First Advisor

Vivek Shandas

Community Partner

Columbia Land Trust

Date of Award

11-30-2011

Document Type

Project

Degree Name

Master of Science (M.S.) in Environmental Science and Management

Department

Environmental Science and Management

Physical Description

1 online resource (50 pages)

Subjects

Restoration ecology -- Oregon -- Clackamas River, Riparian restoration -- Oregon -- Clackamas River, Ecosystem management -- Oregon

Abstract

Natural areas and ecosystem services at the edge of urban areas are threatened by increasing development. This paper examines how community based restoration partnerships can work to identify, protect and restore ecosystem services provided by salmon and our local rivers. Floodplains provide a wide range of ecosystem services to urban and rural communities and we should work collaboratively to protect and restore them. Floodplains are especially valuable and important for salmon recovery. By using a case study, we explore the process and feasibility of restoring off-channel salmon habitat at Fisher's Bend in the lower Clackamas river. A feasibility study was conducted to identify costs, benefits and risks of different design alternatives for the side channel. Hydrology of the river and hydraulics of the site were determined by estimating peak and low flow hydrology then running a HEC-RAS hydraulic model. Results indicate that the river overflows into the side channel near the 2 year recurrence interval. On average there is currently about a 50 % chance each year that the river will enter the side channel. These current flows do not provide much opportunity for juvenile salmon to access the side channel where they can grow and thrive in a protected habitat before their journey to the ocean. Further investigation produced results that indicate 95% of the time from 1959-2009 the river discharge was above 726 cfs from October to June. These results highlight that we will need to excavate about 9 feet from current elevations at the side-channel outlet to gain reasonable assurance of a one foot water depth for good salmon access. This depth will provide access from the river during critical periods when adult and juvenile salmon are seeking refuge from predators and high flood flows in the main channel. Although more design is needed for the inlet and outlet it appears the project is feasible and will meet the objective of providing salmonid access to critical habitat. In closing, I recommend investment in natural area protection and restoration at the edges of the urban growth boundary to maintain valuable ecosystem services provided by river floodplains and salmon.

Description

Funding for this project was provided by the Oregon Watershed Enhancement Board and the Nature Conservancy‘s Salmon Fund in cooperation with Portland General Electric.

Presentation in partial fulfillment of the degree requirements for Master of Environmental Management

Persistent Identifier

http://archives.pdx.edu/ds/psu/15764