The Surprising Truth About a 100-Year Flood

The surprising thing about 100-year events is that they can happen year after year, not just once every 100 years. That's because the term 100-year event is about chance (probability), not a schedule. It’s a statistical term that means a 100-year event has a 1 in 100 chance of happening each year.

It's One in a Hundred, Every Year

Think about flipping a coin. There's a 50/50 chance of getting heads each time you flip the coin. But you might actually get heads three times in a row. Or 50 times!
Each year, a river may flood or not. The chance of it flooding to a certain height is 1 in 100, or 1%. But the river may have flooded that high three years in a row. Or more!

Thousand Year Event 

Up on the Rouge River in Quebec, just north of the Ottawa River, there is so much flooding right now that it's a 1000-year event. Such a high water level is 10 times less likely to happen than a 100-year flood. Each year on the Rouge River, there is a 1 in 1000 chance that the water will rise this high — a 0.1% chance of it happening.

Figuring Out the Chances

How do we figure out the chances of an event happening? Meteorologists (weather scientists) need at least 10 years of data to math out the chances. The more data they have (say, 30 years’ worth, for example) the more accurate their calculations are. As climate change brings us more and more wacky weather, they’ll have to keep recalculating the chances. What was once a 1000-year event may now be 10 times more likely to happen. New calculations will tell us; and they’ll have to keep redoing those calculations as the data changes.

Not Just for Flooding

The terms 100-year event or 1000-year event can apply to anything: storms, cleaning you room, or having chocolate cake for dinner in the bathtub. Though that last thing might be a 1-millennium event, maybe you can make it happen this year and next.

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Want to learn more? There’s a thorough but a bit complex explanation on the USGS (“geological service” that studies our planet) website.

Image by Pete Linforth from Pixabay
Story by Adrienne Montgomerie 

Snow?!? You've got to be kidding!

Over the past week, parts of Atlantic Canada have experienced one of the features ("It's not a bug, it's a feature!") of a Canadian spring -- June snow. In sympathy with the afflicted parts of the country, including those in the North where the winter's snow still lingers, we present this brief poem by Sci/Why contributor Margriet Ruurs - CE

Whether to Like the Weather or Not

Calm wind, clear sky, nice.

Shifting wind, scattered-cloud sky

Stratus clouds drifting by.

Cold front, sleet and ice.

Slightly drifting, shifting snow.

Freezing rain, snow and squall

I don’t like this at all.

Quick inside! Winter, go!

Photo by Margriet Ruurs

Cumulus clouds climbing high,

Cirrus clouds scatter

Back to sunny, warmer weather

And bright blue summer sky.

Naming Weather Highs and Lows

By Adrienne Montgomerie

When the weather forecast calls for a Colorado low or a Texas low, what does that mean?

The name is actually pretty easy to figure out: The low or high refers to the air pressure. The place name tells you where it is coming from. Weather generally moves across the North American continent from west to east, and more often from south to north.

Low pressure tends to bring clouds and warmer temperatures.
High pressure is associated with clear skies and cold.

So a Colorado low is an area of low pressure that formed in the US state of Colorado. It usually forms in winter and brings a lot more precipitation than usual for several days. From Colorado in the centre-west of the USA, that weather can travel up to Winnipeg and right over to the Atlantic ocean. Because it's winter, that precipitation is usually snow, which we can have a lot of fun with!

Another system that usually brings a lot of snowfall is a Texas low. As it moves across the continent, it picks up a lot of moisture from the Gulf of Mexico. When it reaches the colder temperatures of the Great Lakes, it drops that moisture as heaps and heaps of snow. It is said that most snowstorms in Ontario come from a Texas low.

An Alberta clipper is a little harder to figure out. Like the names for highs and lows, the place name tells you where it is coming from; but what does "clipper" mean? It's a system of low pressure too. Unlike the general way that weather systems move, the Alberta clipper heads southeast, toward the Great Lakes into the US. It carries precipitation and a quick drop in temperature plus strong wind. The winds are why this weather system is called a clipper: clippers were the fastest ships in the 19th century.

Sometimes there is more than one of these weather systems happening at once. Then, they can collide or clash, resulting in an even bigger storm.

Keep your ears open. What other storm names do you hear? Can you use what you know about lows and highs now to predict what kind of weather they will bring your way? If you live on the west coast, where do your weather systems come from?

The Science of Snow

I live in Regina, Saskatchewan. We joke that weather is more than small-talk here. Too often, it's what everyone is talking about.

This winter, it's a topic with a vengeance. According to Environment Canada, we've been setting snow records this year:

- a new daily record of 24 cm November 9
- more snow in the first three weeks of November than we had all last winter
- the snowiest November since the 1880s

In December, the snow continued. And with another 20+ cm dump yesterday, January just seems like more of the same.

As you can probably tell, I'm not a fan of snow. But if you can't get away from it, you might as well dig into it. So I'm digging out a copy of Snowflake Bentley by Jacqueline Briggs Martin, searching on the Internet, and turning to science to help me beat the winter blahs.

Snowflake Bentley tells the story of Vermont farmer Wilson Bentley, who studied snow and took pictures of snow crystals. In the book, someone tells Bentley that "snow in Vermont is as common as dust." I laughed when I read those lines. Did you know that snowflakes start out as tiny crystals no larger than a speck of dirt or dust, and join with other crystals when they fall? Most snowflakes are six-sided, and the size of one flake depends on the number of crystals forming it. When I was a child, I remember catching snowflakes on a mitten. An individual snowflake can be quite beautiful.

