Avalanche Glossary: Terrain Traps

What are Terrain Traps?

When we think about avalanche risks, we often focus on the snow conditions, but the terrain itself plays a critical role in how dangerous an avalanche can be. This is where terrain traps come into play. A terrain trap is any natural feature in the landscape that increases the severity of an avalanche by amplifying the amount of snow, debris, or force that collects in one concentrated area. These traps turn what might be a smaller avalanche into a deadly, life-threatening situation.

Whether you’re skiing, snowboarding, or snowmobiling in the backcountry, learning to identify terrain traps is essential for staying safe.

How Terrain Traps Increase Risk

Imagine you’re on a slope, enjoying some fresh powder, and an avalanche releases above you. If you’re in open terrain, the snow might flow down the slope more evenly, spreading out as it travels. But now imagine you’re in a narrow gully or at the base of a steep slope. That same avalanche will channel into the confined space, concentrating the snow and debris into a powerful, dense force. Terrain traps funnel the snow into places where it piles up deeper, turning a moderate slide into a much more dangerous situation.

Metaphor: Terrain Traps as Avalanche Funnels

Think of terrain traps as funnels. If you pour water down an open hillside, it will spread out. But pour that same water into a funnel, and it concentrates into a single stream, flowing faster and more forcefully. In an avalanche, terrain traps act like funnels for snow and debris, channeling everything into a confined space where the destructive power is multiplied.

an avalanche funneling into a terrain trap in the mount baker backcountry
A huge avalanche on the Shuksan Arm at Mount Baker funnels into a terrain trap. Thankfully the guy in the corner was out of harm’s way and not in the gulley.

Common Types of Terrain Traps

Terrain traps come in many forms, and some are more obvious than others. Here are the most common types of terrain traps you might encounter in the backcountry:

  • Gullies and Canyons: These narrow, steep-walled areas are some of the most dangerous terrain traps because they confine avalanche debris into a small space, causing snow to pile up deeply. Avalanches that would otherwise spread out across a wide slope instead funnel into these chutes, burying anything in their path.
  • Cliffs and Rock Bands: Avalanches that sweep skiers or riders over cliffs can cause severe trauma, even if the avalanche itself is not large. Rocks at the bottom of these features act as obstacles, turning a fall into a deadly impact zone.
  • Tree Wells: In forested areas, tree wells can act as mini terrain traps. An avalanche or a fall can bury a rider in deep snow around the base of a tree, trapping them in an oxygen-deprived space.
  • Creek Beds and Flat Spots: Flat areas at the base of a slope may seem safe, but they can act as traps where snow collects deeply during an avalanche. Creek beds can also fill quickly, leaving you buried in snow with nowhere to escape.

Why Terrain Traps are Dangerous

Avalanches in open terrain can be dangerous, but when they involve a terrain trap, the consequences can be much more severe. The concentrated snow and debris bury victims much deeper, making rescue and survival far less likely. Even a small avalanche can become fatal if it funnels into a terrain trap.

The primary dangers of terrain traps include:

  • Deep Burial: Terrain traps like gullies, creek beds, and low spots can collect massive amounts of snow, causing deep burials that are difficult to survive or escape from.
  • Trauma: Avalanches sweeping over cliffs or through rocky terrain increase the risk of severe injury from impacts with rocks or trees.
  • Lack of Escape Routes: In a gully or a narrow chute, there are often no escape routes, trapping riders in the direct path of the avalanche.

Signs of Terrain Traps

Being able to identify terrain traps is crucial when planning your route in the backcountry. Here are some key features to look for:

  • Steep-Walled Gullies: If you’re in a steep gully or chute, consider how an avalanche would behave in that space. If the walls of the gully prevent snow from spreading out, you’re in a terrain trap.
  • Low Spots: Be wary of flat or low areas at the base of slopes. These spots can collect debris, and even a small slide could bury someone deeply.
  • Cliffs and Rocks: Any terrain with exposure to cliffs or rock bands poses a serious trauma risk if an avalanche occurs.
  • Creek Beds: Even if dry, creek beds act like natural troughs that can fill with snow in the event of an avalanche.

How to Stay Safe from Terrain Traps

Terrain traps can’t always be avoided, but by recognizing them and adjusting your travel plans, you can reduce the risks. Here’s how to stay safe:

  1. Avoid Terrain Traps Whenever Possible: The best way to avoid terrain traps is to recognize them early and reroute your plans. Try to avoid narrow gullies, steep chutes, or other confined spaces where avalanches could concentrate.
  2. Travel High on Slopes: If you have to navigate around a gully or low spot, try to stay higher on the slope to avoid getting caught in an avalanche funnel.
  3. Spread Out: When crossing risky terrain, such as a gully or creek bed, spread your group out. This reduces the risk of everyone getting caught in the same avalanche and also lessens the load on the snowpack.
  4. Use Avalanche Reports: Always check avalanche bulletins to assess the overall risk level. If the risk is high, avoid slopes with terrain traps altogether.
  5. Assess Your Exit Strategy: Before committing to a slope, ask yourself: “If an avalanche happens, where will I go?” If the answer is “nowhere,” reconsider your route.

Terrain Traps—Natural Features with Unnatural Risks

In the backcountry, the landscape itself can sometimes be as dangerous as the snowpack. Terrain traps are natural features that funnel avalanche debris into confined areas, increasing the likelihood of deep burial, trauma, and death. Recognizing terrain traps and adjusting your travel route to avoid them can be the difference between life and death in avalanche terrain.

By staying aware of terrain traps, paying attention to the landscape, and making cautious decisions, you can minimize your risk and keep your backcountry adventures safe.

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