Disaster Tier Effects


Disasters of all types can have primary, secondary, and tertiary effects.

Table 1. Examples of Disaster Tier Effects

Primary Effects Secondary Effects Tertiary Effects
Primary Effects occur as a result of the disaster event itself. Secondary Effects occur only because a primary effect has caused them.

Tertiary Effects are long-term effects that are set off as a result of a primary event.


  • Water damage as a result of flood or hurricane.
  • Property damage as a result of an earthquake, tornado, landslide, or hurricane.


  • A tsunami generated as a result of earthquake.
  • Disruption of power and water as a result of an earthquake, tornado, flood, or hurricane.
  • Flooding caused by a landslide into a lake or river.
  • Landslides and debris flows.


  • The loss of habitat caused by a flood as a result of permanent changes in the position of river channel.
  • Crop failure caused by a volcanic eruption.
  • Roads and highways blocked.

Table 2. Relationships of Primary and Secondary Hazards

This table shows the relationships of primary hazards and secondary hazards.

  • Grey boxes – Secondary hazards triggered by the primary hazard.
  • Black boxes  – Intersecting same hazards and represent null.
  • Red boxes – Terrorism is a special case. It is a motivation rather that a physical phenomenon. It uses hazards to create impacts.[1]



  1. Image Source: http://www.seattle.gov/emergency/publications/documents/SHIVA.pdf [Accessed July 14, 2013]