GIS-aided avalanche warning in Norway

Christian Jaedicke n, Egil Syre, Kjetil Sverdrup-ThygesonNorwegian Geotechnical Institute, Sognsveien 72, 0886 Oslo, Norway

a r t i c l e i n f o

Article history:Received 28 August 2012Received in revised form7 January 2014Accepted 9 January 2014Available online 15 January 2014

Keywords:Avalanche warningGISInternetMeteorology

a b s t r a c t

Avalanche warning for large areas requires the processing of an extensive amount of data.Information relating to the three basic requirements for avalanche warning – knowledge of terrain,the snow conditions, and the weather – needs to be available for the forecaster. The information ishighly variable in time. The form and visualization of the data is often decisive for the use by theavalanche forecasters and therefore also for the quality of the produced forecasts. Avalanchewarnings can be issued at different scales from national to regional and down to object specific.Often the same warning service is working at different scales and for different clients requiring aflexible and scalable approach. The workflow for producing avalanche forecasts must be extremelyefficient – all the way from acquiring observation data, evaluating the situation, down to publishingthe new forecast. In this study it has been an aim to include the entire workflow in a single webapplication. A Geographic Information Systems (GIS) solution was chosen to include all data neededby the forecaster for the avalanche danger evaluation. This interactive system of maps featuresbackground information for the entire country, such as topographic maps, slope steepness, aspect,hill shades and satellite images. In each avalanche warning area, all active avalanche paths are plottedincluding information on wind exposure. Each avalanche path is linked to a webpage with moredetails, such as fall height, release area elevation and pictures. The avalanche path webpage alsoincludes information on the object at risk e.g. buildings, roads, or other objects. Thus, the forecastercan easily get an overview on the overall situation and focus on single avalanche paths to generatedetailed avalanche warnings for the client.

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1. Introduction

Avalanche warning can be done at different scales, from largeregions down to single avalanche paths depending on the purposeof the warning service. In addition, the target group of thewarnings depends often strongly on the avalanche danger level.The danger of avalanches is forecasted using an international fivelevel system (EAWS, 2012). For recreational activities avalanchewarning focuses mostly on the low avalanche danger levels and aregional down to local scale. Most recreational activities in themountains occur at 1 (low) to 3 (considerable) avalanche danger.At higher danger levels (4 and 5) the weather and snow conditionsare mostly too tough for backcountry activities. On the other hand,avalanche warning that concentrates on objects and infrastructurenormally focuses on the danger levels considerable to very high atlocal down to avalanche path scale. For exposed infrastructure andobjects, avalanche warning is a method of avalanche hazardmitigation that is used until permanent mitigation is in place orwhere permanent mitigation is not feasible or economically

sensible. Therefore, the scope of an avalanche warning programhas to be based on the needs of the problem owner such as arailroad operator, construction site manager, or tourism operator.The scope of the avalanche warning program, the size of the areacovered, and the required detail to solve the avalanche hazardproblem at hand decide – together with the economical frames ofthe projects – on the type and amount of information available forthe forecaster.

Avalanche warning is based on three main types of data: thestate of the snow pack, the meteorological conditions and theterrain. The sources for this data can range from single weatherstations and observation points in a selected avalanche site, to vastnationwide observation networks, including several different dataformats and providers.

GIS can provide a useful platform for gathering different typesof information from various sources into one system. GIS systemshave been applied in avalanche warning by several authors.Mapping of historical events for the use in avalanche warningwas presented by Scott (2009) for the San Juan mountains, Color-ado. McCollister et al. (2002, 2003) combined the avalanchedatabase of the Jackson Hole ski area with terrain information tocreate a GIS-based-nearest-neighbor-system. In their applicationreal time weather data was used to find similar days in the

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0098-3004/$ - see front matter & 2014 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.cageo.2014.01.004

n Corresponding author. Tel.: þ47 2202 3000; fax: þ47 22230448.E-mail address: cj@ngi.no (C. Jaedicke).

