This project is located in Raleighwood Marsh (SW Portland) from SW Raleighwood Lane downstream to the outlet of the marsh near SW Scholl’s Ferry Road. The project was initially identified in the Fanno Creek Watershed Plan in 1998.
Project Goals
- Protect the water quality and wildlife habitat values of Raleighwood Marsh and Sylvan Creek
- Improve floodwater conveyance and flow
- Improve sediment transport
- Keep maintenance requirements of the project to a minimum
Clean Water Services has been studying Sylvan Creek and Raleighwood Marsh for a number of years. The conditions in the stream and marsh have changed significantly over the past 20 years due to urban development, flooding during the 1990's, land slides and stream bank erosion. The result has been that sediment has moved downstream and into the marsh.
In 2003, Clean Water Services staff and consultants studied the marsh’s hydrology and found that sediment build up above the rock dam at the lower end of the marsh had displaced flood storage capacity and raised flood water surface elevations. The deposited sediment had become overgrown with invasive reed canary grass, resulting in degraded wetland and riparian plant communities and poor wildlife habitat. Conditions in the marsh had also created a breeding ground for environmentally harmful, non-native nutria.
During 2003 and 2004, Clean Water Services conducted an extensive process to determine the best approach to restoring the stream and marsh. As a short-term solution, the District proposed an adjustable dam that could be lowered to transport sediment during high water flows. Regulatory agencies responded that the complete removal of the existing rock dam would be a better alternative. The dam was removed in August 2004 and the District then met with neighbors to discuss ways to enhance the marsh.
A chronology of the Raleighwood Marsh Enhancement Project for 2005-06 including a community visioning workshop, concept plan for the marsh, and recent and planned activities is described separately.
Contact information
Peter Guillozet, Water Resources Project Coordinator, at (503) 681-4470 or guillozetp@cleanwaterservices.org
Jeanna Cernazanu, Public Involvement Coordinator at (503) 681-3619 or cernazanuj@cleanwaterservices.org