Component of risk

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The situation of people, infrastructure, housing, production capacities and other tangible human assets located in hazard-prone areas.

UNISDR 2017 Terminology

Exposure is one of the defining components of disaster risk.

Why does it matter?

If a hazard occurs in an area of no exposure, then there is no risk (GFDRR, 2014a). Take the example of typhoons (tropical cyclones that occur in the Pacific Ocean). In October 2013 a Category 5 super typhoon (known as Lekima) hit the North West Pacific Ocean. Its winds reached peaks of around 240 kilometres per hour, but caused no impact on people or assets. In November 2013 another Category 5 Super Typhoon Haiyan (Yolanda) hit the region, with winds peaking at 315 kilometres per hour. Haiyan affected 11 million people, causing more than 6000 casualties and the loss of more than 1.5 billion US dollars. The difference in impact was because there were no people or property in the path of Lekima; in other words, there was no exposure (see the map comparing the paths of the two typhoons).

Source: UNITAR (2014) with data from NASA

The extent to which exposed people or economic assets are actually at risk is generally determined by how vulnerable they are (UNISDR, 2009), as it is possible to be exposed but not vulnerable (IPCC, 2012).

However, increasing evidence suggests that the case of extreme hazards the degree of disaster risk is a consequence of exposure more than it is a result of vulnerability (UNISDR, 2015a). For instance, in the case of the 26 December 2004 Indian Ocean tsunami all those exposed to tsunamis were at risk, no matter their income, ethnicity or social class (UNISDR, 2011).

Typhoon Lekima and Typhoon Haiyan (Yolanda) comparison Source: UNITAR (2014)

What drives exposure?

People and economic assets become concentrated in areas exposed to hazards through processes such as population growth, migration, urbanization and economic development (UNISDR, 2009b). Previous disasters can drive exposure by forcing people from their lands and to increasingly unsafe areas. Consequently, exposure changes over time and from place to place.

Many hazard prone areas, such as coastlines, volcanic slopes and flood plains, attract economic and urban development, offer significant economic benefits or are of cultural or religious significance to the people who live there. As more people and assets are exposed, risk in these areas becomes more concentrated. At the same time, risk also spreads as cities expand and as economic and urban development transform previously sparsely populated areas (UNISDR, 2009b).

Large volumes of capital continue to flow into hazard-prone areas, leading to significant increases in the value of exposed economic assets. If global exposure continues to trend upwards, it may increase disaster risk to dangerous levels (UNISDR, 2015b).


Increasing exposure of economic assets

Overall and insured losses worldwide, 1980-2013 © Munich Re, 2013: Geo Risks Research, NatCatSERVICE, as of January 2014


Global loss trends indicate that the rapid growth of economic assets in hazard prone areas is increasing disaster risk.

SOURCE: UNISDR (2015a) [GAR15]


Central European floods: increasing exposure of economic assets

Central Europe

increasing exposure of economic assets is driving the economic cost of disasters


How do we measure exposure?

Measures of exposure can include the number of people or types of assets in an area. These can be combined with the specific vulnerability and capacity of the exposed elements to any particular hazard to estimate the quantitative risks associated with that hazard in the area of interest (UNISDR, 2017).

Exposure modelling has a critical role to play in risk assessment. The information used to develop exposure data sets can be derived from various sources and methods (GFDRR, 2014a). Resolution of data sets refers to how thoroughly defined the data are; for instance, exposure data over a large geographical area (low resolution) may hide the true picture at the local level.

At the local scale high resolution exposure data have been developed, but only for specific projects. Common data sources are council and local government agencies, household surveys, aerial photos, and individual architectural/structural drawings. Crowd-sourcing (obtaining information or input into a task by enlisting the services of a large number of people typically via the Internet) has become a common and valuable tool for collecting local level data, as well as validating global-scale data, but this approach is limited by the type and quality of data (GFDRR, 2014a).

At the national scale complete geospatially linked inventories (databases) that include public infrastructures are rare and not publicly available in most developing countries, so there is a great need to develop these inventories (GFDRR, 2014a). State-based agencies, statistical offices, census data, investment and business listings, employment figures, and existing geographic information system (GIS) data are common sources of exposure information at a regional scale and above.

At the global scale efforts to generate globally consistent exposure data sets in terms of the quality and resolution have increased. Methodologies need to consider the dynamic nature of exposure because it evolves over time as a result of (unplanned) urbanisation, demographic changes, modifications in building practice, and other factors (GFDRR, 2014a). At the lowest (coarsest) level of resolution, national statistical agencies, census data, global databases, and remote sensing are used for developing exposure data.


