To answer the question; What are Natural Hazards? it is rational to evaluate it with regards to natural resources, implying that it is needful to begin by answering the question;
“What are Natural Resources?”
In response to this, natural resources refer to resources which are available or provided by “nature” and constitute and integral aspect of the earth and its environs.
This would include mineral deposits, hydrocarbons, soil, water and natural gases, among others.
Therefore, like natural resources, Natural Hazards are simply hazardous occurrences which involve the earth and its environs.
It is rational to expect that such hazards will pose potential harm to the earth, its biomes and ecosystems, its water, gases, minerals and other natural resources.
- Scientific Overview of Natural Hazards
Natural hazards from a scientific perspective, refer to phenomena that are;
2). Potentially harmful
3). Involving elements of the natural environment and the earth
It is also correct to refer to natural hazards as ‘Geologic hazards’, since they affect the earth and its component elements. The field of geology which deals specifically in the study of natural hazards is known as ‘environmental geology’ although other fields like geochemistry and geophysics are also involved in this assessment.
This is due to the fact that natural/geologic hazards have effects on the physical, chemical and biological aspects of the environment. The physical effects of natural hazards include seismicity, deformation, heat release, climate change, and stress propagation.
The chemical effects include soil and groundwater pollution, especially through the release of chemical compounds during such hazardous events. These include poisonous gases and other compounds released during volcanic eruptions and similar events.
Natural hazards may also cause the spillage and outflow of hazardous industrial materials. These may get washed out in floods and may be very harmful when they come in contact with infrastructure and living ecosystems. For example, untreated hazardous chemicals could be washed out of an industrial storage system and into the environment, contaminating streams and other surficial water bodies.
The biological effects of natural hazards can be predicted to include the health implications of these events on living organisms, biomes and the ecosystem.
For example, the destruction of infrastructure, release of toxic materials and loss of life and property caused by natural hazards, directly impact the wellbeing of the human populace, destruction of natural habitats, as well as pollution and contamination of the environment, and harm other living species as well.
Social effects of natural hazards also exist. They include socioeconomic breakdown, loss of human and material resources and collapse of societal schemes.
The economic damage caused by disasters varies. Capital assets and infrastructure such as housing, schools, factories and equipment, roads, dams and bridges are lost. Human capital is depleted due to the loss of life, the loss of skilled workers and the destruction of education infrastructure that disrupts schooling
Summary of Impacts of Natural Disaster (/Hazard)
The impacts of natural hazards and disaster can be summarized into the following points;
1). Loss of life and property
2). Destruction of amenities and social infrastructure
3). Devastation of ecosystems
4). Loss of natural habitats
5). Geomorphological changes (such as formation tectonic and volcanic mountains, ridges, steep slopes, horst and graben structures)
6). Disease outbreak
7). Contamination of the environment
It is also possible to classify impacts or effects of natural hazards into primary, secondary and tertiary.
- Primary effects include those which may occur from the direct impact of the hazardous processes.
- Examples of these include the damage and collapse of buildings during earthquakes, and the deluging of land areas due to flooding. Others are infrastructural damages during hurricanes and landslides.
- Secondary effects of natural hazards may occur due to the indirect impact of primary effects. Examples include fire outbreak due to infrastructural damages and blowouts, as a result of earthquakes. Flooding as a result of tornadoes and landslides, are other examples
- The Tertiary effects of natural hazards include long–term results, which are also due to the impact of primary effects. They include environment pollution due to release of effluents from damaged industrial facilities during earthquakes, agricultural limitations as a result of soil damage and volcanic eruption (larva coverage of the soil), among others.
- Examples of Natural Hazards
Natural (or geologic) hazards (or disaster), may occur in various forms, which could be seen as examples of such hazards. They include;
Earthquake refer to sudden tremors of the ground resulting from the transmission of seismic waves through rocks in the Earth’s crust. These seismic waves are the result of the release of some form of stored energy from the Earth’s crust and this is often at the point of fracture and slippage of rock masses under intense pressure.
Earthquakes usually occur along faults zones where there is relative movement of rock masses to one another. Such fault zones are predominantly situated at continental margins of tectonic plates.
A tsunami is a series of violent marine waves which mobilize large waves and volumes of water that may reach great heights exceeding a hundred feet. Such waves are usually very destructive when they come into contact with the shore.
Tsunamis are known to be resultant of energy releases in the sea or ocean, which may be considered equivalent to submarine earthquakes.
The energy forces large volumes of water out of the sea basin and onto land. The “Ring of Fire” in the Pacific is known to be a major location at which up to 80% of tsunamis occur.
This is due to significant tectonic activity in this region. Volcanic eruption and landslides in the subsea, may also cause tsunamis to occur.
The speed of propagation of marine waves in tsunami events is usually up to 500 miles per hour, meaning that they may travel long distances across the ocean to reach the land within a relatively short period of time. They are also conservative due to their long wavelengths, implying that they may lose very little momentum along the path of travel.
