The final authenticated version is available online at https://doi.org/10.1007/978-3-030-37670-3_7
Climate Change Impact and Vulnerability Analysis in the
City of Bratislava: Application and Lessons Learned
Daniel Lückerath1[0000-0002-4988-5511], Eva Streberová2, Manfred Bogen1,
Erich Rome1, Oliver Ullrich1, Eva Pauditsová3
1 Fraunhofer-Institut für Intelligente Analyse- und Informationssysteme, Schloss Birlinghoven,
53757 Sankt Augustin, Germany
2 Útvar hlavnej architektky, Hlavné mesto Slovenskej republiky Bratislava, Slovak Republic
3 Prírodovedecká fakulta Univerzity Komenského v Bratislave, Ilkovičova 6, 841 04 Bratislava,
Consequences of climate change, like more frequent extreme weather events,
are major challenges for urban areas. With diverse approaches for adaptation
strategy development available to cities, comparability with respect to risks, vul-
nerabilities, and adaptation options is limited. The lack of standardized methods
and approaches to prioritize and select appropriate adaptation options restricts the
exchange of best practices between cities.
This paper presents the application of a vulnerability analysis for the city of
Bratislava, Slovakia. It describes how the approach was employed to analyze the
effects extreme precipitation has on the road network and reports on how differ-
ent stakeholders were involved in the process, how relevant data was employed
for the assessment, and which results were produced. Based on this process de-
scription, typical problems, resulting method adaptations, and lessons learned are
Keywords: Risk Analysis, Vulnerability Assessment, Climate Change, Critical
Infrastructure Protection, Climate Change Adaptation.
Climate models project robust differences in regional climate characteristics between
the present-day state and global warming scenarios with average temperature increases
of 1.5°C and 1.5°C to 2°C. These differences include significant increases in mean
temperature in most land and ocean regions (high confidence), hot extremes in most
inhabited regions (high confidence), heavy precipitation in several regions (medium
confidence), and the probability of drought and precipitation deficits in some regions
(medium confidence).  Urban population centers and their critical infrastructure
components are increasingly vulnerable to extreme events related to these changing
climate characteristics , especially fluvial and pluvial flooding, flash floods caused
by heavy precipitation, temperature extremes, as well as thunderstorms and other heavy
storms . This is also true for the City of Bratislava, capital of Slovakia and home of
Submitted version from Sep 2019. The final authenticated version is available online at https://doi.org/10.1007/978-3-030-37670-3_7
Cite this as:
Lückerath D., Streberová E., Bogen M., Rome E., Ullrich O., Pauditsová E. (2020) Climate Change Impact and Vulnerability Analysis in the City of Bratislava: Appli-
cation and Lessons Learned. In: Nadjm-Tehrani S. (eds) Critical Information Infrastructures Security. CRITIS 2019. Lecture Notes in Computer Science, vol 11777.
Springer, Cham. https://doi.org/10.1007/978-3-030-37670-3_7
approx. 430,000 residents, that already suffers from a temperature increase of 2°C since
1951 and an increase of total annual precipitation amounts. The storms that hit the city
today bring as much as 10% more precipitation compared to average records from the
previous century. Heatwaves and droughts have been appearing with increased fre-
quency and severity in the last three decades .
With an even higher degree of extreme weather events to be expected, Bratislava
decided to take part in the EU-H2020 project “RESIN – Climate Resilient Cities and
Infrastructures” . RESIN was a research project investigating climate resilience in
European cities. Through co-creation and knowledge brokerage between city decision-
makers and researchers, the project developed tools to support decision-makers in de-
signing and implementing climate adaptation strategies for their local contexts. Specif-
ically, Bratislava decided to apply “IVAVIA – Impact and Vulnerability Analysis of
Vital Infrastructures and Built-up Areas”, a standardized process for the assessment of
climate change-related risks and vulnerabilities in cities and urban environments that
was developed as part of RESIN.
This paper describes the process and key findings of the Bratislava city case. The
IVAVIA process was applied over the course of 18 months, contributing key elements
to the “Climate Change Impact Atlas of Bratislava” .
The paper continues with introducing the background of risk-based vulnerability
analysis and a brief description of the IVAVIA process (Section 2). It then presents an
in-depth description of the application of IVAVIA to assess the risk pluvial flooding, a
major threat for the City of Bratislava, poses to its road infrastructure (Section 3), and
concludes with a short summary of the lessons learned and an outlook on further re-
search steps (Section 4).
