Couloir Avalanche Considerations: Why “Small” Avalanches Can Kill in Steep Lines

Steep couloir skiing has gone from a niche discipline practiced by a handful of extreme skiers to a mainstream aspiration. High-production ski films, social media edits, and the “steep is the new normal” zeitgeist have done what they do best: they make narrow lines look standard, and they make backing off feel like you’re missing out.

But couloirs are not simply “steeper skiing.” They are a different risk environment because terrain amplifies consequences. A small avalanche that might be inconsequential on an open slope can become lethal when it is funneled into a confined gully with nowhere for debris to spread. Add overhead hazards, complex terrain interactions, and the reality of other parties above you, and couloirs demand a more conservative operating system than most people expect.

This article is a comprehensive, field-focused guide based on a talk by Mike Austin (Avalanche Geeks), a professional avalanche educator with extensive guiding and forecasting experience. The aim is not doom-and-gloom. It’s to translate couloir-specific avalanche considerations into a practical framework you can use in the mountains — and into a reference you can share with your crew.

Full lecture: Avalanche considerations in couloir skiing – Mike Austin (Avalanche Geeks)

Throughout this piece, you’ll find links to definitions and background concepts from: Avalanche.org’s Avalanche Encyclopedia and Avalanche Canada’s Glossary.

Case Study: A “Size 1” Avalanche That Killed Two People
Why Couloirs Amplify Consequences: Terrain Traps, Trauma, and Runouts
Couloirs as Extreme Terrain: The ATES Mindset
Avalanche Problems That Commonly Affect Couloirs
Why Wind Slab is Often the Primary Couloir Problem
Wet Snow and Overhead Hazard: The Spring Couloir Reality
Persistent Weak Layers: “Less Prevalent” Doesn’t Mean “Not There”
Snowpack Variability Inside a Couloir
Why the Avalanche Forecast Helps Less Than You Want It To
What Assessment Techniques Actually Work in Couloirs
Why Snow Pits in Couloirs (and Aprons) Can Lack Fidelity
Bottom-Up vs Top-Down: Information vs Visibility
Ski Cutting and Cornice Drops: Valid Tools, High Skill
Skins as a Get-Out-of-Jail Card
The “Other Party Above You” Problem (Human Overhead Hazard)
A Couloir Travel Operating System: Practical Rules That Scale

1) Case Study: A “Size 1” Avalanche That Killed Two People

Mike opens with a case study from the Mont Blanc Massif, close to a ski resort. The proximity matters: this wasn’t a remote, expedition-style mission. This was “exit the lift, traverse, drop in.”

The party was three: a ski instructor and two guests. They’d known each other for two decades. The instructor was regarded as a family friend. That matters too — because familiarity and trust can quietly reduce critical thinking. When someone is “the expert,” the group tends to outsource decision-making.

The skiing elsewhere that day was poor. No new snow for roughly two weeks. Off-piste was wind-hammered — the kind of surface that feels like survival skiing rather than joy. The rationale for the couloir was familiar: maybe wind had deposited a pocket of soft snow inside the gully. A small reward, but the hope was for a better experience.

They entered the couloir about 100 meters from the top lift. The incident timeline isn’t perfectly known, but the working theory from investigators was that two snowboarders followed them in. They saw a skier in an instructor jacket and assumed: “He knows where the good snow is.” The snowboarders dropped in behind and triggered an avalanche that caught the party.

Here’s the core: the avalanche was visually small — roughly “tennis court” scale, what many people would casually call “size 1.” In avalanche vernacular, small slides are often described as “generally harmless.” But in this confined terrain, the debris funneled and piled deeply enough to completely bury both guests. The instructor survived (buried to the waist) and could only call for help — because the group did not have full rescue equipment.

The lesson is not abstract: In couloirs, small avalanches can have big consequences. That is the definition of a terrain trap problem.

Useful references: Terrain Trap (Avalanche Encyclopedia) and Avalanche Size / Destructive Force (D-scale).

2) Why Couloirs Amplify Consequences: Terrain Traps, Trauma, and Runouts

Couloirs are a subset of avalanche terrain where consequence tends to spike faster than most people’s intuition. This is not because every couloir is constantly about to avalanche. It’s because when something does move — even a small amount — the terrain geometry multiplies the impact.

Confinement increases burial depth. Debris can’t fan out. It stacks in the gully.
Trauma risk increases. Sidewalls, rocks, constrictions, and cliffs turn even a short ride into a pinball machine.
Runouts are often unforgiving. Bergschrunds, cliffs, terrain benches, boulder fans, and choke points are common.
Overhead hazard is part of the package. Adjacent start zones, hanging faces, cornices, and cross-loaded features can feed into the line.

Mike’s phrasing is blunt: the consequences of being avalanched in a couloir are amplified. A rider can be accelerated and slammed into walls. Even without a major burial, the trauma component can be severe — and trauma is a common cause of fatality in steep, confined avalanche terrain.

