Looking to produce slide path maps with GIS

I'm taking a GIS course this semester and I was thinking about producing a slide path map for maybe the Mt. Baker area, or another WA area for my semester project. I know NWAC would be a great resource to contact for data etc, and I also know of some professors at some of the universities in the PNW I could talk to, but do any of you know of any other sources for good data on slide paths around the Mt. Baker Ski Area, or shit for that matter maybe from just above Glacier to Shuksan?

Within GIS I can preform a slope analysis to see if there are any general trends in what angles these slides tend to trigger on, and additionally I can also look at what aspects tend to be the most prone to sliding as well. Futher, if the data are available I can also include in the digital file at least the temperature/ambient conditions that triggered the slide.

If anyone has any thoughts or resources that I might find useful for this project (other than NWAC) let me know. Thanks.

Look at avalanchemapping.org ( if you haven't already ). WSDOT keeps some pretty old atlases around for slide paths that affect roads. I've never seen a backcountry avalanche atlas for the areas you describe. Microsoft Live Maps ( maps.live.com ) has very high resolution imagery available. ( Far better than Google Earth or Google Maps. ) You can examine the imagery for trim lines indicating avalanche paths and then check the terrain data for steepness. If you're skilled at reading terrain you can differentiate between bare patches and avalanche paths.

This method could work acceptably for determining starting zone and track but won't be very useful at all for determining maximum runout for large events. However with careful work you could determine the beta runout location and perhaps make some educated guesses about runout for maximum events. Not sure about your level of experience or knowledge, but for some mountain ranges a:b are proportional to some degree. Sometimes directly. You can use the alpha:beta ratio to determine a likely maximum runout. I'm not sure about the alpha:beta ratio for the Cascades. In fact I'm not even sure such a value has ever been calculated.

Anyway, not sure if it matters but I'd stear clear of the dynamics models for determining runout. The math behind dense, granular flows is not well understood.

I'm really not too experienced at all with avy/snow science knowledge. I mean I know some of the fundamental principles that govern the processes but beyond that I'm just a noob to the whole thing. I'm planning on moving out to WA though after I finish school and have plans to take avy certification training for sure. I feel pretty competent with my ability to read/interpret aerial imagery and if I'm in doubt the prof I'm working with on this should be able to help me out.

What's this alpha:beta ratio you're describing? I wasn't planning on using models to predict max runouts or anything, but the alpha:beta thing sounds like it would merit further investigation on my part for sure. In addition to the maps, I will be likely producing a paper, or at the very least a powerpoint presentation describing my research and results. And if the maps look good, I'm sure I could make them available to people on here if they were interested in them.

Thanks for the info, I appreciate it.

This may be unimportant for your project. A bit tired. My last post should really have discussed the "relationship" between alpha and beta angles instead of ratio.

An avalanche path has a starting zone, track, and runout. In theory, an avalanche atlas ( a map of slide paths ) should accurately map the starting zone, track, and runout ( along with other parameters such as aspect, elevation of starting zone, and a profile of the path ). Sometimes it's easy to determine the spatial boundaries of the starting zone, track, and runout zone. Sometimes it's very difficult.

If you want to make an avalanche atlas, you're faced with determining the spatial boundaries of the path, including maximum runout for large events that may have a very long return period. ( 1:100. This doesn't literally mean the avalanche returns every hundred years, it means the probability of the maximum event is expressed as 1 chance out of 100 for each year. )

In the past, dynamics models ( after Voellmy ) were used to try and figure out the maximum lower boundary of the path. However most of this work has been discounted. Modern avalanche dynamics models are focused more on granular flows. But forget about that for a moment.

Empirical, statistical methods are more popular these days, especially with the risk management aspect of avalanche hazard mapping. Anyway, the beta angle is the angle between the starting zone and the first ten degree slope in the runout zone. The alpha angle is angle between the furthest known runout distance and the starting zone. Finding the beta angle for any avalanche path is relatively easy. Simply find the first ten degree slope in the runout zone and measure the slope angle from that point ( following a straight line ) to the top of the starting zone.

So how do you determine alpha? It's much more difficult. Often field surveys are used in which vegetation is analysed and possibly the area around the runout zone is examined for damaged vegetation, pseudo-moraines, rocks embedded in trees or rocks found in other unusual places, and other signs of avalanche activity such as flow signatures in soil or on tree trunks. People have been known to take core samples from trees and look for reaction wood that indicates a tree was struck by an avalanche. Simple and complicated. Time consuming as well.

