Disaster Risk Management¶

Before we get into the details of using InaSAFE, we first will look at some core themes of disaster management planning.

This module aims to provide participants with the following knowledge:

understand the concepts of hazard, vulnerability, exposure, impact and risk
understaning the disaster management cycle
what are risk and impact assessments

Components of impact and risk¶

Hazard¶

A hazard is considered any natural or human caused event or series of events that may negatively impact the population, infrastructure or resources in a community.

Some examples of natural hazards:

a flood (caused by overflowing rivers, storm surge, localised precipitation that cannot drain effectively, or by engineering failure such as a dam or levee breach)
an earthquake and the resulting ground shaking that is produced by it
a tropical cyclone that causes high winds
a tsunami

Some examples of non-natural hazards:

a chemical spill
a nuclear plant failure
an industrial fire / explosion

Vulnerability¶

Vulnerability is a measure of susceptibility to the impacts of a disaster event. This can take the form of structural vulnerability for buildings and infrastructure hazards, and this is often a quantitative measure. The vulnerability of a community is influenced by the characteristics and circumstances that make it susceptible to the damaging effects of a disaster.

Vulnerability is measured in a range of ways, depending on the element in question. It is always related to the intensity of the hazard (wind speed, ground shaking, etc.). For example, the vulnerability of a house can be measured by the cost of repairs required, compared to the incident wind speed.

Social impacts are more difficult to quantify, because different communities may respond to a disaster in different ways. Poverty and inequality, marginalisation, social exclusion and discrimination by gender, social status, disability, pshcological factors and age (amongst other factors) are all factors that contribute to the vulnerability of a community. These factors impact the ability to respond to and recover from a disaster. Quantified measures of social vulnerability are limited, so it is more common to use qualitative descriptions.

Vulnerability and fragility: occasionally you may hear reference to the term fragility as well as vulnerability. Vulnerability is the expected level of damage that would be sustained if a given hazard magnitude affected an asset. The vulnerability of a community is based on the characteristics and circumstances that make it susceptible to the damaging effects of a hazard event. Fragility refers to the likelihood of a (qualitative) level of damage (e.g. no damage, slight, moderate, extensive or complete damage). This can be translated into a quantitative estimate of the damage (often referred to as a damage index or damage ratio).

Damage states¶

The damage state of an asset (e.g. people, buildings) is a qualitative description of the level of damage suffered by a building (or components of a building). In some applications, the damage state is linked to a damage ratio, which quantifies the damage as a fraction of the complete replacement cost of the building. In this case, it is possible to determine the direct economic costs of a disaster, based on the accumulated damage.

An example of damage states for residential buildings for tropical cyclone winds:

Insignificant	Little or no visible damage from the outside. No broken windows, or failed roof deck. Minimal loss of roof cover, with no or very limited water penetration.
Light	Moderate roof cover that can be covered to prevent additional water ingress. One window, door or garage door broken.
Moderate	Major roof damage, moderate window breakage. Minor roof sheathing failure. Some water damage to interior.
Severe	Major window damage or roof sheathing loss. Major roof cover loss. Extensive damage to interior from water.
Complete	Complete roof failure and/or failure of wall frame. Loss of more than 50% of roof sheathing.

Damage state descriptions are routinely used in post-event damage surveys, to ascertain the impacts of disasters.

Exposure¶

Exposure refers to the assets, populations, and other elements that are part of the landscape and may be impacted by a hazard event. This can include things like buildings, people infrastructure and agriculture. For example exposure can refer to any or all of the following:

Buildings: houses, public/government, commercial, industrial, cultural/religious, health, education, etc.
People: number, demographics (age profile, gender, social disadvantage)
Infrastructure: power, radio and telecommunications, water and sanitation, roads
Agriculture: (commercial) crops, subsistence crops, forests, etc.

Often exposure is used to describe only those elements that are in the footprint of a hazard event. In some other contexts, exposure is used to refer to all elements in a community.

Common sources of exposure information are government agencies (e.g. building approvals, infrastructure owners/operators), surveys (including censuses) and aerial photos. Crowd-sourcing, through platforms like OpenStreetMap has been used to great effect in Indonesia for collecting local level data, as well as validating larger-scale data.

A key issue is open access to up-to-date, well-maintained geospatial exposure data. Without roads, buildings and population data, a tool like InaSAFE would be impossible to use. It is critical for government to take a leading role in making data freely available so it can be used for the benefit of their citizens.

Impact and risk¶

Impact¶

Impacts are the outcomes of a disaster on the community, it’s people, buildings, landscape and other assets. They can be defined in qualitative terms, or quantitatively measured. Some indicators of impacts include:

Economic loss
Casualties, including physical injuries, deaths, mental breakdown
Number of evacuees
Damage to buildings, infrastructure, networks, etc.
Business interruption period
Intangible impacts such as community breakdown and loss of cultural identity

Risk¶

Risk is the likelihood that a loss will occur as a result of a hazard event, given the magnitude of hazard, exposed elements and the vulnerability of those elements. Usually, it is quantified in terms of economic losses, where we use a range of different measures to describe risk. It is intrinsically linked to the likelihood of a disaster event occuring, so often the reported levels of risk link a loss level to a probability. Measures of risk include:

Average annual loss - the average loss from disasters over a long period of time.
Average reccurence interval loss - the loss expected to occur, on average, every 10, 50 or 100 years (or some other frequency)
Loss-exceedance curves - a graph of the loss from disasters compared to the chance of the disaster occuring.

Note

Impacts are the outcomes of a single disaster event on the community. Risk describes the likelihood of different levels of impact due to different events.

Impact and Risk Assessment¶

Impact and risk assessments are conducted to analyse the consequences of one (impact) or many (risk) hazard events, with the goal of informing decisions on prevention, mitigation and response activities. It is an integral part of decision and policy-making processes, and requires close collaboration among various parts of society to fully understand the impacts and risks (UNDP).

The analysis of impacts, through the use of tools like InaSAFE, is only one step in a comprehensive risk assessment process. A complete assessment includes hazard assessments, vulneraility analsyes, risk profiling and formulation of disaster risk reduction strategies and plans. The reports created through InaSAFE can be used in formulating strategies and action plans.

The disaster management cycle¶

The disaster management cycle is a continuous loop that connects four core elements in managing disasters.

Prevention
Preparedness
Response
Recovery

Fig. 4 The disaster management cycle.

Note

You may see other definitions of the disaster management cycle, which have other phases included in the loop. The core concept of a cyclic process remains the same.

Prevention is the activities and measures taken to avoid existing and new disaster risks.

Preparedness describes the knowledge and capacities of governements and communities to effectively anticipate, respond and recover from the impacts of an imminent disaster.

Response is the actions taken directly before, during or immediately after a disaster to save lives, reduce health impacts and ensure public safety for the people affected by a disaster.

Recovery describes the restoration and improvement of the economic, physical, social, cultural and environmental assets, systems and activities of a community to avoid of reduce future disaster risk.

Represented in a cycle, the recovery phase leads into prevention, where the goals are the same – avoiding or reducing future disaster impacts.

InaSAFE can be used to inform the preparedness and response phases of the disaster management cycle, by enabling emergency management officers to plan for scenarios and improve the understanding of resources required to respond quickly and effectively to a disaster.

More information on disaster risk concepts is available on the Understanding Disaster Risk site.