The Most Dangerous Natural Hazard Discovered: Rip Tides Claim Lives

What's the most dangerous natural hazard? It turns out that bushfires, floods, cyclones and sharks all combined pale in comparison to ocean rip currents--at least in Australia. Scientists have discovered that rip currents claimed more lives than any of these other natural hazards.

On average, rip currents are the cause of about 21 confirmed human fatalities per year. That's compared against 5.9 for bushfires, 4.3 for floods, 7.5 for cyclones and 1 for sharks. These particular averages, though, are perhaps not surprising considering Australia's landscape. It has about 11,000 mainland beaches with an estimated 17,500 rip currents operating at any given time.

So what are rip currents exactly? They're strong, narrow seaward-flowing currents. When unsuspecting swimmers go into the water, these currents can easily carry them significant distances offshore. This, in turn, can lead to exhaustion, panic and often drowning.

In order to find out exactly how deadly these currents are, the researchers analyzed data from Australia's National Coronial Information System. In the end, they found that there was an average of 21 confirmed deaths involving rip currents per during a period from 2004 to 2011.

"And this is likely to be an underestimate because there has to be a witness to an event who saw the person was caught in a rip, and then this information has to be included in the coronial report," said Rob Brander, one of the researchers, in a news release. "Other types of hazards, like bushfires, have the capacity to claim large numbers of lives in a single event. On the other hand, rip currents are almost always present and rarely result in more than one death at a time. But in the end, more people die as a result of them."

Rip currents aren't just a problem for Australia, either; they're a global issue. They can carry off swimmers on beaches across the world. Because of this, it's crucial to understand exactly how dangerous they can be and take proper precautions to prevent loss of life.

"As rip currents are a global problem, it is hoped that this study can be applied to other countries to more appropriately place the rip current hazard in perspective with and context of other natural hazard types," said Brander in a news release.

The findings are published in the journal Natural Hazards and Earth Science Systems.