What is risk?
In physical sciences, risk is defined as a function of hazard, exposure, and vulnerability 1. Thus, whether or not something poses a risk depends on a wide range of factors within these categories.
As a result, the risk of the same hazards e.g. a flood, can vary. Below we explore each contributing factor.
Figure 1: Diagram to illustrate risk in physical sciences. Here, for example the hazard is given as a flood, exposure refers to the inundated area, and vulnerability stretches over the wider community. Even though the flood itself has definitive boundaries, the impact zone can stretch much further. Credit: Caroline Taylor.
What is a hazard?
Generally, in physical sciences, a hazard refers to a process or phenomenon that may cause disruption, damage and/or loss of life 2, as shown above in figure 1.
Whether something is a hazard or not depends on the probability than an event will occur and its expected magnitude 3. For example, a dormant volcano has a very low hazard as the probability of eruption is near zero.
Given that the same type of hazard can have differing probability and magnitude we often ‘scale’ our hazards, referring to them as low or high hazard.
What is exposure?
Exposure generally refers to the likely economic, social, or cultural human impact of the hazard 4. For example this can include;
- People
- Livelihoods
- Services and resources
- Infrastructure
To quantify exposure, information such as population count, number and type of houses, number of bridges, area of agricultural land and other infrastructure or activity of economic value must be collected within the likely ‘hazard zone’ 5.
What is vulnerability?
Vulnerability, in the contexts of natural hazards, is generally defined as an individual’s or community’s capacity to anticipate, cope with, resist and recover from the adverse effects of physical events 2.
There are a number of physical, social, and environmental factors within the community that exacerbate or lessen the overall impact of a hazard 6,7, such as age, gender, risk perception.
Historically, people knowingly inhabit areas with known hazards 9; due to economics or work prospects 10, historical and cultural connections 11 or for religious and tourism related reason 12.
FACT: Women are more vulnerable to natural hazards than males, due to their lower levels of education and other social, religious, and political conditions 8.
Summary
In summary, in physical science studies hazard, exposure, and vulnerability all work together to determine risk. All three factors can and do vary over time and can be impacted by external events such as climate change, making managing risk difficult. Thus it is vital we continue to build understanding of physical hazards, human exposure to them as well as community vulnerability if future disasters are to be avoided.