The Risk Equation

The teacher introduces the risk equation, i.e. the equation that allows us to identify the elements that, when multiplied, result in risk.

R = H x V x E

H = Hazard

Hazard is the probability that a phenomenon of a given intensity will occur in a given period of time, in a given area.  

V = Vulnerability

Vulnerability is the propensity to suffer damages from an event. In other words, it indicates the propensity of people, buildings, infrastructure and economic activities to be damaged as a result of the stresses induced by an event of a certain intensity.

E = Expoxure (or exposed value)

Exposure is the number of people and elements (or 'value') at risk in a given area.

You can find the full definitions in the Sendai Framework Terminology on Disaster Risk Reduction (link).

The class at this point tries to give numerical values to each component of the equation to see how the final result increases or decreases based on the changes made.

The teacher now leads a group discussion by asking the class:

Which elements do you think we can intervene on and which we cannot?

The correct answer will be: if dangerousness cannot be changed, exposure and vulnerability Propensity to suffer damages from an event can.

This is where Adaptive Capacity comes in, that is to say "the ability to find strategies to adapt to a situation", i.e. the ability to take action to reduce vulnerability and exposure and increase the resilience The ability to cope with calamitous events and overcome their effects of a community.

The teacher proposes the following activity to empirically observe what happens in the event of an earthquake Sudden ground shaking resulting from movements of the earth’s crust to structures and people and thus test the risk The possibility that a phenomenon may cause harm to people, settlements and the environment in a given period of time and in a given area equation.

On a bench the teacher arranges 6 paper cups arranged in a pyramid (3 below, 2 in the middle, 1 above) and 10 marker caps of different colors (which will represent people). Two different scenarios are imagined:

Scenario 1: the pyramid is formed by placing the paper cups very close together and the caps are arranged as follows: 2 below the pyramid, 3 at a greater distance and the others near the edge of the counter.

Scenario 2: The pyramid is formed by placing the glasses as far apart as possible, and the caps are arranged half below the pyramid and half farther apart, but not near the edge of the bench.

In both scenarios, the seismic hazard is determined to be 10. 

The class shakes the bench, observes how many glasses and caps will fall in the two scenarios, and notes them on a sheet of paper. The fallen glasses and caps are the vulnerable ones. The reason for the vulnerability Propensity to suffer damages from an event is determined for example:

- Pyramids are built with different materials and techniques.

- Some caps do not know where the collection point is.

- Some caps did not follow the directions of emergency managers.

- One stopper has a motor disability.

- Some caps have reached a distant but unsafe area.

At this point Adaptive Capacity, or duct tape, intervenes. Everyone can choose where to intervene and how. Each intervention will mean taping one or more items to the bench.

The experiment is to “stick” as many elements with the tape as possible and each time enter new values into the equation. 

Here are some examples:
You can establish that at the collection point you are safer and therefore 5 or more caps can be secured with the tape all together. Or that an earthquake Sudden ground shaking resulting from movements of the earth’s crust -resistant structure is strong and therefore put all caps underneath. This activity can be done in small groups.

The only value that cannot be changed is the hazard value 10.

Capacity plays a fundamental role. Indeed, it allows in all phases of an emergency to intervene to lower the risk The possibility that a phenomenon may cause harm to people, settlements and the environment in a given period of time and in a given area by reducing exposure and vulnerability Propensity to suffer damages from an event .

In the final phase, the class discusses the choices made and how the capacity of each and every one of us can change the outcome and lower the risk. For example, the class can reason about the difference it can make to:

• Follow the teacher's directions in the event of an evacuation;
• Know where the assembly point to be reached is located;
• Know about the difficulties that people with disabilities may have in an emergency.