Natural Hazards and Disasters

Natural Hazards, Vulnerability and Risk

The terms hazard and disaster are often used synonymously, but they actually have very different meanings.   A hazard can be described as "A perceived natural/geophysical event that has the potential to threaten both life and property" (Whittow). For example, if an earthquake occurred nowhere near people or their belongings, it would not be a hazard.    A disaster is the realisation of a hazard, when it causes a significant impact on the functioning of a community or society. The greater the scale of the natural hazard and the more exposed the people are, the greater the disaster is likely to be.   The Centre for Research on the Epidemiology of Disasters (CRED) states that a hazard becomes a disaster when 10 or more people are killed and/or 100 or more people are affected.   Degg's Model (shown below) shows that overlap is needed for a hazard to become a disaster.   Vulnerability can be defined as the diminished capacity of an individual or group to anticipate, cope with, resist and recover from the impact of a hazard.   Risk is the exposure of people to a hazerdous event or the probability of a hazard occurring. Risk is mainly understood through perception. The diagram below shows the risk-perception process. The same event in two areas may pose different risk. This is shown on the Vulnerability Quadrant.   Risk = hazard x exposure x \(\frac{vulnerability}{manageability}\)

Why stay in a hazardous area?

As the world population continues to rise, more and more people are living in danger of tectonic and climate hazards, but continue to stay in the same area for several reasons:   Cost-benefit: Sometimes the benefits of staying in an area outweigh the risk. This is common in volcanic areas. Fertile soils formed by volcanic ash bring opportunities for farming. Volcanic areas are often very popular tourist locations for their unique views. Volcanic mineral mining is often a choice made by unskilled workers in poorer areas, so the volcano provides job security for these workers. Volcanic areas hold huge opportunities for harnessing renewable geothermal energy.   In many cases, populations are too poor or sick to move away from hazardous areas. Some stay in their area for sentimental reasons or for family and friends.   It's not always predictable when or where an event will take place or what the magnitude of the event will be. Some countries don't have the technology to monitor and predict natural hazards at all.   "Russian Roulette Reaction": People are usually comforted by the statistics which show that the risk of death during a disaster is lower than that from influenza or car accidents. They also believe that if a high magnitude event occurs then it may be safe for a few years, this is not always true.  

Pressure and Release Model (PAR)

The Pressure and Release (PAR) model understands a disaster as the intersection between socio-economic pressure and physical exposure.   The PAR model understands that a disaster is the interaction between two processes: processes generating vulnerability on one side and a natural hazard event on the other.    It is suggested to be like a nutcracker, with increasing pressure being applied to people from either side.    The release idea is incorporated to conceptualise the reduction of disaster: to relieve the pressure, vulnerability has to be reduced.   The physical factors and processes of natural hazards are difficult to change and are sometimes are impossible to predict. However, small things such as building barriers to divert lava flows may be possible and can reduce vulnerability to the hazard.

Factors that increase vulnerability to hazards:

  Physical Factors: Location - For example, areas around the Pacific Ocean in particular are susceptible to tectonic hazards due to their location near the Pacific Ring of Fire. Location also plays a large role in determining climate.   Population - A larger population will mean more people are vulnerable to natural hazards.   Nature of settlements and the buildings within - durability of buildings within a settlement will often determine the amount of damage after an earthquake or eruption.   Telecommunications - though lines may be damaged in an event, good telecommunication networks in an area can affect responses to an event   Human Factors: Economic Development - The level of development in an area is one of the most substantial factors in determining the severity of a natural hazard. Development will not only determine some physical factors of vulnerability, but also the amount of money that can be used on hazard mitigation and recovery after an event. Overall, poorer areas are much more vulnerable to disasters.   Education - Education in an area will often bring improvements in science and technology, and thus, mitigation strategies.   Governance - Governance will directly impact the decisions made in mitigation and responses to natural disasters.   Gender - In poorer countries, women are often more vulnerable to natural hazards; they are often unskilled, unemployed, and politically marginalized. Women are usually the caretakers of families in these situations are often the ones tasked with protecting children and the elderly during disasters.

Hazard Profiles

A tectonic hazard profile is a technique used to try to understand the physical characteristics of different types of hazards.    Hazard profiles can also be used to analyse and assess the effects of the same type of hazard when it takes place in other areas (for example, a magnitude 7 earthquake in the developing world versus in the developed world).    Hazard profiles are developed for each type of hazard and are based on criteria such as frequency, duration and speed of onset.    One of the difficulties with hazard profiling is the degree of reliability when comparing different event types. For example, it is easy to compare two earthquake events, but it's difficult to compare a tsunami to a volcanic eruption because they have different impacts on society.   To accurately link different hazards on one scale, certain elements of the hazards become inaccurately displayed or have to be omitted.   The image below shows two different hazard profiles. The first is of earthquakes at two different plate boundaries (destructive and constructive) and the second compares different types of natural hazard. 

Development and Vulnerability

In the "root cause" phase of the PAR model, most important causes of vulnerability are those which have economic, demographic or political foundation. Inequality of access to education, housing, healthcare and income opportunities can influence vulnerability and resilience to natural hazards.   People and communities in developing countries only have access to livelihoods and resources that are insecure.  The lack of access to insurance and social protection means that people in poverty are often forced to use their already limited assets to buffer disaster losses, which drives them into further poverty.    People's basic health and nutritional status correlates directly with their ability to survive disruptions to their livelihood. There is also a clear relationship between lack of nutrition and disease, which is common after the occurrence of a hazard. People who are malnourished are at a greater risk of disease because they have weaker immune systems.   Looking at the types of vulnerability (shown below), there are several elements of development that relate to vulnerability and disaster risk.  Things like marginalisation, violence and armed conflict can turn a hazard into a disaster. These are called cross-cutting factors.   Internal factors happen within a country and are often politically derived, whereas external factors may be longer term and are much harder to control, for example, climate change and drought.   The World Risk Index (WRI) considers measures of exposure, susceptibility, coping capacity and adaptive capacity (see all of the factors below). Japan was ranked 17th and Haiti 21st. Both countries have disaster risks, but for different reasons: Japan for its exposure to natural events and Haiti for its lack of development and inequality.

Governance and Vulnerability

Weak political organisation and political corruption are factors that contribute to a more vulnerable population.   Governance encompasses a number of formal and formal arrangements and procedures, which can change over time. There are three main components of governance; economic, administrative and political (see below). These vary in scale from local to regional and to national.   Risk governance is the result of the interaction of several socio-economic forms of governing. Governance should be considered in the following wider characteristics and processes: an increase in economic activity on a global, transnational scale increased activity of institutions such as the European Union, operating across national boundaries the rise of neo-liberal ideology values (market-led) the spread of information technology, which made it easier to link different organisations and introduce changes

Reason's Swiss Cheese Model of Disaster Causation

Reason's Swiss Cheese Model of Disaster Causation is also referred to as the cumulative act effect model. It is widely used in risk management and analysis.   It likens human systems to multiple slices of Swiss cheese, stacked side by side, in which the risk of a threat becoming a reality is mitigated by the differing layers and types of defenses which are "layered" behind each other.    In natural hazards science, a disaster is thought to occur as a result of a series of coincidental events and processes. It highlights the fact that a particular disaster can be linked to a single hazard event, but then there is a cascade of other events that provide context for the hazard.   Generally the hazard becomes a disaster when holes in the layers line up, which creates the conditions for loss of life,property and livelihood.