Building exposure databases through community mapping in Indonesia


Open data initiatives, combined with bottom-up approaches such as citizen mapping initiatives, can be an effective way to build large exposure databases.


How do we reduce exposure?

Economic exposure in high-hazard areas is trending upwards. If we do not reverse this trend, disaster risk is set to increase. We need to act now to reduce exposure and build capacity and resilience in these areas of growing exposure.

When it is not possible to avoid exposure to events, land use planning and location decisions must be accompanied by other structural or non-structural methods for preventing or mitigating risk (UNISDR, 2009a and ICSU-LAC, 2010a,b in UNISDR, 2015). In the case of the Boxing Day 2004 Indian Ocean tsunami, for instance, the only possible strategy to save lives would have been to reduce exposure through timely evacuation, which depends on the existence of reliable early warning systems and effective preparedness planning, and then to compensate for loss through insurance of other risk financing instruments (UNISDR, 2015).


Indian Ocean tsunami: warning system could have saved lives

Tsunami 2004: Aceh, Indonesia © Photo CC BY-ND 2.0

Indonesia, Sri Lanka, Thailand, India and Somalia

The Indian Ocean tsunami was an extreme event, but many of the deaths could have been prevented by using an early warning system.

SOURCE: UNISDR (2015a) [GAR15]


Components of Risk

Disaster Risk
Risk is a forward looking concept, so disaster risk can be understood as the likelihood (or probability) of loss of life, injury or destruction and damage from a disaster in a given period of time (adapted from UNISDR, 2015a).
A dangerous event that may cause loss of life, injury or other health impacts, as well as damage and loss to property, infrastructure, livelihoods and services, social and economic disruption and, or environmental damage is known as a hazard (UNISDR, 2009b).
The presence and number of people, property, livelihoods, systems or other elements in hazard areas (and so thereby subject to potential losses) is known as exposure (UNISDR, 2009b and IPCC, 2012).
The name given to the set of characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard is vulnerability.

Risk Drivers

Climate change
Climate change can increase disaster risk in a variety of ways – by altering the frequency and intensity of hazard events, affecting vulnerability to hazards, and changing exposure patterns.
Environmental degradation
Environmental degradation is both a driver and consequence of disasters, reducing the capacity of the environment to meet social and ecological needs.
Globalized economic development
Globalized economic development can lead to increased exposure of assets in hazard-prone areas, leading to further increases in intensive risk if not managed.
Poverty & inequality
Poverty is both a driver and consequence of disasters, and the processes that further disaster risk related poverty are permeated with inequality
Poorly planned urban development
Whether or not disaster risk is factored into investment decisions in urban development will have a decisive influence on the future of disaster risk reduction.
Weak governance
Governance of disaster risk management must be improved, not only through specialized and stand-alone sectors, but also through strengthened governance arrangements across sectors and territories in order to address disaster risk.

Key Concepts

Capacity refers to all the strengths, attributes and resources available within a community, organization or society that can be used to achieve agreed goals.
Deterministic & probabilistic risk
Deterministic risk considers the impact of a single risk scenario, whereas probabilistic risk considers all possible scenarios, their likelihood and associated impacts
Direct & indirect losses
Direct disaster losses refer to the number of people killed and the damage to buildings, infrastructure and natural resources. Indirect disaster losses include declines in output or revenue and generally arise from disruptions to the flow of goods and services.
Disaster risk reduction & disaster risk management
DRR is the policy objective of anticipating and reducing risk. Although often used interchangeably with DRR, DRM can be thought of as DRR implementation, since it describes the actions that aim to achieve the objective of reducing risk.
Intensive & extensive risk
Extensive risk is used to describe the risk of low-severity, high-frequency disasters, mainly but not exclusively associated with highly localized hazards. Intensive risk is used to describe the risk of high-severity, mid to low-frequency disasters, mainly associated with major hazards.
Resilience refers to the ability of a system, community or society exposed to hazards to resist, absorb, accommodate to and recover from the effects of a hazard in a timely and efficient manner.
Sovereign risk
Sovereign risk is the economic impact a government would face in the event of a disaster.


Risk modeling
We need data on hazard, exposure, vulnerability and losses in order to understand and assess disaster risk.


Data and statistics are important in understanding the impacts and costs of disasters.
Data Viewers
Open access, online data viewers present hazard, disaster, and risk data in an easily accessible manner.