19 research outputs found
Spatial consistency and bias in avalanche forecasts – a case study in the European Alps
In the European Alps, the public is provided with regional avalanche
forecasts, issued by about 30 forecast centers throughout the winter,
covering a spatially contiguous area. A key element in these forecasts is the
communication of avalanche danger according to the five-level, ordinal
European Avalanche Danger Scale (EADS). Consistency in the application of the
avalanche danger levels by the individual forecast centers is essential to
avoid misunderstandings or misinterpretations by users, particularly those
utilizing bulletins issued by different forecast centers. As the quality of
avalanche forecasts is difficult to verify, due to the categorical nature of
the EADS, we investigated forecast goodness by focusing on spatial
consistency and bias, exploring real forecast danger levels from four winter
seasons (477 forecast days). We describe the operational constraints
associated with the production and communication of the avalanche bulletins,
and we propose a methodology to quantitatively explore spatial consistency
and bias. We note that the forecast danger level agreed significantly less
often when compared across national and forecast center boundaries (about
60 %) than within forecast center boundaries (about 90 %).
Furthermore, several forecast centers showed significant systematic
differences in terms of more frequently using lower (or higher) danger levels
than their neighbors. Discrepancies seemed to be greatest when analyzing the
proportion of forecasts with danger level 4 – high and 5 – very high. The
size of the warning regions, the smallest geographically clearly specified
areas underlying the forecast products, differed considerably between
forecast centers. Region size also had a significant impact on all summary
statistics and is a key parameter influencing the issued danger level, but it
also limits the communication of spatial variations in the danger level.
Operational constraints in the production and communication of avalanche
forecasts and variation in the ways the EADS is interpreted locally may
contribute to inconsistencies and may be potential sources for
misinterpretation by forecast users. All these issues highlight the need to
further harmonize the forecast production process and the way avalanche
hazard is communicated to increase consistency and hence facilitate
cross-border forecast interpretation by traveling users.</p
Future of Communicating Digital Design in Architecture: overcoming the divisive power of Computer Aided Design
A few decades ago architects, engineers and the building industry relied on a set of self-developed tools for drawing and standards for communication within the profession and beyond. Everyone involved in the process of building understood these standards that were developed, controlled and updated by the profession. Today the situation appears more ambiguous. The introduction of Digital Media, and specifically Computer Aided Design, has greatly enhanced the potential for productivity gains. On the other hand, the lack of standardized open file exchange formats in CAD has created communication barriers by making data exchange more confusing and ambiguous. Frequently this has consumed the very productivity gains that were originally envisioned by industry. Problems with proper and fluent data exchange between software applications to no small extent are due to fundamental disagreements between software designers on the proper digital description of a building, leading to nearly insurmountable communication obstacles, designed to potentially divide the profession, practitioners and the educational environment. Consequently construction has not partaken in the productivity gains that other industries have enjoyed. Proprietary file formats and closed software systems have fostered the development of design camps that rally behind one software. Others reluctantly buy into certain “solutions” for they are perceived to be standards. Innovation is hampered as development of industry design tools is no longer controlled by architects, engineers and the construction sector but instead by private software companies frequently pursuing their Based on 20 years of experience with CAD in the profession and academia this paper critically investigates the status quo of CAD in the building industry. It points towards strategies of overcoming the current problematic situation and putting the profession back in control of its own communication process
Point observations of liquid water content in wet snow – investigating methodical, spatial and temporal aspects
Information about the volume and the spatial and temporal distribution of liquid water in snow is important for forecasting wet snow avalanches and for predicting melt-water run-off. The distribution of liquid water in snow is commonly estimated from point measurements using a "hand" squeeze test, or a dielectric device such as a "Snow Fork" or a "Denoth meter". Here we compare estimates of water content in the Swiss Alps made using the hand test to those made with a Snow Fork and a Denoth meter. Measurements were conducted in the Swiss Alps, mostly above tree line; more than 12 000 measurements were made at 85 locations over 30 days. Results show that the hand test generally over estimates the volumetric liquid water content. Estimates using the Snow Fork are generally 1 % higher than those derived from the Denoth meter. The measurements were also used to investigate temporal and small-scale spatial patterns of wetness. Results show that typically a single point measurement does not characterize the wetness of the surrounding snow. Large diurnal changes in wetness are common in the near-surface snow, and associated changes at depth were also observed. A single vertical profile of measurements is not sufficient to determine whether these changes were a result of a spatially homogeneous wetting front or caused by infiltration through pipes. Based on our observations, we suggest that three measurements at horizontal distances greater than 50 cm are needed to adequately characterize the distribution of liquid water through a snowpack. Further, we suggest a simplified classification scheme that includes five wetness patterns that incorporate both the vertical and horizontal distribution of liquid water in a snowpack
