Natural disaster
A natural disaster is the highly harmful impact on a society or community following a natural hazard event. Some examples of natural hazard events include: flooding, drought, earthquake, tropical cyclone, lightning, tsunami, volcanic activity, wildfire.[1] A natural disaster can cause loss of life or damage property, and typically leaves economic damage in its wake. The severity of the damage depends on the affected population's resilience and on the infrastructure available.[2] Scholars have been saying that the term natural disaster is unsuitable and should be abandoned. Instead, the simpler term disaster could be used, while also specifying the category (or type) of hazard.[3][4][5] A disaster is a result of a natural or human-made hazard impacting a vulnerable community. It is the combination of the hazard along with exposure of a vulnerable society that results in a disaster.
For other uses, see Natural disaster (disambiguation).
In modern times, the divide between natural, human-made and human-accelerated disasters is quite difficult to draw.[6][7][8] Human choices and activities like architecture,[9] fire,[10][11] resource management[11][12] and climate change[13] potentially play a role in causing natural disasters. In fact, the term natural disaster was called a misnomer already in 1976.[5]
Natural disasters can be aggravated by inadequate building norms, marginalization of people, inequities, overexploitation of resources, extreme urban sprawl and climate change.[6] The rapid growth of the world's population and its increased concentration often in hazardous environments has escalated both the frequency and severity of disasters. Extreme climates (such as those in the Tropics) and unstable landforms, coupled with deforestation, unplanned growth proliferation and non-engineered constructions create more vulnerable interfaces of populated areas with disaster-prone natural spaces. Developing countries which suffer from chronic natural disasters, often have ineffective communication systems combined with insufficient support for disaster prevention and management.[14]
An adverse event will not rise to the level of a disaster if it occurs in an area without a vulnerable population.[15][16] Once a vulnerable population has experienced a disaster, the community can take many years to repair and that repair period can lead to further vulnerability. The disastrous consequences of natural disaster also affect the mental health of affected communities, often leading to post-traumatic symptoms. These increased emotional experiences can be supported through collective processing, leading to resilience and increased community engagement.[17]
Multi-hazard analysis
Each of the natural hazard types outlined above have very different characteristics, in terms of the spatial and temporal scales they influence, hazard frequency and return period, and measures of intensity and impact. These complexities result in "single-hazard" assessments being commonplace, where the hazard potential from one particular hazard type is constrained. In these examples, hazards are often treated as isolated or independent. An alternative is a "multi-hazard" approach which seeks to identify all possible natural hazards and their interactions or interrelationships.[90][91]
Many examples exist of one natural hazard triggering or increasing the probability of one or more other natural hazards. For example, an earthquake may trigger landslides, whereas a wildfire may increase the probability of landslides being generated in the future.[91] A detailed review of such interactions across 21 natural hazards identified 90 possible interactions, of varying likelihood and spatial importance.[91] There may also be interactions between these natural hazards and anthropic processes.[92] For example, groundwater abstraction may trigger groundwater-related subsidence.[93]
Effective hazard analysis in any given area (e.g., for the purposes of disaster risk reduction) should ideally include an examination of all relevant hazards and their interactions. To be of most use for risk reduction, hazard analysis should be extended to risk assessment wherein the vulnerability of the built environment to each of the hazards is taken into account. This step is well developed for seismic risk, where the possible effect of future earthquakes on structures and infrastructure is assessed, as well as for risk from extreme wind and to a lesser extent flood risk. For other types of natural hazard the calculation of risk is more challenging, principally because of the lack of functions linking the intensity of a hazard and the probability of different levels of damage (fragility curves).[94]