Deadly Swiss Avalanches, in Maps

In my previous post, I explored a dataset on fatal avalanches in Switzerland from the Swiss Institute for Snow and Avalanche Research (SLF). The dataset also contains the location of each avalanche, and here I’ll explore a few ways to show the data geographically.

In the map above, the location and date of each avalanche is used to make a time lapse with CartoDB’s Torque function. Each flashing white marker is one fatal avalanche. Besides the general location of avalanche risk in Switzerland and the seasonal pulsation of events, this map does not convey all that much information. However, I think it is worthwhile because it drives home the sheer number of deadly avalanches – 361 – during this period. We have to keep in mind that each of these flashing markers is a separate tragedy that together represent the loss of  465 lives.

This map shows the geographical distribution of fatal avalanches by the activity or location involved in the accident. As I discussed in the last post, the great majority occurred in open country during recreational activities like backcountry touring or off-piste skiing. The map illustrates that backcountry touring accidents are distributed fairly evening across the high Alps, while off-piste skiing and snowboarding accidents tend to be clustered. Closer inspection reveals that these clusters occur around high mountain lifts, like this, the largest cluster, one on the north slope of Mt. Gele and Mt. Fort near the resort of Verbier:

Screen Shot 2016-04-01 at 9.43.47 PM

This map also lends itself well to exploration. The Open Street Map base has great detail upon zooming, and you can click on each point to get more information about each avalanche, such as elevation, aspect, date, and number of fatalities.

Finally, here’s a heatmap showing the density of fatal avalanches, with red areas having the highest densities. The cantons of Valais (in the southwest) and Grisons (in the east) have the highest concentrations of deadly avalanche accidents. I used a Landsat mosaic as a base map, which allows for comparison of the relationship between terrain and avalanche density.

All avalanche data from WSL Institute for Snow and Avalanche Research SLF, 25 March 2016. Data and code available here. Maps generated using CartoDB.

Deadly Swiss Avalanches, in Charts

Snow-covered mountains are one of the most beautiful sights in nature, but in the wrong circumstances they can kill you. Skiers and other mountain enthusiasts sometimes refer to avalanches as the “white death”, and for good reason. Hundreds die in avalanches every year, and a great deal of effort is spent on trying to understand the factors that cause avalanches in the hope of decreasing this toll.

Located in the Alps and a mecca for winter sports, Switzerland takes avalanches seriously. The Swiss Institute for Snow and Avalanche Research  (SLF) monitors snow conditions, issues warnings, and collects data on avalanches. Their web site is very interesting for those interested in winter sports in the Alps. I find the snow maps particularly useful. But for this post I will use their data on fatal Swiss avalanches in the last 20 years to experiment with different ways to visualize some patterns and relationships.

The dataset includes information on the date, location, elevation, and number of fatalities, in addition to the slope aspect, type of activity involved (e.g. off-piste skiing), and danger level at the time of the avalanche. Over the last 20 years there have been 361 fatal avalanches in Switzerland, for a total of 465 deaths. Most avalanches killed only one victim.

Because I wanted to experiment with radial plots, I’ll focus on the variable of slope aspect in this post. Aspect is the compass direction that a slope faces. In this case we’re looking at the slope where the avalanche occurred. In Switzerland, the majority of avalanches occur slopes facing NW – NE, as you can see from this plot:

rose

The gaps at NNE and NNW are probably artifacts of how the aspect data was reported.

This pattern is common in the temperate latitudes of the northern hemisphere. Avalanches are more common on north-facing slopes because they are more shaded and therefore colder, which allows snowfall to remain unconsolidated for longer. When more snow falls, these unconsolidated layers can act as planes of weakness on which snow above can slide. It’s much more complicated that that, with factors like wind and frost layers coming into play. To learn more about how aspect and avalanches, see here. The pattern is unmistakable, but does it hold all year long? I separated the data by month to find out:

rosefacet

Fatal avalanches occurred in all months, but are much more common December – April

A few interesting insights emerge from this plot. First, February is clearly the most deadly month for avalanches.  In December there are actually quite a few avalanches on SE facing slopes, but by January the predominate direction is centered around NW. In February, and to some extent in March, it changes to N-NE. In April it’s NW again, but by then there are significantly few avalanches. So there are some monthly patterns, but I’m not exactly sure what the explanation is. Of course to really nail this down we’d want to do some statistics as well.

One pattern I expected, but did not see, was a decrease in the dominance of northern aspects later in the spring. I expected this because as the days get longer, the shading effect of north facing slopes decreases. It’s important to remember that these are fatal avalanches, and a dataset of all avalanches would look different. For example there are probably a lot of wet avalanches on southern slopes in the spring. But these are much less dangerous than the slab and dry powder avalanches, and therefore not reflected in the fatality data.

