The International Scale of River Difficulty & Risk Factors.
There is a great deal of confusion about what the classification system means. Rafting companies hardly ever utilise the actual American Whitewater designated classification of a river in their marketing; rather, they often utilise a number that represents the value proposition of the river they are promoting; as a result, the concept of classification has been lost, and the public in general does not understand the relationship between difficulty and skill (on a guided trip the guide is primarily responsible for navigating the raft, while the guests are largely “along for the ride” and may not be tuned in to the actual challenge the guide is experiencing).
Many times, guests book a trip on a river based on the advertised classification of it, without knowing any statistics on risk probabilities and information related to what they often really want to know; “is someone in my group likely to become injured or killed”…. Classification does not address this, and as a result we are seeing many people lose their lives on rivers, followed by lawsuits where the plaintiffs allege (and often prove) there was a failure to warn them of the risks of the river.
The International Scale of River Difficulty is the American Whitewater version of the rating system used to compare river difficulty worldwide. The scale is not exact, and it is designed, if anything, to be shared among those who are NAVIGATING the river; it is much less relevant to customers who are paying guides to take them down said river. In addition to this scale being focused on the difficulties of navigating, rivers do not always fit easily into one category, and regional or individual interpretations may cause misunderstandings. As a result you get a lot of local slang terms; in Washington, for example, we have rivers like the Nooksack or the Suiattle, which are called “Class 3 with Class 5 consequences”… this flippant jargon makes some sense to those initiated, but it does not match the definitions of the AW system, as it has nothing to do with consequences explicitly, and so as a result there are many assumptions made as to what potential outcomes arise in Class 5 water.
Utilising classification for commercial trips is also problematic. If a guiding company advertises a river as Class 3, even if that is the correct definition according to AW, there may be another, larger company, that calls it Class 4; these two companies will compete for customers, who are expecting two very different things, and the one naming a river “Class 4”, will then have guests leave that river overconfident and unaware that the river they thought was Class 4 (an advanced level designation) was actually not very difficult at all, and then they will book a more difficult, and perhaps much more dangerous river, that is accurately labeled Class 3, and there will be an incredible risk there.
To a guest on a river trip what makes the river seem difficult are often not the things that make it dangerous. Rivers with big, rolling waves, but little to no obstacles, and warm water, are relatively low risk compared to rivers that meander, change with rain, and feature wood hazards and cold water, but sometimes the feeling of riding large towering waves (the “roller coaster” effect) brings people the sense that “this must be a high class”, when in fact the rapids could have been safely swam or navigating on an inflatable pool toy and the guide did nothing more then call an all forward paddle command and listen to the giggles.
The Classification System is not a substitute for a guidebook, first-hand descriptions of a run, or other sources of river information. As river difficulty increases, the danger becomes more severe. As rapids become longer and more continuous, the challenge increases. While these things are generally true, there is no substitute for actual statistics, and what we know is that there are some rivers that have a lower Classification, but much higher probabilities of injury or death; an example of this would be the Nooksack Canyon section near Glacier, WA, which has had numerous fatalities, but is rated Class 3 by American Whitewater, while the Upper Skagit River, which has been run 20-30 times more in the past 20 years, has had no fatalities, but has a higher Class 3+ rating (due to its challenges of navigation). Further, running an occasional Class IV rapid on a stretch of river is less consequential than dealing with an entire river run of this category, and as a result, rivers such as the Skykomish (rated Class 3 with a potential Class 4 crux) are advertised as Class 5 due to one particularly large rapid. Anyone who would then advertise the river as Class 3 would be subject to people misinterpreting the actual difficulty and running the Class 4 (often called “Class 5”) crux without realising it is the same section of river being called Class 5 by someone else.
There is no way to standardise the Classification System.
sources cited: American Whitewater
Whitewater Classification Applied to Triad River Tours Popular Rafting Sections
Sauk River/Sauk2 (high water; 4,000-7000 cfs)
Classification: 4
Sauk River/Sauk2 (medium water; 2500-4,000 cfs)
Classification: 3+
Sauk River/Sauk2 (low water; 800-2500 cfs)
Classification: 3+
Snoqualmie River/Sno2 (high water; 2400-5000 cfs)
Classification: 4
Snoqualmie River/Sno2 (low water; 1200-2400 cfs)
Classification: 3+
Skykomish River/Sky1 (high water; above 5,000 cfs)
Classification: 5-
Skykomish River/Sky1 (low water; below 2500 cfs)
Classification: 4
Skagit River/SK5 (low water; below 8,000 cfs)
Classification: 3-
Risk Formula
Years ago an article in Paddler Magazine brought to the surface the need for more logical and data driven conclusions to be drawn for whitewater river runners. The Risk Formula (probability x consequences) was adopted. This system is utilized by our staff as part of our extensive risk analysis for all river protocols. Here is a diagram showing how it works. Note that the X-axis (horizontal) measures severity, while the Y-axis (vertical) measures probability. Taking these two into account through multiplication, a new variable emerges as the total risk factor of a river as it relates to the probability and severity of physical harm to an individual.
