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A RuckSack primer on
By Michael A. Neiger
Last modified of May 14, 2006
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Great Lake's rip currents--some rivaling those of southern California--represent a life-threatening hazard to the uninformed wader, bather, swimmer, surfer, diver, or overturned paddler. Swimmers, paddlers, and waders must beware deadly rip currents, especially when winds are high or breakers crash ashore.
Rip currents on Lake Superior as well as the other Great Lakes have drowned numerous swimmers over the years. For example, on Lake Michigan, where swimming is more popular, deadly rips claimed the lives of at least 30 swimmers during one two-year period--on one beach alone, these currents killed seven swimmers in a single day. On beaches with breaking waves, rip currents account for 80 percent of all rescues by lifeguards. Nationally, rips kill more people than floods, tornadoes, or lightning.
A rip current is a fast-moving, narrow jet of surface water flowing out into the lake. As a coastal current, they return water back to the lake that has piled up along shore as the result of incoming breakers and swells. These mini-rivers are typically very narrow--usually less than 30 feet--and just long enough to penetrate the surf zone and breaker line.
In extreme cases rips can exceed 50 yards in width and several 100 yards in length. While rip currents have been referred to as rip tides or undertows, these are misnomers since rips are neither created by tides nor capable of pulling people underwater (however, they do pull people away from shore and out into the lake).
Rip currents--which represent the last stage of a horizontal, near-shore, circulation system--form as excess water piled up along the shore from wind-driven waves and swells attempts to run back into the lake, seeking its natural level. Many times, this excess water returns to the lake by running out along the bottom of the lake--beneath the incoming waves--in the form of undertow, which is also called backwash, backrush, or runback.
However, in certain situations, this piled-up, excess water is prevented from returning to the lake by a lake-bottom feature such as a shoal (a sandbar), reef, or bank that runs parallel to the shoreline, just offshore. Acting like a dam, these hidden structures tend to create channel-like reservoirs, known as longshore channels, between the underwater structure and the shoreline. Prohibited from flowing back out into the lake, the water accumulated in these channels ends up flowing sideways, along the shore, creating what are known as longshore or littoral currents.
In addition to the forces of gravity that help the water return to its natural level, longshore currents can be further strengthened by high winds, breakers, and swells that strike the shoreline diagonally. Such forces can be further amplified by the funneling effect of curved shorelines common to coves and bays, especially those framed in by headlands.
Longshore currents continue flowing along the shoreline until they can overcome a line of weaker incoming breakers, find a natural outlet in a bottom structure, pass over a sandbar at a low area, or rip a channel through a bar at a weak location. Longshore currents can also turn lakeward when they meet another longshore current head-on or when they encounter a shoreline irregularity or obstruction, whether manmade or natural, that redirects them out into the lake.
As the longshore current is turned lakeward and forced through a narrow outlet, it accelerates and becomes what is known as a rip current--a strong, fast-running, narrow channel of surface-flowing water flowing perpendicular to the shoreline. Fed by the longshore current, the rip current surges through the surf zone and the breaker line before spreading out in a fan- or mushroom-shaped manner and dissipating its energy.
While rip currents can occur anywhere waves break, they are at their deadliest during periods of high winds or big waves. Spotting a deadly rip, or the signs of one, can be tricky at best. However, polarized sunglasses may help since they can reduce glare and cut reflected sunlight.
Some rip currents can appear as streaks of choppy or churning turbid water that flow away from shore, through a break in the incoming waves. Sometimes, they are marked by an off-color plume of floating debris and sediment--foam, driftwood, vegetation, litter, and swirling sand and silt--that is moving lakeward or has become trapped in the no-man's-land along the very edge of the rip.
Cusps of sand protruding from the shoreline, breaks or gaps in the surf line, interruptions in incoming wave patterns, or breakers that appear to steepen prematurely may also mark the location of a rip.
While rips are usually associated with underwater sandbars near long, straight sand beaches, they can also be found near any irregular, shoreline-area feature capable of redirecting a longshore current lakeward. These features would include the naturally-occurring, such as coves, bays, reefs, islands, and headlands, as well as the manmade, such as piers, seawalls, artificial reefs, and erosion-control devices.
Keep in mind that rips can be fickle. They can vary in intensity by the minute, as wave trains come and go or winds change. Rips can also appear or disappear as quickly as shifting sand creates or alters underwater sandbars.
Highly-skilled surfers, paddlers, and rescuers have been known to utilize a rip current's assests--quick lakeward flow through areas where the breakers are either nonexistant or substantially moderated--to penetrate the surf zone and incoming breakers and reach the calmer waters beyond.
Since some rip currents can flow at speeds in excess of 5 miles per hour, swimmers caught in such a strong current should not try to swim (or wade) against it as even the best swimmer--an Olympic swimmer--can't out-swim it. Trying to buck such a strong current head-on could lead to premature exhaustion, a leading cause of drownings.
Instead, people caught in rip currents should conserve their energy by remaining calm and avoiding the tendency to panic. Proficient swimmers should take the shortest and fastest route out of the rip by either swimming sideways (laterally, parallel to the shoreline) or diagonally across the rip until the pull of the current weakens and they can calmly begin to swim back to shore, often pushed along by shore-bound waves and swells.
Less-proficient swimmers can float or tread water until the currents carries them into the calmer water beyond the breaker line where they too can begin working their way back to shore through the adjacent, incoming breakers.
To learn more about rip current safety, point your Internet browser to the National Oceanic & Atmospheric Administration's (NOAA) Web site at http://www.ripcurrents.noaa.gov or the U.S. Lifesaving Association's (USLA) Web site at http://www.usla.org.
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Content Copyright © 1984 -- 2006-05-14 by Michael A. Neiger
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