Abstract. Snow avalanche hazard is threatening people and infrastructure in all alpine
regions with seasonal or permanent snow cover around the globe. Coping with
this hazard is a big challenge and during the past centuries, different
strategies were developed. Today, in Switzerland, experienced avalanche
engineers produce hazard maps with a very high reliability based on avalanche
database information, terrain analysis, climatological data sets and
numerical modeling of the flow dynamics for selected avalanche tracks that
might affect settlements. However, for regions outside the considered
settlement areas such area-wide hazard maps are not available mainly because
of the too high cost, in Switzerland and in most mountain regions around the
world. Therefore, hazard indication maps, even though they are less reliable
and less detailed, are often the only spatial planning tool available. To
produce meaningful and cost-effective avalanche hazard indication maps over
large regions (regional to national scale), automated release area
delineation has to be combined with volume estimations and state-of-the-art
numerical avalanche simulations. In this paper we validate existing potential release area (PRA) delineation
algorithms, published in peer-reviewed journals, that are based on digital
terrain models and their derivatives such as slope angle, aspect, roughness
and curvature. For validation, we apply avalanche data from three
different ski resorts in the vicinity of Davos, Switzerland, where
experienced ski-patrol staff have mapped most avalanches in detail for many
years. After calculating the best fit input parameters for every tested
algorithm, we compare their performance based on the reference data sets.
Because all tested algorithms do not provide meaningful delineation between
individual PRAs, we propose a new algorithm based
on object-based image analysis (OBIA). In combination with an automatic
procedure to estimate the average release depth (d0), defining the avalanche
release volume, this algorithm enables the numerical simulation of thousands
of avalanches over large regions applying the well-established avalanche
dynamics model RAMMS. We demonstrate this for the region of Davos for two
hazard scenarios, frequent (10–30-year return period) and extreme (100–300-year
return period). This approach opens the door for large-scale avalanche
hazard indication mapping in all regions where high-quality and high-resolution
digital terrain models and snow data are available.
Automated Detection of Field Monuments in Digital Terrain Models of Westphalia Using OBIA
