Tanglewood Park Stabilization Project

tanglewood 1HENDERSON partnered with the City of Lake Oswego’s Mountain Park HOA to environmentally and aesthetically return a local tributary to Springbrook Creek from an incised channel with no associated riparian habitat.

The Springbrook Creek watershed contains a 1,219-acre urbanized area. Springbrook Creek is a perennial stream approximately three miles long. It has ten (10) tributary streams and drains into Oswego Lake. The high point in the watershed is Mt. Sylvania at an elevation of 974 feet and the low point is Owego Lake at an elevation of 98.6 feet. Much of Springbrook Creek is deeply entrenched and is disconnected from its natural floodplain. Springbrook creek and many of its tributaries have low sinuosity with little natural riparian vegetation due to historic straightening and adjacent land use.

Pre-restoration conditions of the project site provided very little ecological function. The “park-type” turf presented a monoculture of largely non-native grass, and the lack of wetted channel bottom area left little room for wetland plant species. This simplified ecosystem provided little to no habitat function for aquatic and terrestrial wildlife, and was becoming increasingly more incised, with no connection to the surrounding floodplain.

tanglewood 2To improve habitat function and stream health HENDERSON re-created a more naturally structured stream channel, including a widened channel width, large wood, and a sinuous shape. Grade control structures were added to decrease flow velocity and increase storm water capacity. Stone benches and a flat-topped boulder stream crossing were installed as design elements for park goers. This project was planted by the Mountain Park HOA and volunteers with riparian species to provide additional habitat and stabilize the newly graded banks, thereby reducing streamside erosion. Selected plants included specific aquatic grasses aimed at the phytoremediation of storm water.

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