Flush Drowning as a Cause of Whitewater Deaths

Most recreational whitewater fatalities are caused by fixed underwater entrapment or by "flush drowning," an obscure term frequently associated with high-volume rivers, continuous rapids, cold water, and a lack of prolonged underwater entrapment. Although entrapment drowning is typically associated with submersion hypoxia, flush drownings likely involve diverse mechanisms of death; as such, a concise definition is elusive. This said, certain risk factors may be predictively associated with flush drownings. We attempt to further characterize causes of fatal river accidents and possible effects of water temperature on injury pattern.

We reviewed river mortality data collected from the American Whitewater Association accident database comparing fatal whitewater accident trends in the Rocky Mountain region versus the Southeastern United States. We limited data from the Southeast to the months of June through August to create a warm water cohort. We then divided lethal accidents into flush drowning, entrapment submersion, or miscellaneous events, defining each category in specific terms.

Flush drownings were more common in the Rocky Mountains than in the Southeast subgroup and involved older victims on average than entrapment drowning or miscellaneous events. Entrapment drownings were common in both regions, primarily occurring at fallen trees or rock formations.

Flush drownings appear to occur more frequently in older persons. Although hypothetical, the relative increase in flush drowning in the Rocky Mountains might partly be the result of colder water temperatures. If the cause of flush drowning is better understood, safety in whitewater recreation may be improved.