Changes in climate patterns, plate tectonics, or other natural systems can cause changes in the frequency of particular natural hazards, regardless of whether the cause of the changes are natural, like El Niño, or manmade, like climate change.
Changes in frequency for technological or intentional hazards can be the result of many factors, such as increased or decreased regulation of industry and increases in international instability (e.g., terrorism).
As populations move, they inevitably place themselves closer or farther from the range of effects from certain hazards.
For instance, if a community begins to develop industrial facilities within a floodplain that was previously unoccupied, or in an upstream watershed where the resultant runoff increases flood hazards downstream, it increases its risk to property from flooding.
Changes in What Happens as a Result of Disasters (Disaster Consequences)
Like changes in disaster likelihood, changes in consequences can be the result of changes in the attributes of the hazard itself or changes in human activity that place people and structures either at more or less risk.
Changes in the attributes of the hazard can occur as part of short- or long-term cycles, permanent changes in the natural processes if the hazard is natural, or changes in the nature of the technologies or tactics in the case of technological and intentional hazards.
The consequences of natural hazards only rarely change independent of human activities.
The attacks on the U.S. embassies in Kenya and Tanzania and the September 11 attacks on the World Trade Center and the Pentagon display an increase in the consequences of terrorist attacks aimed at Americans.
A mutation of a certain viral or bacterial organism, resulting in a more deadly pathogen, can cause a drastic increase in consequences.