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Fish Passage Improvement Effectiveness Monitoring
Background
The Oregon Watershed Enhancement Board (OWEB) has continued to see fish passage improvement rank among the most numerous restoration actions on the landscape.   The main objective for fish passage improvement is to re-connect fish to stream habitat that has been made inaccessible through road building activities and other land uses.  This restoration action can provide an almost immediate benefit to fish populations by expanding spawning and rearing areas in many cases, immediately following completion of the project.   
 
Effectiveness monitoring of this action is based upon determining whether these investments are continuing to function over time. In addition, if the investments are not functional what is the cause for failure?
 
Project Summary
Using OWEB’s database, a random sample of fish passage improvement projects installed between 1997 and 2000 were selected.  Contractors set out to rediscover the project sites and collect field data that would determine the likelihood of the project site to pass fish in 2009.  Additionally, snorkel surveys were conducted to find out if juvenile salmonids were occupying the habitat upstream from the improvement.  The study also used computer modeling software in conjunction with actual field measurements to determine the functional hydraulics of the culverts.
 
In 2009, OWEB contracted with Duck Creek Associates, Inc. to monitor the effectiveness of 64 fish passage improvements in the South Coast and Rogue River basins (42 culverts, 14 bridges and 8 “other” projects).  The Executive Summary and Final Report are posted below.  

 

Outcomes
When data from the sixty four projects were analyzed results indicate that:
  • 54 of 64 sites (84%), had juvenile salmonid use upstream from the projects, seven sites (11%), were considered unable to determine juvenile salmonid use upstream from the project, and only three sites (5%), did not have juvenile salmonids upstream from the project.  Additionally, the three sites that did not have juvenile salmonids upstream from the project had poor upstream habitat conditions reported.
  • All bridges included in the study were considered to be fish passable at all flow conditions.
  • Using computer modeling software to calculate culvert velocities the study found that all culverts were partial barriers to juvenile fish passage at certain flow conditions.  However, actual field sampling revealed that only three culverts did not have juvenile salmonids above the project.  
  • Additionally, eight culverts were identified as being 100% barriers to juvenile fish passage in the computer simulation, but these culverts also had juvenile salmonids upstream of the culvert.
  • These results highlighted deficiencies in the current computer model.
A few lessons learned from the project are:
  • A stream simulation installation design (when the culvert bottom emulates the natural channel with streambed material) could be a partial barrier to fish passage by computer modeling, but this is probably not the case on the ground. 
  • This same software also predicted that all culverts could be partial barriers at certain flow conditions; this however is most likely a reflection of the conservative nature of the software and the inability to estimate results of varying types of culvert designs. 
How will OWEB use this information:
  • This information will help guide future fish passage improvement efforts and provides a good starting point to evaluate additional areas of the state for fish passage improvement effectiveness over time.
  • To begin developing more accurate computer modeling software that can simulate new types of culvert designs that are occurring on the landscape.

Executive Summary and Final Report
 
Executive Summary (235KB, PDF)                          Final Report (large file - PDF 18MB)