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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

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Willamette Tributaries Report Card

Photo of sampling along tributary

This is a summary of conditions in the Willamette Tributaries Watershed based on data from the 2015 Watershed Health Index. The scores are a snapshot of conditions across the entire watershed. Conditions can vary in smaller parts of the watershed.

Link to introduction page on the watershed report cardsLearn more about the Willamette Watershed

Program and Projects


Willamette Tributaries Hydrology Score: D

This watershed has a lot of streets and other hard surfaces that create stormwater runoff instead of letting rain soak into the ground. In many areas, stormwater washes pollutants from streets into pipes that drain directly to streams. Fast-moving runoff can erode stream beds and banks.

Many of the streams that once flowed freely in the watershed today flow through underground pipes. The city is planning projects such as green street planters and neighborhood stormwater wetlands that will capture runoff and allow it to soak into the ground as soil and plants filter pollutants. Better stormwater management will improve these hydrology scores.

Willamette Tributaries
Hydrology Average Score

Hydrology score: 3.5

3.5

What is this?
Effective impervious area
Effective impervious area: 3.8
3.8
What is this?
Stream connectivity
Stream connectivity: 3.2
3.2

Willamette Tributaries Water Quality Score: B

Water quality conditions vary greatly in Willamette tributary streams. Highly developed areas contribute a lot of stormwater pollutants like copper and total suspended solids to small streams like Stephens Creek. Runoff from streets and highways is a major source, and E. Coli bacteria can come from sewer leaks or animal waste. Other streams, such as Miller Creek in Forest Park, have much better conditions. But even streams in natural area parks have challenges with erosion due to a combination of steep slopes, human activities and aging infrastructure. This can cause solids and related pollutants to wash into streams.

The work Portland is doing to protect and improve streams, wetlands and forests in places like Forest Park and the River View Natural Area help protect water quality. New green street planters and parking lot swales in commercial areas will reduce solids, metals and other pollutants that wash into local streams. Planned projects, similar to a past project on SW Texas Street, will couple green street and rain garden projects with other infrastructure improvements, beginning in the Stephens Creek area.

Willamette Tributaries
Water Quality Average Score

Water quality score: 6.1

6.1

What is this? Ammonia-nitrogen Ammonia-nitrogen: 9.9
9.9
What is this?
Dissolved copper
Dissolved copper: 5.6
5.6
What is this?
Dissolved oxygen
Dissolved oxygen: 8.7
8.7
What is this?
E. coli
E. coli: 6.1
6.1
What is this? Temperature Temperature: 5.6
5.6
What is this?
Total mercury
Total mercury: 1.7
1.7
What is this?
Total phosphorus
Total phosphorus: 6.6
6.6
What is this?
Total suspended solids
Total suspended solids: 4.8
4.8

Willamette Tributaries Habitat Score: 6.3

Scores for tree canopy, stream bank condition and the land and vegetation next to streams (riparian area) are good in many parts of the Willamette Tributaries watershed because of large protected natural areas and forested neighborhoods throughout southwest and northwest Portland. But habitat conditions are not the same across the whole area and projects to protect forests, wetlands and streams are important.

Invasive plants threaten forests in this and other Portland watersheds. Efforts to manage invasive plants, like Early Detection Rapid Response, are important to protect and improve habitat.

Stream accessibility is poor because of the large number of piped streams. Culverts and pipes, like those under Highway 30, block fish access between the Willamette River and Forest Park’s relatively healthy streams.

Willamette Tributaries
Habitat Average Score

Willamette Tributaries habitat score: 6.3

6.3

What is this? Bank condition (hardening) Bank condition: 10
10
What is this? Floodplain condition Not applicable  
What is this? Large wood Large wood: 4.8
4.8
What is this? Riparian integrity Riparian integrity: 8.1
8.1
What is this?
Stream accessibility  Stream accessibility: 0.7  0.7
What is this? Substrate composition Substrate composition: 6.5
6.5
What is this?
Tree canopy
Tree canopy: 10
10

Willamette Tributaries Fish and Wildlife Score: C-

Cutthroat trout and other fish live in streams in Forest Park, but the watershed’s fish score is low because of the many barriers that block fish access. Good tree canopy and protected natural areas provide habitat for birds and aquatic insects in this watershed. More than 104 species of birds have been identified in Forest Park, and the park’s relatively healthy streams support insects, amphibians and other wildlife.

The city’s continued efforts to protect and improve connections between Forest Park and other natural areas on the west side, and improved stormwater management, will help improve these fish and wildlife scores.

Willamette Tributaries
Fish and Wildlife Average Score

Fish and wildlife score: C-

4.2

What is this? Birds Birds: 5.4
5.4
What is this?
Fish
Fish: 1.3
1.3
What is this?
Macroinvertebrates
Macroinvertebrates: 5.9
5.9

For more information about what we measure and where these scores come from, visit the About Watershed Report Cards page.

See some of what Environmental Services is doing for healthy rivers and streams on the Explore Portland’s Watersheds map.