Design by Studying Nearby Roads, Topography, and Land Use Content Layers

Seattle Department of Construction & Inspections GIS

Licton Springs Park Ravenna Park

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Park and Tree Canopy 2021 Green Lake Ravenna Park Licton Springs Park

Local Streetscape The local streets have poor rainwater infiltration capacity, given the lack of roadside green spaces. Additionally, the flat surface of the pavement hinders effective rainwater drainage in areas.

The site's buildings and uses are mostly neighborhood residential, with some commercial and lowrise multi-family located on the east and north sides of Green Lake.

Public green spaces near Green Lake are Licton Springs Park to the north, Ravenna Park to the southeast, and Woodland Park extending south from the lake.

Wetland and Riparian Corridor

On-site Stormwater Management (OSM)

Wetland

A small amount of wetlands are around Green Lake's west and south shoreline.

Existing riparian corridor at Ravenna Park helps with stormwater harvesting and transportation.

There is a lack of OSM between Green Lake with Licton Springs Park and Ravenna Park.

The lakeside presents a sparse aquatic habitat, with scant vegetation, and lacks clear access points for people to observe, but not disrupt, the habitat and wildlife.

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Zoning Neighborhood Residentatial Neighborhood Commercial Lowrise Multi-Family

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CADMAPPER: https://cadmapper.com

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https://seattlecitygis.maps.arcgis.com/apps/webappviewer/index.html?id=f822b2c6498c4163b0cf908e2241e9c2

FRAMEWORK Refining Sponge City Theory into Practical Implementation

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Applying Theory to Site B

Building Sponge Cities: Steps & Visions

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Retention

Rainwater Harvesting Drainge

Infiltration

During the design process, I use the principles of point, line, and surface, applying varied rainwater management methods across three distinct areas to address the needs of both the community and the ecology. This design vision aims to culminate in the realization of a sponge city design in North Seattle.

Discharge

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Reuse The strategy involves collecting and using rainwater for non-potable purposes to reduce the demand on potable water supplies. Common urban practices include rainwater harvesting systems for irrigation, toilet flushing, and cooling systems.

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Infiltration

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SPONGE CITY

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COMMUNITY SHARING

The strat egy lets rain water s oak into the ground naturally, recharging groundwater, reducing runoff, and preventing flooding and erosion. Urban an infiltration methods include permeable eM c pavements, rain gardens, bioswales, r u Reso and green roofs. ater

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Surface Runoff

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Retention This strategy reduces stormwater runoff by promoting natural retention and infiltration, not immediate drainage. It involves creating water bodies and green spaces like wetlands, green roofs, and rain gardens in cities.

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Sponge City Theory

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2. GREEN LAKE + WETLAND + CISTERN Retention

Purification

Habitat Pedestrian

Storage

Green space

Reuse

Purification

ENVIRONMENTAL SUSTAINABILITY

The strategy improves water quality by removing contaminants through filtering and treating stormwater.

Urban practices include constructed wetlands, bioretention cells, green roofs, and vegetated swales.

With the goal of constructing a sponge city, enhancing community sharing and ecosystem services promotes environmental sustainability. This design process involves six methods of sponge city construction, including Retention, Infiltration, Storage, Purification, Discharge, and Reuse.1 1

Liu, Qianhui, et al. “Stormwater Management Modeling in ‘Sponge City’ Construction: Current State and Future Directions.” Frontiers in Environmental Science, vol. 9, 2022, https://doi.org/10.3389/fenvs.2021.816093.

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The strategy involves capturing and holding rainwater for later use or controlled release.

This reduces runoff, prevents flooding, and manages water supply. Urban storage practices include rain barrels, cisterns, detention basins, and green roofs.

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The strategy releases excess rainwater into natural water bodies or sewer systems to prevent flooding and erosion.

Urban practices include outfalls, overflow channels, and storm drains to divert water from developed areas.

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Discharge

ECOSYSTEM SERVICES

Rainwater Harvesting

Surface Runoff

3. RAVENNA BOULEVARD Infiltration

Swale

Discharge

SPONGE CITY DESIGN FOR GREEN LAKE

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Applying Sponge City Strategies in 4 Zones to Enhance Ecology and Community for Sustainable Environments

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Urban Channel--providing raingardens and gathering spaces within a streetscape.

Wetlands + Infrastructure--with terraced filtering wetlands alongside paths and rainwater harvesting cisterns.

Wetlands + Infrastructure--with floating wetland habitats and interpretive boardwalk.

Ecological Corridor--with a swale that filters water and supports dense tree canopy to cool pedestrians and bicyclists on adjacent trail.