2.1 State of the Art: Impact and Vulnerability analysis
Several methods and tools for risk analysis exist, with the “Words into Action Guide-
lines for National Disaster Risk Assessment” from the United Nations Office for Dis-
aster Risk Reduction giving a comprehensive overview for the most frequently em-
ployed approaches .
On behalf of the German Federal Ministry for Economic Cooperation and Develop-
ment, Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ), together with
Adelphi and EURAC, developed the Vulnerability Sourcebook  in 2014, based on
the Fourth Assessment Report of the IPCC. In 2017, the same authors provided a Risk
Supplement  to the Vulnerability Sourcebook, based on the changes promoted in the
Fifth Assessment Report  to provide guidance for indicator-based vulnerability and
risk assessments. In this method, the usually massive amount of information and data
about hazards, exposure, vulnerability, and other risk components is simplified by ag-
gregating it to index scores (i.e. a number out of a full score), which are subsequently
combined (e.g. using weighted arithmetic/geometric mean) to present risk levels as a
In contrast, the German Federal Office of Civil Protection and Disaster Assistance
(BBK) employs a multi-criteria impact and likelihood analysis based on risk matrices,
an instrument also promoted as an ISO standard . In this approach, impacts and
probabilities of hazard scenarios are estimated (e.g. based on historical data or simula-
tion models) and classified by defining threshold values for the different impact/prob-
ability classes, i.e. in which value range do potential impacts/probabilities have to lie
to be classified in a certain way. Typically, risk matrices have four to seven impact
classes and a similar number of probability classes. For any combination of impact and
probability, a risk level or class (BBK: very high, high, intermediate, low) is deter-
mined. Both determining the thresholds and assigning risk levels requires political de-
cisions that have to be taken with extreme care: It requires deciding when a certain
number of fatalities is regarded as ‘moderate’ or ‘significant’ and which risk level re-
quires which type of reaction, or, more simply put, which risk level is acceptable and
which is not.
If no (or not enough) information or means for carrying out an indicator-based multi-
criteria analysis is available, expert elicitation approaches might be employed. Here,
individuals with a good understanding of the various components of disaster risk com-
ponents of the area under study conduct a qualitative analysis using their expert judge-
ments. The “Risk Systemicity Questionnaire” developed during the “Smart Mature Re-
silience project – SMR”  and the “UNISDR Disaster Resilience Scorecard for Cit-
ies”  are recently developed expert elicitation approaches. Both employ spread-
sheet- and/or web-based questionnaires to elicit knowledge from experts and combine
the gathered information into comprehensive overviews, e.g. by assigning scores to
predefined answers and visualizing them using spider charts.
Other research projects investigated climate change-oriented resilience in European
cities too: The project “Reconciling Adaptation, Mitigation and Sustainable Develop-
ment for Cities – RAMSES”  developed methods and tools to quantify the impacts
of climate change and the costs and benefits of adaptation measures to cities, while the
project “Smart Mature Resilience – SMR”  aimed at developing a resilience man-
agement guideline to support city decision-makers in developing and implementing re-
The RESIN project developed practical and applicable methods and tools to support
decision-makers in designing and implementing adaptation and mitigation strategies
for their local contexts and in a participatory way. One of these methods is the risk-
based vulnerability assessment methodology IVAVIA, which combines the indicator-
based method from the original Vulnerability Sourcebook with the multi-criteria impact
and likelihood analysis by the BBK.
2.2 IVAVIA: A Process for Impact and Vulnerability Analysis of Vital
Infrastructures and Built-Up Areas
The IVAVIA process consists of seven modules in three stages: the qualitative stage,
the quantitative stage, and the presentation of the outcome. Each module consists of
three to six individual steps.
The modules and steps are described in detail in the IVAVIA Guideline document
, with the more technical details of the process and reference information being
covered by the IVAVIA Guideline Appendix. A more detailed explanation of the meth-
odology with brief descriptions of example applications in Bilbao, Spain and Greater
Manchester, UK can also be found in . Here, only the key elements of IVAVIA will
be introduced briefly.
The central element of the qualitative stage of IVAVIA are impact chains. They are
cause-effect models describing the elements that contribute to the consequences a given
hazard has on an exposed object (see Fig. 1). Each element of an impact chain is to be
described in a qualitative way by specifying attributes1. Usually, impact chains are de-
veloped during collaborative workshops with domain experts. As a result, impact
chains are not exhaustive, but describe the common understanding of these experts.
