Factors Influencing Natural Hazard Risk (Frequency of Hazard (Frequency of…
Factors Influencing Natural Hazard Risk
Magnitude of Hazard
If the hazard is a larger event e.g. a more powerful EQ, then more people are likely to be affected and so the risk increases.
Measure the following hazards - using a number system - EQ richter scale, volcanoes - Volcanic explosivity index, tropical storms - saffir simpson scale.
Frequency of Hazard
Frequency of hazard - how often the event occurs.
High frequency environment - in this case people are always recovering from the last event.
Middle frequency events - reduces the risk as people have knowledge of what to do in the event of the hazard occuring.
Low frequency events - high risk - people don't prepare as they feel it won't happen.
Higher population density increases the risk from hazards. More people in danger.
Squatter settlements - Very high risk from natural hazards. Buildings are poorly constructed and there is very high population density.
Size of population
The number of people who live close to a hazard zone.
In an EQ soft rock will make the shaking worse - increasing the risk
Flooding - The risk is lower if houses are built on permeable rock
In an EQ - liquefaction is where soil that is shaken behaves like a liquid. This causes buildings to collapse. The risk of this increases if the rock is impermeable.
Relief of the land
This is the shape of the land.
In an earthquake - a bowl shape can increase the shaking risk and mean more buildings collapse. E.g. Nepal EQ 2015.
Tropical Storm - One of the major hazards is a storm surge. If people can get to high land they are in less danger.