A related, underappreciated detail: many couloirs require you to cross an apron or exit slope sitting at a classic avalanche angle. The “getting to” and “getting out of” phases can be as serious as the couloir itself.

3) Couloirs as Extreme Terrain: The ATES Mindset

One of the most useful ways to communicate couloir seriousness (especially for groups) is to treat couloir objectives as complex to extreme avalanche terrain by default. The Avalanche Terrain Exposure Scale (ATES) exists to describe terrain consequence and exposure.

ATES references: ATES (Avalanche Encyclopedia) and ATES overview (Parks Canada).

The practical translation: if you choose to ski couloirs, you are often starting your day high on the “consequence axis” before you even consider today’s hazard rating. There’s less green room up there. That means you need bigger margins.

4) Avalanche Problems That Commonly Affect Couloirs

There isn’t a huge volume of couloir-specific avalanche research compared to general backcountry terrain, but the talk highlights a consistent field pattern: certain avalanche problems show up repeatedly in couloirs.

A working shortlist:

Wind slab — definition
Storm slab / new snow — definition
Wet loose / wet slab — wet loose, wet slab
Cornice fall — definition

Avalanche Canada glossary for consistent terminology: Avalanche Canada Glossary.

5) Why Wind Slab is Often the Primary Couloir Problem

If there’s one avalanche problem to keep “front and center” in many couloir contexts, it’s wind-drifted snow. Wind can load a couloir in ways that feel disconnected from what you see on surrounding open slopes.

Wind slab becomes especially relevant because:

Funneling: wind-transported snow gets captured and concentrated in the gully.
Cross-loading: side-loading creates reactive pockets along one wall, even if the other wall feels supportive.
Rotoring: plateau edges and ridge features create deposition “hot spots,” often at the exit slope or just below the ridge.
Micro-variability: stability can change sharply over tens of meters — especially near the top.

Wind slab reference: Wind Slab (Avalanche Encyclopedia).

6) Wet Snow and Overhead Hazard: The Spring Couloir Reality

The talk connects back to a common springtime pattern: point releases and wet loose avalanches — often triggered by solar warming — can be particularly dangerous in couloirs because the debris has nowhere to spread.

Wet loose reference: Wet Loose Avalanches.

Overhead hazard in couloirs isn’t only about cornices. It’s also about adjacent slopes feeding into your line. A sunlit hanging face might release above and “pour” into the gully. This is why couloirs are often best understood as a terrain system, not a single slope.

7) Persistent Weak Layers: “Less Prevalent” Doesn’t Mean “Not There”

One potentially “good news” element Mike raises is that persistent weak layers can be less prevalent in many couloirs. Why? Couloirs often hold deeper snowpacks, and deeper snowpacks are generally less prone to the thin, faceting-friendly structures that create persistent weak layers on shallow slopes.

Also, constant sloughing can mechanically disrupt clean, planar interfaces that become bed surfaces — which may reduce certain failure pathways.

But the important nuance is the one Mike states explicitly: if a persistent weak layer exists and you trigger it in a couloir, the consequences are amplified. The case study itself likely involved a persistent weakness near the top.

References: Persistent Weak Layers, Persistent Slab.

8) Snowpack Variability Inside a Couloir

A couloir can start near a summit and drop hundreds (even thousands) of vertical meters. It’s not one snowpack. Expect major changes with elevation, exposure to wind, exposure to sun, and the degree of sloughing.

In the case study: reactive wind slab near the top; bullet-hard snow lower down requiring crampons. Same couloir. Different worlds.

Treat your line as a sequence: apron → midline → choke features → upper start zone → exit slopes. Each section can behave differently.

9) Why the Avalanche Forecast Helps Less Than You Want It To

Avalanche forecasts are regional and generalized — they have to be. They describe patterns and problems across a zone, not your exact line. On a normal ski tour, you might take that regional forecast and distill it down onto multiple slopes, aspects, and elevations, using observations as you go.

In a couloir, you’re often committing to one aspect and one confined feature across a large elevation band. You’re now distilling: region → slope → micro-feature. That additional step is where uncertainty grows.

Mike’s framing: the forecast remains the starting point — always. But its slope-specific value is reduced in couloirs because couloir conditions can diverge from surrounding terrain and because wind loading can be extremely localized.

10) What Assessment Techniques Actually Work in Couloirs

If we accept that the forecast is less precise for micro-terrain, then the question becomes: what works? Mike emphasizes real-time, location-specific observations — especially during a bottom-up ascent.

High-value couloir assessment tools:

Hand shears / quick slab isolation: can you peel a slab? does it fail cleanly?
Pole probing: do you feel a cohesive slab over weaker snow? hollow drum feel? stiffness changes?
Cracking / shooting cracks: direct feedback that a slab is present and reactive
Spatial mapping: “left wall feels slabby; right wall is softer” — log it for descent decisions

These observations are “bullseye” because they are time-, location-, aspect-, and elevation-relevant. That relevance is exactly what you want when you are operating in a high-consequence terrain trap.

