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Hazard landslides map of a regional area may be regarded in historical perspectives of the already happened phenomena (feasible by specific detailed cartography) and in perspective of triggering potential (the probability of the producing phenomena, including those already developed).
The Romanian legislation which standardizes the means of elaboration the maps of hazards and risks of landslides maps, settles 8 influence factors of their trigger action: lithological (Ka), morphological (Kb), tectonic (Kc), hydro-climatic (Kd), hydro-geologic (Ke), forester (Kf), seismic (Kg) and anthropic (Kh). They are grouped into 3-6 classes, conformable to a standard scale of 0-1. The probability of landslide producing is calculated by special formula (1).
The maps of trigger factors, based on the values of the already mentioned factors, grouped into standard intervals: 0-0,01; 0,01-0,1; 0,1-0,3; 0,3-0,5; 0,5-0,8; 0,8-1, is meant to create a probability image, as consolidated as each detail is bigger (scales bigger than 1:25.000 are recommended and the most recent cartographical sources possible). These 8 factorial maps (which become layers in the hazard maps processing) will be vectorized, and the attached data base will compulsory accommodate the value factor, the color, qualitative attributes, toponyms etc. A grid (the same for all factorial layers) is to be created on the whole area, as dense as the scale map is bigger (ideally of 10x10). The grid nodes of all layers will gather the values from the polygon on which they are placed (Map Info operations). Mathematical processing the probability values (the hazard environmental factor - Km) is performed on the equivalent nodes (l) of the 8 factorial layers.
The hazard map elaboration starting with the Km values calculation on the mentioned nodes, will be solved by continuous interpolation (Km with 0-1 values) or grouped into 6 classes of values (Km with 6 classes), for the following probabilities: null, reduced, medium, medium-high, high, very high. The risk map is based on the selection of big - very big risk areas on which the material and human loss is evaluated in case of landslide producing. The risks estimation on a quantified area is obtained by formulas (2) (material loss) and (3) (human loss), where: V = vulnerability, P = value /number of the potentially affected patrimony, registered after field research.
Using this methodology, the landslides hazard map (scale 1: 25.000) for regional territory, or hazard and risk maps (scale 1: 5.000) for local areas (municipal, villages), have been performed. The risk maps represent a norm (standard) model to be extended at national level.
Comparing the hazard maps performed on these bases with the active or fossil landslides of the target areas, an overlapping of more than 75% of the last categories over the areas with medium-high, high and very high probability of landslides occurring, is evidenced.
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