Fig. 1. Impact chain for the hazard-exposure combination “pluvial flooding on road infrastruc-
ture” in the city of Bratislava. Hazards and drivers in blue, exposed object in grey, coping ca-
pacity in green-blue, sensitivity in green, and impacts in orange. Rectangles: attributes; Hexa-
For each attribute defined in an impact chain, measurable indicators need to be iden-
tified and associated data needs to be gathered. To ease the indicator selection process,
established directories of standard indicators should be employed, for example, the an-
nex of the Vulnerability Sourcebook (, p. 14-17) or the annex of the Covenant of
Mayors for Climate and Energy Reporting Guidelines (, p. 61-67).
Communicating a multitude of complex, multi-dimensional indicators in a compre-
hensive way can be extremely complicated. Therefore, the calculated indicator values
1 Attributes are inherent characteristics of the objects under analysis, such as sensitivity and cop-
ing capacity; they are the basis for determining indicators.
are normalized (e.g. via min-max normalization ), weighted, and aggregated (e.g.
using weighted arithmetic mean ) to composite scores for different risk compo-
Subsequently, risks are estimated. If sufficient historical data about impacts and oc-
currences of hazards for the definition of damage functions is available, these are used
to estimate potential consequences, which are then classified using discrete, ordinal
classes (e.g. “insignificant”, “minor”, or “disastrous” for impacts and “very unlikely”,
“likely”, and “very likely” for probabilities). The resulting impacts and probability
pairs, i.e. the risk scores, are then assigned to discrete, ordinal risk classes using a risk
If not sufficient historical data about past consequences and occurrences of hazards
to derive damage functions is available, an alternative approach is to employ the avail-
able data to define aggregated hazard and exposure indicators as described in the Risk
Supplement of the Vulnerability Sourcebook . For example, data about flood depth
and velocity can be combined to a single hazard indicator, while data about population
density in flood-prone areas and exposed build-up area can be combined to an exposure
indicator. These can then be combined with the composite risk components calculated
to a single risk score.
3 Analyzing Risks and Vulnerabilities Regarding Climate
Change for Bratislava
3.1 Situation in Bratislava
The City of Bratislava, capital of Slovakia, lies in the southern part of the country,
which has suffered from a temperature increase of 1°C since 1988. Higher temperatures
in warmer seasons have led to increased evapotranspiration, which results in occasional
but heavy rainfall. However, southern Slovakia has suffered an almost 20% decrease in
total annual precipitation and serious drought have been occurring almost every year
since the 1990s . A more complex analysis on intensity and length of warm and
cool weather spells in the period 1951-2017 shows a continuous increase of above-
normal temperature warm spells while below-normal cold temperature spells are con-
tinually decreasing .
Bratislava’s sectoral master plan on management of sewage water and rainwater
sewage systems dates back to 2008 and is not suited anymore for the amount of urban
development that occurred in the past 10 years, which resulted in an increase of imper-
meable land-cover. As a result, underpasses and whole street segments are often
flooded after substantial rainfall, resulting in blockages and traffic jams.
To tackle these and other climate change-related issues, Bratislava committed itself
to the Mayors Adapt initiative in 2014 and in the same year completed the EU Cities
Adapt program with a climate change adaptation strategy. In 2017 an action plan to
implement adaptation measures was developed. However, both the adaptation strategy
and the action plan are based on a qualitative vulnerability assessment. Therefore, a
new quantitative assessment applicable for spatial planning and permission procedures
for development projects needed to be conducted.
3.2 Applying IVAVIA in the City of Bratislava
Following the IVAVIA process as described above, the assessment started with the
identification of the most pressing climatic hazards for the city, i.e. heatwaves,
droughts, and pluvial flooding, followed by a kick-off meeting with stakeholders from
several departments of the municipality as well as external experts including health and
environmental authorities, the Slovak Hydrometeorological institute, and other organi-
zations operating in the area of health, sewage water management, and drinking water
provision. The goals of this meeting were to introduce the participants to the method-
ology and design initial impact chains.