Note: There is no calculation regarding psychological harm involved in risk classification. This is perhaps the most subjective measurement of all and is most challenging to quantify. We should not disregard the magnitude of the after effects of trauma associated with river incidents, especially with children, who may be more survivable in most whitewater accidents, but who typically suffer more psychological trauma and sometimes do not fully understand the risks they are undertaking at the time, further adding to the subsequent pain that can be potentially endured.
Risk Formula as applied to river rafting accidents
Risk Formula Applied to Triad River Tours’ Popular Commercial Rafting Activities (unofficial)
This is made using historical data, incident reports of American Whitewater, and the subjective opinions of staff/guides and other knowledgable/historical resources. Note that this is based on the events that have happened. Anyone can suffer a tragic accident or death on a river, but using a statistically significant analysis, we can gauge the severity based on what is most likely to occur.
Probability Metrics
Less than or near .01% (1 in 10,000). Rare
Less than or near .1% (1 in 1000). Unlikely
Less than or near 1% (1 in 100). Possible
Less than or near 10% (1 in 10). Probable
More than 10% = very likely or almost certain
Severity Metrics
No First Aid required (all is well)
Minor Injury requiring first aid
Injury requiring Doctor or Hospital visit
Major Injury
Fatality
Popular Commercial Whitewater River Sections of Western Washington
Sauk River (high water; above 4,000 cfs)
Probability: 3.5
Severity: 4
Risk Factor: 14
Sauk River (low water; below 2500 cfs)
Probability: 4
Severity: 2.5
Risk Factor: 10
Skykomish River (high water; above 5,000 cfs)
Probability: 4.5
Severity: 4
Risk Factor: 18
Skykomish River (low water; below 2500 cfs)
Probability: 4
Severity: 3
Risk Factor: 12
Skagit River (low water; below 8,000 cfs)
Probability: 2
Severity: 3
Risk Factor: 6
Skagit River (high water; above 8,000 cfs)
Probability: 3
Severity: 3
Risk Factor: 9
Snoqualmie River (low water; below 2400 cfs)
Probability: 4
Severity: 2.5
Risk Factor: 10
Snoqualmie River (high water; 2400-5000 cfs)
Probability: 3
Severity: 4
Risk Factor: 12
Combining Risk Formula with Generalized Whitewater RIsk Classification
Correlating the risk formula factor with classification
Controlling Risk Variables & Guest Accountability
It is important to recognize that the risk classification of a river is entirely separate from the ability of the participant to perform the tasks required for safe(r) passage, as well as the ability of the participant to sustain an injury or bad swim on a river trip. Further, the craft being utilized is also separate. A 13’ raft may be more likely to flip than a 15’ raft, but a 15’ raft may be slower to respond to a rescue; there are multiple variables to be accounted for. It is our best effort to provide you with this outline that showcases the primary variables that must be accounted for. Note that the river is the most objective aspect, and in fact, the participants are often the ones most likely to do something out of the ordinary.
River Conditions & Risk Assessment of River
High water risk increases flush drowning. Low water increases blunt trauma. Of the two, the higher water is the more significant risk to human life, so it is typically identified as higher risk, even though there are more incidents in lower water (see: Risk Formula above).
Participant Ability Level & Experience Level
Beginners increase likelihood of incident, as well as severity of incident due to lack of experience and familiarity with rescue procedures.
Participants who are not physically fit are less likely to be able to maintain the levels of exertion needed to paddle through big and long rapids, and therefore present an added risk.
Participants who cannot swim are not any less likely to end up in the river, but are more likely to be involved in a serious incident or fatality once in the river as they are not able to self rescue as easily as a person adept as swimming.
Equipment
Old worn out equipment can fail during a rescue, and must be replaced with new equipment.
Incorrect equipment being utilized, or a craft unfit for the conditions can increase the likelihood of an incident as well as hamper the response to the incident. In this case it is necessary to spend more money on diverse craft and equipment for varying conditions (especially in Washington where river levels constantly change).
Equipment that the guides are unfamiliar with does no good. Training must be included in every piece of equipment added to the safety system.
Staff
Beginner guides are more likely to be involved in incidents, and therefore are typically relegated to lesser risky river sections to build skill through diligent practice of safety maneuvers.
Entry level guides must be given the same training regarding hard skills as veteran guides, including but not limited to:
flip recovery drills
advanced first aid training
Swiftwater Rescue Training (SRT-1)
Veteran guides tend to be overconfident, and rely too much on their skills, therefore hubris is seen as a risk variable.
The “Dunning-Kruger Effect” is common among 2-4 year guides, who have a decent amount of experience, but may perceive their abilities being higher than they are.