In some mountain ranges there is a relationship between the alpha and beta angles for many of the avalanche paths. I'm not sure that any such number has been determined for the Cascades. But ... If you know the beta angle, it is theoretically simple to use a regression equation to determine the alpha angle. Then you can find the maximum runout distance for large events. With this information in hand, you can create an accurate map of the avalanche path. You should look at Donna Delparte's paper: http://www.ucalgary.ca/asarc/publica...uthor/Delparte and the filename is: DelparteThesis_AvTerrainModelling.pdf. I'm sure you'll find her work quite fascinating.

There are other complications with constructing avalanche atlases. First and foremost, you have to understand terrain and geography fairly well because an avalanche path isn't necessarily simple. There are alpine paths, sub-alpine paths, channelized paths, and open paths. Sometimes avalanche paths have very nice trim lines and sometimes not. Starting zone and track are sometimes relatively easy to determine for sub-alpine paths. It just depends - starting zone geometry can be awfully complicated as well. Alpine avalanche paths often have no visible boundaries and can be very difficult to sort out.

Also keep in mind, avalanches aren't always neat confined by drainages, and dry flowing avalanches in particular often travel wherever the day takes them. Over ridges, over large obstacles, etc. The unpredictable behaviour of dry flowing avalanches sometimes makes the concept of an avalanche path a bit less important. It's very important to remember than an avalanche path only shows you where avalanches have run in the *past*. However, with avalanches, sometimes past behaviour is a good indicator of future behaviour, at least in some paths.

So for fun, you can remember that most avalanches do not run full path but an avalanche atlas should describe the full path.

Try this link for more information on avalanche atlases: http://www.wsdot.wa.gov/Research/Reports/000/008.8.htm

FKNA man, thanks for all of that. I knew the stuff about 100 year slide events already as far as them being based on the 1/100 probability from doing a lot of fluvial geomorphological work already, but a lot of this info is new for sure. Thanks again for the extra resources and input. I really appreciate it. I'll keep you posted as to what's going on as I move further into this endeavor. Today is only the 4th day of the semester, and our GIS course will have its second meeting tomorrow, but from the sounds of what you're saying I'm going to be working on this most of the semester and won't have any time to procrastinate if I want to do this well. :)

Some good info CM.


My first instinct to get started would be talk to the Washington department of transportation. Those guys HAVE to know high risk areas that involve any of the roads, if if only plowed once a year in spring. Most of the guys I've talked to from the California dept know the zones where accidents have occurred, and probably have incidents recorded somewhere.

It would be an easy place to start and likely to be a good source of records.

And let's be honest. Most backcountry jaunts start by roads. :D

Happy to provide information. I hope your project goes smoothly and I'm interested to see your results. Kidwoo good suggestions as well ( and I love your upside down dog link ).

The Utah GIS site has a slide paths shapefile that would save you from digitizing slide paths. One of the PNW states may have a similar layer.

If you end up digitizing, I would look for a hazard map from the USGS or state geo survey that you could scan and digi. That will give you better results then trying to use aerial imagery. If you end up using imagery, I'd recommend using digital ortho Quads, they have been rectified for optical/perspective distortion and will give you better results. (if you didn't already know that)

A project idea I have been throwing around was to build a slide path map that also included aspect/elevation info to correspond with an Avi Rose. I always thought this would be useful for planning objectives and alternatives.

I'm interested to hear what you end up doing, and seeing a product. Good Luck.

-E

I did some around Colorado. I started with DEMs and converted to slopes, and highlighted the slopes that are in the range for starting zones. Then I overlayed those highlights over topo and orthophotos and looked where the paths auctually were. I didn't end up making a shapefile for each path, but just did highlights over a topo to show some kids at a local school where the potential was around that area.

Topos are a nice starting point instead of imagery, because it pretty clearly shows most slides with the cleared out swatches of trees, but they aren't usually as up to date as most image sets that are easy to get.

What software are you using?

try the folks @ i.s.s.w. they came to jackson a couple of years ago and there goodie bags had a map that shown all the resort slide paths.really cool topo/shaded/color coded shit . i'll have to find it and post it.out

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Originally Posted by Fenris

What software are you using?

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I'll be using ERSI's ArcMap v9.3. I'm really hoping to get my hands on some LIDAR data for this project, but I'm not holding my breath about that. We'll see though. I'm just kinda starting to do some digging right now as well for scholarly articles (via google scholar) to see what similar studies/attempts have been made.

Thanks for the input everyone. Hopefully I can produce something that would be beneficial.