11) Why Snow Pits in Couloirs (and Aprons) Can Lack Fidelity

Mike’s argument isn’t anti-snowpit. It’s about fidelity. A pit on the apron may be unrepresentative of what’s happening 400 vertical meters higher. And in steep couloirs, constant sloughing can remix layers and erase clean stratigraphy, meaning you may not see a stable, readable structure.

In other words: a pit result may be true for the hole you dug — but not for the start zone you’re about to enter.

12) Bottom-Up vs Top-Down: Information vs Visibility

Mike expresses a preference for bottom-up travel, largely because of the information density it provides. You learn stability as you climb. You learn snow quality as you climb. You build a mental map of where slabs exist and where they don’t.

Top-down has real advantages too: it can be the only access option in some lines (lifts, rap stations, cliff bands), and it gives better visibility of cornices and overhead start zones.

But top-down without a bailout plan can create a psychological trap: once you’re 50–100 meters in, booting out feels expensive. This is where equipment strategy matters.

13) Ski Cutting and Cornice Drops: Valid Tools, High Skill

Ski cutting can be a useful technique for assessing wind slabs near the entrance or on exit slopes — but Mike calls it what it is: an expert technique. Most recreational skiers do it rarely, and do it poorly. In his view, the true specialists are ski patrollers who practice it frequently in their work environment.

If you do use ski cuts in steep terrain, you need:

Controlled setup and belay/rope options where appropriate
No exposure of people below
A clean escape line
A realistic understanding that even a “small” result can be catastrophic in a couloir

14) Skins as a Get-Out-of-Jail Card

One of the most actionable points in the talk: carry skins, even on lift-accessed days.

If you drop into a couloir and within the first turns you feel shooting cracks, or you find it terrifyingly icy, or you realize wind slab is worse than expected, skins allow you to transition and climb out efficiently. Without skins, the alternative is booting out — which can push groups into denial and continuation bias: “it’ll be fine… let’s just keep going.”

Carrying skins in your pack costs little, and when you need them, they are vastly better than wallowing upward in deep snow with skis on your back.

15) The “Other Party Above You” Problem (Human Overhead Hazard)

A modern couloir issue — especially in popular zones — is other groups. In the case study, the group was avalanched by riders behind them. More broadly, Mike flags a growing trend: it’s increasingly hard to be in a couloir without another party above or below.

In confined terrain, having other people above you is not just annoying; it’s dangerous. They can trigger wind slabs onto you. They can knock ice and debris down. They can pressure your decision-making. And if something goes wrong, you now have complex rescue logistics with multiple parties stacked in a terrain trap.

Practical takeaway: if another party is in your line above you, consider choosing a different objective.

16) A Couloir Travel Operating System: Practical Rules That Scale

If you want a couloir framework that scales across regions — Alps, Norway, Rockies, Himalaya — this is a conservative operating system based directly on the themes of the talk.

16.1 Choose better couloirs (not all couloirs are equal)

Prefer “hourglass” shapes with clean fans and forgiving runouts
Avoid lines that terminate in bergschrunds or cliffs unless you have the full technical plan and margin
Seek objectives with minimal overhead hazard and limited terrain feeding into the line

16.2 Start early (time = options)

Time reduces decision pressure and improves judgment
Time allows you to pivot to another aspect if conditions are wrong
Time helps you beat other parties into the line — reducing human overhead hazard

16.3 Move one at a time in exposure

Use radios to confirm safe zones
Do not stack the group in the fall line
Define islands of safety and communicate clearly

16.4 Treat wind slab as “guilty until proven stable”

Expect cross-loaded pockets near the top
Expect reactive slabs near exit slopes where deposition occurs
Expect different conditions wall-to-wall inside the same couloir

16.5 Use mountaineering tactics when skiing tactics are not appropriate

Side-step or downclimb icy choke points
Use boot crampons where needed
Rappel or belay where consequences demand it

16.6 Carry the kit (and know how to use it)

Beacon, shovel, probe — and practice
Skins as a bailout tool
Radios for communication

16.7 Ask “juice vs squeeze” before you commit

If surrounding slopes look wind-scoured and miserable, and you’re entering a couloir hoping for a small pocket of better snow, it’s worth asking the question Mike asks: Was the juice worth the squeeze? High consequence terrain for low reward is not a good trade.

Closing

Couloirs can be some of the most rewarding terrain in the mountains. They’re aesthetic. They’re focused. They’re often memorable in a way that open slopes aren’t. But the risk equation changes because the consequence curve rises fast.

In couloirs, the goal isn’t to eliminate risk. The goal is to manage it with better terrain choices, better timing, better communication, and a bigger margin — because when things go wrong in confined terrain, they go wrong quickly.

Key references: Avalanche Encyclopedia, Avalanche Canada Glossary, Terrain Traps, ATES.

Search This Blog

Ski Touring and Splitboarding in Himalayas