| Although various methods to carry out quantitative landslide
risk analyses are available, applications are still rare and mostly
dependent on the occurrence of disasters. In Iceland, two catastrophic snow
avalanches killed 34 people in 1995. As a consequence the Ministry of the
Environment issued a new regulation on hazard zoning due to snow avalanches
and landslides in 2000, which aims to prevent people living or working
within the areas most at risk until 2010. The regulation requires to carry
out landslide and snow avalanche risk analyses, however, a method to
calculate landslide risk adopted to Icelandic conditions is still missing.
Therefore, the ultimate goal of this study is to develop such a method for
landslides, focussing on debris flows and rock falls and to test it in
Bíldudalur, NW-Iceland.
Risk analysis, beside risk evaluation and risk management, is part of the
holistic concept of risk assessment. Within this study, risk analysis is
considered only, focussing on the risks to life. To calculate landslide
risk, the spatial and temporal probability of occurrence of potential
damaging events, as well as the distribution of the elements at risk in
space and time, considering also changing vulnerabilities, must be
determined.
Within this study, a new raster-based approach is developed. Thus, all
existent vector data are transferred into raster data using a resolution of
1m x 1m. The specific attribute data are attributed to the grid cells,
resulting in specific raster data layers for each input parameter. The
calculation of the landslide risk follows a function of the input parameters
hazard, damage potential of the elements at risk, vulnerability, probability
of the spatial impact, probability of the temporal impact and probability of
the seasonal occurrence. Finally, results are upscaled to a resolution of
20m x 20m and are presented as individual risk to life and object risk to
life for each process. Within the quantitative landslide risk analysis the
associated uncertainties are estimated qualitatively.
In the study area the highest risks throughout all of the analyses
(individual risk to life and object risk to life) are caused by debris
flows, followed by rock falls, showing that risk heavily varies depending on
the process considered. The resultant maps show areas, in which the
individual risk to life exceeds the acceptable risk (defined in the
aforementioned regulation), so that for these locations risk reduction
measures should be developed and implemented. It can be concluded that the
newly developed method works satisfactory and is applicable to further
catchments in Iceland, and potentially to further countries with different
environmental settings. |