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Originally Posted by CookieMonster

In some mountain ranges there is a relationship between the alpha and beta angles for many of the avalanche paths. I'm not sure that any such number has been determined for the Cascades. But ... If you know the beta angle, it is theoretically simple to use a regression equation to determine the alpha angle. Then you can find the maximum runout distance for large events. With this information in hand, you can create an accurate map of the avalanche path. You should look at Donna Delparte's paper: http://www.ucalgary.ca/asarc/publica...uthor/Delparte and the filename is: DelparteThesis_AvTerrainModelling.pdf. I'm sure you'll find her work quite fascinating.

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I was going to suggest Donna's work. Always good stuff under Bruce's direction. Torsten Geldsetzer has done some good GIS avalanche work under Bruce, but I can't find a link to the modeling paper/project that I was thinking of. he did something very similar to what you are describing, and takes into account the convexity or concavity of the terrain in the now velocity and runout length calculations.

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Originally Posted by passholer

try the folks @ i.s.s.w. they came to jackson a couple of years ago and there goodie bags had a map that shown all the resort slide paths.really cool topo/shaded/color coded shit . i'll have to find it and post it.out

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I think this might be the paper you're speaking of:

McCollister, C., K. Birkeland, K. Hansen, R. Aspinall, R. Comey. Exploring multi-scale spatial patterns in historical avalanche data, Jackson Hole Mountain Resort, Wyoming. Cold Reg. Sci. Tech. 37(3), 299-313. [Abstract] [Article]

You can find it here under the 2003 papers:

http://www.fsavalanche.com/Default.a...arentLinkId=40

You can find most of Bruce Jamieson's work from the University of Calgary here:

http://www.schulich.ucalgary.ca/asarc/publications

Happy reading!

For elevation imagery try http://seamless.usgs.gov/

You can download very high quality digital elevation model and ( sometimes ) imagery for a wide variety of areas from this web site. It's a bit tricky to use the site but everything is free.

Yeah, and I guess the USGS has digi ortho aerials for every quad in the country. Too bad most of them were probably taken during the summer time. That will make determining and interpreting slide paths much more difficult I'm sure. Its funny though, 'cause I really hadn't been considering grad school too much but this is definitely something I could get in to. Especially if field work means I have to spend time in the backcountry on my board...man that would be rough :rolleyes:

I also think it would be pretty ambitious but definitely beneficial to create an av map database for the US. But that's a whole 'nother ball of wax. Bet there could be some grant money for something like that though. Especially under the new administration "restoring science to its rightful place."

I don't know how meaningful lidar and other methods would be to most end users. Sure, we all like to have the most comprehensive dataset, but the cost of flying lidar whenever the conditions are right for nattys to rip out is beyond the scope of any avi or snow science org.

The spotty avi stats from different sources presents a statistical challenge as well. Sure, include as many attributes as you can for each event, that's the great thing about the science of GIS - it can use the info we have to answer questions we won't even think to ask for years.
But don't expect it to be easy or cheap to collect data that can qualitatively aid snow science any time soon - here's just not enough data density out there yet. For a long time to come, it's gonna take a mastery of statistics to be able to extract meaningful data for the hard science.

Avi safety could be enhanced for the typical skier by having a basic topo map of slide zone extents and a greyscale or subtle color code to represent frequency. Linetype can be used to convey many particularities in weather that may precipitate a specific slide zone (ie wet storm, upside down storms, deep hoar, etc).

I would urge you to read Edward Tufte , "The Visual Display of Quantitative Information". It is a masterwork and contains much specific info that may make your life easier and your maps better from now on.


Buena Suerta

Poor weather is often cited as the reason winter imagery is not collected. Is this believable? Who knows.

It is definitely easier to identify slide paths when they're full of snow. On the other hand, this won't necessarily tell you very much about maximum runouts. The main problem is record-keeping: North American recording keeping is well inside the return period for the largest events. Some records do go back to the time of AB Rogers, the exploration of the Yukon, and First Nations in Canada have some interesting cultural records of related avalanching ( but just in general ). The precedings of ISS 2004 contain a couple of interesting papers on indigenous cultures, including their knowledge of avoiding avalanches, and some ( rather melancholy ) poetry related to the subject.

As I mentioned earlier, it's also difficult to estimate runout distances for large, dry-flowing avalanches because their behaviour is highly unpredictable. This may or may not be relevant for your work. There is an interesting paper in the precedings for ISSW2008 that discusses avalanches affecting the Kitimat-Kemano powerline in British Columbia. I believe this paper discusses the use of dynamics models for estimating flow velocity. ( Although I've heard, more than once, that dynamics models rely on risky assumptions and/or have an uncomfortable element of black magic in their application. I don't use dynamics models or probability models so I really am not qualified to comment further. ) There is another paper in the precedings that discusses the RAMMS simulation software from Switzerland. You might find this interesting.

