WES Three Creeks Floodplain Enhancement Project

Ecological restoration provides water quality improvements to a highly urbanized stream system and re-establishes diverse hydrologic floodplain conditions.

Clackamas Water Environment Services (WES) operates a large, regional detention facility at the confluence of Mt. Scott, Phillips, and Dean Creeks. Known as the 3-Creeks Natural Area, it includes a complex of wetlands, uplands, and open space areas. The detention facility consists of an active flow control gate system and a large passive storage pool behind the control gates that can fill during large rainfall events. This pool, when full, can inundate much of the site along Mt. Scott Creek. The creek channel is highly degraded with 6’–8’ eroding banks.

A key member of a team led by Parametrix, Biohabitats helped WES integrate nature-based solutions in the retrofit the 3-Creeks facility to improve water quality and habitat, increase floodplain flood storage, optimize facility storage and peak flow reduction, enhance public use of the site. After reviewing all available data and participating in a workshop to introduce the project and solicit input from WES staff and agency partners, Biohabitats conducted a physical site assessment to characterize the streams. Biohabitats developed three different concept designs to restore the creek and floodplain. Biohabitats then participated in an alternatives analysis of opportunities to improve riparian and instream habitat, enhance channel stability, and optimize floodplain habitat diversity.

Biohabitats prepared rendered plan views and cross sections for three stream restoration concepts and worked with WES and partners to select the preferred alternative.