Canoeing in a thunderstorm
What are your chances of getting struck by lightning in a canoe? I've done a lot of canoeing on stormy lakes before, but when the thunder comes what is the real risk of getting struck by lighting?
My thinking is, if you're on a mountain lake surrounded by mountains, the lighting is much more likely to strike the mountainside than it is to strike the water; the size of the lake, and the elevation of the storm clouds would of course have to be factored into your risk assessment, but even if the lake was wide enough, and the storm low enough and out over the middle of the lake so the lightning would strike the water, is there a chance that the lightning will strike a person sitting in a kevlar canoe? Does the construction of the canoe make you more or less likely to be struck by lightning? Will striking the water be the path of least resistance?
How likely are you to be struck in a canoe and what should you do if caught in a thunderstorm?
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I've been inquiring about lighting safety in general, and the more I read the less certain I am about anything.
A: While boating incidents are a big fraction of lightning deaths, and deaths of fishers are over twice as great as of beach bums, there's a confounding factor: Fishermen spend more time on the water, and are not dismayed by cloudy weather.
B: The actual ground strike density is fairly low. Alberta Forestry has a lightning detection system that is about 90% efficient at detecting ground strikes, and plotting them to an error of about 1/2 km. Peak strike densities run about 4 per km2 per year.
C: Strike density is not what you would expect. The foothills an hour's drive from the mountains have over twice the strike density as the mountains themselves.
D: Height isn't as big a win as you think. All other things being equal the protective cone is only about 30 degrees wide: That is, a 100 foot high tree will have few strikes within 50 feet of the base. A thousand foot high cliff will have few strikes within 500 feet of the base. In mountains, average slopes aren't that steep. (I'm trying to get data from Alberta's detection network to see if there is strike clustering on ridges compared to passes.)
E: In terms of risk the U.S. typically has 15-20 lightning deaths a year. For comparison some 7000 people a year die slipping on the soap in their bath. *
(As a commenter points out, most people bathe more frequently than they experience thunderstorms. Absolute risk: chance of an event happening. Relative risk: chance of an event happening with other constraints. The absolute risk of bathing is much lower than the absolute risk of thunderstorms. The risk per bath or per storm shows bathing safer. If you compared risk per bath vs per audible strike, it gets murky.
F: The shoreline may not be safer. Given the partial attraction to taller objects, the fringe of trees around a lake may get more strikes than the lake itself. So you want an even spread of lower trees a few hundred meters away from a stand of taller trees. This discussion on reddit's askscience https://www.reddit.com/r/askscience/comments/1mm794/when_lightning_hits_a_large_body_of_water_how_far/ suggests that strikes have to be very close (20-50 feet) to have a dangerous effect. You may be safer paddling near the shore rather than going onto the shore.
G: Consider the following scenario: You're out for a day paddle, and are about an hour away from your cottage. Storm comes up, lightning crashes, and icy rain is pouring out of the sky. You go to shore, but you are still wet, and rain keeps you wet, and the wind's evaporation cools you more, and now not moving and not generating heat. You cool off. You start to shiver. So the question then is: Does being on shore reduce the risk of harm by lightning more than it increases the risk of serious hypothermia? In the outdoors we often have to make this decision of relative risk of alternative actions.
H: I have been caught by thunderstorms canoeing, and have gotten off the lake post haste. Associated with these storms are often very strong winds. I consider the wind to be far more dangerous than the lightning.
This does not mean ignore thunderstorms, but overall I consider the risk (Probability of death or serious harm) to be inflated. Does not mean that you shouldn't avoid the hazard when reasonable to do so. LOTS of things in outdoor pursuits have an element of danger. The risks however are as much from the weather in the rest of the storm as the lighting -- wind can capsize your canoe, drive you onto a lee shore, or blow you far from shore to where the water is really rough. Rain can be blinding. The combination cold enough to induce hypothermia.
One time on Reindeer Lake in Saskatchewan, we saw a squall line coming at us. We made for shore and beached in dead calm, unloaded the canoes, and started to set up camp. We brought the canoes up on shore. 10 minutes after we landed we had 3 foot breakers pounding the rocks. Our camp was chosen in a hurry, and was a ridge of rock about 50 feet wide, and 8 feet off the water. It was a spit sticking out then paralleling the lake. The wind picked up one of canoes and carried over the spit into the water behind. This was a 26 foot voyageur canoe weighing some 280 lbs.
