Hazard Identification
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Exoosure Assessment
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Exposure-Response Assessment
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Minimisation of Risks in Built Environment
Risk Assessment -
A Key to Prevention
J~isks are inherent in everyday rife and in air our decision making.But they always indicators of sometning baa happening. Since ages it has been termed as intuitive feeling for wnat hazards and risks are and somehow have been rated as undesirable though always present during life time. Risks have many dimensions, and importance of eacn dimension is aifferent for aifferent actoi 5 For example, risks mean financial loss to finance company on its investments, may have health risks fora worker working in hazarduous industry and to some nsks are of running into accidents while driving. Whatever the risk be - it does relate to quantification of occurrence of events that may have unpleasant or unwanted impacts. Risk assessment is precisely estimating probability of occurrence of an event and tne probable magnitude of adverse effects. It can have on human values or ecology This is a single but “scientific” definition of risks, where magnitude is only one dimension and misses out societal definition which tend to rest on equity control, trust etc. — which is normally ‘soft” version of a risk based on intuitive perceptions and acceptance.
in the new paradigm, both risk science and public values are considered part objective and part subjective and both are seen as pivotal to sound risk management The type of Questions which arise from the situations are
What can go wrong and why?
How iikeiy is it?
How bad it can be? and
What can we do about it?
All these questions provide indication of ial type of risks, ibi probability of their occurrence, ici extent of damage they can cause; and (dl options or alternatives to manage the risks
Risks of Natural Hazards
in case of natural hazards, the impacts are totally time and location dependent Evaluation of risk or anaiysis would require information on type and frequency of hazard in an area and the vulnerability of human settlements as well as environment, which is site and time specific.
Risk assessment is therefore a function of Hazard intensity and the vulnerability of the area, where a hazard may be a chemical, biological, or physical agent or set of conditions that presents a source of risk, in present case, it is natural hazard and evaluation of its impacts,is based totally on historical information,
Vuinerabiiity is dependent on exposure to the hazard, which comprise of type and location of buildings and settlements, socio-economic character of communities, the site conditions and duration time of exposure The magnitude of risks is directly proportional to vulnerability and intensity of hazard, Intuitive risk assessments and decisions on such assessments can have dire consequences as tne complexities of uroan faorics presentiy require holistic approach which cannot be comprehended without using analytical tools The potential of tools can be appropriately exploited through simulation exercises using computers and mapping systems.
lnfact, risk criteria provide an effective frame of reference for prioritizing problems, ailocating resources and making
Taranjot K Cadhok
senior Fellow, HSMI (1-WOCO)
decisions while reducing risks. Evidence to date suggests that a well designed targetted rIsk analysis can yielo reduce costs by focussing on highest source of risk and reducing associated uncertainties.
Risk estimates, including probabilistic estimates do not answer the question Safe or unsafe. it is upto tne policy makers and risk managers to judge what is a safe or acceptable level based on many criteria including benefits versus risks.
Therefore steps involved in risk assessment are essentially’
1 Hazard Analysis which comprise of identification of hazard and its historical frequency and intensity of occurrence, probability of its occurrence and location All the information when put together in a physical form of a map is known as hazard map.
2. vulnerability Analysis which comprise of extent of exposure and length of exposure in terms of time.
As the focus of the present paper is on potential of risk assessment For prevention and minimisation of impacts of natural disasters, attempt has been made to quote vulnerability I exposure of built environment to such hazards as a demonstration of risk analysis Vulnerability of buildings and lifelines are the basis of estimation of risk to the quality Of life, in this context vulnerability is expressed as the degree of expected damage which may be quantified in terms of costs as ratio of cost of repair to cost of replacement
in case of buildings, in order to quantify vulnerability, it i~ important:
• To prepare an Inventory of prevalent types of construction, construction materials, structural proportions, symmetry in planning.
• A distinction must be made between elements With special design, requirements e g hospitals, schoops, residential buildings, housing.
ALVAYS RISK
A QUALIFIED ?ERSON
TO DESIGN t
S(J1’ER VISE
DISASTER
RESISTANT
SHELTERS
HOW SAFE IS SAFE ENOUGH?
cost vs Safety
Maximum stable angie b engineering caicuiation
New
road
Cheapest Design
Possible Scenario
Greater lactor of
safety
Factor
of safety
Max stable
angle
Safer1 but more expensive
very safe, very expensive
• The estimateo costs ano oenefits of these actions
As most vulnerable are the low income settlements in disaster prone areas, these structures are non-engineered, made out of stone masonry buildings, wooden buildings, earthern buildings, masonary buildings, with weak mortatrs and rigid foundations or no founda tions. These settlements find location for settlement in places like flood plains or hazarbuos sites due to constraint of land tenure rights in oig cities
The other elements of risk are physical infrastructure, which includes communication, transport, energy ana infor mation lines of a region or a country. Blocking of water ways, disruption in commu nication systems. choking of drains, as a consequence of landslides, earthauakes. result into different types Qf hazards, for which one may not be prepared. Often their mainte nance and operations is a government responsibility.