The initial workshop yielded three impact chains covering the effects of heatwaves
and pluvial flooding on health and quality of life as well as droughts on green infra-
structure. These were later on supplemented by two additional impact chains covering
the effects of pluvial flooding on buildings and road infrastructure (see Fig. 1). During
the initial workshop, the participants were not given explicit guidance on potential at-
tributes, resulting in the identification and definition of more than 90 different potential
attributes across all impact chains, mostly based on experience and knowledge of the
Therefore, the identified attributes underwent a thorough review to filter out unsuit-
able and duplicated attributes, re-categorize attributes to correct for misunderstandings
(e.g. participants identified “low implementation of building-level adaptation measures
for reducing the impacts of rainfall” as a sensitivity attribute), and reducing the number
of attributes to a more manageable amount in order to facilitate result validation. Fol-
lowing this process, initial indicators for each attribute where defined and required data
The subsequent months focused on data acquisition: For each indicator the available
data, its spatial and temporal resolution, its data format, and the necessary licensing
agreements were identified. This included data from the Slovak Statistical Office on
borough level, published annually in the statistical yearbook, as well as data by the
National Healthcare Information Centre of the Slovak Republic and the Slovak Hydro-
meteorological institute. In addition, Bratislava City and local research partner Come-
nius University in Bratislava processed their own data sources as well as open source
data (e.g. from OpenStreetMap ) to calculate indicator maps. For example, a digital
elevation model of Bratislava was used to identify existing and potential drainage ba-
sins and their outlets using hydrological and terrain modelling tools. This drainage ba-
sin model was then used to identify critical terrain depressions by vectorising the raster
output and identifying the lowest sections of the drainage basins with depths up to 1 m.
This information was subsequently used to calculate different indicators, e.g. “density
of terrain depressions per borough” or “length of infrastructure exposed to terrain de-
pressions”. This method has also been used in , p. 73f. Fig. 2. shows part of the
combined drainage basin and terrain depression model with identified critical sections
of transport infrastructure and high-density terrain depression zones.
Other calculated indicators include pressure on the sewage system from the amount
of surrounding impermeable area and estimated amount of water coming from imper-
meable areas into the combined sewage system, groundwater level depth, pressure on
the sewage system based on population density in every borough and drinking water
consumption in households, availability of different types of implemented adaptation
measures, and share of (semi-)permeable areas.
Fig. 2. Elevation model with analysis of drainage basins and terrain depressions, showing also
zones of high density of terrain depressions (in yellow) – used for creating exposure indicators.
Single indicators were normalized using min-max normalization and combined to
composite indicators for sensitivity, coping capacity, exposure, and hazard using
weighted arithmetic mean. Initially, an expert judgment approach was to be employed
for selecting indicator weights, reflecting the perceived importance of indicators. How-
ever, this process was judged as too subjective by the participants and subsequently,
weights were chosen based on the results of a correlation analysis, allocating lower
weights for indicators that were correlated to correct for statistical effects.
The resulting composite indicators were visualized as choropleth maps (see Fig. 3
and Fig. 4) and validated by experts. Afterwards, the composite sensitivity and coping
capacity indicators where combined to a vulnerability indicator (see Fig. 5, left), which
in turn was combined together with the exposure and hazard indicator (see Fig. 4) to a
final risk indicator (see Fig. 5, right). These results were in turn validated by local ex-
perts based on historic occurrences of flooding events.
The assessment approach employed in Bratislava differs from the process description
in section 2 in that risk are not estimated based on a multi-criteria impact and likelihood
analysis but using an indicator-based approach as described in . This is due to the
limited amount of historical records about hazard occurrences and related impacts,
which prohibits the definition of robust damage functions and the estimation of likeli-
hoods. However, a non-probabilistic assessment for the present situation can be con-
ducted with the indicator-based approach. In the future these results can easily be ex-
panded to a probabilistic assessment.
The results of the assessment show for all impact chains that the city center located
in the “Stare Mesto” (Old town) borough and the adjacent boroughs such as the more
urbanized “Ružinov” and “Petržalka” usually yield the highest scores for vulnerability
and risk (see Fig. 5). The more peripheral city boroughs have a rather rural character,
with the majority of their area covered by permeable land-use or the Danube river run-
ning on their territory. These kinds of land use effectively mitigate the negative impacts
of pluvial flooding, which is reflected in the assessment. The only exemption in this
regard is the peripheral “Čunovo” borough. Although infrastructure density is relatively
low here, the infrastructure that is located here is often affected by terrain depressions.
Fig. 3. Choropleth maps, left: Sensitivity of road infrastructure to torrential rain; right: Coping
capacity of road infrastructure to torrential rain. Source: .