The other problem with finding money for a national atlas is the concept of "hazard". For obvious reasons, most avalanche paths pose no hazard because hazard only exists when people or facilities are exposed. Therefore, from a financial perspective, there really isn't any need for a comprehensive avalanche atlas for the entire country. Although I definitely think such a resource would be useful and fascinating. There would be some question about including alpine paths, which might be very difficult to map properly. The Kitimat paper shows you the general difficulty with respect to alpine paths.

You'd really have your work cut out maintaining this because at least a few new paths are created each season and the existing paths sometimes increase in size depending on the severity of avalanches during a given season. Some avalanche paths are quite good at devouring trees. Some interesting video here ( found in the Interior BC ski conditions thread: http://www.new.facebook.com/video/vi...1125132&ref=nf )

It's a really interesting subject. But you obviously know that!

Yeah, my prof and I have talked a bit about the "hazard" mapping approach. His experience with this was when he was working for the State of Oregon doing a bit of landslide mapping. The huge problem is of course, if you say that a "hazard" exists somewhere where someone already has a home and their insurance rates go up, are you then liable? What if you miss a slide path that then causes someone to loose property or worse, their life. So yeah, we've talked a little about some of the trickier issues surrounding this, but it is pretty wild stuff, and I like what highangle was saying about basically creating something that would help backcountry recreationalists better understand where potential danger lies via topo maps with paths mapped on them. In addition using symbology that can integrate weather conditions, snowpack obs for the event etc would be excellent. For the "hard science" end of my project, I would like to preform some sort of slope analysis to see what trends are occuring, as well as a conditions analysis. Its all pretty cool stuff though, and the ball is just beginning to roll on the project. Thanks again to all of you for helping me out with the links and articles.

IMHO, GIS needs to be a major tool of snow science. While much effort is devoted to the micro aspects of pits, lemons, fracture propagation, etc - a thorough GIS dataset can reveal macro trends that will answer many many empirical questions and aid prediction.
To this end, a comprehensive yet inexpensive and empiric standard of data collection needs to evolve.

GIS has the power to commensurate widely disparate data and represent it in a way that that makes many things very clear. Snow science can only benefit from a rigorous application of GIS.


Here's a classic example of inspired mapmaking. 7 statistical parameters explained with the absolute minimum amount of ink. Even though it's in French, it tells Napoleon's Russian story better than I ever could in English.



http://upload.wikimedia.org/wikipedi...0px-Minard.png


full size:

http://upload.wikimedia.org/wikipedi.../29/Minard.png


Look how he lost 32,000 men crossing the Berezinia River at -20 below...

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Originally Posted by highangle

IMHO, GIS needs to be a major tool of snow science. While much effort is devoted to the micro aspects of pits, lemons, fracture propagation, etc - a thorough GIS dataset can reveal macro trends that will answer many many empirical questions and aid prediction.
To this end, a comprehensive yet inexpensive and empiric standard of data collection needs to evolve.

GIS has the power to commensurate widely disparate data and represent it in a way that that makes many things very clear. Snow science can only benefit from a rigorous application of GIS.

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So then you're telling me that I could make a case for going to grad school for free and possibly maybe even getting paid to do it....:fmicon:

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Originally Posted by pbourdon

So then you're telling me that I could make a case for going to grad school for free and possibly maybe even getting paid to do it....:fmicon:

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I like the way you think.

:biggrin:

Yeah, I mean come on, field work for such a project consists of BC touring/ski area riding to collect spatial data via a GPS. Then the other work is hangin' out in the lab working on GIS.....doesn't sound like a bad gig to me.

a helicopter could significantly enhance the efficiency of a single observer as well...



:biggrin:

^^^Now you're talkin'.....

Hmm....

Dear University of Alaska Anchorage....It has recently come to my attention that a severe deficiency exists in the discipline of snow sciences...................with the Chugach experiencing more and more backcountry travel each year.............for my project I would need access to a helicopter, an experienced local guide, and my own lab based in Valdez...............

Sincerely,
pbourdon



I mean what's the point in dreaming if you're not gonna dream big right?
:biggrin:

get a faculty sponsor and publish a technical paper as an undergrad

you'll get lots of heli time then, as well as your choice of grad schools


:cool:

^^^ That's what I'm working on doing right now. Only trouble is, I'm in Michigan. My prof is a geomorphologist by trade, but is backing this project 100%. Of course, right now its just a simple project required as part of a class, but part of the requirements of the project is that I write up a technical report of my findings so.......

