Risk Assessment for Rivers and Avalanches

Disclaimer: This discussion is based on my personal experience, collaborators’ feedback on The Packraft Handbook, and publications (see references at bottom). This discussion benefited from the feedback of Trip Kinney, Heather Thamm, Chris Erickson, Betsi Oliver, Huw Miles and others on the email list, but the opinions are mine.

Trip Kinney, one of The Packraft Handbook‘s peer reviewers, commented: “You need to define risk.” So, I sat down and was like, no problem, “Risk is …. risk… is… hmm.” Then I googled it.

I ended up in a deep dive learning about risk as discussed by the avalanche and natural disaster communities. The avalanche literature was particularly helpful and relatable; it feels the most similar to the river setting and is familiar given my training and personal experience in avalanche terrain (see: Mt. Logan traverse).

Part of the problem when discussing risk is that many terms are similar: hazard and danger, exposure and vulnerability, etc. Another Packraft Handbook reviewer said, “I don’t like the use of these terms because I can think of three different interpretations for each one.” I agree, but then I realized that was part of the problem. Adopting the definitions designated by risk professionals will make it easier to discuss risk before and during our outings.

Risk is the likelihood of harm due to exposure to a hazard. You can assess risk with these questions: 

• What can happen?
• How likely is it that it will happen?
• If it does happen, what are the consequences?

The degree of risk depends on hazard, exposure, and vulnerability.

• Hazard: Hazards are environmental dangers, the things we can’t control.
• Exposure: Exposure refers to the people and possessions that the hazards can influence.
• Vulnerability: Vulnerability is the likelihood that exposure to a hazard will have harmful consequences.

I appreciate this hazard/exposure/vulnerability framework; it helps me make sense of my previous decisions and intuition regarding risk in the outdoors. I pictured these factors as dials on a mixing board and asked Sarah Glaser to illustrate them for The Packraft Handbook. I got some sweet tattoos out of the deal (cover photo).

Probability and Consequence

The hazard/exposure/vulnerability framework works well for big-picture decision-making: where to go and what to bring. But when we are actually on the river, a simpler assessment is preferable. On-the-fly risk assessment boils down to probability and consequence:

• Can I stay upright?
• How bad will it be if I don’t?

Probability and consequence are treated differently by the avalanche and river communities. The probability and consequence of an avalanche are part of the hazard—things we can’t control. We can’t control the likelihood and size of an avalanche.

In contrast, the probability and consequence of swimming a rapid depends on the swimmer—a swimmer without a life vest is more likely to experience harmful consequences than a swimmer with proper safety equipment. In river settings, probability and consequence are part of exposure and vulnerability—things we can control, or at least influence. (With the notable exception of dynamic river hazards like floods and moving logs, which have probability and consequence like avalanches.)

Danger

Another way to describe the difference between avalanche and river risk assessment is to be explicit about the danger. Hazard and danger are synonymous in avalanche terrain. The slide is just as dangerous to anyone caught in it. An airbag could keep you on top of the debris, but the airbag changes your vulnerability, not the danger of the slide.

Hazard and danger are not the same on the water. The danger depends on the paddler and their equipment. As with the previous example, a swim is more dangerous for someone without a life vest.

Real vs. Perceived Risk

The real and perceived risks of an activity aren’t always the same. In packrafting, two of the most likely perceived risks identified by expert boaters and swiftwater rescue instructors are strainers (objects that let water pass through but not bodies) and foot entrapment (getting a foot stuck on the river bottom while standing in swift water). However, there have not been any known packraft fatalities due to these risks. Statistically, the most significant real risks involved with the twelve known packraft fatalities are cold water and paddling solo. Packraft safety courses should be emphasizing drysuits and paddling with capable partners.

Conclusions

We would all benefit from adopting standard definitions of risk assessment terms to the degree that it is possible. Risk in terms of hazard, exposure, and vulnerability provides an excellent framework for decision-making during trip-planning. On-the-fly assessment is easier if you focus on probability and consequence: How likely is something to go wrong, and how serious are the consequences.

Your willingness to expose yourself to risk depends on your risk tolerance. That sounds like a great discussion for a later post.

These two examples might be of interest to people who want to keep exploring the hazard/exposure/vulnerability framework:

Playing with the Dials: Avalanche Terrain

In avalanche terrain, the hazards are the snowpack, weather, terrain, etc. We can choose to expose ourselves to a slope or not; exposure is kind of an on/off switch that we control. Vulnerability is our susceptibility to being harmed. We have a lot of influence regarding vulnerability; we can reduce our vulnerability with training, practice, releasable bindings, and capable partners.

Hazard, exposure, and vulnerability are like dials that can be adjusted to match our risk tolerance. Take avalanche airbags as an example. Avalanche airbags can be inflated to make you more buoyant and less likely to get buried. Using an airbag reduces your vulnerability: the consequences should be less harmful if caught in a slide. If your risk tolerance remains constant after buying an airbag, your overall degree of risk is reduced. But a concern with airbags is that your tolerance might change. You might think, “I can ski this slope; the airbag will keep me safe.” In this case, turning down the vulnerability dial is countered by turning up the exposure dial, making you more likely to get caught in a slide (greater degree of risk).

Playing with the Dials: Rivers

River hazards are rocks, holes, waves, water temperature, etc. Exposure can be an on/off switch (paddle or portage) but may depend on your boat control skill (can you maneuver around the hazard). Vulnerability is our safety net: equipment (life vest, drysuit, safe rigging on the boat?), training and practice (able to perform a wet re-entry, deploy a throw rope?), and paddling with capable partners is a huge boost to the safety net.

We recognize that the vulnerability dial is cranked up during remote trips in Alaska. No one is available to help if something goes wrong, and a small accident (a swim in glacial water) could have harmful consequences (hypothermia). We choose to compensate for the increase in vulnerability by decreasing our exposure: committing to portage difficult rapids and reducing our risk by choosing rivers with fewer hazards, say, Class II water instead of Class III.

References

• Technical Aspects of Snow Avalanche Risk Management (2016)
• AVALANCHE HAZARD, DANGER AND RISK – A PRACTICAL EXPLANATION (G. Statham, 2008)
• THE AVALANCHE TERRAIN EXPOSURE SCALE (G. Statham, B McMahon, I Tomm)
• Understanding Risk (website)