Equivalent Clearcut Area Just Isn’t Cutting it Anymore: It’s past time to switch up our primary watershed impact assessment tool

May 11, 2026

Pelletier Creek slash pile, logged by West Fraser Cochrane. Photo © C. Hunter

Wildlands Advocate article by Cameron Hunter, AWA Conservation Specialist

Read the PDF version here.

Alberta is home to some of Canada’s most crucially important headwaters, forming four of Canada’s great rivers that provide water to many parts of not only Alberta, but also Western Canada and the United States. The importance of Alberta’s Eastern Slopes has been recognized since the early 1900s, with federal and provincial governments establishing the Eastern Rockies Forest Conservation board in 1948, although the significance of these places was known long before that. The protection of our headwaters, forests, and ecosystems is vital for maintaining, cleaning, and filtering water.

Trees and vegetation play a key role in the process of hydrological control. They delay snowmelt by intercepting snowfall and providing shade to reduce evaporation from solar radiation. Trees and vegetation also cool the air through evapotranspiration, diminish erosion through obstructing and slowing rainfall, slow the flow of water into soils to reduce erosion and flooding, and act as a physical support system for soils, among other important hydrologic functions. Trees are vitally important beings in the complex hydrologic function of our watersheds. Clearcutting, where most or all of the trees in a given area are cut during logging operations, is the most common type of industrial-scale logging in the province.

The negative effects of clear-cut logging are known to us. Sedimentation, warming rivers, erosion, and changes in the frequency and magnitude of peak flows are just a few of the issues that trouble the rivers and streams that provide critical habitat for some of Alberta’s species at risk. These species are under pressure from surface erosion, runoff, and drainage density, as roads constructed for logging become watercourses that then deliver more water and sediment into receiving waters where threatened trout populations live.
Native trout species such as bull trout live and breed in these waters and are listed under Canada’s Species at Risk Act (SARA).

Increasing demand and expectations are placed on Alberta’s watersheds, which have been up against drought conditions and continued threats from industry, from coal to forestry. The need for comprehensive, detailed, and rigorous risk assessments across our headwaters is more dire and necessary than ever before. One way this can be accomplished is by implementing modern and improved forestry management tools.

The Eastern Slopes contain the Rocky Mountain forests, which are found predominantly on public lands. They are divided into Forest Management Units (FMUs) that are managed under long-term, typically 20-year, Forest Management Agreements (FMAs). Other areas are also managed under shorter-term timber permits and quotas. These FMAs require Forestry Management Plans (FMPs) that are renewed on a five-to-ten-year cycle to ensure they align with current practices.
The main watershed impact assessment tool found within FMPs is Equivalent Clearcut Area (ECA) and it is a required part of the timber supply analysis. ECA refers to the percentage of a watershed that is disturbed by logging or past disturbances, accounting for forest regrowth. Often, ECA is leaned upon as the sole metric for estimating the hydrologic alteration from land-cover changes, such as clearcut logging or harvesting, and it is represented as a percentage from 0 to 100. An ECA of 100 percent represents a fresh clearcut, and since ECA values have an inverse relationship with hydrologic function, an ECA of 100 percent would have no (or zero percent) hydrologic function.

Within FMPs, ECA values equal to or below 30 percent are considered the target, But, studies on ECA assessments have shown that ECA levels around 20 percent have a small but insignificant effect on the magnitude and frequency of peak flows. Values beyond 20 percent and within areas of higher elevation have a much larger impact on peak flow magnitudes and frequency.

ECA analyses often rely on regional assumptions, qualitative observations, and/or expert judgement, making it difficult to provide quantitative estimates of hydrologic change. The lack of quantitative estimates provided from ECA-based assessments means that we see variability in what an acceptable level of harvest is, with forest managers pushing that boundary to optimize their harvest. ECA as a metric lacks a level of certainty in depicting the impact of forestry on hydrologic response in watersheds.

UBC forest hydrologist Dr. Younes Alila explains that the research that underlies ECA was conducted at the scale of small stream water catchments, and its ability to predict the magnitude and severity of floods falls apart at larger scales and when considering larger precipitation events — the scales that are relevant to people. The larger the scale we are looking at, the larger the effect logging has on flood severity and frequency. This has been reported in the scientific literature, but that knowledge has not been incorporated into forest management planning. This is one example of how current forestry regulations do not reflect the best available science when it comes to protecting water.

Other hydrologic models for watershed assessment do exist, in the form of a framework named after a clever bird.

Raven is a process-based hydrological model that replicates watershed processes, can simulate landcover, and includes climate change scenarios that together can provide quantitative estimates of hydrologic change. In particular, it can be used in watersheds that lack streamflow monitoring gauges, also known as ungauged watersheds. This is an important feature as many forestry decisions are made within ungauged watersheds.

An additional benefit of the Raven model is that it has a modest data requirement, and recent improvements in datasets used within this kind of modelling make it more accessible than it has been in the past. Additionally, it is touted for how well the model can represent physical processes, such as forestry’s effect on snowmelt within a basin. The tool is beginning to be used in conjunction with ECA-based assessments, and the model allows for iterative refinement, allowing assessors to model different scenarios quickly to understand how different location-specific harvests would affect the hydrologic regime. This can help to guide forest management decisions by providing accurate quantitative estimates of the likelihood of hydrologic change.

So, why are these modern assessment tools not more commonly being used within Alberta to improve risk-based forest management? The research is there, showing us that there are more rigorous and quantitative models available to improve our understanding of the impacts forestry and climate change have on our watersheds. The development of Raven has been supported by many associations and provincial governments across Canada, including the Alberta government, and discussions with professionals in the industry speak highly of the application and outcomes that come from Raven hydrologic modelling. Recent studies show the effectiveness of pairing Raven with ECA-based assessments.

Improved hydrological assessment tools are available for assessing the impact clearcut harvesting has on our watersheds, and the science is firm that clear-cut logging is not sustainable. As stated by many who have come before me, we need to switch the way Alberta’s forests are considered sustainable — away from focusing solely on sustainable timber supplies, and to sustainable forest ecosystems that support healthy watersheds for our wildlife, wild spaces, and us.