URBAN CHANNEL STRATEGY

Zone1: Carex obnupta

Groundcover: Sarcococca hookeriana humilis

Zone2: Iris missouriensis

Groundcover: Veronica liwanensis

Zone3: Galanthus elwesii

Flower: Iris pallida ‘Variegata’

Zone4: Ajuga reptens

Flower: Echinacea purpurea Tree: Ginko biloba ‘Princeton Sentry’ Groundcover: Autumn Moor Grass

Groundcover: Mexican Feather Grass

Road: Permeable Pavement Pedestrians: Permeable Pavers

Residential

Pedestrian

Roadway

URBAN CHANNEL --PROVIDING RAINGARDENS AND GATHERING SPACES WITHIN A STREETSCAPE. ECO: Green Roof

ECO: Rainwater Harvesting

ECO: Permeable Pavement ECO: Permeable Pavers COM: Book Share Box COM: Parking Space

ECO: Roadside Rain Graden

COM&ECO: This versatile green space functions as a rain garden in the winter and serves as an informal gathering area in the summer.

Fine Gravel Gravel Crushed Stone Base Drainage Pipe

Compacted Soil

Soil Organic materials that accommodate and filter rainwater Drainage Pipe Adapted from Google Street View image

WETLANDS + INFRASTRUCTURE STRATEGY The resilient lakeshore can adapt to varying rainfall intensities Filter Plant | Water Flowing | Waterfowl Habitat | Balance of Trace Elements in Water

Now People have often walked to the shoreline edge and thus compacted the soil so that plants can't grow there.

Non-flood Season Biological habitats increase, and the ecosystem improves

Enhancements Connect the lake shore, allowing people to immerse in nature without disrupting the shoreline vegetation.

The rainwater collection system under the square feeds a sustainable fountain with fresh water

Green Roof Fountain

Permeable Pavement

Diving Platform

Water Supply

Surface Runoff Subsurface Runoff

Rainwater Infiltration

Overflow Pipe

Pump Basin Sedimentation Tank Water Storage Tank

Water Storage Tank

Flood Season The lake's capacity to manage stormwater increases

WETLANDS + INFRASTRUCTURE --WITH FLOATING WETLAND HABITATS AND INTERPRETIVE BOARDWALK.

COM: Educational signs convey information to visitors about the natural environment, animal behaviors and ecosystems.

COM: Boardwalk in the lake promotes the integration of people with nature and wildlife.

ECO: Floating wetland provides additional habitats for nesting birds.

COM: The steps connected to the boardwalk encourage people to engage in water activities.

ECO: Duck Platform in the lake provides an animal-friendly resting area.

COM: Permeable surface trail around the lake.

Adapted from Google Street View image

ECOLOGICAL CORRIDOR STRATEGY

Transportation

Design optimizes pedestrian and bicycle traffic by improving bike lanes, adding a pedestrian path and providing accessibility features (ADA).

Pavement Material

Increase permeability, reduce surface runoff, enhance rainwater management, and lessen the burden on the sewer system.

Sustainable Nature

Enhance stormwater management and recycle rainwater within the community.

Improving Water Quality

The overflow weir controls water levels, drainage rocks help rainwater quickly infiltrate into the soil, preventing pooling, and filtering plants purify the water by absorbing and degrading pollutants.

Community interaction space

Integrate natural elements to foster resident interaction and harmonious coexistence with nature.

Environmental Improvement

Increase tree plantings and enhance carbon cycling while also expanding habitats for biodiversity.

ECOLOGICAL CORRIDOR --WITH A SWALE THAT FILTERS WATER AND SUPPORTS DENSE TREE CANOPY TO COOL PEDESTRIANS AND BICYCLISTS ON ADJACENT TRAIL.

COM: This ADA path provides individuals with mobility impairments the opportunity to connect with nature.

ECO: Two rows of street trees provide cooling for pedestrians and those who linger.

ECO: Redesign the bike lane with permeable pavement.

COM: The wooden platforms in the corridor provide a recreational space for the neighborhood.

COM: The ecological corridor serves both as a rainwater filtration system and a habitat for wildlife.

Adapted from Google Street View image

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SYMBIOSIS WITH STORMWATER Creating Resilient and Regenerative Hydrology in North Seattle

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The project aims to transform North Seattle into a model sponge city, fostering a "Symbiosis with Stormwater" to mitigate the impacts of climate disruptions and cultivate a resilient and regenerative hydrology. By integrating sustainable design strategies such as green infrastructure, community involvement, ecological restoration, and rainwater harvesting, I envision a city that not only manages stormwater effectively but also enhances urban aesthetics, biodiversity, and quality of life.

The project long-term vision includes increased green space and habitat quality, improved water quality and access, enhanced urban resilience to rainfall, and reduced waterlogging of roads. Through these initiatives, I imagine a sustainable urban environment that thrives in harmony with natural water cycles, promoting ecological health and community wellbeing in North Seattle.

UW MLA CAPSTONE STUDIO 2024