Computers & Geosciences 66 (2014) 31–39

historical database as a background for the evaluation of thepresent situation. Marienthal et al. (2010) give a comprehensiveoverview on the use of GIS in avalanche work and specifically foravalanche warning. Recently Statham et al. (2012) presented theCanadian AvalX system, which provides a complete workflow foravalanche forecasters. The system concentrates on presenting themost relevant information on the current avalanche hazard inshort concise texts and graphical outputs for the user.

Avalanche warning in Norway started already in the 1970s. Fora better understanding of the involved processes the NGI researchstation Fonnbu was established in the Stryn Mountains in 1973(Lied, 1993; Jaedicke et al., 2008). Threshold values for avalanchereleases were defined and a probabilistic forecasting method wasadopted for Norwegian conditions (Fitzharris and Bakkehøi, 1986;Bakkehøi, 1987). The opening of the new Highway 15 through thesteep Stryn mountains increased the demand for an improvedavalanche warning service and daily avalanche warning wasstarted at NGI for the highway in 1980.

Until January 2013, a general national avalanche warning wasonly issued by the Norwegian Meteorological Office for large areasat danger levels 4 and 5. These warnings were mostly based onthreshold values linked to meteorological models. Therefore, anew national warning service run by the National Water andEnergy Directorate (NVE), the Rail (JBV) and Road administration(NPRA) based on input from NGI was started in January 2013(Jaedicke et al, 2009). This national service covers 22 selectedmountainous regions, uses local observers and a centralized expertteam (Engeset, 2013) in the forecasting.

Today, NGI issues detailed, client-oriented warnings for NGIcontractors, such as the road and railroad administration localmunicipalities and contractors, on a daily basis. All of theseprojects have the common aim to protect lives and infrastructureon a local or regional scale. The objects are usually not threatenedat danger levels 1 – low or 2 – moderate avalanche danger. Whilecontracts for transport routes and settlements are continued overmany years, short-term projects that are only operated for awinter season or two often cover construction sites and inter-mediate activities at hydro-power installations. Such projects canbe located anywhere within the country and have often to beoperational on short notice. The contractors use the evaluation ofthe avalanche danger as an input to their risk analysis anddecision-making support system and they make all the operationaldecisions on road closures, evacuation, or travel restrictions.

In total NGI avalanche warning areas cover 29,000 km2 andspan 2900 km from the South to the very Northern tip of thecountry (Table 1 and Fig. 1). As a result, several climate zones aswell as extremely different weather conditions must be consideredduring a so-called typical day. The avalanche forecasters arelocated in Oslo and they are in charge of projects for the entirecountry. Therefore, fast and easy access to all information availableis needed to allow for such a wide-range coverage from acentralized location. In this paper we present a GIS based ava-lanche warning tool for local to regional avalanche warning

services in Norway. The flexible system covers the entire countryand allows setting up new warning projects in a fast and effectivemanner to meet changes in the contractor0s needs. We provide anoverview over the available data and the applied technical plat-form of the warning system.

2. Materials and methods

The large area covered and the scope of the avalanche warningprojects focusing on the three highest danger levels suggests theforecasters to use an airport approach method, similar to theavalanche rescue method proposed by Genswein (2008). Theforecaster works fast to get an overview on the overall situationin the whole country during situations of low and moderateavalanche danger. When the danger level rises to 3 – considerable– or higher, the detail in the analysis increases and the situationwill be evaluated for single avalanche paths and objects.

In general, three components have to be known for day-to-dayavalanche warning: (a) terrain, (b) state of the present snow cover,and (c) the current weather conditions and forecast for the next24 h (LaChapelle, 1980; Table 2). In addition, information relatingto the static environment is needed, such as infrastructure,mitigation structures, and endangered objects.