An example of the destructive potential of tsunamis is exemplified by the 2011 incident in Rikuzentakata, Japan, which left up to 1,550 people dead. Tsunamis occur in series of waves, which may compound their damaging impact.
A landslide is simply the mobilization of rock masses, rubble, debris, or other earth materials, down a slope. This phenomenon can be categorized under the compound term; “Mass Wasting”, which refers to any process involving the mobilization of soil, rock, debris and other earth materials, in a downslope direction, under the force of gravity.
Other terms which denote similar mass wasting processes, include Rock fall, Topples, Mudslides, Mud flows, and Debris flows.
In general, there are multiple factors which can be held accountable for the occurrence of landslides. Slope movement is itself the result of the action of forces downward, along a slope. Other causative factors are all related to the increase in downward force or pull, on earth materials which rest on a slope.
This is equivalent to an increase in the force of gravity on earth materials, due to an increase in weight which may be a result of moisture, tectonic influence, erosion, groundwater changes, anthropogenic impact, or volcanic activity. Landslides may also occur under water, forming turbidite deposits and submarine fans.
4). Volcanic eruptions
A volcano refers basically to a rupture or opening in the crust of the earth, which permits the escape of earth materials from the asthenosphere and mantle, including volcanic ash, magma and gases.
Volcanoes generally occur where at the margins or meeting points of tectonic. They may however, also occur within tectonic plates, due to upwelling from beneath the crust, at zones known as mantle plumes or hotspots.
Volcanic eruption can be said to occur when gas and lava are ejected from a volcano, and is often an explosive event. Volcanic eruption can also be classified into categories based on the mode of occurrence and degree of explosiveness, such as Vesuvian and Strombolian eruptions. Hazards related to volcanic eruption include land devastation by lava flow, ash fall, and debris flow.
Subsidence refers to a process by which the ground may sink below its original level, mostly due to underground movement. This movement is often as a result of the loss of subsurface matter, which may be water, natural gas, minerals, or oil, which may be lost due to anthropogenic activities.
Natural processes can also lead to subsidence. Such processes include consolidation of the soil, earthquake, isostacy, and dissolution of evaporitic rocks in the subsurface. The scale of subsidence may also vary, from relatively small expanses of land to vast areas which may cover an entire province. The severity of subsidence can be assessed on the basis of the depth of sinking and the associated level of damage.
In some cases, subsidence may be very severe, causing collapse of structures and formation of sinkholes, whereas in other cases it may be less prominent and may require the use of geodetic equipment to monitor its occurrence.
A flood can be described as a surge of overflowing water which deluges land area that is usually dry. The study and prediction of floods is very important in our present society, due to the increase in frequency and severity of occurrence, which is in turn a result of aggravating conditions of climate change and global warming.
Predictably, flooding can be described as the process by which large volumes of water overflow or deluge land that is usually dry. The primary, secondary and tertiary effects of flooding can be described as follows;
6a). Primary Effects
These include the effects of flooding that occur as a result of direct contact with the overflowing water. They include;
1). Loss of property, which can be carried away by strong currents when the flood volume and velocity are high.
The materials may be transported as suspended load, or by traction and saltation, depending on its weight and the capacity of the flood currents. In some cases, floods may be powerful enough to mobilize vehicles, bridges and buildings
2). Extensive and severe erosion can occur due to the abrasive effects of floods and their transported load. This erosion can damage roads, levees, bridges and other infrastructure
3). Floods may enter into buildings and destroy important components like walls, floors, furniture, electrical appliances and automobiles
4). Flooding may cause the loss of crops and soil in farmlands. In the process, livestock may be harmed
5). Floods with large volume and high velocity can cause the drowning of humans
6). Floodwaters may carry toxic pollutant materials like sewage and industrial effluents which can cause environmental pollution and may be hazardous to health.
6b). Secondary Effects
These include the effects that are resultant of the primary effects of flooding. Examples include;
1). Pollution of drinking water supplies, which is very likely to occur where sewage or industrial plants are in close proximity. This may lead to illnesses.
2). Interruption of electrical services and gas supply.
3). Disruption of transportation systems may occur due to infrastructural damage. This will most often have devastating socioeconomic impacts
6c). Tertiary Effects
1). Inundation of river banks
2). Destruction of ecosystems and habitats
7). Meteoric collision
While this is a rare incident, there is an existent danger of collision of the cosmic planetary bodies with the earth. Such bodies usually orbit the sun at a distance close to the earth, and may be termed asteroids.
An example of the potential effect of meteoric collision is the mass extinction event which is predicted to have occurred in the Mesozoic due to meteorite impact, causing the death of several prehistorical organisms including the dinosaurs.