Automatic classification of manual snow profiles by snow structure
Manual snowpack observations are an important component of avalanche hazard
assessment for the Swiss avalanche forecasting service. Approximately 900
snow profiles are observed each winter, in flat study plots or on
representative slopes. So far, these profiles have been manually classified
combining both information on snow stability (e.g. Rutschblock test) and
snowpack structure (e.g. layering, hardness). To separate the classification
of snowpack stability and structure, and also to reduce inconsistencies in
ratings between forecasters, we developed and tested an automatic approach to
classify profiles by snowpack structure during two winters. The automatic
classification is based on a calculated index, which consists of three
components: properties of (1) the slab (thickness), (2) weakest layer
interface and (3) the percentage of the snowpack which is soft,
coarse-grained and consists of persistent grain types. The latter two indices
are strongly based on criteria described in the threshold sum approach. The
new snowpack structure index allows a consistent comparison of snowpack
structure to detect regional patterns, seasonal or inter-annual differences
but may also supplement snow-climate classifications
Analysis of avalanche risk factors in backcountry terrain based on usage frequency and accident data in Switzerland
Recreational activities in snow-covered mountainous terrain in the
backcountry account for the vast majority of avalanche accidents. Studies
analyzing avalanche risk mostly rely on accident statistics without
considering exposure (or the elements at risk), i.e., how many, when and
where people are recreating, as data on recreational activity in the winter
mountains are scarce. To fill this gap, we explored volunteered geographic
information on two social media mountaineering websites –
bergportal.ch and camptocamp.org. Based on these data, we present
a spatiotemporal pattern of winter backcountry touring activity in the Swiss
Alps and compare this with accident statistics. Geographically, activity was
concentrated in Alpine regions relatively close to the main Swiss population
centers in the west and north. In contrast, accidents occurred equally often
in the less-frequented inner-alpine regions. Weekends, weather and avalanche
conditions influenced the number of recreationists, while the odds to be
involved in a severe avalanche accident did not depend on weekends or weather
conditions. However, the likelihood of being involved in an accident
increased with increasing avalanche danger level, but also with a more
unfavorable snowpack containing persistent weak layers (also referred to as
an old snow problem). In fact, the most critical situation for backcountry
recreationists and professionals occurred on days and in regions when both
the avalanche danger was critical and when the snowpack contained persistent
weak layers. The frequently occurring geographical pattern of a more
unfavorable snowpack structure also explains the relatively high proportion
of accidents in the less-frequented inner-alpine regions. These results have
practical implications: avalanche forecasters should clearly communicate the
avalanche danger and the avalanche problem to the backcountry user,
particularly if persistent weak layers are of concern. Professionals and
recreationists, on the other hand, require the expertise to adjust the
planning of a tour and their backcountry travel behavior depending on the
avalanche danger and the avalanche
problem
Natural hazard fatalities in Switzerland from 1946 to 2015
A database of fatalities
caused by natural hazard processes in Switzerland was compiled for the period
between 1946 and 2015. Using information from the Swiss flood and landslide
damage database and the Swiss destructive
avalanche database, the data set was extended back in time and more hazard
processes were added by conducting an in-depth search of newspaper reports.
The new database now covers all natural hazards common in Switzerland,
categorised into seven process types: flood, landslide, rockfall, lightning,
windstorm, avalanche and other processes (e.g. ice avalanches, earthquakes).
Included were all fatal accidents associated with natural hazard processes in
which victims did not expose themselves to an important danger on purpose.
The database contains information on 635 natural hazard events causing
1023 fatalities, which corresponds to a mean of 14.6 victims per year. The
most common causes of death were snow avalanches (37 %), followed by
lightning (16 %), floods (12 %), windstorms (10 %), rockfall
(8 %), landslides (7 %) and other processes (9 %). About 50 %
of all victims died in one of the 507 single-fatality events; the other half
were killed in the 128 multi-fatality events.
