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Natural Drainage Systems
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Street Edge Alternatives
Landscape Architecture
The landscape elements serve an important role in both providing an aesthetic benefit as well as contributing to the management of rainfall. Trees will help to restore more of the evaporation and transpiration that was present before development.
The other vegetation in the drainage swales will also help to filter and slow the flow of storm water. Over 100 deciduous and evergreen trees and 1100 shrubs were added as part of the project.
Design involvement
The landscape architect was involved more during the design than a typical project. The most apparent example of this is a sidewalk design that not only serves but attracts pedestrians.
There also was an emphasis on retaining existing large-scale trees and relocating vegetation to meet homeowner needs and project goals. The swales and surrounding areas are artfully graded and planted with native wetland and upland plant species. Granite boulders and various sizes of washed river rock provide both function and beauty.
Landscape design
The landscape design complements the drainage system function and focuses on native and salmon-friendly plantings. The system is unique in its use of grading, soil engineering, plant selection and layout as components that function together -- much as they do in a natural ecosystem.
Natural systems approach
Returning drainage and vegetation in the area to a natural systems approach is an important element of this demonstration project.
For example, native soil from excavations was mixed with organic compost to provide rich topsoil and reduce water and fertilizer needs.
As another example, clay was the preferred liner material for swales. This helps to ensure vegetation can survive in the summer months by allowing moisture to move up through the soil. A liner fabric would be less effective in this role.
Related links
Salmon-friendly Gardening
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