2.1. Input data and sources

The terrain details are well known in areas where avalanchewarning has been successfully implemented years ago and isactively pursued. Nevertheless, on an annual basis, new short-term projects are started. Consequently, such new areas must bevisited by the forecasters and the results will be documented in areport. GIS is used to create and manage terrain models, avalancherelease areas and paths, exposed objects, and infrastructure. Therunout length of avalanches is roughly analyzed in order toprovide the forecasters with more information about the proper-ties of the avalanche path for which they are to produce a forecast.In that way, all information is readily available for theforecasting group.

A national terrain model with 15 m resolution allowed for thecalculation of terrain parameters, such as aspect and slope for thewhole of Norway. For each warning area, the outline of the mostactive and critical avalanche paths were mapped and added to adatabase. The information collected about each path contains apicture, physical characteristics, such as fall height and size ofrelease area, information on exposed objects (house(s), street(s),and railway), and a classification on the wind directions to whichthe path is most exposed. The information is used in the GIS tocreate interactive maps. For example with a wind direction fromSW, all areas steeper 4301 in the lee of SW are highlighted in themap. In addition, there is a graded color scheme showing thosepaths in shades of red that are most prone to avalanche hazardswith this wind direction (Fig. 2). The wind exposure is expressedas a value from 0 to 1, implying that at 0 drifting snow is not likelyto be accumulated in the release area, while at 1 drifting snowcertainly will accumulate in the release area. This evaluation isdone manually for each path by an avalanche expert when theavalanche path is added to the system. A click on the path itselfopens a webpage displaying the photo and additional informationon the path (Fig. 3). Different background maps allow choosingfrom grayscale, topographic or satellite imagery maps. Thus, theforecaster can get an overview of large areas and quickly pick outthe most exposed paths.

Information on the state of the snow cover is crucial forforecasting of avalanche danger. Local observers appointed bythe contractor can provide some information and the warning

Table 1The six avalanche warning areas included in the 2011/2012 service (see Fig. 1 forlocation).

Name Type Area (km2) No. aval. paths

Bergen railway Daily 1700 50Highway 15 Daily 140 9Høyanger hydro-power installations Daily 20 14Stranddalen construction site Daily 20 3Sunnmøre road district Client 4500 200North Norway Client 22,300 130

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Fig. 1. Map of Norway showing the areas covered by the NGI avalanche warning service (season 2011/12).

Table 2Three classes of information to be used in avalanche warning (LaChapelle, 1980).

Data Information Examples

Class I Direct information on instability of the snow cover Observations of new avalanches, collapsing sound and fractures in the snow,instability tests and fracture quality

Class II Information on the snow pack: gives indirectinformation on instability of the snow pack

Layering, particle size and form, hardness, density and temperature

Class III Information on the weather conditions; gives indirectinformation on the snow pack

Precipitation, wind, air temperature, radiation, weather forecast

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areas are regularly visited by the forecasters. Unfortunately directobservations of class one (LaChapelle, 1980) data gathered by fieldwork is limited to 1–2 times a month. Field work is done in theareas when the weather or observations by the observer indicatethat there may be instabilities in the snow cover that call for closerinvestigation. The Norwegian Water Resources and Energy Direc-torate (NVE) has recently established a snow and avalancheobserver network in 22 mountain areas to support the regionalavalanche warning service (Ekker et al., 2013). These observationsare openly available and all new observations from the last 24 hare displayed on the map.

Snow avalanche forecasting is heavily dependent on automaticweather observations. Each warning area is equipped with one orseveral stations, in or close to the area. The stations are operatedby different agencies, such as the road or railroad administration,the Norwegian Meteorological Institute, NGI, and hydropowerplants. Therefore, each station has its own logging interval, dataformat, and the transmission system. In daily operation, thecomplexity of data retrieval is the weakest spot of the warningsystem. Introduction of national standards on data transmissionare currently under development (Humstad, 2010). Data from thestations is visualized and published on the net using C#-basedservices that collect XML-based data from different sources(Fig. 4).

