Tryon Creek Aquatic Habitat Restoration

Tryon Creek Aquatic Habitat RestorationThe City of Portland’s Bureau of Environmental Services’ Tryon Creek Aquatic Habitat Enhancement Project was funded through grants received by the City to correct negative effects to the stream from extensive logging which took place in 1961.  Historic removal of riparian vegetation including low canopy cover and stream shade, lack of large in-steam woody debris, and stream channel incision, has resulted in extensive sedimentation accumulating in riffles and pools.  In-stream habitat loss has been a central contributor to the decrease in native Coho salmon which historically utilized the Tryon Creek watershed.  Studies have shown that if fish passage improves in this area, Coho salmon will repopulate this area and join cutthroat, steelhead, and rainbow trout which continue to reside in Tryon Creek despite its limited to poor fish habitat.

In an effort to restore Tryon Creek, HENDERSON environmental design-build professionals worked with City staff in the field implementation of proven stream restoration techniques.  HENDERSON first pumped all stream flows around the isolated work site, with extensive fish-rescue efforts to minimize fish loss within the approximately 600-foot restoration reach.  An entirely new channel alignment, in proper configuration with Tryon Creek Aquatic Habitat Restorationcurrent watershed hydrology, was then constructed.  Stream banks were laid back to a minimum 3:1 slope, providing improved channel embankment stability.

Soil forms were created to further stabilize the stream channel and decrease the potential for embankment erosion.  Large woody debris and boulders were strategically placed in the stream to create habitat for resident native fish and other aquatic species.  Careful attention was given to the creation of appropriate in-stream channel features; including a stable meandering thalweg with pools, riffles, glides, and runs.  Streambed cobble and spawning gravel were placed in several alternating lifts to re-establish natural streambed materials throughout the restoration reach.  Biodegradable erosion control fabric(s) were placed and staked over native seed on all disturbed embankments.  Native plants, trees, and shrubs will be planted along the stream bank to restore the Tryon Creek vegetation community.

HENDERSON’S Tryon Creek channel re-location and restoration project will provide improved spawning and rearing opportunities for resident steelhead and cutthroat trout, while creating habitat for potential return of historic Coho salmon populations.

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