TECHNIQUES TO EVALUATE THE EFFECTIVENESS OF FISH HABITAT RESTORATION WORKS IN STREAMS IMPACTED BY LOGGING ACTIVITIES

Abstract

The Watershed Restoration Program (WRP) in British Columbia was initiated under the auspices of Forest Renewal B.C. to restore, protect and maintain fisheries, aquatic and forest resources adversely impacted by past forest-harvesting practices, by carrying out community-based remedial work on hillslopes and streams. Specific restoration components focus on impacted hillslopes, gullies, riparian areas, stream channels and fish habitat. Fish habitat restoration is typically carried out after an assessment of upslope risks (followed by rehabilitation) and instream conditions. Restoration techniques include restoring fish access, streambank stabilization, rehabilitating channelled reaches to provide fish holding pools and riffles, re-establishing instream cover and structure by addition of boulder clusters and large woody debris (LWD), restoring and creating off-channel habitat, and resupply of nutrients. After the restoration work is completed, research evaluation and operational monitoring are conducted to determine the overall success and ultimate benefit of the work. Research evaluation is not project-specific, but may involve evaluation of a specific technique (e.g., LWD placements), and synoptic studies and ’paired assessments’ of experimental control and treatment streams. Routine and project effectiveness monitoring is project-specific and is carried out after the instream work is completed and has passed post-construction inspection. Routine monitoring is a low intensity activity to determine functionality and condition of the restoration works. It is mainly a visual activity, and may include simple measurements or indicators (e.g., for structural stability), and can be undertaken on an annual basis or after each major storm. Project effectiveness monitoring is of higher intensity, and is conducted on a selected sub-set of projects where there are uncertainties of outcome or adaptive management benefits. This monitoring typically includes fish sampling and physical measurements: pool widths and depths, stream gradient, channel form, and channel substrate characteristics. Engineering level surveys (to tie bed and water surface elevations and cross sections to a specific benchmark) are frequently required for quantitative comparisons of restoration works (before, as-constructed and post-restoration). Where possible, project effectiveness monitoring should be related to published estimates of increases in fish abundance due to habitat improvements (bio-standards) established during the planning and prescriptive phase. Evaluation and monitoring of fish habitat restoration projects, both in the shorter and longer term, are essential to improve biological, technical and cost effectiveness of projects, and to identify and incorporate innovations. Evaluation techniques described in the paper were developed to evaluate activities to restore streams impacted by past logging practices, but the underlying principles apply to stream restoration wherever forest, urban or agriculture practices have resulted in stream and riparian impairment.