Build on your work every year. If you play this right, you'll be a rock star and your GIS will be your thesis.


Start small and then scale up, with rigorous keepable work all the way through.

I would start by identifying objective standards of data collection that any observer can use, even a satellite. This is the key to scaling the dataset nationally and globally. Your statistics classes should make much of this clearer as you learn the methods of making valid extrapolations from representative samples of spatial, or any other observational data.
In this way, I think you'll find the Bayesian approaches used in the biological and husbandry sciences quite powerful tools for updating what we know about 'A' based on what we've learned from 'B'.

Don't shy away from something this cutting edge because you're young and untrained. Nathaniel Bowditch was made a Fellow of the American Academy of Arts and Sciences when he was 25. This is something well beyond a PhD or professorship.

As the goals become clearer and you refine your approaches, don't be surprised to find lots of support cropping up from odd places. NASA, for example, has a lot of interest in snow science and GIS...

On the flip side, don't be surprised to find other people viciously competitive, even to the point of being underhanded. If you think people will steal your work and stab you in the back for class standing, wait until you experience the grownup adult world of REAL hacks playing for real money. The higher up you go, the bigger hazard this becomes. Watson and Crick kyped info from 'competitors', Eisenhower and Bradley stole ideas from Patton and took the credit...

Counterintuitively, the best way to 'guard' your work is to make it as public as possible. This is why I support the community being involved in this at some level. There's a lot of specific knowledge here. Maybe the little insight stoke that gives you inspiration to charge a very rewarding line?

:cool:

Hi Guys,

I have been working with GIS and Snow and Avalanche data for 10 years. pbourdon's ideas for Mt Baker were already done about 5 years ago by a couple of other students at Western Washington,in Alaska alot of work has already been done. Also to correct Cookie Monster the USGS DEM's that are available are very poor accuracy approximatly 70-100ft of vertical error. High res lidar is the best you can get but expensive and hard to come by they also need to be shot snow off and then snow on to be effectively used in GIS modeling. Just a heads up on this. Hazard modeling is ok on DEMs and I have done a fair bit as well. But maps tend to be turned all red in the zones most people look at so the detail is poor and we can just say that the general areas poses avalanche risk. This is all still evolving and there is much room for improvement the biggest challange is getting funding for this. I worked on the Colorado State Wide GIS Avalanche Database for 7 years before I saw a nickle. Last year we completed digitizing all the State Washington Highway Avalanche Altas's and produced GIS mapbooks for the corridors and have not gotten anything out of it yet. Currently we have over 4000 historically observed avalanche paths in our GIS database for Alaska, Arizona, Colorado, Idaho, Utah, Wyoming. We are currently working on California and then will do Montana. I have an article in the Feburary issue of the Avalanche Review on the best uses for GIS for snow and avalanche studies.

Sounds to me like you are in an intro GIS course. Good for you, even if it a second semester so called advanced course, the subject matter discussed here is going to be incredibly work intensive.

My 2 cents is that you want to come away from the course understanding some of what GIS can accomplish. Scaling back a bit, not worrying whether someone has done the exercise previously, may help you. If you take an area that has identified slide paths, say one mtn. pass, digitize them, then do a simple analysis of slope and aspect, you'll walk away from the class with some great intro skills. Find it interesting and more GIS courses may be in your future, where you may dive a little deeper into the previous mentioned ideas.

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Originally Posted by Chowda

A project idea I have been throwing around was to build a slide path map that also included aspect/elevation info to correspond with an Avi Rose. I always thought this would be useful for planning objectives and alternatives.
-E

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Agreed, this could be a fairly simple, very usable product.

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Originally Posted by gunniride

Sounds to me like you are in an intro GIS course. Good for you, even if it a second semester so called advanced course, the subject matter discussed here is going to be incredibly work intensive.

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It is an "advanced" course of sorts, but on the other hand it is still very basic. There were pre-req requirements for the course requiring that we had all taken the "intro" course or the geomorphology course taught by the same professor that was quite GIS intensive. That being said, the course is very interdisciplinary with majors ranging from geology, and natural resources management to geography and earth science education.

If these maps have indeed been produced by some stu's at WWU, does anyone know where I can find them? Or the accompanying technical papers? For the purposes of this class, I'm not opposed to duplicating these works, not to mention the experience it would offer me.