Prognosis and observation data has been freely availablethrough the Norwegian Meteorological Institute since 2007. Prog-nosis data is delivered as point prognosis for up to 10 days, as wellas meteorological grid data (fields). Satellite and radar observa-tions are also included. The interactive avalanche warning mapgives access to weather charts for 200 stations throughout thecountry. For the time being, meteorological fields are only displayedwith customized software by the Norwegian Meteorological Insti-tute; the software is called DIANA (Bergholt et al., 2006). The

software allows, just as the traditional GIS, to stack all information,such as wind and pressure fields, satellite images, and precipitationprognosis, in one map. The map shows the prognosis for severaldays in a loop (Fig. 5). Once this data is made accessible as a service,these features are to be included in the avalanche warning map. Allneeded information will then be available in one single map.

Visual impression of the weather conditions are often a valu-able addition to the observations fromweather stations. Therefore,a number of open web cams from Norway are also linked to themap. The forecaster can easily access pictures from the relevantareas around the country. The example for an evening in Aprilshows the weather situation at Finse station just 3 h apart (Fig. 6).Mountain areas are usually only covered by cameras installed atski resorts but the number of cameras is increasing also atlocations relevant for avalanche forecasting.

Road closures announced by NPRA and RSS feeds from newswatch services provide for updated information relating to newavalanche events. Such information is currently not fed into thesystem. The NVE together with the Meteorological Institute andNPRA – are developing a new portal showing interpolated obser-vation data (Engeset, 2011). This data is available as web mapservices (WMS) and is integrated into the GIS.

2.2. Technical platform and publication tool

The warning publication tool is also accessible by the forecastervia online service. The forecaster chooses the warning area to workon, fills in all the required fields about observations, weatherforecast and the avalanche danger evaluation. After a peer-reviewby another forecaster, the completed bulletin is published viaemail and SMS to a preselected list of persons who were appointedfor each warning area. For some areas, the avalanche danger levelis also automatically published on the web. All avalanche warnings

Fig. 2. Detailed map of the Grasdalen area showing avalanche paths active with winds from SW. The darker red the path is, the more likely an avalanche will be releasedwith this wind direction. Each path is linked to a webpage containing additional information on the path (Fig. 3). The location of the Fonnbu NGI research station is shown bya cross marker which also hyperlinks to current weather information from the station. (For interpretation of the references to color in this figure legend, the reader isreferred to the web version of this article.)

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are stored in the database. The publishing tool helps to documentdaily evaluations and guarantees efficient posting for clients. Since2011 an application for IPhone is also provided.

The central component of the system is the database whichcontains all information needed for publishing avalanche warnings(Fig. 7). The database is an enterprise geodatabase based on anOracle database management system, which has been extendedwith ArcSDE to enable geospatial data. Data is mainly managedthrough three tools: the Oracle SQL developer to administer thesystem configuration, ArcGIS with a Workflow Manager extensionto manage geospatial components of the data, and an administra-tion website for the management of avalanche warnings andwarning areas.

A map viewer is available for avalanche experts in a webbrowser. The application accesses data from the database throughmap services which are published using ArcGIS Server.

Production and publication of avalanche warnings is performed ina web application which is created in C# using Microsoft VisualStudio. This website interacts directly with the database and providesthe user with the ability to directly enter and edit avalanchewarnings (Fig. 8). The warnings are published both as emails and

SMS, for mobile phones, through the use of web services offered by amobile phone network provider. Furthermore, an additional websitewas created which accesses a subset of the data and allows forintegration into other NGI websites, namely for data publication viathe Internet, for the broader public.

Meteorological data is retrieved directly from the NorwegianMeteorological Institute. The Meteorological Institute offers obser-vations and prognoses through open web services. In the observa-tion web services, which are accessible through the URL wsklima.met.no, data is published using the web service definition lan-guage (WSDL). The prognoses web services, available at api.met.no, use the REST API for data access. The avalanche warningsystem uses Visual Basic.net services to retrieve data from bothof these services; the data is intermediately stored in the enter-prise database. New data is retrieved at intervals of approximately1 h. The data in the database is subsequently made available toavalanche experts via a map (Fig. 4). The map displays the latestobservations for each location; the location is linked to the webapplication which displays meteorological data, both as text andmeteograms. A backup system also exists for the retrieval ofmeteorological observations and prognoses for certain locations,

Fig. 3. Example for an automatically generated webpage for an avalanche path in Northern Norway.

