Natural disasters are classified in various ways; however, the most common classification is based on the source or sphere where the disaster originates. Additionally, natural disasters can also be classified by intensity, damage level, and geographical regions.
Classification of Natural Disasters by Origin
Natural disasters can be categorized in several ways, but the most widely accepted classification is according to the source or sphere of origin. Accordingly, the main types of natural disasters can be divided into the following categories:
- Atmospheric Disasters (thunderstorms, tornadoes, hurricanes, severe cold, wildfires, lightning, etc.). Among these, wildfires can occur naturally under particularly dry and hot weather conditions, with many such incidents in the United States and Australia belonging to this category.
- Hydrospheric Disasters (hailstorms, floods, flash floods, droughts, high tides, sea-level rise, etc.). In countries with cold climates, other types of natural disasters can occur, such as ice floods in mountainous regions.
- Biospheric Disasters (epidemics, outbreaks of plants and animals, etc.). Diseases caused by various viruses and parasites often exist in nature, but sudden changes in climate can lead to outbreaks. Similarly, harmful plant outbreaks can pose disasters for humans, such as pest infestations and locust swarms.
- Geospheric Disasters (earthquakes, volcanic eruptions, tsunamis, land subsidence, landslides, etc.). Earthquakes, volcanic eruptions, and tsunamis are typically linked to specific structures in the Earth’s crust, thus occurring in limited areas but causing significant destruction.
- Cosmic Disasters: meteorite impacts, gamma-ray bursts, solar waves and radiation, etc. These disasters receive less attention from humans as they are rare events; however, cosmic disasters are currently being studied more closely by developed nations.
Meteorite fall in Chelyabinsk, Russia. The meteorite explosion occurred at 9:20 AM (03:02 GMT) on February 15, 2013, in the city of Chelyabinsk, Russia, causing 2,000 homes to have shattered windows and injuring 500 residents from flying glass shards. According to scientists, the explosion was caused by a meteorite with a diameter of 17 meters that exploded at an altitude of 30 km above the city. The energy released was equivalent to that of 300 atomic bombs dropped on Hiroshima, Japan, in 1945. Russian scientists recovered the largest fragment of the meteorite weighing nearly 500 kg from a frozen lake near Chelyabinsk. Research results indicated that the meteorite primarily consists of silicate – a type of stony meteorite according to geologists’ classification.
- The first three types of natural disasters are often related to climate change on Earth.
- The last two types of disasters are generally less connected to climate change, occur infrequently, and in narrow scopes, but when they do occur, they can cause significant damage, sometimes resulting in catastrophe.
Examples include the Fukushima earthquake and tsunami in Japan in 2011, the earthquake and tsunami in Indonesia in 2004, and the Tunguska event in Russia in 1906.
Classification of Natural Disasters by Intensity and Damage Level
Hazard: A natural phenomenon that can cause loss of life, property, environment, living conditions, and disrupt economic and social activities. The term “Natural Hazard” typically refers to extreme events or processes of meteorological, hydrological, or geological origin, and is generally divided into two main groups based on the speed of hazard occurrence:
- Sudden Hazards, which are natural hazards that occur rapidly (e.g., earthquakes, storms, flash floods).
- Slow Hazards refer to hazards that develop over an extended period, leading to dangerous conditions (e.g., prolonged droughts resulting in food shortages, malnutrition, and potentially famine). It is increasingly difficult to distinguish between natural hazards and those caused by human activity.
For instance, deforestation on mountain slopes can lead to flash floods and landslides during heavy rains. Landfills, obstructions in drainage systems, or improper construction can also result in flooding. Landslides, floods, droughts, and wildfires are examples where the causes may stem from both natural phenomena and human activities. One hazard can trigger others; for example, earthquakes can lead to tsunamis, landslides, and fires, while storms can result in flooding and storm surges.
Catastrophe: A catastrophe is a state of significant damage to a country, region, or community when a natural disaster occurs, such as substantial loss of life, housing, and infrastructure, pollution, and destruction of living environments. A catastrophe represents the highest manifestation of a natural hazard, causing severe impacts on communities with widespread effects, leading to large-scale damage and disruption of normal community life. The consequences of a catastrophe can include loss of life, injuries, epidemics, and adverse effects on human health, mental well-being, and social welfare, material losses, destruction of property, interruption of services, disruption of economic activities, and environmental degradation.
According to the Disaster Prevention and Control Law of Vietnam in 2013, the level of disaster risk is divided into 5 levels based on criteria such as the intensity or danger level of the disaster, the scope of its impact, and the potential for loss of life, property, infrastructure, and environmental harm. Internationally, disaster risk is usually categorized into 5 levels (from 1 to 5) based on increasing disaster intensity, where level 5 indicates a disaster emergency requiring decisions from national leaders. For example, the Saffir-Simpson hurricane scale used in the United States and many Western countries classifies storms into 5 categories based on wind speed and wave height at the hurricane’s center.
Table 1: Saffir-Simpson Hurricane Scale.
Classification of Natural Disasters by Geographical Regions
In the context of disaster risk prevention activities according to the Disaster Prevention and Control Law of 2013, Point b, Section 1, Article 17 specifies the task of “assessing risks, zoning disaster risks, and creating disaster warning maps.” Zoning activities enable local authorities and communities to develop optimal strategies for mitigating and reducing risks with a high probability of occurrence. This work will be conducted across the entire territory of our country in the near future. In this document, we propose a classification of natural disasters by geographical region based on two groups of parameters: the frequency of disasters and the intensity/expected impact of disasters.
- Frequency of Disasters is categorized into levels: Very Frequent (VF), Frequent (F), Rarely Occurring (R), and Unlikely to Occur (U).
- Intensity/Level of Impact of Disasters is categorized into levels: Very Strong (VS), Strong (S), Moderate (M), Weak (W), and Zero.
The qualitative classification table according to the above levels for the 6 specific geographical regions of our country is presented in Table 2.
Table 2: Proposed classification of natural disasters by specific geographical regions in Vietnam.
According to Table 2, for instance, tsunamis cannot occur in the northern mountainous region, the Central Highlands, and the Southeast region, while the other four regions rarely experience them, but if they do, the impact would be substantial.