Avmapper, on the one hand I find it surprising there isn't much funding available for this sort of work but then again most of the administrations since the late 70s and early 80s haven't focused their funding into such arenas much any way. You would think though that this kind of work, especially around ski areas, residential settlements, and highways would be very important and when combined with the analytical potential of GIS very useful in aiding forecasting work.

And if you're not getting compensated for any of this work, how do you get by then? What do you do in the summer?

Thanks for the input.

edit-doing an avy rose seems like it would be fairly easy to do and fairly useful as well. Still, field data are critical for creating the best possible maps.

Avmapper, looking for any help with your work? :biggrin:

I was gonna say you had a pretty solid grasp on the capabilities of GIS for just starting an intro class!
What about building a few hypotheses related to area of continuous high-risk slope(ie acres in the 35-55 range)/aspect/whatever based on your best data available and test the results against documented avy paths. Doing any remote sensing? You could maybe get Imagine to find the young vegetation for you and throw that in the mix. Regardless what you do, based on what you've written so far and the grad-level GIS classes I have taken I can almost promise you that you will have the best project in the class. Don't try to get too crazy with your analysis and spend more time on your presentation and making sure everyone understands your project/analysis. Beyond the basics GIS isn't all that difficult...getting others to understand its capabilities and figuring out how to use it to solve their problems is the hard part.

"Also to correct Cookie Monster the USGS DEM's that are available are very poor accuracy approximatly 70-100ft of vertical error."

Are you referring to the DEM or high-resolution GEOTIFF data? I gather you mean "stock" without error correction?

I did a hazard analysis for a SWUG (South West ESRI User Group). Just after the Tsunami that hit Indonesia in 2004 I wanted to pose a hazard map for the western coast of the usa. I took raster elevation data from a coastal dataset converted it to pixels and created levels every 10 meters from below sea level to 100 meters above sea level. THis gave me a starting point to procede. I chose to use 30 meters ASL as the cut off for inundation since Banda Ache wave heights were approx 30 meters. I selected elevations from below sea level to 30 meters above sea level and created a hazard shapefile. THere was a bit of editing to show a continous connection to coastal areas, intercoastal waterways, river mouths etc. I then used the US census data for Population (2000) and clipped it to my coastal extent. thus giving me a term coastal population. Then it was easy to run an intersect of coastal pop vs elevation hazard. this provided coastal pop in the Tsunami hazard zone. in 2005 I came up with just over 16 million people. crazy crazy numbers. Yes it can happen here. I would love to see a discovery channel "it could happen tommorrow" on this subject. But who knew 250,000 people could die in Indonesia from the 4th largest ever recordable quake 8.9 to 9.2 depending on source.

I won a cool 1000.00 for the poster and ppt from SWUG.

P-16

My figure broke out the hazard into 4 areas, west coast inset, Pacific NW, NoCAL and So CAL. PM me for the powerpoint and pdf figure.

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Originally Posted by CookieMonster

This may be unimportant for your project. A bit tired. My last post should really have discussed the "relationship" between alpha and beta angles instead of ratio.

An avalanche path has a starting zone, track, and runout. In theory, an avalanche atlas ( a map of slide paths ) should accurately map the starting zone, track, and runout ( along with other parameters such as aspect, elevation of starting zone, and a profile of the path ). Sometimes it's easy to determine the spatial boundaries of the starting zone, track, and runout zone. Sometimes it's very difficult.

If you want to make an avalanche atlas, you're faced with determining the spatial boundaries of the path, including maximum runout for large events that may have a very long return period. ( 1:100. This doesn't literally mean the avalanche returns every hundred years, it means the probability of the maximum event is expressed as 1 chance out of 100 for each year. )

In the past, dynamics models ( after Voellmy ) were used to try and figure out the maximum lower boundary of the path. However most of this work has been discounted. Modern avalanche dynamics models are focused more on granular flows. But forget about that for a moment.

Empirical, statistical methods are more popular these days, especially with the risk management aspect of avalanche hazard mapping. Anyway, the beta angle is the angle between the starting zone and the first ten degree slope in the runout zone. The alpha angle is angle between the furthest known runout distance and the starting zone. Finding the beta angle for any avalanche path is relatively easy. Simply find the first ten degree slope in the runout zone and measure the slope angle from that point ( following a straight line ) to the top of the starting zone.

So how do you determine alpha? It's much more difficult. Often field surveys are used in which vegetation is analysed and possibly the area around the runout zone is examined for damaged vegetation, pseudo-moraines, rocks embedded in trees or rocks found in other unusual places, and other signs of avalanche activity such as flow signatures in soil or on tree trunks. People have been known to take core samples from trees and look for reaction wood that indicates a tree was struck by an avalanche. Simple and complicated. Time consuming as well.

