Lower Cedar

Lower Cedar River. View other habitats.

The Cedar River—the largest tributary to Lake Washington—has its origin along the crest of the Cascade Mountains, south of Interstate-90, and flows into Lake Washington in the City of Renton.

Cedar River: Landsburg to Cedar Falls

In contrast to its broad floodplain downstream between Landsburg and Lake Washington, the Cedar River becomes confined to a relatively narrow floodplain upstream of Landsburg for approximately 12.6 river miles. This confinement is a result of its downcutting into glacial outwash deposits from the vast Cordilleran ice sheet that last covered the Puget Sound lowlands 13,000 years ago. (See map of lower Cedar River Watershed (pdf)).

This reach of the Cedar River between Landsburg and Cedar Falls is characterized by long runs of smooth water broken by short stretches with numerous boulders that provide fast water and greater habitat complexity. Historically, large woody debris was likely abundant in this reach but is currently below levels considered optimal for fish habitat.

The flow in this reach is largely regulated by operation of the Masonry Dam upstream, with tributaries such as Taylor Creek adding substantial flow during high rainfall events.

Lower Watershed Tributaries

Important tributaries to the Cedar River below Cedar Falls include:

  • Taylor Creek
  • Rock Creek
  • Williams Creek
  • Steele Creek

Rock Creek is the only tributary with extensive habitat accessible to anadromous fish (ocean-dwelling fish that breed in fresh water). It has about 7.5 miles of low gradient habitat and also supports a large wetland complex created by a series of beaver dams about 2 miles upstream of its confluence with the Cedar River.

Coho salmon juveniles are now using this stream for rearing habitat, following the completion of the Landsburg Dam Fish Passage in 2003. The Landsburg fish passage facility opened up 12.6 miles of the Cedar River and 8.0 miles of tributary habitat to anadromous fish access for the first time in over 100 years.

Cedar River: Cedar Falls to Cascade Crest

Between Cedar Falls and Chester Morse Lake, much of the reservoir outflow is usually diverted through a penstock to generate electricity at the 30-megawatt hydroelectric facility operated by Seattle City Light. In this reach, a minimum of 30 cubic feet per second (cfs) is maintained in the river for fish rearing habitat. (See Map of Upper Cedar River Watershed (pdf)).

Upstream of Chester Morse Lake, the Cedar River is a mountain stream with a variety of channel types. The river flows into Chester Morse Lake across a broad delta.

Upstream of its delta, the river has a sinuous pattern, sometimes with multiple channels. It is one of the primary spawning and rearing habitats in the watershed for the federally listed bull trout.

About 8 miles upstream of the lake, the river becomes more confined and steep as it climbs to the crest of the Cascade Mountains, splitting into the Cedar River North and South forks.

The Rex River, another major tributary to Chester Morse Lake, has similar characteristics to the reaches of the Cedar River above Chester Morse Lake.

Upper Watershed Tributaries

In the more mountainous portion of the watershed above Cedar Falls, the Cedar and Rex rivers have numerous tributaries, most of which are steep gradient with cascade and step-pool habitat.

Major upper watershed tributaries include:

  • Rack Creek
  • Boulder Creek
  • Findley Creek
  • Seattle Creek
  • Bear Creek

Fish in these streams are generally confined to the lower reaches near the Cedar River, but there is abundant habitat for amphibians, especially tailed and Cascades frogs.

Habitat types in the watershed: