Analysis and Mapping the Landslide Hazard in Bulgaria

Mapping the landslides is one of the main activities in the overall spectrum of geological hazards and geological risk. Landslides form the most serious part of the geological hazard in Bulgaria after the earthquakes. They are widespread in the all country's territory. All known landslide types of internationally accepted classification of Varnes (Landslides, analysis and control, 1978) are represented there. The main attention is paid to the level of activity and the territorial scope of landslides according to the criteria involved in the National Programme for Landslide Prevention of Bulgaria (2014) aimed at prioritizing landslides depending on the level of activity and the risk they carry. Thus 5 degrees of landslide hazard are accepted. Hazards and vulnerabilities are considered to be weighed, i. e. they can be assessed in advance in terms of what will be the weight of the probability of landslide hazard of the research area and what will be the results (vulnerability) due to its occurrence. The vulnerability is represented by indicators of GDP per capita and density of population. The intensity of the hazard can be very low, low, medium, high and very high, which correspond respectively to classes from I to V. The third stage is the determining factor of landslide hazard. This stage is determined by the intensity of the landslide hazard for the study area. It is obtained according to the district class of intensity for landslide hazard. The results express the weighted average hazard. They are obtained through a combination of the weight of the landslide hazard and its intensity that is accepted for the zone concerned. The weights for landslide hazard and its ratios derived from the potential intensity are multiplied to obtain individually weighted hazard score.