In some mountain ranges there is a relationship between the alpha and beta angles for many of the avalanche paths. I'm not sure that any such number has been determined for the Cascades. But ... If you know the beta angle, it is theoretically simple to use a regression equation to determine the alpha angle. Then you can find the maximum runout distance for large events. With this information in hand, you can create an accurate map of the avalanche path. You should look at Donna Delparte's paper: http://www.ucalgary.ca/asarc/publica...uthor/Delparte and the filename is: DelparteThesis_AvTerrainModelling.pdf. I'm sure you'll find her work quite fascinating.

There are other complications with constructing avalanche atlases. First and foremost, you have to understand terrain and geography fairly well because an avalanche path isn't necessarily simple. There are alpine paths, sub-alpine paths, channelized paths, and open paths. Sometimes avalanche paths have very nice trim lines and sometimes not. Starting zone and track are sometimes relatively easy to determine for sub-alpine paths. It just depends - starting zone geometry can be awfully complicated as well. Alpine avalanche paths often have no visible boundaries and can be very difficult to sort out.

Also keep in mind, avalanches aren't always neat confined by drainages, and dry flowing avalanches in particular often travel wherever the day takes them. Over ridges, over large obstacles, etc. The unpredictable behaviour of dry flowing avalanches sometimes makes the concept of an avalanche path a bit less important. It's very important to remember than an avalanche path only shows you where avalanches have run in the *past*. However, with avalanches, sometimes past behaviour is a good indicator of future behaviour, at least in some paths.

So for fun, you can remember that most avalanches do not run full path but an avalanche atlas should describe the full path.

Try this link for more information on avalanche atlases: http://www.wsdot.wa.gov/Research/Reports/000/008.8.htm

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I didn't say this before, but thanks for the great post and great data. It shows a very high level of thought and knowledge on the subject.

I too am interested in the physical science basis for modeling avalanches.
I think a better understanding of the physics of snow on slopes combined with a GIS analysis of snow hydraulics and dynamics can work to objectifying and simplifying avi prediction.

I'm interested in what work has been done quantifying not just the fluid dynamics of a flowing slide, but the statics of slabs and wet slides - what structures can exist, and what it takes to make them break and slide.

Me and everyone else, huh?

[MATH warning!...]

I've read some Mears, and I am aware of the nonlinearity of the Navier-Stokes equations wrt convective accelerations and the frictions of packet (granular) flow that you have touched on, but I wonder has this been approached from a systems analysis pov?

We can look at a slide in 4 dimensional terms of Scope, and Resolution.
Scope is simply spatial boundaries (and boundary conditions) of our system, including time.
Resolution could be defined as the smallest definition between 2 alternative system configurations, ie spatial configs pre and post slide.

Now the problem becomes an exercise in smoothed particle hydrodynamics between 2 equations of states within a spatial geometry (or perhaps matrices thereof). Irrelevant degrees of freedom are integrated out and we come down to vector LaPlacian operators within a defined space.
Now we are talking about the relationship between a system in 2 points of time, a perfect condition for a walking algorithm. Moreover, it can efficiently be applied within a GIS to predictively model "slide space".

[/MATH Warning!...]

I know I sound like I'm talking some crazy esoteric shit, but I'm painting with a broad brush and, as you noted, that is the nature of viscid flow...

I think if we can make a valid physical model of a type of slide, we can apply appropriate statistical techniques to learn much more via GIS.

Thanks for listening.

You guys still aren't getting it as far as the USGS DEMs go they are not good enough to do forecasting they can give you an approximate idea f slope but still have between 70-100 ft of error. There have been avalanche deaths in pockets of 30ft in terrian traps that there is no way a model at this scale can show. Therfore mapping and modeling with this can be very misleading. To quote highangle "simplifying avi prediction" you can't simplify this type of procedure. There is too much spatial variablity and unless you have a hi res dem terrian model say less than 2 ft resolution and weather stations say every 5 kilometers your modeling will not be very accurate. pbourdon, as far as how I keep things going for many years I have run Avalanche Mapping as a slightly paid hobby project. I do full time GIS consulting of all types as my main bread and butter. It has only been the last 3 years or so that I have gotten a good amount of paying work for this avalanche stuff the rest of the time it ran on my map sales and sponorships. I run an internship program with CU boulder and have had 10 interns working on this project over 5 years. So the best way to do this full time is get a Masters degree in Snow Hydrology, Meterology or Civil Engineering with a emphsis in GIS and then get a job with a avalanche center that is progressive. The only other work for this is with the DOT's and almost all of them use their maintanence crews to do this type of work and involve very little GIS. Don't mean to be a downer on this but it is a tough business to get into and takes alot of experience of being out there(like ski partroling/winter guiding for 5-10 years or so) to understand variables before you just shove it into the GIS and think you are doing something good. Email me and I'll send you a copyof the work that the guys did on Mt Baker. Also go to my website and read some of the papers that are on there and the most current Avalanche Review has several articles on this topic.

