Mass Movement Processes Under Changing Climatic and Socioeconomic Conditions - Sustainable Development in Mountain Regions: Southeastern Europe - page 27

last centuries the area was populated more densely than nowadays. Despite the
moderate development in this region, there is additional demand for infrastructure
and settlements with increasing property values. Whatever the conclusion, it is not
serious to claim that there have not been similar precipitation events in the area
before. They simply do not cause that much damage. Maybe because there have
been less roads (impact of road constructions to landslide susceptibility, compare
Chapter 3.2.2), people had a better understanding of natural contexts and inherent
hazards and there were much less property values. Also, one cannot exclude historic
documents describing such events got lost in the course of time.
The landslides that occurred 2005 in the communities of Gasen and Haslau are
well documented and allow the analysis in varying terms whereas already results
like first hazard index maps are available (Fig. 3.7 ). Further activities will focus
on determining the sphere of action and how objects are affected (vulnerability),
developing a transparent methodology for risk assessment, especially in the case of
landslides and resulting debris flow.
3.5 Working with Scenarios - An Approach
As the further increase of frequency and magnitude of extreme precipitation events
at a regional or local scale is insecure, scenario techniques will help to describe the
frame of assumed developments. These scenarios should not cover only climate but
also socioeconomic changes. Land use planning, agriculture and forestry should be
involved in the design as well as damage limitation and preventative measures. In
order to be able to calculate the further impact of events on economy and society, it
is necessary that the vulnerability of communities be assessed.
As a first step, scenarios should be developed separated for each process, show-
ing the effects of changing frame conditions to triggering, transport and deposition
processes. As a second step, interaction between the processes should be considered
as it can build up or mitigate adverse effects.
Scenario modelling is a common approach operating with insecure further devel-
opments. In the case of natural hazards and especially in the case of mass movement
transport processes there are some hurdles to clear. The crucial point is the fragmen-
tary database covering nowadays hazards and risks. There are hardly any practical
hazard maps available and risk maps even less. Area information is often inadequate
to generate even hazard index maps like, for example, the susceptibility map of the
region Gasen and Haslau (Fig. 3.7 ).
While knowledge about triggering factors and processes is already on a rather
satisfying level, the issue of frequency and magnitude of spontaneous, shallow
landslides and debris flow has not been solved so far.
Classical frequency functions are based on series of measurements using statis-
tical approaches. The assumption is that the extreme events are independent from
each other, which means one event does not influence the other. This is true for pre-
cipitation and nearly always for flood events. Triggered landslides lead to changed
slope conditions, which affect the sliding disposition. Therefore, the assumption is