For prioritizing the vuiner-ability, following factors are important:
• Populations vulnerable due to a risk.
• Cost of expected damage.
Roads, railways, waterways, telecorfimunication are highest on priority Of vulnerability criteria, as larger populations get affected by their destruction and are cost intensive. TO reduce risks due to any hazards reduction of vulnerability of these need to be emphasized. Vulnerability analysis can always be based on regional and iocal historical data of damage. in the anaiysis, it Is important to estimate probabie degree of damage that may be expected for each element at risk resulting from a hazard of a given magnitude.
Different hazards pose variable size and type of risks and the vulnerability analysis is totally dependent upon the nazard type and magnituoe Prioritisation of actions for vulnerability reduction are different for each type of hazard e g. in case Of earthquakes damage to buildings and roads are much more importance than in case of a drought or cyclones
one of the major initiatives in this direction in India is. publication of vulnerability Atlas of india which has already accomplished task of identifying regions/districts which are disaster prone with hazard identification and data on type of settlements and their condition in the form of existing structures and materials used in the buildings Almost 139 districts have been covered ,for which data has been made available. The atlas has provided basis for working on microzonation maps of these areas. With this information available, it is now possible to prepare hazard maps and quantify risks
The next priority is to link the abstractions of policy objectives with a concrete plan of execution, by identifying the following
• The range of possible actions to mitigate these risks; and
The initial appraisal will identify areas of greatest risk, to which priority should be given, scope for futher action will depend largely upon the type and extent of resources available; for example, funding may be available for some types of action but not for others, or may be subject to varIous conditions
It may seem that the extent o~ action required i~ Far in excess of the funding available. However, finance is only one of several resources that should be utilized; labour, political mechanisms, specialist skills, and sources of information can be equally important to progress. For example, labor-intensive projects can be particularly appropriate for low-income communities; the financial cost of sucn projects couio be reiativeiy low, the degree of community Involvement and support correspondingly high.
The Cost Benefit Analysis
The principle of cost-benefit analysis should be applied at this point, cost-benefit analysis is a process of assessing all of the costs of a particular action or project, and all of the benefits which it will bring when completed. Actions or projects for which the benefits will be greater than the costs are described as ‘cost-effective’ and should be given higher priority than those for which the costs are greater than the benefits -
Costs and benefits include social, political and environ mental factors, as well as financial factors. These factors neeo to oe given values, tO enable the total costs benefits to be assessed A difficulty with cost-benefit analysis is that different groups of people disagree about the value of various factors; for example, the construction of a new road may be supported by those who place more importance on economic factors out opposeo by otner on environmental grounds. The benefits Of disaster mitigation actions also inciude reduced risk; the value of these benefits will be based upon the estimated social, physical and economic costs of the risk
A major difference in carrying out a cost-benefit anaiysls for a disaster mitigation programme, compared with a single major development, is that the programme will
you have to take risks.
consist of a iarge number of separate and interrelated mitigation activities, some activities will give a better cost-benefit ratio than others; judgement needs to be applied.
Haying considered these points, the stakeholders should agree upon a set of actions which address high priority concerns and can be achieved within the prevaiiing constraints. The relative costs of alternative measures should be estimated to allow decision makers to select the more appropriate strategy. TO facilitate this, the proposed measures can be evaiuated for their likely impact Thus the costs can be compared to the value Of the assets protecteo.
Assessment of risks would further allow possibilities of prioritising areas of major concern requiring short term and long term action, allocation of resources. The next step is to identify time bound actions to mitigate risks
and estimated costs and benefits of these actions. It would require assigning values to the existing assets as well as heaith, environment and social costs, to assess the benefits, risk management is likely to bring.
Next is to ascertain available resources for risk management on account of reduction of vulnerability or hazard, preventIon, relocation of communities away from hazard prone areas
Simulation exercise to prioritise issues and actions using computer? has become much easier and with GIS and remote sensing techniques available, it is possible to oevelop hazard maps Complexities of faster development due to globailsatlon and opening of economies, human activities towards systems — which is being felt and observed much more In recent years than before Hence risks with an estimation of consequence can always throw light on path least advance.
‘Nothing in fife is safa..