Avmapper, thanks for the heads up. And to those of you that think I was considering making a avy model, that wasn't the plan. Cookie pointed out early on that modeling the types of flows that occur during a slide is very tricky. I mainly wanted to produce maps that depicted the slide paths in an area, and then do analysis to see what slopes and aspects are generally the most "active". Avmapper, you make a great point about the vertical error on most DEMS. I was working on a project for this prof on stuff we've been looking at on the Salmon River in Idaho and something he had me do was to check the elev. data off the DEM against the topo's elevation data. Basically, I had to manually calculate the elevation on the topo. Generally, the DEM we were using was no more than about 10ft off from the topo. But I know that can change significantly in steep terrain with a low res DEM. I'll send you an email later today. Thanks again.

Quote:

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Originally Posted by pbourdon

...something he had me do was to check the elev. data off the DEM against the topo's elevation data. Basically, I had to manually calculate the elevation on the topo. Generally, the DEM we were using was no more than about 10ft off from the topo.

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you don't suppose that the DEM and DRG were created from the same data, or that one was created from the other, do you? ;)

^^^^ No, I had never given that any thought....:rolleyes:

we were just covering our asses since its so much quicker to just point an click on the DEM. But we also wanted to see what our error was with the DEM...

Quote:

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Originally Posted by Avmapper

You guys still aren't getting it as far as the USGS DEMs go they are not good enough to do forecasting they can give you an approximate idea f slope but still have between 70-100 ft of error. There have been avalanche deaths in pockets of 30ft in terrian traps that there is no way a model at this scale can show. Therfore mapping and modeling with this can be very misleading. To quote highangle "simplifying avi prediction" you can't simplify this type of procedure. There is too much spatial variablity and unless you have a hi res dem terrian model say less than 2 ft resolution and weather stations say every 5 kilometers your modeling will not be very accurate. pbourdon, as far as how I keep things going for many years I have run Avalanche Mapping as a slightly paid hobby project. I do full time GIS consulting of all types as my main bread and butter. It has only been the last 3 years or so that I have gotten a good amount of paying work for this avalanche stuff the rest of the time it ran on my map sales and sponorships. I run an internship program with CU boulder and have had 10 interns working on this project over 5 years. So the best way to do this full time is get a Masters degree in Snow Hydrology, Meterology or Civil Engineering with a emphsis in GIS and then get a job with a avalanche center that is progressive. The only other work for this is with the DOT's and almost all of them use their maintanence crews to do this type of work and involve very little GIS. Don't mean to be a downer on this but it is a tough business to get into and takes alot of experience of being out there(like ski partroling/winter guiding for 5-10 years or so) to understand variables before you just shove it into the GIS and think you are doing something good. Email me and I'll send you a copyof the work that the guys did on Mt Baker. Also go to my website and read some of the papers that are on there and the most current Avalanche Review has several articles on this topic.

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My apologies for being a little too abstract. My point was that there are perhaps techniques that haven't been fully exploited in our fledgling science.

My reasons for asking about systems analysis as a possible perspective for slide modeling and prediction was not random. SA has shown some promise, as well as some interesting results when applied to water and gravity....

http://ocw.mit.edu/NR/rdonlyres/51C1...556/0/math.jpg



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On a more 'practical' note, i think a hell of lot of avi specific map info can be represented with hatching and hatchures themselves. In highest practice, hatchures can convey much about a fall line that contours can't do as simply or clearly.
Subtle shading can also represent many completely different dimensions about an avi zone, and not just spatial ones...

http://www.avenza.com/images98/examp...ainier1024.jpg


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I admire your work and think your site is fantastic Doug. A gold mine. Thank you for years of difficult work.

I have to beg your forgiveness for talking to pb like almost nothing had been done in his direction. This might have been a little calculated for my own benefit.... :D

Anybody up in here know of any DEMs for Southeast Alaska w/ better than 30m resolution, and where I can find them?