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Watersheds
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d3b.  Watersheds

Watersheds Map
Portland Watersheds (PDF)
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Portland contains five watersheds, each with differing natural characteristics, hydrology, water quality, and habitat issues. In each of the watersheds, the future health of watersheds and the natural environment is dependent on addressing existing problems and on how future growth and development is managed. Portland’s watersheds:
  • Willamette River Watershed
  • Columbia Slough Watershed
  • Johnson Creek Watershed
  • Fanno Creek Watershed
  • Tryon Creek Watershed

 

Portland's watersheds are based around its rivers and largest urban streams. A watershed is an area that catches rain and snow, beginning at ridge tops and draining to a river, stream, lake, or wetland. Watershed health is influenced by the condition of natural hydrologic systems, water quality, physical habitat, and biological communities. The following highlights characteristics of Portland’s watersheds:

General characteristics of Portland’s watersheds
  • Roads, buildings and other impervious surfaces account for 22-36% of the surface coverage in Portland’s watersheds (from 22% in Tryon Creek to 36% in Columbia Slough).
  • Tree canopy covers approximately 26% of the City.
  • The City’s draft natural resource inventory identified over 200 miles of rivers and streams, and about 30,000 acres of riparian corridor and wildlife habitat.
  • Overall, water quality has improved, but each major water body has problems with bacteria, nutrients, and toxics.
  • The watersheds provide habitat for a plethora of fish, bird, mammal, amphibian and reptile species, including many with state and federal protected or “at risk” status.
  • Watershed councils and stewardship groups are instrumental in restoration efforts.
Willamette River Watershed
  • The river is 187 miles in length (the lower 17 miles, including the confluence with the Columbia River are in Portland); drainage area of 11,478 square miles (69 square miles in Portland).
  • Diverse topography of floodplain, low lands and steep drainages.
  • 22% of area is parks/open space, including 5,000 acre Forest Park; 36% is inventoried natural resource area; 13% is protected by environmental zoning.
  • Provides habitat for Chinook and Coho salmon, rainbow/steelhead trout, lamprey, beaver, river otter, red-legged frog, Western pond turtle and over 100 resident and migratory bird species (bridges provide nesting sites for Peregrine falcon).
  • Oak woodlands, such as those located on the bluffs, are one of the most threatened habitat types in this watershed.
Columbia Slough Watershed
  • The slough is 18 miles in length; drainage area of 51 square miles (42 in Portland).
  • Topography is generally low land with relatively few steeply sloped areas.
  • The middle and upper floodplain is managed by a system of levees and pumps.
  • 14% of area is parks/open space; 21% is inventoried natural resource area; 8% is protected by environmental zoning.
  • The 2000 acre Smith and Bybee Wetlands Natural Area is considered one of the nation’s largest urban freshwater wetlands.
  • Provides habitat for Chinook salmon, rainbow/steelhead trout, beaver, river otter, red-legged frog, Western pond and painted turtles, and over 160 resident and migratory bird species of birds.
Johnson Creek Watershed
  • The creek is 25 miles in length; drainage area of 54 square miles (20 in Portland).
  • Topography includes extensive floodplains as well as steep slopes in upland buttes.
  • 13% of area is parks/open space; 24% is inventoried natural resource area; 8% is protected by environmental zoning.
  • Provides habitat for Chinook and Coho salmon, cutthroat and rainbow/steelhead trout, lamprey and many bird species.
  • Beaver are active in helping shape conditions along portions of Johnson Creek.  
  • Threatened red-legged frogs have been found throughout the watershed.
Fanno Creek Watershed
  • Includes nearly 23 miles of open channel (main channel is 15 miles in length); drainage area of 32 square miles (7 within Portland).
  • Topography characterized by steep slopes along the creek and its tributaries.
  • 5% of area is parks/open space; 28% is inventoried natural resource area; 8% is protected by environmental zoning.
  • Cutthroat trout are known to spawn and rear in upper Fanno Creek.
  • Provides habitat for over 100 resident and migratory bird species.
Tryon Creek Watershed
  • Includes nearly 27 miles of open channel (main channel is 7 miles in length); drainage area of 6 square miles (5 within Portland).
  • Topography characterized by steep slopes along the creek and its tributaries.
  • 19% of area is parks/open space; 42% is inventoried natural resource area; 17% is protected by environmental zoning.
  • Provides habitat to cutthroat and rainbow/steelhead trout, Coho and Chinook salmon, lamprey, and about 60 resident and migratory bird species.
  • Portland’s smallest watershed, but natural resources cover almost half its area.
  • The 630 acre Tryon Creek State Natural Area is Oregon’s only state park within a major metropolitan area.