Module 2: Developing Impact Chains

Impact chains are a good foundation for a qualitative vulnerability assessment. An impact chain describes a cause-effect-relationship among elements that contribute to the conse- quences of a given combination of hazard and exposed object. You develop impact chains by means of impact chain diagrams, which make these relationships visible (for an exam- ple, see Figure 9). This development takes place usually in joint workshops with experts and stakeholders. Be aware that impact chains are not exhaustive, but describe the common understanding of the stakeholders present at the workshop. A major rule is: keep it simple!

The IVAVIA impact chain diagrams used in RESIN differ intentionally from the diagrams of the Vulnerability Sourcebook. We are using IPCC AR5 definitions for central notions like ‘expo- sure’, ‘sensitivity’ and ‘vulnerability’. These notions are elements of impact chain diagrams. Hence, we have adapted the syntax and semantics of the IVAVIA impact chain diagrams ac- cordingly. Each of these elements may be described in a qualitative way by a set of specific variables, and then in a quantitative way by assigning measurable indicators to each variable.
The relevance of possible variables essentially depends on the considered hazards and sec- tors of the analysis. If several hazards (e.g. extreme precipitation and heat waves) or sectors (e.g. road-traffic infrastructure and health) are considered, then you should use a separate hazard exposure combination for each of those. As a prerequisite to develop impact chains, you must therefore identify the hazards and exposed objects of interest. The example in Figure 9 considers public health as an object exposed to the hazard heat wave. If there are more exposed objects to be covered, you should create additional impact chains.


Figure 9: Sample IVAVIA impact chain diagram for the hazard exposure combination ‘heat wave on public health’ with impacts, sensitivities, coping capacities, drivers, and stressors


The vulnerability assessment is based on attributes and impacts within the impact chain diagrams. For example, the age dependency of population is an attribute of the city’s sen- sitivity to heat waves. On the other hand, the availability of cooling rooms is an attribute of the city’s coping capacity for heat waves. Exposure, sensitivity, and coping capacity will vary depending on the urban development projections and the temporal stage you chose for your scenarios.

The key question is: ‘Which sensitivities and coping capacities might influence the nature and extent of impacts?’ In the following modules, you will use this information as a basis for the actual vulnerability assessment. It is quite obvious that the result of the vulnerability assessment will be better when a sufficient amount of data is available for the indicators. However, be aware that quantifiable indicators will not be available in all cases. And be careful, an indicator cannot be in both sensitivity and coping capacity (otherwise, the in- dicator would be counted twice). If you are in doubt, please re-read the definition of these two terms and choose the category you feel is more adequate for the indicator in question.

Although the IVAVIA impact chain diagrams are created initially for single combinations of hazard and exposed object, dependencies and interdependencies can lead to cascading effects – those will be considered later in the analysis (see module 5).

Iconography of IVAVIA impact chain diagrams

There are some simple rules for the construction of IVAVIA impact chain diagrams regard- ing the use of shapes and colours. First, IVAVIA impact chain diagrams are composed of elements with specific shapes (see Table 1).



Table 1: Meaning of shapes in IVAVIA impact chain diagrams


Second, you should use colours in a consistent way (see Table 2).


Table 2: Meaning of colours in IVAVIA impact chain diagrams

Figure 10 shows a generic IVAVIA impact chain diagram scheme, including definitions of terms.

Relevant experts and stakeholders collaborate to develop the IVAVIA impact chain dia- grams in an incremental way consisting of five steps, which are described in detail in the next sections. Note that there might be reasons to change the suggested sequence, e.g. to perform step 2.5 before step 2.2. For instance, in case the ranking of hazard exposure com- binations for further assessment is difficult, the stakeholders might first discuss potential impacts in order to decide the sequence. As a general rule, you should start with step 2.1 and then continue with the aspects for that the most amount of information is available.

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Figure 10: Generic IVAVIA impact chain diagram scheme


The first step towards creating impact chain diagrams consists of selecting a set of combina- tions of hazards and exposures (objects affected by the hazard). The selection of the hazard and exposure combinations should be guided both by strategic assessment or adaptation goals, and by the available resources. If you have severely limited resources for climate change adaptation planning, then a good way to proceed is to make a list of relevant hazard exposure combinations, prioritize them, and select as many of the top-ranked combina- tions as you can manage. If you would restrict your assessment to the qualitative phase, you might be able to handle more hazard exposure combinations than if you would apply the full IVAVIA method. To give you an impression of a plausible number of combinations, we provide an example from the RESIN city case studies. There, we have considered in total the six most common types of hazards (related to flooding and extended periods of dry weath- er), combined with exposure like health or well-being of the population (or more vulnera- ble parts of it), built infrastructure, green infrastructure, and critical infrastructure sectors or specific parts thereof. Therefore, a comprehensive coverage could yield some 50 to 100 combinations. However, none of the cities considered more than 2 or three hazards, and it is also possible to cover all vulnerable population groups in one impact chain or several critical infrastructure elements in one assessment. This would reduce the number of combi- nations to 10-20. A typical number of combinations for an initial assessment is three to five.