Overall if the choice was to go out in stormy weather or sit inside waiting for your next heart attack, I suspect that sitting inside is the higher risk activity.
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Being struck directly is very unlikely though.
Canoes are often made from wood, aluminum or fiberglass, although some plastic is used as well.
Lightning strikes insulating materials all the time, like wooden trees or wooden houses. This is why lightning rods are found on wood buildings, to stop any lightning bolt from setting the building on fire.
Lightning often strikes trees. There are plenty of pics and videos on line showing tall trees being blown to pieces by lightning. If a massive tree trunk cannot stop a lightning bolt, a half-inch plastic boat hull will not stop the bolt either.
Lightning can blow a hole in the bottom of the boat and cause it to sink.
Finally, the hazard of being out on a lake in a lightning storm is the boater is the only object sticking up above the water for quite a distance. Lightning tends to strike prominent objects (trees, buildings etc) rather than flat ground. So in turn the boater is in serious risk if they are the only object sticking above the water.
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Your chances of getting hit by lightning while on the water are actually higher then if you are on the beach. (unless you are fishing)
Fishing contributed to almost half - 46% - of the water-related deaths involving lightning strikes; while boating (power boats, canoes, sailboats, tubes) added another 25%. About 20% of the victims were relaxing on a beach, while about 9% of the victims had been swimming. Source
One boat insurance company reports the odds of your boat being hit is 1.2 in 1,000. It later goes on to say that a multi hull boat in Florida is the most likely to be struck.
According to the most recent (2000-2005) BoatUS Marine Insurance claim files, the odds of your boat being struck by lightning in any year are about 1.2 in 1000. source
If you can get out of the water, do.
Even though the odds are in your favor that your boat may never be hit by lightning, if it happens it can have devastating effects. Don't take a chance, protect yourself. If you are in a small boat and close to shore when a thunderstorm approaches, get in and off the water immediately. Source
Lightning safety tips
AVOID: Avoid water. Avoid all metallic objects. Avoid the high ground. Avoid solitary tall trees. Avoid close contact with others - spread out 15-20 ft. apart. Avoid contact with dissimilar objects (water & land; boat & land; rock & ground; tree & ground). Avoid open spaces.
SEEK: Seek clumps of shrubs or trees of uniform height. Seek ditches, trenches or the low ground. Seek a low, crouching position with feet together with hands on ears to minimize acoujstic shock from thunder.
KEEP: Keep a high level of safety awareness for thirty minutes after the last observed lightning or thunder. Source
If you can't get out of the water, stay 20 to 50 feet (6 to 15 meters) away from other boats and tall objects (like cliffs). Get as low in the boat as you can, don't touch anything wet or metal.
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I don't know how to compute the odds, but being out on a lake in a lightning storm is a really bad idea.
The mountains around the lake aren't going to provide cover. There are several models about how nearby tall object protect you from getting directly hit by lightning. None of these are accurate or guarantees, as there is still much chance associated with the path of any particular lightning strike. Think of these models in terms of probability. They are too far away and at a low angle. If these mountains did provide protection, then lightning shouldn't ever strike the side of the mountain. However, this happens frequently. If a peak can't protect the side of the mountain, it certainly isn't going to protect a more distant lake.
The old model says that a tall object provides about a 45° cone of protection. Newer models use something like a 30 m sphere. Either way, mountains rising from the shore of a lake don't offer any practical protection.
When you're in a canoe on a lake, you're the tallest thing for quite a distance around. That increases the chance of lightning hitting you relative to the same spot on the lake if you weren't there. Put another way, think you your head sticking up as attracting lighting strikes that would have otherwise hit within a few 10s of meters at least.
No, the fact that the canoe is made of a insulating material is irrelevant. Since there is no current to define the static electric field, as long as there is any connection between you and the water, regardless of how resistive, the static field will be the same. It is this static field that in part determines the path of the lightning strike.
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