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namely through websites generated using a matlab script. Thisredundancy reduces the risk of meteorological data not beingavailable.

All, the database, the tools, and web applications are locatedwithin NGI0s internal network. One major reason for using webbased tools in the entire production line for the avalanche warning

was to allow for forecasters to be able to work at any internetconnected PC. Therefore, the web applications are made availablevia ISAPI technology. Access is restricted to registered users of theavalanche warning group.

Data security is ensured through the database backup routineand by logging all user activities. For instance, each sms and email

Fig. 4. Screenshot of the map application. The map shows the latest wind observations for over southern Norway from all available weather stations. Arrows indicate thewind direction and numbers the wind speed in m/s.

Fig. 5. Screenshot taken from DIANA, the meteorological visualization tool for weather prognosis.

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sent to a client is logged in the database. As for system backup, abackup website has been established at a secure, external site. Thewebsite contains the most essential data which makes it possibleto publish warnings even in the event of complete system failure.

3. Application and discussion

GIS-based avalanche warnings provide for unique access to alarge amount of data. Today, the avalanche warning map includesdetailed information on six warning areas. In total, 394 avalanchepaths are documented in the database, most of them with picturesand detailed description of the path. While, in earlier days, theforecaster had to open a large number of different websites togather the information required for the warning process, now, asingle map-based gateway enables direct access to all information.Experience has shown that forecasters prefer certain meteorolo-gical stations for their work in a given area as they would notknow the names of all nearby stations. The new system shows allstations on a map which allows the experts to use all stations in acertain area for their analysis. Also the question, namely howrepresentative the station is for the area, is now much easier toevaluate because its location is displayed in relation to thewarning area and wind direction.

The warning areas that receive evaluation upon client requestmay be rather large. Therefore, avalanche warnings are only issuedfor selected locations where the weather conditions are severe.Here, the maps enable the forecaster to use basic information,such as “strong wind from NW with heavy precipitation inthe Northern Lofoten Islands”, to zoom in on the exact pathsthat actually endanger the population and the infrastructure inthis area.

Objects exposed to avalanches can vary in type and size. Inmany cases, the avalanche hazard threatens one well definedobject. Fig. 9 shows an example with the Svartisen hydropower

plant, located below the Svartisen glacier in the northern part ofthe country. The fall height of the avalanches is over 1500 m andannual precipitation in this maritime climate is 3000 mm. Threemain avalanche paths were identified to threaten the constructionsite at the valley0s bottom. The GIS system allows for an inclusionof detailed construction design information provided by thecustomer in maps. Consequently, the maps allow zooming throughall scales from national wide view to view of single design featuresof the construction works. The level of details is important whendiscussing with the clients, in particular during situations ofaccidents or evacuations.

The alpha–beta model (Lied and Bakkehøi, 1980) is applied toeach avalanche path to find the beta and alpha points in theprofile. The location of the exposed object is then related to thebeta point, giving an estimate of the likelihood of the object beinghit by an avalanche. The method is described in detail inKristensen et al. (2008).

The results obtained from meteorological and terrain informa-tion enable the forecaster to fill in the web-based registration forthe avalanche bulletin, for each area. Finally, the bulletin is sentout by email and SMS (text message) to the clients. Additionally,the danger level is posted on a webpage that informs recreation-ists about avalanches and snow conditions.

As a result of the rather limited resources of the centralized NGIavalanche warning service, actual options for physical presence offorecasters in warning areas are strongly reduced. On a daily basis,two persons on duty have to do an avalanche evaluation of vastareas. The establishment of a map-based information platformsignificantly reduces the workload for the forecaster. The wholeprocess – from studying the current snow and weather condition,the terrain, and possible further weather developments, to issuingthe bulletin – is part of one single system and all informationnecessary is integrated on a map. As a result, normally no othertools are needed for the forecaster0s work. For further improve-ments of the system must be made more user-friendly and has tobe adjusted to the workflow of the forecaster0s duties so that it iswell accepted by the users.

