River Terrace houses a number of streams and wetlands that channel the area’s stormwater into eight drainages. Many of the stream channels show signs of degradation and erosion, likely caused by past land uses and development. To ensure area streams and wetlands are protected as River Terrace develops, a draft Stormwater Master Plan has been prepared outlining measures to address both water quality and quantity treatment. In the steepest and most sensitive areas of River Terrace, site level Low Impact Development Approaches (LIDA) is proposed to achieve water quality treatment and to provide a buffer as regional facilities are developed. In larger storm events, water from these areas is conveyed in small by-pass piping to a network of street level storm conveyance pipes and swales.

In the most southern drainage basins, located between SW April Lane and SW 150th Avenue, poor soils and steep terrain will require either a large high flow by-pass pipe discharging directly to the Tualatin River or reconstruction of an existing stream. This potential stream reconstruction/restoration will allow the stream to withstand higher flows but still function as a healthy stream corridor. Stormwater detention facilities are strategically sited in each basin to protect stream and wetland resources and minimize potential flooding. In basins where site specific LIDA is not required, these facilities will also provide water quality treatment.

The timing and locations of regional water quality, detention, and conveyance facilities will be carefully considered to ensure that development is not unnecessarily hampered by properties not yet planning to develop and so that appropriate funding is in place.

See the draft Stormwater Concept Plan Diagram and the Draft Stormwater Master Plan

Go to the description of the multi-agency River Terrace coordination meeting.