By Roy Iwai, Multnomah County Water Quality Program

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Have you ever seen salmon spawn? It’s kind of magical. I saw my first salmon spawning in 1996 when I was in my twenties. It moved me so much I began a career in water quality to help salmon recover. Seeing the new Stark St culvert on Beaver Creek being built last summer brought back the goosebumps. The massive 40-foot steel arch was cavernous inside. The stream inside was a mere trickle, dwarfed by the structure’s immensity. And that was the idea.

Beaver Creek swells to enormous proportions in winter when rain runs off our streets in Gresham and Troutdale during storms and flows straight into the creek. Rain also flows off of farms and nursery lands upstream. Then in summer flows return to less than one half of a cubic foot per second. You can cross the stream then without getting your feet wet. In all these flow conditions, young coho and steelhead survive. It’s quite a surprise.

“The stream produces as many fish per stream mile as the pristine forested tributaries in the upper Sandy River.”

According to smolt trap data from the Portland Water Bureau, Beaver Creek produces on average 4% of the juvenile coho among the major tributaries of the Sandy River, and 3% of the steelhead juveniles. In a good year, up to 9% of the coho juveniles produced in the major tributaries of the Sandy River come from Beaver Creek. The stream produces as many fish per stream mile as the pristine forested tributaries in the upper Sandy River. The juvenile coho in Beaver Creek even grow to sizes larger than coho in other tributaries of the Sandy River. This is a bit of conundrum because Beaver Creek is not a pristine stream.

During the construction of the Stark St culvert last summer, we removed over 120 juvenile coho and steelhead from the 200-foot long work zone where the old culvert was removed. We also removed over 150 speckled dace, 240 sculpin, and 5 lamprey, all resident fish in that same 200-foot reach. It’s not entirely clear why fish are so abundant in Beaver Creek, but we might look at the abundance of beaver as a first clue. Beaver create ponds that are wonderful summer and winter habitat for juvenile fish. C oho and steelhead stay in the stream for at least a year before they head out to see, so like resident fishes, having refuge from the heat and floods are needed. (Left: lamprey, Right: cutthroat trout)

The high flows in winter have an impact on fish health, not only because of the high flows. We know that pollutants in stormwater can cause the premature death of returning adult salmon, killing fish before they can spawn. We know many fish survive through spawning in Beaver Creek , but we also have reports of premature death. Juvenile fish may also be harmed. Yet despite this, many young fish live to tell the tale, and swim out to the Columbia to continue their lifecycle in the ocean.

Since the Stark St culvert was completed last summer, Fisheries Program students at Mt Hood Community College have spotted the first adult spawning Chinook salmon upstream of Stark St since salmon spawning surveys have been conducted in earnest in 2011. I would guess that reach has not seen Chinook salmon in decades. We are making progress. Yet there is still more work to be done.