The rose style plots above are useful, but I wanted to try to illustrate more variables at once. So I tried a radial scatter plot:

Fatal Swiss avalanches 1995 - 2016: Slope aspect, elevation, and activity

Click on the image for the interactive Plot.ly version

This plot is similar to the previous ones in that the angular axis represent compass direction (e.g. 90 degrees means an east-facing slope). The radial axis (the distance form the center) represent the elevation where the avalanche occurred. And color represents the type of activity that resulted in the fatality or fatalities. Each point is one avalanche. The data are jittered (random variations in aspect) to minimize overplotting. This is necessary because the aspect data are recorded by compass direction (e.g. NE or ESE). The density of the points clearly illustrates the dominance of north-facing aspects. It’s also clear that most avalanches occur between 2000 and 3000 meters (in fact the mean is 2507 m). In terms of activity, backcountry touring and off-piste skiing and boarding dominate. And avalanches at very high altitudes are mostly associated with backcountry touring, which makes sense, as not many lifts go up above 3000m. Perhaps especially perceptive viewer can make out some other patterns in the relationships between variables, but I can’t. Any thoughts on the usefulness of this plot for the dataset?

Finally, I want to share a couple graphics from SLF (available here). Here is a timeline of avalanche fatalities in Switzerland since 1936:

The average number of deaths per year is 25, but this has decreased a bit in the 20 years. There were also more deaths in buildings and transportation routes prior to about 1985. Presumably improvements in avalanche control and warnings reduced fatalities in those areas. And what happened in the 1950/51 season. That was the infamous Winter of Terror. The next plot shows the distribution of fatalities by the warning level in place when the avalanche occurred:

Interestingly, the great majority of deaths happened when warning levels where moderate or considerable. There were significantly fewer deaths during high or very high warning periods. One reason must be that high/very high warnings don’t occur that frequently, but it’s also likely that skiers and mountaineers exercise greater caution or even stay off the mountain during these exceptionally dangerous times. There’s probably some risk compensation going on here. To really quantify risk, you have to know more than just the number of deaths at a given time or place. You also have to know how many people engaged in activities in avalanche country without dying. One clever approach is to use social media to estimate activity levels, as demonstrated in this paper.

Have fun in the mountains and stay safe!

Data and code from this post available here.

All data from WSL Institute for Snow and Avalanche Research SLF, 25 March 2016

A Map of All the Mountains in Switzerland Accessible by Public Transport

In honor of Swiss National Day I made a map of all the mountains in Switzerland accessible by public transport (cable car, gondola, cog-wheel railroad, funicular, and chairlift). With the Swiss transportation system you can get to almost all the base stations by train or bus. Having such great access to high places is one of my favorite things about Switzerland.

I made the map in CartoDB using data from a great Wikipedia page. There are about 100 peaks on the list, all with an elevation of at least 800 m, a topographic prominence of at least 30 meters, and a transport station within 120 m of the summit. The highest is the Klein Matterhorn, where you can take a cable car to within 20 m of the 3,883 m summit. The current weather at the time of writing? You guessed it – snow. Here’s the webcam.

For the base map, I used Open Street Maps Switzerland (easily done in CartoDB using XYZ map tiles). While it’s a little more cluttered than I’d like for a base map, the level of detail in the mountain areas is great. You can really zoom in to plan your trip.

Screen Shot 2015-08-01 at 4.42.57 PM

One more feature I played with in CartoDB is the customizable infowindows. I added a photo and a link to the Wikipedia page of each peak so it’s more enjoyable to to explore the map and use it as a tool for planning your summit assaults.

10 Maps that Explain Switzerland

Ah, Switzerland. Land of fondue, chocolate, and neutrality. If you want to learn more about this unique little country, maps are a great way to start. Not only does Switzerland have fascinating geography, but it also has a long and storied tradition of cartography and design.

1. Where in the world?

But you already knew that, right? And you also knew that the capital is Bern, not Zurich or Geneva. Switzerland is not very big. It’s the world’s 135th largest country. Four U.S. counties are larger. But what it lacks in size it makes up in other ways. For example, The Economist ranked it the best country in the world to be born in.

2. Confoederatio Helvetica

cantons-page-001
Switzerland is made up of 26 cantons, many of which were established as sovereign states hundreds of years ago. Then, in 1848, with the establishment of the Swiss Constitution, the cantons joined together to form the Swiss Confederation, or in Latin,  Confoederatio Helvetica. That’s where the abbreviation “CH” comes from.

Switzerland is a federal states and the cantons still retain strong identities and policy autonomy, in a way that’s analogous to the states in the U.S.

3. A multilingual nation

Switzerland has four official languages: German (the most prevalent), French, Italian, and Romansh. Romansh is spoken by less than 1% of the population, and only in a few places in Eastern Switzerland. I personally have never heard an utterance of Romansh. But it’s the only language unique to Switzerland, so I suppose it has a special place in the Swiss national identity.

The Swiss have a well-deserved reputation as polyglots. Almost all Swiss people I know speak at least two Swiss languages plus English, and some many more.

4. Let’s get physical

land use-page-001

This map shows the terrain of Switzerland together with land use. You can immediately see that Switzerland is a mountainous country, with the Alps  dominating the southern 2/3 and the smaller Jura Mountains along the northwest border. The bit in the middle, which is also where most of the people live, and most of the agricultural land and industrial production are located, is called the Swiss Plateau.

