Monitoring the Effectiveness of Fish Passage Restoration at Road-Stream Crossings: A Pilot Study Conducted by the Pacific Northwest Region, U.S. Forest Service

More than 3,500 road-stream crossings, which do not pass all species and life stages of fish, have been identified on National Forest System lands in the Pacific Northwest Region (Heller and Sanchez, 2005).  In the past five years, more than 200 road stream crossings have been restored to provide passage for fish and other aquatic organisms.  A Pilot Study was conducted from 2008 to 2010 to develop and test a protocol to determine the effectiveness of this type of restoration work for future use at a broad scale.   There were two primary monitoring questions: 1) Are the simulated crossings capable of passing all species and life stages of fish utilizing the stream at all stages of flow? and  2) Are the restored crossings simulating natural channel conditions?

Biological and physical stream channel survey methodologies were developed and tested to address the monitoring questions. At the conclusion of the 2008 field season, the data on 10 stream simulated crossings (eight bottomless arch culverts and two bridges) were analyzed. The protocols were reviewed, refined, and applied in the 2009 assessment of 15 randomly selected crossings on the Deschutes, Ochoco and Olympic National Forests (nine bottomless arch culverts, two bridges, three decommissioned roads, and one embedded culvert). 

Results of the combined 2008 and 2009 assessments indicate that the objectives of providing fish passage and simulating natural channels are being achieved for the majority of surveyed crossings.  All surveyed crossings met or exceeded bankfull width for both the up and downstream channels and also likely improved sediment and woody debris routing through the restored crossing. However, compared to the natural stream channel segments, streambed forms within the majority of crossings were typically more homogeneous or simplified and provided less hydraulic velocity breaks and pocket pool habitat. 

Costs for the assessment were approximately four percent of the total restoration investment used to treat the road-stream crossings.  The protocol is believed effective in answering the primary monitoring questions and suitable for future application by Forest Service aquatic resource personnel