That's hard to believe when you look at the pile of snow in my front yard these days. Thank goodness for neighbours with snowploughs! Lately I haven't been looking at the individual snowflakes, like Bentley did, because there's just been too much of it. Some of it is packed hard; some is powdery; some has already melted and frozen often enough to form ice underneath.

The National Snow and Ice Data Centre (NSIDC) has collected a whole database of types of snow. The NSIDC site talks about blizzards, flurries, and snowbursts like the ones we've experienced this winter. We're too familiar with blowing snow and drifting snow. That's all we seem to see on the roads lately. The site lists some unusual types too, like "névé" (refrozen and compacted) and "graupel" (rounded snowflakes or snow pellets).

My favorite is hoarfrost. We've certainly had what feels like record amounts of hoarfrost on the trees this winter, but I haven't taken the time to enjoy the beauty of it. I think I'll go out and take some more pictures, as soon as it warms up.

Meanwhile, I thought I'd share some of the snow sites I found:

National Snow and Ice Data Centre

http://nsidc.org/cryosphere/snow/science/index.html

Science of snow: FamilyEducation.com

Snow Day by L L Melton

http://fun.familyeducation.com/childrens-science-activities/winter/35037.html

Study snow science: University of Montana

http://www.montana.edu/wwwes/programs/snow.htm

Please leave a comment and share interesting facts about snow or snow science with us.

By Marie Powell

Christmas counts - to the birds

By Marie Powell

As we start preparing the annual Christmas turkey (photo by tuchodi), tens of thousands of volunteers are out in search of other birds - on the annual Audobon Christmas Bird Count.

Before the Twentieth Century, many bird and animal species would need to fear the annual hunting parties in search of sport and/or food for the holidays. According to the Audobon website, this annual hunt turned into a bird-counting census on Christmas Day in 1900, when the idea was suggested by ornithologist Frank Chapman. In its first year, the bird count included sites from Ontario to California.

Today, Christmas bird counts are held across North and South America from December 14 to January 5. Bird counting usually takes place in groups within a defined area, and in all kinds of weather. The data collected helps scientists and researchers study the health of bird populations over time. That helps identify declining bird populations - and ultimately, declining populations tell us about the health of a given area or ecosystem.

It's a way of giving back - and when could that be more appropriate than at Christmastime?

For more about Christmas bird counts, or to find one near you, try these links:

Audobon: Christmas bird count: http://birds.audubon.org/christmas-bird-count#

Audobon: Get Involved: http://birds.audubon.org/get-involved-christmas-bird-count

Bird Studies Canada: http://www.bsc-eoc.org/volunteer/cbc/index.jsp?targetpg=cbcparticpate&lang=EN

Marie Powell is a freelance writer and author of Dragonflies are Amazing (Scholastic).

Harvest Time in the Forest

posted by Claire Eamer

It's harvest time here in the Yukon, at the northern edge of the boreal forest. The leaves on the aspen trees are beginning to turn sunshine-yellow, the fireweed is crimson, and the high alpine bushes are showing red. People are out in the bush every weekend, picking berries and gathering mushrooms.

So, I might add, are the bears, so the wise human berry-picker makes plenty of noise!

The forest here can look pretty sparse -- spindly trees and a forest floor covered with tiny plants, mosses, and lichens. You'd think that by the time the big two-footers and four-footers were done harvesting, there wouldn't be much left for anyone else.

But you'd be wrong. A lot of little creatures depend on the foods provided by the boreal forest to make it through the long winter, and they're out harvesting too. If you look closely at the tiny plants that flourish beneath the trees and along the forest's edge, you'll find plenty of goodies to gather.

In the alpine, where forest gradually gives way to alpine tundra, pikas are building up their haystacks. A small cousin of rabbits, a pika can stash away 20 kilograms of grasses, leaves, seeds, and flowers over the summer, much of it in large piles just outside the entrance to its burrow. When the winter wind whips across the bare mountainside, driving snow before it, a pika doesn't have to go far for a snack.

Down on the forest floor, the voles are also tucking away winter groceries. They're less ambitious than pikas, and a lot smaller -- like tiny, delicate mice. Still, a single northern red-backed vole might store up to 3 kilograms of seeds, berries, and fungi near its winter burrow.

But voles and many other creatures of the forest floor don't just depend on food hoards all winter. When snow covers all that autumn bounty and the forest looks barren, many of the forest's smallest creatures are still out there, awake and busy.

They scurry around all winter under the snow, in an area called the subnivean zone where the warmth of the ground partially melts the snow above it. There, tiny animals search the buried vegetation or scoot through tunnels in the snow above, still harvesting frozen blueberries, bearberries, cranberries, rosehips, seeds, kinnikinnick berries, fungi, and all the other tiny jewels of the boreal forest's treasure chest.

If you'd like to know more about what people and animals are harvesting in the Yukon forest, Jozien has a blog called Yukon Wild Berries.

To find out more about the physics of the subnivean world, the Cable Natural History Museum of Wisconsin has a nice online article about Subnivean Temperatures.

And here's a nice article in the St. Albert Gazette (Alberta) about subnivean life a little farther south in the boreal forest.

Or you can check out the chapter about life in the cold -- "Ice is Nice" -- in my book Lizards in the Sky: Animals Where You Least Expect Them.

Best of all, go for a walk in the autumn woods, with your local guidebook and a berry bucket. Happy harvest!

http://www.claireeamer.com/