I n s t r u m e n t s

a n d

M e t h o d s

forecasting systems using snowdrift data ornot would be
veryinteresting.Butletusadvancestepbystep.The
experienceshows that avalanchesaredueto unstable snow
accumulations and that snowdrift is more related to snow
accumulationthanwind. Theexperiment showsthat snow-
drift index and avalanche activity are correlated, and that
P(A1|S1)=1.Therefore we believe that snowdrift data are
useful forlocal avalancheforecasting.
Infuture,snowdriftcharacteristicsmaybecalculated
from real-time multiple snowpack simulationsand wind
fields computations. Snowdrift may also be automatically
measured.Thiswillrequirehigh-techequipments.At
present,usingadriftometerisalreadyeffectiveand...
cheaper!

CONCLUSION

The main results of this study are:

*thedriftometerisasimpleinstrumentwhichmakes
quantitative snowdrift assessments without energy pos-
sible,

*the driftometerindex ismore predictive ofavalanche
activity during days without snowfall than wind data.
Thus,the driftometerhelps to achieve reliable local ava-
lanche forecasting.
This is the reason why we included the driftometerin-
dex in the input data set ofthe decisionsupport system
NxLog.

ACKNOWLEDGEMENTS...

...toO.Buser(SFISARDavos),JM.Daultier,Ch.Reverbel
(SATAAlped'Huez),G. Brugnot,F.Naaim,F.Ousset
(CEMAGREF,Grenoble),Y.Gaillard(ISER'OUTILS,
Grenoble)whosupportedthisstudy,andtothereview
group of SFISAR.

REFERENCES

Berg N., 1986Blowingsnow at aColoradoalpine site:meas-
urementsandimplications.ArcticandAlpineResearch,
volume 18, nº2, pp.147-161.

Bolognesi,1994Local avalanche forecasting in Switzerland:
strategyand tools. Proceedings of the International Snow Sci-
ence Workshop, pp.463-472, Snowbird.

Castelle T., Hertig J.A., Fallot J.M., 1991 Protection des routes
alpines contre les congères.EPFL,IHE,LASEN,Lausanne.

Duclos A.,1995 Plaques àvent:nouvelles données.Neigeet
Avalanches,nº72, A.N.E.N.A., pp.2-7

Fellers G.,MellorM.,1986Concentration andfluxof wind
b lo wnsno w.C o ldR egio nsR esearchandEngineering
Lab oratory, special report 86-11.

FöhnP.,1980Snow transport overmountaincrests.Journal
of Glaciology,volume 26,nº94, pp.469-480.

Föhn P., Meister R., 1983 Distribution of snow drifts on ridge
slopes: measurements and theoretical approximations. Annals
of Glaciology 4 , International Glaciological Society, pp.52-57.

Guyomarch' G., Mérindol L., Castelle T., Sivardière F., Buisson
L.,1994Blowingsno w andslabavalanches.Proceedings of
theInternationalSnowScienceWorkshop,pp.211-2 21,
Sno wbird.

IshimotoK.,1991Observationofblowingsnowbyasnow
particle counter with a real time processor. Proceedings of the
Japan-USWorkshoponSnow Avalanche,Landslide,Debris
Flow Prediction and Control.

Jairell L., 1975 An improved recording gage for blowing snow.
WaterResources Research,volume 18, nº5.

Martinelli M., Schmidt R., Tabler R., 1981 Research application
helps solve blowing snowproblems.RockyMountainForest
andRangeExperiment Station,ForestService,U.S.dep.of
Agriculture, Fort Collins.

MeisterR., 1987 Wind systems and snowtransport in alpine
topography. Avalanche Formation, Movement and Effects, pro-
ceedings of the Davos Symposium, IAHS Publ. nº162, pp.265-
279.

Meister R., 1989 Influence of strong winds on snow distribu-
tion and avalanche activity. Annals of Glaciology 13,Interna-
tional Glaciological Society, pp.195-201.

MellorM.,1965Blowingsnow.Cold Regions Researchand
Engineering Laboratory.

Naaim.,BrugnotG.,1992Transport deneigeparlevent:
connaissances de base et recommandations. CEMAGREF, Di-
vision Nivologie,Saint-Martin d'Hères.

SatoT., Kimura T., Ishimaru T., Maruyama T., 1993 Field test
ofanewsnow-particulecounter(SPC)system.Annalsof
Glacilogy 18,International Glaciological Society, pp.149-154.

Schmidt R., 1984 Measuring particle size and snowfall inten-
sityin driftingsnow.Cold Regions Science and Technology,
pp.121-129,Amsterdam.

Schmidt R., Meister R., Gubler H., 1984 Comparison of snow
drifting measurements at an alpine ridgecrest.Cold Regions
Science and Technology,pp.131-141,Amsterdam.

Schmidt R.,TablerR., Jairell R., 1982A newdevice forsam-
pling mass flux of blowing snow. Proceedings of the Western
Snow Conference, pp.102-111, Reno.

Takeuchi M., Ishomoto K., Kajiya Y., 1990 Blowing snow prob-
lems and their countermeasures in Hokkaido Japan. Civil En-
gineering Research Institute, HokkaidoDevelopment Bureau,
Sapporo,Japan.

TügH.,1988Apulsecountingtechniqueforthemeasure-
ments of drifting snow. Annals of Glacilogy 11,International
Glaciological Society, pp.184-186.

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