Flood risk map perception through experimental graphic semiology
Institute of Mountain Risk Engineering, University of Natural Resources and Applied Life Sciences, Vienna, Austria
W. Dorner & K. Spachinger
Department of Civil Engineering, University of Applied Sciences, Deggendorf, Germany
J. Rochman & K. Serrhini
UMR CNRS 6173, University of Tours, Tours, France
The procedure of risk assessment emerged as an appropriate tool to analyse the impacts resulting from natural
hazards. However, despite from a considerable amount of approaches and guidelines, only little work has been
carried out with respect to the harmonisation of risk mapping, the information necessary, and the required
quantification of possible impacts on decision-makers. A particular gap exists with respect to the perception of
information provided in risk mapping for different stakeholder groups.
Within the RISKCATCH project, risk maps were created for catchments located in the Alps and the related
forelands. Based on the assessment of historical and possible future development of hazard, values at risk
and vulnerability, these maps were created on different scales using scenario technique. The information cre-
ated was evaluated by presenting the maps to several stakeholder groups, above all political decision makers,
practitioners and laypersons from European countries, using the method of graphic semiology. As a result, pos-
sible improvements in design and content of such information were deduced.
The respective hydrological processes (precipitation, land use, geomorphology) and the rivers (structure,
flood plain and flood defence) were analysed on a regional and temporal scale for three catchments in the
Austrian Alps and two catchments in the German alpine foreland. Existing data of synthetic floods derived
from hydrological models in combination with stream routing was linked with data of real flood and debris
flow events to analyse the relations between precipitation and the development of hazards in the river system.
Based on the modelling results of defined design events, the associated damage potential was assessed. Multi-
temporal data on damage of previous inundations and data on the associated damage potential in the test sites
was collected and edited for the use within a GIS-environment. The elements at risk—which were defined as
those buildings within the test sites located in endangered area—were analysed with respect to their spatial
location and extension using GIS. Intersecting this information, risk maps were generated on different scales in
order to analyse possible improvements in information content and design.
To quantify risk perception, the maps were presented to a group of stakeholders from different European
countries. The method used was based on the approach of experimental graphic semiology, reversing the tradi-
tional communication pattern from transmitter to receiver. Starting from receiver, the maps were presented to
the test persons using an ophthalmic device for the record of eye movements during picture reading. The test
was accompanied by a specific survey; hence, the cognitive perception of risk maps was evaluated. All maps
were presented to the test persons for a relatively short time period to identify the most attractive components
of each map. The eye movements were subsequently statistically analysed in order to assess patterns of visual
perception for each map and to study the reading behaviour for text elements included in the maps. The visual
strategies of each test person were quantified.
The study resulted in guidelines of how to include information on natural hazard risk for different stakehold-
ers, in particular with respect to visual information contained in risk maps. Thus, the results of the study can be
used by administrative bodies for communication strategies within the concept of integral risk management, in
particular with respect to non-structural flood mitigation.
Flood risk management, risk mapping, experimental graphic semiology, European research