Watershed assessments for upper Highwood-Loomis Creek proposed logging 2023-2025
Abstract
West Fraser Cochrane (WFC), formerly Spray Lakes Sawmills (SLS), manages most of the Rocky Mountain East Slopes forest under Alberta jurisdiction in the Bow and Oldman River headwaters through a Forest Management Agreement (FMA) with the Government of Alberta. The company plans to log the lower watershed of Loomis Creek and much of the local forest draining to the Highwood River in 2023 through 2025.
High-value trout populations, including bull trout (Salvelinus confluentus) protected under Canada’s Species at Risk Act (SARA), occupy waters in the area likely to be affected by logging. The limited forest management plan for the whole FMA broadly assesses the total managed area, but doesn’t provide sufficiently detailed information to allow for a reasonable assessment of the effect of its planned logging on species at risk, other high-value trout species, or watershed integrity. Accordingly, we assessed the risk of changes to watercourses, riparian zones, and hillslopes in the Loomis Creek watershed and a selection of 36 small sub- watersheds using the BC Forest Service’s Interior Watershed Assessment Procedure Level 1 supplemented with field observations and consideration of relevant technical documents and scientific literature.
Overall, 75% of the main watercourses in the 36 sub-watersheds (13 in the Loomis drainage, 14 in the Highwood mainstem drainage) were assessed at high to highest risk of significant alteration from the interaction of increased peak flows and increased surface erosion expected to result from WFC executing its logging plan. A remaining 8 (Loomis 6, Highwood 2) sub- watersheds scored as at moderate risk. Only one, draining to the Highwood River mainstem, scored as at low risk due to the small fraction of it being proposed for logging. The Loomis Creek watershed as a whole ranked as at moderate risk due to much of its headwater area being in a protected zone unavailable for logging. As the lower part of the Loomis basin is proposed for intensive logging, that part was assessed to be at highest risk, as is shown by the assessments of most of the tributary sub-watersheds there.
Although nearly all the sub-watercourses studied are not fish-bearing, they drain directly into habitat used by SARA-listed bull trout and a population of near-pure threatened westslope cutthroat trout of high value for that species’ recovery. The assessed risk of increased sediment delivery is due to road erosion and increases in the magnitude and frequency of peak flows resulting from removing the forest from parts of these sub-watersheds. An increase in local stream temperatures is also likely. Planned mitigations under Alberta’s Best Management Practices and Operating Ground Rules are uncertain to be as effective as required, and do not meet SARA legal requirements to protect threatened bull trout. This is a level one analysis, identifying problem areas needing further study in the field by a hydrologist and a fish biologist team to evaluate the potential effects of the proposed logging on critical habitat for protected at-risk bull trout, near-pure westslope cutthroat trout, and highly valued hybrid rainbow-cutthroat trout populations. Our results suggest that the proposed logging as planned poses a substantial threat to critical habitat for all life-history stages and individuals of all trout species in the study area.