<br><br>
The number of natural hazard fatalities that occurred annually during our
70-year study period ranged from 2 to 112 and exhibited a distinct
decrease over time. While the number of victims in the first three
decades (until 1975) ranged from 191 to 269 per decade, it ranged from 47 to
109 in the four following decades. This overall decrease was mainly driven
by a considerable decline in the number of avalanche and lightning
fatalities. About 75 % of victims were males in all natural hazard events
considered together, and this ratio was roughly maintained in all individual
process categories except landslides (lower) and other processes (higher).
The ratio of male to female victims was most likely to be balanced when
deaths occurred at home (in or near a building), a situation that mainly
occurred in association with landslides and avalanches. The average age of
victims of natural hazards was 35.9 years and, accordingly, the age groups
with the largest number of victims were the 20–29 and 30–39 year-old groups,
which in combination represented 34 % of all fatalities. It appears that
the overall natural hazard mortality rate in Switzerland over the past 70 years has been relatively low in comparison to rates in other countries or
rates of other types of fatal accidents in Switzerland. However, a large
variability in mortality rates was observed within the country with
considerably higher rates in Alpine environments
Survival probability in avalanche victims with long burial (≥60 min): A retrospective study.
The survival of completely buried victims in an avalanche mainly depends on burial duration. Knowledge is limited about survival probability after 60 min of complete burial.
We aimed to study the survival probability and prehospital characteristics of avalanche victims with long burial durations.
We retrospectively included all completely buried avalanche victims with a burial duration of ≥60 min between 1997 and 2018 in Switzerland. Data were extracted from the registry of the Swiss Institute for Snow and Avalanche Research and the prehospital medical records of the physician-staffed helicopter emergency medical services. Avalanche victims buried for ≥24 h or with an unknown survival status were excluded. Survival probability was estimated by using the non-parametric Ayer-Turnbull method and logistic regression. The primary outcome was survival probability.
We identified 140 avalanche victims with a burial duration of ≥60 min, of whom 27 (19%) survived. Survival probability shows a slight decrease with increasing burial duration (23% after 60 min, to <6% after 1400 min, p = 0.13). Burial depth was deeper for those who died (100 cm vs 70 cm, p = 0.008). None of the survivors sustained CA during the prehospital phase.
The overall survival rate of 19% for completely buried avalanche victims with a long burial duration illustrates the importance of continuing rescue efforts. Avalanche victims in CA after long burial duration without obstructed airway, frozen body or obvious lethal trauma should be considered to be in hypothermic CA, with initiation of cardiopulmonary resuscitation and an evaluation for rewarming with extracorporeal life support
Avalanche fatalities in the European Alps: long-term trends and statistics
Avalanche accidents, particularly those resulting in fatalities, attract
substantial attention from policy makers and organizations, as well as from
the media and the public. Placing fatal accidents in a wider context requires
long-term and robust statistics. However, avalanche accident statistics, like
most other accident statistics, often rely on relatively small sample sizes,
with single multi-fatality events and random effects having a potentially
large influence on summary and trend statistics. Additionally, trend
interpretation is challenging because statistics are generally explored at a
national level, and studies vary in both the period covered and the methods.
Here, we addressed these issues by combining the avalanche fatality data from
the European Alps (Austria, France, Germany, Liechtenstein, Italy, Slovenia,
and Switzerland) for three different periods between 1937 and 2015 and
applying the same data analysis methodology. During the last four decades,
about 100 people lost their lives each year in the Alps. Despite considerable
inter-annual variation, this number has remained relatively constant in the
last decades. However, exploring fatality numbers by the location of the
victims at the time of the avalanche revealed two partly opposing trends. The
number of fatalities in controlled terrain (settlements and transportation
corridors) has decreased significantly since the 1970s. In contrast to this
development, the number of fatalities in uncontrolled terrain (mostly
recreational accidents) almost doubled between the 1960s and 1980s and has
remained relatively stable since then, despite a strong increase in the
number of winter backcountry recreationists. Corresponding to these trends,
the proportion of fatalities in uncontrolled terrain increased from 72 to
97 %. These long-term trends were evident in most national statistics.
Further, the temporal correlation between subsets of the Alpine fatality
data, and between some of the national statistics, suggests that time series
covering a longer period may be used as an indicator for missing years in
shorter-duration datasets. Finally, statistics from countries with very few
incidents should be compared to, or analysed together with, those from
neighbouring countries exhibiting similar economical and structural
developments and characteristics