Other examples of natural hazards (which are not categorized as geologic hazards) are;
It has been acknowledged that cyclones represent a notable threat to life and property in parts of the world. They may be said to include a number of hazardous processes like powerful wind propagation, lightning storms and tornadoes. The term is often used when there is a simultaneity or collaboration between any two of these events
9). Thunder Storms
A thunderstorm typically refers to a momentary, violent weather condition which occurs in association with dense clouds, hail, wind and lightning. They may occur when there is a rapid uprising of moist and warm air to colder atmospheric regions. At height, this air may condense to form cumulonimbus clouds.
When precipitation occurs, cooled air may surge downward and strike the earth powerfully, while electrical charges which have accumulated over a period of time, in the clouds. may be discharged as lightning. The surges of air may become sufficiently powerful to form tornadoes.
Tornadoes refer to violent rotating clouds of air which may have a small diameter and is usually in contact with the earth, extending from a convective cloud. They most often occur alongside thunder storms. They are known to produce wind of up to 500km per hour. Such winds are usually destructive when they come in contact with settlements.
11). Disease outbreak
A disease outbreak can be described as the incidence of cases of disease, in numbers and frequencies that are beyond normal. Disease outbreak can be categorized in terms of its scope of spread, which may be across a region, or community. Outbreaks may also be restricted to a particular season or period of the year. The spread of diseases in such cases is pioneered and sustained by infectious organisms which may be animal or insect vectors. The minimization of the devastating socioeconomic effects of disease outbreak is possible by early observation and mitigating action.
Based on coverage, disease outbreak may be termed as either Epidemic, Pandemic, or Endemic. Difference between these three categories is given briefly below;
An epidemic may be described as an unexpected rise in the number and frequency of occurrence of disease cases within a defined geographic region. This brings up a list of examples including measles, yellow fever, polio and small pox, which have had episodes of sudden, exaggerated spread across the United States.
It is needful to note that epidemics do not always involve contagious diseases, rather they ate characterized by the rate and magnitude of spread. Therefore, cases like obesity and mental illness still qualify as epidemics, when the rate and magnitude of incidence is significant and unexpected within a given geographical area
This is a similar concept to epidemic, however, the disease outbreak and spread are relatively exponential. In such cases the number of new incidents may progressively and continuously increase on a daily basis. Pandemic scenarios typically exceed a single geographical area and may span across countries and/or continents. The severity of the disease is not usually a factor involved in this categorization.
A notable example of a pandemic is the corona virus (COVID-19) outbreak, which is said to have commenced within the Asian continent in late 2019, and spread exponentially in the following months, constituting a global threat and dominating most parts of the world in barely six months.
While a pandemic is also not necessarily supposed to involve contagious diseases, the corona virus case has been particularly notorious due to the highly contagious nature and fatality of the disease.
An endemic refers basically to a disease outbreak which is relatively consistent and occurs within a definite geographical region. It obviously differs from an epidemic in its predictability, since it is a consistent condition within an area, and is not generally unprecedented or unexpected. An example is the outbreak of malaria in West African countries such as Nigeria.
A wildfire or wildland fire refers to a phenomenon involving the propagation of fire in an uncontrollable manner, within a grassland, forest, agricultural terrain or brushland. Some terms such as forest fire or grassland fire can be applied to account for such distinctions in the nature of the affected area. Wildfires also differ markedly in their rate of spread and severity.
The prevalence of wildfires especially within the United Sates, has recently been intensified by climate change conditions. This is because wildfire outbreak has a higher risk of occurrence under certain conditions of temperature and humidity.
These conditions are all driven by climate change, which of recent, has been inclined toward a drastic shift in the direction of higher temperature. Such temperatures encourage dry vegetation which is the main fuel for wildfire, and also reduces the soil moisture in most vegetative areas.
The phenomenon of drought is characterized by prolonged periods of dryness and lack of moisture/precipitation. This implies that in drought cases, rain, dew, or snow may be unexperienced for long periods of time.
Drought is generally intensified by the abstraction of available water by humans within the period of non-precipitation. Because of the notable dependence of organic survival on water, drought is a potentially detrimental condition. The definition of “drought” however varies from region to region, since some areas are more prone to dryness than others.
Other hazards may be caused by man-made or anthropogenic processes, and include;
16). Ozone layer depletion
17). Acid rain
18). Acid Mine Drainage
- Management of Natural Hazards
Because natural hazards occur in “nature” and are not generally predictable, the likelihood of preventing them entirely is small. However, some measures can be taken to ensure that they are mitigated and their effects minimized.
These include the following, among others;
1). Monitoring of hazard risk indicators using geodetic, geospatial and geophysical technologies. For example, seismic monitoring can warn of the impending occurrence of tsunamis and earthquakes
2). Early detection of disease cases may aid in mitigating the occurrence of epidemics, pandemics or endemics.
3). Identification of major risk indicators
4). Warning and evacuation of inhabitants from high risk areas
5). Geo-mechanical investigation of sites before construction of structures
6). Dam construction to manage impact of flooding
7). Terracing of slope land to reduce risk of mass movement