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Executive Summary
Snow avalanche is a type of slope failure that can occur whenever snow is deposited on
slopes steeper than about 20 to 30 degrees. Avalanche-prone areas can be delineated with
some accuracy, since under normal circumstances avalanches tend to run down the same
paths year after year, although exceptional weather conditions can produce avalanches that
overrun normal path boundaries or create new paths. Unlike other forms of slope failure,
snow avalanches can build and be triggered many times in a given winter season.
In the United States, as elsewhere, snow avalanches are a mounting threat as devel-
opment and recreation increase in mountain areas: the recorded incidence of avalanches
is greater, and the number of people affected by avalanche events and avalanche hazard is
also increasing. Data from avalanche accidents show that avalanche activity occurs in about
one-third of the states and is a significant hazard in much of the West, where avalanches
are the most frequently occurring lethal form of mass movement. Present annual mortality
due to snow avalanches exceeds the average mortality due to earthquakes as well as the
average mortality due to all other forms of slope failure combined. Avalanches pose hazards
that affect a significant sector of the public; involve a number of private organizations; and
require cooperation and action by government agencies at the federal, state, and local lev-
els. Avalanche hazard causes economic loss to residents, businesses, transportation systems,
and government agencies. It can have a negative impact on the local economy of many
mountain regions and affects the management of federal lands. Avalanche-related litigation
is a growing problem.
Hazard mitigation requires measures ranging from appropriate land-use management
and effective building codes in avalanche-prone areas to the timely issuance of emergency
warnings and programs of public education. Centralized avalanche information and forecast
centers currently play an important hazard-reduction role in Colorado, Utah, and Washing-
ton. These centers are funded by a variety of state, federal, and private organizations, but
the funding base is not secure in all cases and their survival is an issue of concern. The
Alaska Avalanche Center lost its state funding after the winter of 1985-1986 and has not
resumed operations.
Direct avalanche control is appropriate for areas used intensively by the public, though
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it is too difficult or costly for the vast areas open to recreational use. Control is ordinarily
exercised through structural engineering systems or by the artificial release of built-up snow
cover. Engineering techniques such as snowsheds and wedges can be applied to modify
terrain so as to divert moving snow from facilities, and various fence structures have been
devised to stabilize snow on mountainsides. Artificial release techniques focus on the fre-
quent release of small avalanches to inhibit the formation of a large avalanche ant! employ
explosive charges delivered by hand, artillery, or mechanical conveyance. Improved stan-
dards and operational procedures need to be instituted for the safe deployment of explosive
systems. This problem should be addressed at the federal level since U.S. military weapons
and stockpiles are involved. Issues to be considered include safety training, certification
standards, the inventory of critical ammunition, spare parts, aging ammunition, ammuni-
tion storage and transportation, and the growing problem of lost shells. A conservative
calculation suggests that several thousand armed but unexploded military artillery shells
deployed for avalanche control now exist in backcountry areas of the United States. Since
many operational problems associated with artillery control are eliminated by cable delivery
systems, further attention to cable delivery should be encouraged.
Despite the destructive nature of snow avalanches and the hazards they pose to moun-
tain residents and vacationers, the United States lacks coordinated national leadership on
avalanche issues. There is currently no national program for avalanche prediction, land-use
planning, research, and education. There is an inadequate basis for the exchange of informa-
tion among government personnel, scientists, engineers, forecasters, and control specialists.
Support for avalanche research has almost vanished in the United States, although research
is relevant to all aspects of avalanche control and hazard mitigation. Closely associated with
the decline of research is a reduction of the national institutional capability in avalanche
expertise and a decline in technology transfer that seeks to take advantage of the extensive
avalanche work done in other countries.
From the late 1930s until 1985, the U.S. Department of AgriculturefForest Service
played the major role in snow avalanche mitigation in the United States. Toward this
end, the agency conducted its own research, funded outside research, provided technology
transfer and guidance, and set policy in areas of avalanche safety and education. Due in
part to restricted funding, the Forest Service abnegated this responsibility in 1985. Although
avalanche hazard continues and is increasing, individuals involved in the identification,
evaluation, and solution of problems related to avalanche hazard no longer have a specific
agency or facility to consult for guidance and expertise.
There is much that can be done to reduce avalanche hazards in the United States.
There are obvious needs for geologic and engineering research. for the development of
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hazard-delineation techniques, for improved understanding of avalanche initiation and the
dynamic processes that influence structural controls, for expansion of forecasting services
and better-coordinated dissemination of information about avalanche hazards, and for the
resolution of serious problems associated with the use of explosives. There are no widely
accepted guidelines or regulatory approaches for taking avalanche hazards into account in
community planning, and the programs that exist vary considerably. Apart from lands under
federal jurisdiction, the reduction of avalanche losses through And-use management and
the application of effective building codes are essentially functions of local government, with
enabling legislation by the state. Avalanche insurance, although in principle a viable option,
is virtually unobtainable.
Reduction of avalanche hazards should be viewed as a national goal requiring national
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leadership. Such leadership is essential for promoting more effective implementation of
existing organizational capabilities and improving cooperative support, information, and
technical assistance. The federal government should assume its specific but limited re-
sponsibilities for avalanche hazard delineation and control, including the development of
relevant methodologies on a variety of scales, pilot mapping and control demonstrations,
and avalanche mapping and control in support of the missions of federal agencies. Research
under national leadership should be undertaken to improve the technical base for avalanche
forecasting, control, land-use planning, and public warning systems through (a) interdis-
ciplinary research by appropriate federal agencies and (b) support and maintenance of a
research capability by universities through funding by the National Science Foundation.
To assist the federal government in assuming a more active and sustains role, the pane!
recommends the formation of a short-lived interagency task force or committee to initiate
program coordination among federal agencies having responsibilities related to slope fail-
ure, snow research, forecasting centers, and the administration of federal lands containing
avalanche-prone areas. Next, sustained nationwide coordination of avalanche management
and research programs could be performed most effectively by a national-level committee
composed of representatives from government, academia, industry, and professional or-
ganizations. Whatever its nature, there should be adequate representation of the specific
interests of federal, state, and local agencies and of private groups with responsibilities for
various aspects of avalanche mitigation. The purpose of the committee would be to provide
direction and momentum for the solution of these problems. Such a committee could be
organized and maintained over the long term by a committee of the National Research
Council (NRC) charged with reduction of natural hazards or, alternatively, a pane! within
the Committee on Glaciology of the NRC's Polar Research Board.
In the development of any national program, useful ideas can be obtained from the
successful and cost-effective national avalanche-mitigation programs in operation in Japan,
France, Norway, the U.S.S.R., and Switzerland, where avalanches have long been recognized
as the single greatest natural hazard to venter activities in mountain areas. The International
Decade for Natural Disaster Reduction program (National Research Council, 1987) suggests
possible avenues for international cooperation in this area and should provide motivation
toward the establishment of an effective avalanche-mitigation capability in the United States.
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Representative terms from entire chapter:
slope failure