With regard to the morphology of the city area, several boroughs are strongly af-
fected by the vicinity of the Male Karpaty (Small Carpathians) mountain range in the
north and northwest. Although the vicinity of the mountains is an asset in mitigation of
extreme heat, the terrain also creates natural drainage basins which accumulate precip-
itation and channel it into the lower and more urbanized sections of the boroughs at the
The results of the vulnerability assessment were compiled into an Atlas that has been
created with the aim to provide useful information for city administration practitioners
at all levels, local research institutions, as well as practitioners from private sector (such
as architects, landscape architects, and development companies) and be also a support-
ing tool to decision-makers and policy makers across all scales – borough, city, re-
gional, as well as government level. Besides more than 90 choropleth maps (displaying
borough level assessments), there are finer thematic maps showing possible combina-
tions of different indicators, which can be used as stand-alone tools in spatial planning
and evaluation of investment projects.
The city will include the visual outputs into its open map portal after a public con-
sultation process and a formal acceptance of the Atlas by a resolution of the City Par-
4 Conclusion and Lessons Learned
This paper presented a case study on a climate change impact and vulnerability analysis
for the City of Bratislava, Slovakia. It shared some background on the state of the art
for impact and vulnerability assessment and gave a brief introduction to the applied
methodology. The paper described the initial situation in Bratislava at the outset of the
process and detailed the application of the assessment methodology exemplarily for the
effects of extreme rainfall on the road infrastructure in Bratislava.
While the initial goal of conducting an indicator-based vulnerability assessment fol-
lowed by a multi-criteria impact and likelihood analysis could not be met due to lack
in historical records, it was possible to conduct a non-probabilistic indicator-based as-
sessment that reflects the present conditions in Bratislava. After further validation of
the results by public consultation processes, a probabilistic assessment covering differ-
ent climate change scenarios is planned, availability of sufficient historical records pro-
vided. This assessment should also employ a higher (i.e. sub-borough) resolution to
enable detailed planning of adaptation options. This iterative refinement approach is in
line with how impact and vulnerability analyses for climate change should be under-
stood: as a continuous process with regular, frequent updates and adjustments accom-
modating new developments and newly available data.
In addition, applying the methodology in Bratislava showed the need for a European
– or even globally – unified reference indicator set for impact and vulnerability analysis
in urban areas with standardized temporal/spatial resolution and scope as well as stand-
ardized data structures to enable comparability between different urban areas and facil-
itate development of better supporting tools. The availability of reliable, sufficiently
extensive data sources is a serious problem that limits the applicability of probabilistic
assessment methodologies (see also BBK , p. 94, right box).
Fig. 4. Choropleth maps, left: Exposure of road infrastructure to torrential rain; right: Hazard
indicator for torrential rain. Source: .
Nonetheless, non-probabilistic assessments are highly valuable for a multitude of
stakeholders in urban areas. Developing cause-effect models with experts from differ-
ent municipal departments facilitates joint understanding and better communication of
complex climate change-related issues. Discussing these issues across different depart-
ments and stakeholder groups can also pave the way for other processes that enable a
better assessment in the future. For example, as a result of applying IVAVIA in Brati-
slava, the Office of the Chief City Architect was invited to join a working group devel-
oping a GIS portal for Bratislava that can be employed for further refinement of the
The results presented in the Atlas will be an important tool for identifying where to
implement adaptation measures listed in the action plan for climate change, e.g. sus-
tainable drainage systems, bio swales, green retention trenches and infiltration basins,
rain gardens, or increased permeable paving. On a city-wide level, more initiative needs
to be taken in terms of strategic land-use planning by incorporating the results of the
assessment into the new master plan. While the city can do this in public spaces, private
property owners also need to be incentivized to take action. For example, the city pro-
vides municipal grants of up to 1,000 € to encourage the implementation of adaptation
measures in households, such as upgrading buildings with sustainable drainage systems
or other nature-based approaches for rain water retention.
Fig. 5. Choropleth maps, left: Vulnerability of road infrastructure; right: Risk of torrential rain
on road infrastructure. Source: .
This paper is based in part upon work in the framework of the projects “RESIN – Cli-
mate Resilient Cities and Infrastructures” and “ARCH – Advancing Resilience of his-
toric areas against Climate-related and other Hazards”. These projects have received
funding from the European Union’s Horizon 2020 research and innovation program
under grant agreement nos. 653522 and 820999. The sole responsibility for the content
of this publication lies with the authors. It does not necessarily represent the opinion of
the European Union. Neither the EASME nor the European Commission are responsi-
ble for any use that may be made of the information contained therein.
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