There are several challenges due to the fact that the presentsystem is rather dynamic. A large number of different data sourcesmake the system highly dependent upon the stability of theintegrated web services. Another aspect that comes into play isthe variability of the data quality from the different sources.Meteorological data is often accurately measured, but the scheduleof observations and data transfer does not only differ from datasource to data source, but also from station to station. Displaying

Fig. 6. Web cam pictures from the Bergensbanen railway. The images date April 04, 2008, at 5:45 p.m. and 09:00 p.m., illustrating the direct feedback on the weatherconditions.

Warning mapapplication

Warning web application

(C# application)

Map services(ArcGIS server)

Geospatial data (ArcSDE)Observations

wsklima.met.noWeather webapplication

(C# service)

System setup(SQL developer) Warning

Database (Oracle)

Prognosesapi.met.no

Weatherdatabase(Oracle)

Fig. 7. Main components of the avalanche warning system.

Warningarea

Warningrecipients

appliesto

Warning is sentto

Fig. 8. Simplified relationships between the main database tables for publication ofwarnings.

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the “latest observed temperature” for each station on the map mayshow data that was observed in the range from 1 to 36 h making acomparison between stations impossible. Moreover, displayingonly data collected in the course of the last hour may fail todisplay the data gathered by the majority of the stations thatsimply need more time for data transfer. A similar problem ariseswhen using web cams from multiple sources. Dead links andfunctional failure decrease the reliability of the application.

The three levels of information listed by LaChapelle are basicfor avalanche warning. In addition, pictures and observer reportscan be useful as well. In a complex information system asdescribed in this study, data quality is another piece of informationthat is new and important. Expert judgment is not only needed forthe avalanche warning itself but also for the selection of correct,proper input data with regard to data reliability and quality. TheGIS system makes high amount of data readily available for theforecaster but there is the danger of accepting the displayed datawithout being critically enough in terms of data quality. For futuredevelopment, use of metadata is important to allow the dataimport routines to rule out data of bad quality. Unfortunately, opensource data often lacks such metadata information and internalimport rules have to be develop to exclude bad data.

NGI avalanche warnings are highly customized products forindividual clients. Reliable and fast delivery of warnings in themorning is essential for clients to support their operationaldecision making in the avalanche exposed areas. The map hasbeen applied successfully in the season 2011/2012 and will befurther developed so to include meteorological fields and theoption to display loops for several days.

4. Conclusion

Avalanche warning is a dual process with two major para-meters, time and space. Therefore, dynamic maps are an obviousapproach to gather all information needed for the forecaster0swork. Today0s GIS tools allow easy linking of information fromdifferent sources with output in a single map. The challenge is toprepare the data from all these sources in such a way that thesystem can be updated automatically with new data – at least onceevery hour. Acceptance of the system by forecasters depends uponits reliability and user friendliness. Both aspects are subject toconstant improvement – in close cooperation with users deliver-ing feedback. Today0s technology does not impose any limitationsfor the efficient functioning of such a system. The systemdescribed constitutes the very beginning for finding “the” solutionwhich allows for the generation of detailed local and regionalavalanche warnings – for a broad variety of clients, and also with arather restricted budget.

Acknowledgments

This work was partly financed by the Avalanche Research Grantof the Norwegian Water Resources and Energy Directorate. It wassupported by the Norwegian Public Roads Administration, theNorwegian National Rail Administration and Statkraft. Manythanks to all colleagues at in the NGI avalanche warning groupfor feedback on the GIS system and this paper.

Fig. 9. Details from the situation at the Hålandsfjord hydropower station. GIS allows for the inclusion of terrain data and details of the construction works at the power plant.

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