The Difference Between Hazard and Risk

There are many definitions of risk, but in broad terms disaster risk refers to the impact of natural hazards on communities, infrastructure, and agricultural lands. For example, maps are frequently produced showing regions of high hazard - regions that are more or less likely to experience earthquakes, floods, cyclones, and so on. However, to really understand the potential impact of a natural disasters on communities, provinces and countries, it is necessary to move beyond this understanding of just hazard to a more comprehensive appreciation of the risks posed to communities. For example, rather than simply identifying which provinces have the highest chance of an earthquake or flood, risk assessments can provide information on which communities are most vulnerable to earthquakes or how many people would be left homeless by a 1 in 100 year flood or a magnitude 6.5 earthquake.

Below we give examples of the type of questions that a natural hazard risk assessment could answer:

What is the earthquake risk?

  • Where do the most damaging earthquakes occur that generate the most risk and how often are they likely to take place?
  • How does the calculated earthquake hazard compare to building standards and the resilience of the most common building types and infrastructure?
  • What is the likely impact of an earthquake (e.g. what percentage of buildings and/or infrastructure would be damaged)?

What is the flood risk?

  • How high will floodwaters be during different sized flood events?
  • What buildings, infrastructure and farming land are within potential flood zones?
  • Which provinces have the most people that will be affected by floods for different sized flood events?

What is the volcanic eruption risk?

  • Which volcanoes, and what size eruptions, pose a risk to communities?
  • What type of volcanic hazards (e.g. ash fall, tsunami) might be expected in an eruption and what could the impact be?
  • What would be the impact of an eruption on horticulture and thus local food supply?