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Columbia Slough Watershed Council

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Slough FAQs

The Columbia Slough is a wonderful place to visit and the home to many amazing living organisms, including humans. But, what is a slough? What is a watershed? Read on to learn the answers to those questions…

What is a Watershed?

A watershed is the area that drains into a common body of water.  All of us live in a watershed.  Any time it rains, any time you water your lawn or wash your car, the water soaks into the ground or runs off into the streams and sloughs of the watershed.

What is a Slough?

A slough is a slow, low flow water body.  It is often a side channel of a main river.

Where is the Columbia Slough?

The Columbia Slough is a shallow, slow following waterway that flows 18 miles from Fairview Lake through North and Northeast Portland to Kelly Point Park.  It flows parallel to the Columbia River, but does not connect to it.  The Slough empties into the Willamette River near its confluence with the Columbia River.

How Clean is the Slough?

The Columbia Slough has a long history of contamination.  The watershed is highly developed with industrial uses and residences.  Despite this history, the Slough is cleaner today than it has been in the last one hundred years.

What are the sources of pollution?

Sources of pollution are the typical urban pollutants: failing septic systems, industrial discharges, illegal dumping, equipment cleaning, stormwater runoff from streets, paved surfaces, and roofs, and historic containments such as PCBs.