You’ll also notice the lakes. Switzerland has a lot of them, including some of the biggest lakes in Europe. Most Swiss lakes, including Geneva, were formed when the ice sheets of the last glacial period retreated, leaving deep basins carved by ice, and filling with water from the melting glaciers. More on the ice age below.

5. A geologist’s paradise

Ok, this one’s not a map. It’s a geologic cross section (source) showing a very simplified version of what the earth might look like if you cut out a slice 50 km deep and several hundred km long from Italy in the south, through the heart of the Swiss Alps, and north into France. The diagram gives an idea of the folding and faulting wrought by the massive tectonic collision that created the Alps.

In simplest terms, the Alps formed when two tectonic plates, the African and Eurasian plates, collided over millions of years. It all started in the Late Cretaceous, around 100 million years ago, when the ocean that separated what are now Eurasia and Africa began to close. Eventually the two continental masses themselves collided, with rocks on African side thrust up and over the Eurasian plate. The suture where the two plates became fused is called the Insubric Line.

The Alps are tectonically active to this day, raising up on the order of 1 mm per year. To geologists, the Alps are special because they were the first collisional mountain range to be studied extensively and much of the early understanding of structural geology comes from those pioneering Alpine studies.

6. The ice age

LGM

Made with the Swiss Federal Geoportal mapping tool

If the great tectonic collision provided the medium of folded, faulted and uplifting rock, the ice ages were the sculptor who fashioned the Swiss Alpine landscape into the wonder that we recognize today. The map above shows the extent of the ice cap that covered much of present-day Switzerland during the last glacial maximum, about 20,000 years ago.

The glaciers carved the spectacular U-shaped valleys and jagged peaks of the Alps. They also created the basins that would eventually be filled with water and form the Swiss lakes. Other evidence of the the glaciers is often visible in Switzerland, such as great boulders carried by the ice and stranded, and gentle hilly moraines that dot the Swiss Plateau.

7. The trains run on time

Back to the present day. One of the best things about Switzerland is the passenger train network, depicted on the map above, which you’ll find in every train car and station in the country. It’s the densest passenger network in Europe. You really can get just about anywhere on the train, even high into mountain villages on the many cog wheel and narrow gauge lines. And the trains are on time. Well, 95% of them, according to the Swiss national railway company. To really appreciate the attention to detail that the Swiss give to rail travel, check out this incredible diagram.

8. Let’s hit the slopes

When you think of Switzerland, you think of skiing, and the Swiss Alps have some of the top ski resorts in the world. One thing I love about the alpine ski resorts, aside from the great slopes, are the beautiful hand drawn piste maps. Here’s one of the Grindlewald/Wengen area in the Bernese Oberland. Just looking at it makes me want to start planning next year’s ski trip.

9. Direct democracy

Anti-Einwanderungsinitiative 2014.svg

“Anti-Einwanderungsinitiative 2014” by Furfur, based on the file Kantone der Schweiz.svg, made by KarzA. – Own work, data source: Neue Zürcher Zeitung: SVP-Abstimmungskrimi vorbei: Die Überraschung ist perfekt. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

Switzerland is famous for its direct democracy, the process whereby voters frequently weigh in on referendums, popular initiatives, and even have veto power over laws.  The Swiss vote a lot. Elections happen about four times a year and often contain several referendums at the national, cantonal, and local level, as well as ballots for elected representatives.

The map above shows the results of a popular initiative in 2014 that sought to restrict immigration by EU nationals into Switzerland. It passed narrowly, with strong support from the Italian- and German-speaking regions and despite opposition in the French-speaking regions.

Immigration is a contentious issue in Switzerland (as in many other parts of the world). Relative to its population, immigration levels are quite high, compared to say, Germany or even the U.S. In some cases, xenophobia wins out in popular initiatives, such as when the Swiss voted in 2009 to prohibit the construction of minarets.

10. A rich cartographic history

Dufour
With its varied geography and strong scientific and educational traditions, it’s no surprise that Switzerland has produced some stunning cartography. The first official map series to encompass all of Switzerland was produced by Guillaume-Henri Dufour and published from 1845-1865. The result of decades of surveying, drawing, copperplate engraving, and printing, the map achieved a high level of accuracy and detail for its time, and is also distinguished by the attractive use shading to show topography. More information on the Dufour map, as well as the equally impressive Siegfried map is available here.

Swiss excellence in mapping continues to this day. For example, the Federal Geoportal has a great mapping tool that allows you to access and display hundreds of data layers, from road networks to wetlands.

Swiss Railways Diagram

One of the great things about Switzerland is its passenger rail system. Service is frequent and convenient, and the network is dense so you can get almost anywhere in the country by train. And you can even ride the rails high into the Alps on the many cog wheel railways and funiculars. But Swiss railways really outdid themselves with this rail service diagram. If you download the full sized version (and you should) and zoom in, you will see that the diagram contains train arrival times for every station pictured (for those train services that run daily). With only a copy of this diagram you’d have all the information you needed to navigate the entire Swiss rail network, although you might need a magnifying glass to read the small print. The Human Transit blog explains how to read the notation.

Swiss railways