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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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Carolina-Terwilliger Subwatershed Facts

  • The Carolina-Terwilliger subwatershed covers about 854 acres of southwest Portland.
  • About 500 feet of natural riverbank remain on the Willamette River in this subwatershed.
  • Cottonwood Bay is used as stop-over habitat for osprey, hawks, herons, and other birds.
  • The subwatershed has 28,770 (5.4 miles) feet of open stream channels.
  • Parks and open space make up 234 acres of the subwatershed; 190 acres of land are in public ownership.
  • The central portion is extremely steep and has not been developed.
  • 420 acres of the subwatershed are forested.
  • 31 acres of the subwatershed have woodland type tree canopy.
  • Three streams that originate in Marquam Nature Park and Terwilliger Wildlands flow to a combined sanitary and stormwater pipe near Barbur Boulevard.
  • About half of this subwatershed is impervious area, mostly streets.
  • The forested areas and streams of the subwatershed provide an important link between the West Hills and the Ross Island-Oaks Bottom ecosystem complex to the east, and between Marquam Nature Park to the north and Tryon Creek State Natural Area to the south.