Natural Hazards | National Risk Index (2024)

Natural hazards are defined as environmental phenomena that have the potential to impact societies and the human environment. These should not be confused with other types of hazards, such as manmade hazards. For example, a flood resulting from changes in river flows is a natural hazard, whereas flooding due to a dam failure is considered a manmade hazard, and therefore excluded from the National Risk Index.

In the National Risk Index, natural hazards are represented in terms of Expected Annual Loss, which incorporate data for exposure, annualized frequency, and historic loss ratio.

The 18 natural hazards included in the National Risk Index are:

Natural hazards can also cause secondary natural hazard events that create additional hazards. For example, Volcanic Activity can create other hazards, such as ash and lava spread. The National Risk Index only considers main natural hazard events and not their results or after-effects.

Natural hazards and natural disasters are related but are not the same. A natural hazard is the threat of an event that will likely have a negative impact. A natural disaster is the negative impact following an actual occurrence of natural hazard in the event that it significantly harms a community. The National Risk Index is designed to help communities understand their relative natural hazard risk and the impacts they could expect during or after a disaster.

For comprehensive details about natural hazards in the Risk Index, see the National Risk Index Technical Documentation.

• Learn about exposure
• Learn about annualized frequency
• Learn about historic loss ratio