H a z a r d

M a n a g e m e n t

a n d

P u b l i c

Wa r n i n g

EvolutionofPublicAvalancheInformation:

The

NorthAmericanExperience

withAvalanche

DangerRatingLevels

Ala nDennisand

Mark

Moore

Canadian Avalanche Centre, P.O. Box 2759, Revelstoke, B.C. V0E 2S0

e-mail: canav@mindlink.bc.ca

Northwest Avalanche Center, C-15700,7600 Sandpoint WayNE

Seattle, WA USA 98115-0070, e-mail: moore@seawfo.noaa.gov

KeyWords:Avalanche,Danger,Scale,NorthAmerican,

Safety, Public

ABSTRACT

For many years after theintroductionof regionalavalanche
forecast centres in North America,the United States and
Canada employeda 4-levelavalanche hazard rating sys-
tem for describing public avalanchedanger,the basic com-
ponentsofwhich weredeveloped inthe late1970's.In
contrast,theEuropeanavalanche communityutilizeda
variety of public avalanche danger levels from country to
country in the 1970's and 80's.To help minimize confu-
sion and allow for better understanding andmore uniform
disseminationofpublicavalanche information,a transi-
tion toward a "unified5-level avalanche risk scale" was
recently undertaken throughout much of western Europe.
Aftermuch discussion, a 5-level risk/danger/hazard scale
evolved in 1993.With some debate Canada adopted this
5-level rating system in 1994, and slightly revised some of
the definitionsin 1995.In order to accommodate this trend
toward an "international unified rating level", the United
Statesavalanchecommunitydiscussedthispotential
transition at length during the past year,consulting with
Canadiancounterpartsandhotlydebatingthe meritsas
well as the definitions of the 5 danger levels.The history
of this North American transitiontoward the 5-level scale,
as well as the currentaccepteddanger level definitions for
Canada and the United States are presented.

INTRODUCTION

Sincethe 1970's,greatly increasing wintertimeusage of
publiclands outsidedeveloped and controlled skiareas
has been experienced throughout North America,Europe
and indeed much ofthe world.In order to accommodate
an associated need forbetteravalanche information,and
to help promote the safe use of snow-covered mountain-
ous terrain, an expandingbody of public avalanche infor-
mationhasevolvedthroughoutmanycountrieswhere
avalanches constitute a significant problem.Recent tech-
nological advances along a variety of fronts,ranging from
fast and relatively inexpensive computers to increasingly
sophisticated remote weather instrumentationandforecast
modelstoenhanced informationdisseminationsystems
havealsocontributedtothisevolutionofavailable
avalanche information.
Although the form, content and dissemination methods
of such public avalanche information has varied widely,
an increasingeffort has beenmade to standardizethe usage
of certain dangerlevels and basic terminologyregarding
humanexposuretoavalanches.Indeed,considerable
recent debate has revolved around not onlythe levels of
danger,buthowmanylevels andwhat theirdefinitions

should be.In some regions ofthe world,the numberof
avalanche danger levels has rangedfrom three to as many
asseven,withthe associateddefinitionsproducing fur-
ther confusionto public users.Toadd to this, other debate
hascenteredaroundhowbesttopresenttheavalanche
problem--should avalancheinformation be given in terms
of risk,danger, hazard, instabilityorpotential?
Until relativelyrecently,averitable"snow smorgasbord"
of avalanche information and danger rating levels existed
fromcountry tocountry and sometimeseven within the
same country.Aftermuch heated discussion and debate
throughoutEurope,amajorshifttowardstandardizing
avalanche risk levels from country to country occurred in
the early 1990's,resulting in the five-level"Unified Risk
Scale".Whilestillpresentingsomeproblemsandnot
agreed upon byallEuropean nations,especially eastern
Europe where four danger ratinglevels are still being used
(asof1995),thisunifiedriskscalehas been adopted by
mostof western Europe and the British Isles.In response
to this"international" standard and some meetings with
IKAR representatives, Canada adoptedthe five level scale
in the winterof 1994,with some revisions in 1995.
In the United States, a meeting of forecasters from most
major avalancheforecastcenters in the late-1970's resulted
in general usage of a 4-level standard in both the govern-
ment and private sector throughout most of the US.How-
ever,with the advent of the "Unified Risk Scale" and its
recent adoption byCanada,US forecasters began to con-
siderthe merits of changing to this "international" stand-
ard in 1995.After much debateandconsiderablerevisions
ofthedefinitionsofthefivelevels,theUSisplanning
official adoption of thenewavalanchedangerratingsystem
in the winterof 1996/97.
Althoughthistransformationtowardaquasi-interna-
tionalstandard ofavalanche dangerratinglevelsisstill
ongoing, much hasbeenaccomplishedsincethe 1970's and
much more duringthe past few years.This paper attempts
to outline and discuss this transformation toward a new
standard fordisseminationofpublic avalanche informa-
tion, presentingthe evolution from both the Americanand
Canadian experience.

THE UNITED STATES EXPERIENCE

HISTORY

In the United States, as late as the early 1970's,some pub-
licavalanchebulletinsandstatementswarnedofava-
lanches throughterminology like "conditions are about as
bad as they can get",and "people should stayout of the
mountains until furthernotice".While information such
as this did attract attention and did alert the public to ava-

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