The quantitative assessment requires more resources than the qualitative assessment. However, once you have managed initial overheads (internal organisation of the assess- ment process, training and learning curve, data acquisition), the effort required for investi- gating further hazard exposure combinations will substantially decrease.

Since the full definition of an impact chain is time-consuming, the selection and prioritisa- tion is a crucial decision. Therefore, the hazards and sectors identified in modules 0 and 1 should be reviewed in this step. The results of the review and the reasons for making selec- tions should be documented.

For each of the final set of hazard exposure combinations, create a draft impact chain dia- gram template (see Figure 10 for a generic diagram), to be extended and completed in the remaining steps of this Module 2.
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Figure 11: Sample IVAVIA impact chain diagram template for the hazard exposure com- bination ‘heat wave on public health’. Here, ‘DRIVER’, ‘STRESSOR’, ‘IMPACT’ and ‘ATTRIB- UTE’ are placeholders for items to be provided in the next steps of module 2

Step 2.2: Identify drivers and stressors

In the second step of module 2 you identify drivers that influence the probability or strength of the selected hazard(s), and stressors (non-climatic drivers) that could intensify negative effects on your exposed system.

Examples of drivers and stressors are listed in the description of step 0.3 in module 0.

Examples of more specific stressors:

  • frequent strikes could be a stressor for public transport infrastructure;
  • lack of wastewater treatment is a stressor of water quality;
  • poor air quality is a stressor for people during a heat wave;
  • lack of road maintenance is a stressor of road transport

Continuing the example given earlier, the maintenance state of the sewer system (deteri- oration due to mining subsidence) and possible obstructions of parts of it (wipes, grease) may act as a stressor that increases an urban district’s sensitivity. Many of these stressors will show different characteristics dependent on the future scenario you are examining.

Warning: Keep the analysis simple and stay with the stressors that are immediately rele- vant for your city or system!



Step 2.3: Determine sensitivity



In the third step of module 2 you identify sensitivities of your exposed system towards the selected hazard(s). IPCC AR5 defines sensitivity as “The degree to which a system or species is affected, either adversely or beneficially, by climate variability or change. The effect may be direct … or indirect ….”.

In this step, you need to clarify what characteristics make your exposed system susceptible to the effects of the hazard(s). An urban district might be susceptible to fluvial flooding because it consists of a low-elevation area next to a river, while an above-average age dis- tribution might make the population of another urban district susceptible to heat waves.

There are basically two types of sensitivities: those that cannot be changed, and those that could be changed and therefore constitute a potential for adaptation. For a further discus- sion of sensitivity, we refer to the Vulnerability Sourcebook (BMZ 2014a, p. 64–65).

14Step 2.4: Determine coping capacity15

In step 2.4 you identify coping capacities of your exposed system that enable it to handle the effects of the selected hazard(s). You need to identify what makes your exposed system resilient to the effects of the hazard(s).

As an example, the coping capacity of a city district with respect to pluvial flooding could be determined by the green area of the city district (size, nature of soil, state of soil) and the capacity of the sewer system. The latter is typically designed for being able to cope with an amount of pluvial water that is expected to occur once in a certain period of years (based on historical data). If climate change is expected to change the periodicity of this amount of pluvial water, it might be an adaptation option to increase the capacity of the sewer system.

16Step 2.5: Identify potential impacts


In the fifth step of module 2 you identify potential direct and indirect impacts that the selected hazard(s) have on your exposed object(s). We recommend doing this in a partici- patory workshop in collaboration with the stakeholders from the city.

One source for the identification of potential impacts is the collection of historical data that you have created in step 0.2. Probably, most of the impacts listed there will also be relevant for future occurrences of the hazards.

A brainstorming session, with the participation of experts, regarding the hazard or the ex- posed object under consideration will help to complete your list of potential impacts. You should avoid overly extensive discussions on direct and indirect impacts. When it comes to impact chains, there is a fundamental motto: keep it simple. Otherwise, you might get lost in a huge amount of indirect, e.g. socio-economic, consequences of the given combination of hazard and exposed object.

It is recommended that the participants of the workshop assign priorities to the clusters according to their opinions on which are the most critical effects to the exposed object. Ethical aspects like ‘protection of humans must come first’ will play an important role here.

At the end of module 2, you will have a set of preliminary IVAVIA impact chain diagrams for all selected hazard exposure combinations. These impact chain diagrams structure the qualitative information provided by the experts from your city. The structured information already sketches areas for possible adaptation actions, aimed at reducing sensitivity, in- creasing coping capacity, and reducing impacts and stressors.

21828-200Proceed to Module 3