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5 Things to know about the Potomac River and water temperature

Posted by George Stevens on Thu, Feb 02, 2012 @ 03:05 PM

Potomac River at Belle Haven Marina


1) The risk of falling overboard or capsizing may be small, but the threat-to-life of such accidents is most serious.

More than half of the fatal boating accidents on the Potomac River occur when the water is cold. Most such accidents occur in calm weather, relatively close to shore. Because fewer boaters are on the water, the likelihood of a prompt rescue is greatly reduced. Off-season boaters must be as self-sufficient as possible.

Immersion in cold water rapidly incapacitates and may kill boaters who are not wearing protective clothing. Surfers, sailboarders, and river paddlers wear wet suits or dry suits when the water is cold. Off-season sailors, fishermen, hunters, and other folks out in open boats can use these same precautions to greatly improve their safety on the water.

2) What happens in cold water?

Cold water removes heat from the body 25 times faster than cold air. About 50% of that heat loss occurs through the head. Physical activity such as swimming, or other struggling in the water increases heat loss. Survival time can be reduced to minutes. Strong swimmers have died before swimming 100 yards in cold water. In water under 40 degrees F, victims have died before swimming 100 feet.

3) Cold Shock

Without a life jacket, a victim may inhale while under water (involuntary gasping reflex) and drown without coming back to the surface. This can only be prevented by wearing a life jacket at all times on the water in the off-season. There is no second chance. Exposure of the head and chest to cold water causes sudden increases in heart rate and blood pressure that may result in cardiac arrest. Other responses to cold water immersion result in immediate loss of consciousness and drowning.

4) Hypothermia

Hypothermia (decreased body temperature) develops more slowly than the immediate effects of cold shock. Survival curves show that an adult dressed in average clothing may remain conscious for an hour at 40 degrees F and perhaps 2-3 hours at 50 degrees F (water temp.). The crisis is more serious than these numbers suggest. Any movement in the water accelerates heat loss. Survival time can be reduced to minutes. Without a life jacket, drowning is unavoidable.

Even with a wet suit/dry suit on, one's hands rapidly become useless in water in the low 40's degrees F. Protective fingerless gloves for fishermen can be important. Shivering occurs as body temperature drops from 97 degrees F down to about 90 degrees F. Uncontrolled rapid breathing follows the initial gasping response and may cause loss of consciousness. The victim must attempt to recover control of his/her breathing rate.

5) Once in the water

Try to get back in or on your boat immediately. Do not leave the boat. If you are not wearing thermal protection and can not get out of the water, stay as still as possible. Fold arms, cross legs and float quietly on the buoyancy of your PFD until help arrives (Heat Escape Lessening Posture; H.E.L.P.). If 2 or more people are in the water, put your arms around one another. Stay still and close together (Huddle posture).



Tags: boating, Cold Water, Hypothermia