Natural hazards are naturally occurring physical phenomena caused either by rapid or slow onset events which might have a negative effect on humans or the environment; these events can be can be geophysical, hydrological, climatological, meteorological, or biological.
Classification of natural hazards
- Geophysical hazards: These are hazards driven by geological (i.e. Earth) processes, in particular, plate tectonics. Examples are, earthquakes, landslides, tsunamis, volcanic activity, etc.
- Hydrological hazards: These are hazards driven by hydrological (i.e. Water) processes. Examples are, avalanches, floods, etc.
- Meteorological hazards: These are hazards driven by meteorological (i.e. Weather) processes, in particular those related to temperature and wind. Examples are, cyclones, storms/wave surges, etc.
- Biological hazards: These are hazards driven by biological processes. This includes various types of disease, including infectious diseases that spread from person to person, threatening to infect large portions of the human population. Examples include, disease epidemics, insect/animal plagues, etc.
- Climatological hazards: These are hazards caused by long-lived, meso- to macro-scale atmospheric processes ranging from intra-seasonal to multi-decadal climate variability. Examples include, extreme temperatures, drought, wildfires, etc.
Difference between natural hazards and natural disasters
Natural hazard includes all atmospheric, hydrologic, geologic (especially seismic and volcanic), and wildfire phenomena that, because of their location, severity, and frequency, have the potential to affect humans, their structures, or their activities adversely.
Natural disaster is a hazardous event that causes unacceptably large numbers of fatalities and/or overwhelming property damage. Natural Disaster can be caused either by natural phenomenon or human activity.
NOTE: Most natural hazards can also result to natural disaster. Example – Earthquake is the hazard which caused the 1906 San Francisco earthquake disaster.
List of natural hazards
- Coastal erosion
- Volcanic eruption
- Heat wave
- Cyclonic storm
- Ice storm
- Climate change
- Geomagnetic storm
- Tephra (ash, cinders, lapilli)
- Lava flows
- Projectiles and lateral blasts
- Pyroclastic flows
- Fault ruptures
- Ground shaking
- Lateral spreading
- Coastal flooding
- Erosion and sedimentation
- River flooding
- Storm surges
Human action and natural hazards
Although humans can do little or nothing to change the incidence or intensity of most natural phenomena, they have an important role to play in ensuring that natural events are not converted into disasters by their own actions. It is important to understand that human intervention can increase the frequency and severity of natural hazards. For example, when the toe of a landslide is removed to make room for a settlement, the earth can move again and bury the settlement. Human intervention may also cause natural hazards where none existed before. Volcanoes erupt periodically, but it is not until the rich soils formed on their ejecta are occupied by farms and human settlements that they are considered hazardous.
Steps to managing natural hazards
- Understanding Geologic Processes: A fundamental understanding of processes requires research that typically is the domain of academic and government researchers, exploring basic science issues and concepts. Fundamental questions may include: What triggers an earthquake, and why do some events have great magnitude while most remain small-magnitude events? What processes are responsible for triggering a landslide? Can we predict the severity of an impending volcanic eruption? Can we predict an impending drought or flood? Can we determine the height of a storm surge or storm track associated with coastal storm well in advance of landfall so that the impact can be mitigated?
- Hazard Assessment: A hazard assessment, which is often conducted by governmental geoscience institutes, focuses on the spatial extent of where a hazard exists, its severity, and when it may occur. For example, earthquakes occur along faults as accumulated strain is released, so if fault locations can be identified, geoscientists will have information relative to the earthquake hazard in particular areas. Unfortunately, precise identification of hazard sources is often very difficult. For example, the significance of the earthquake hazard in the Pacific Northwest of the United States was underestimated until detailed mapping and research on the nature of the tectonics of the area was completed.
- Monitoring Conditions: The third element of the hazard identification approach is monitoring. Monitoring coverage both by type of hazard and spatial distribution of monitoring locations varies globally. The ability to actively monitor for hazards is often controlled by the ability to monitor at the spatial scale that is useful, while sometimes it is a function of uncertainty in the dynamics that trigger a hazard.
- Timely and Effective Delivery of Information: Of course, hazard information is most valuable when it is used effectively by non-geoscientists to save lives and to reduce the economic and social consequences of events.
- Mitigation and Resilience: Finally, any effective hazard management system must strive to increase resilience, which is defined in a 2005 report of the U.S. National Science and Technology Council (NSTC), Subcommittee on Disaster Reduction as “the capacity of a system, community, or society potentially exposed to hazards to adapt, by resisting or changing, in order to reach and maintain an acceptable level of functioning and structure (Executive Office of the President, 2005, p. 17).” The only way to gain resiliency is to learn from past events and to decrease risk. To succeed in increasing resiliency requires having strong hazard identification programs with adequate monitoring and research components and very robust mechanisms to deliver timely, accurate, and appropriate hazard information to a broad audience that will use the information in a wide variety of ways to meet their specific goals.
In summary; Natural hazards are inherently part of the human condition and experience. However, it is within the realm of geoscientists, emergency managers, policymakers, and the general public to mitigate their impacts and prevent the occurrence of natural hazards from becoming regional, national, and global disasters.