Ecological Infrastructure
1) How The Pattern Works
As watersheds are deforested, floodplains are constrained, stormwater is directed through pipes, and rivers are channelized, many ecological services are severely impaired. Flooding becomes more frequent, extreme, and expensive; the recreational benefits of surface creeks are lost; habitat is degraded; water quality is impaired; and wastewater treatment facilities may be overburdened.
Ecosystem Services like water purification, flood control, recreational amenities, and climate stabilization are particularly valuable when provided to thousands of people in urban or rural areas. By recognizing such ecosystem services, it is possible to create economic and social incentives to preserve and restore them. They can be recognized as core features of an Ecological Infrastructure that meshes seamlessly with existing urban infrastructure.
The most critical part of the Ecological Infrastructure is the movement of water, stormwater, and wastewater throughout the city. The urban hydrological cycle begins with water captured and purified in nearby watersheds. Recent studies suggest that the water purification services provided by National Forest lands near urban centers rival timber harvests in economic value.
Ecological approaches to stormwater management treat rainwater as an important resource to be held on-site as long as possible. When residential and commercial developments employ permeable paving (e.g. paving tiles), rooftop rainwater catchment systems, or water-retaining eco-roofs, they allow water to infiltrate on-site, often after one or more uses. Neighborhood-scale gathering and infiltration of stormwater can be accomplished with bioswales (gentle drainage trenches planted with water-purifying vegetation) and retention ponds. Stream and wetland restoration, tree planting, and landscaping can all slow the flow of water, helping to smooth a storm’s spike of rainfall into a gradual release lasting several days.
When stormwater management is properly integrated into the Ecological Infrastructure of a town or city, it can mitigate flooding and improve the quality of water entering local waterways. The flow of water through the city can be celebrated through a decentralized system of open spaces, restored creeks and wetlands, swales, and retention ponds. Such a system, combined with an emphasis on, can decrease the size and complexity – and therefore the expense – of pipes, pumping stations, and other infrastructure.
Treepeople, in Los Angeles, has developed a series of rigorous design standards, engineering analyses, and cost-benefit studies for ecological stormwater management. They are now retrofitting homes and schools throughout Los Angeles, with very rapid payback on investment from improved water quality, stormwater retention and filtration, and the cooling effects of trees. They have developed an extraordinary collaboration with dozens of Los Angeles area bureaus and agencies, Trans-Agency Resources for Environmental and Economic Sustainability (T.R.E.E.S.), which is completely transforming the city’s water and stormwater infrastructure.
Technologies like constructed wetlands and living machines extend Ecological Infrastructure to wastewater treatment. They rely on the inherent capacity of complex aquatic ecosystems to purify water, are cost-effective, and have been used successfully to treat sewage, refinery wastewater, dairy wastes, brewery waste, and many other waste streams. They provide water of exceptional quality to downstream ecosystems.
Other pieces of the Ecological Infrastructure include urban forests and plantings which create favorable microclimates and purify the air; areas of restored habitat in parks and open spaces which form pearls in a Wildlife Corridor meeting up with regional systems of Connected Wildlands; and fire control services obtained by mimicking the effects of natural fires. Ecological infrastructure embodies the hope that cities and towns may function as ecosystems, purifying their own waste, providing their own energy, metabolizing their own materials, and providing excellent habitat for human and other species.
Create an ecological infrastructure for cities and towns that partially replaces materials, energy, and engineering with the self-organizing intelligence of living systems.
2) Stories: Examples of this Pattern in Everyday Life
City of Seattle – Natural Drainage Systems
Natural drainage is critical to the health of watersheds and their ecosystems. Trees, plants, and their root systems, percolating soil, and naturally graded slopes all allow for the regulation of water flow in and out of stream beds and natural filtering of impurities. This ensures the natural distribution of clean water to the fauna and flora that need it, and provides flood control. Hard surfaces such as rooftops, streets, and parking lots interfere with this process. Consequently, the water flows quickly, and in great volumes into streams, carrying with it excess sediment load and a wide range of chemical pollutants such as detergents, nitrogen and phosphorus based fertilizers and detergents, motor oil, pesticides, and more — pollutants that would have been filtered out in undisturbed watersheds. Without the flood control of a natural watershed, heavy rains turn quickly into torrents that can scour streambeds destroy fish and wildlife habitat, and deposit unnatural sediment loads. At its worst, this can even threaten homes and lives.
In May of 2004, the city of Edmonds, WA experienced a painful example of what can happen when urban planning neglects the importance of natural watershed drainage. Willow Creek, a small spring fed stream that flows into Puget Sound drains a portion of this rural Seattle suburb. The creek supports runs of coho and chum salmon, as well as a small run of searun cutthroat — all of which are struggling to recover from decades of urban impacts to its riparian habitat and water quality caused by pollution and development. After a heavy spring downpour, stormwater runnoff denied access to the water table and soil by paved parking lots, streets, and other forms of development flooded the small creek with more pollutant carrying water than it could handle, killing 9500 salmon fry and several searun cutthroat. There is a hatchery on Willow Creek that has been struggling to restore its failing salmon populations. The searun cutthroat were a particularly painful loss for this creek, whose trout population is on the verge of collapse. A loss which though superficially small, represents a significant percentage of what is left.
To mitigate problems like these, the City of Seattle is implementing a Natural Drainage System program in which streets, right of ways, and drainage systems are being designed to mimic natural watershed features like open, vegetated swales, stormwater cascades, and small wetland ponds. Designing infrastructure this way from the beginning helps urban areas restore the services natural watershed provide like infiltration and slowing of stormwater flow, filtering and bio-remediation of pollutants by soils and plants. Streets and sidewalks are being designed with more nature-like features including less impervious surface, porous paving, increased vegetation, and related pedestrian amenities. The result is neighborhoods and business districts that are more green and natural, less damaging to salmon runs and wildlife, less risk of flood related injury and property loss, and a more human and nurturing commons.
SEA Street
A number of streets above Carkeek Park in Seattle are transformed into beautiful avenues that are pedestrian and eco-friendly and add economic value to the homes.
Located in northwest Seattle, an alternative street design called Street Edge Alternative, or “SEA Street,” has successfully shown that streets can be redesigned to achieve both community and creek protection goals. SEA Street breaks most of the “rules” of standard American street design, developed over the last 150 years, with narrow, curved streets, open drainage swales, and an abundance of diverse plants and trees. Residents along SEA Street maintain city infrastructure in the form of street “gardens” in front of their homes. In this case, Natural Drainage Systems united the community visually, environmentally, and social — something traditional piped systems simply can’t do.
110th Cascade
110th Cascade, also located in northwest Seattle, was built in response to the success of the Viewlands Cascade project, due to a flooding problem at Third Avenue Northwest, and because it was in a priority watershed — the Pipers Creek watershed near Carkeek Park. The project was altered to a natural system approach. A creek-like cascade now intercepts, infiltrates, slows and filters over 21 acres of stormwater draining through the project.