Real Risk

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UILDING DAMAGE ASSESSMENT

forms a key component of

overall disaster impact and reconstruction needs assessment.

By summarizing the types of building damage assessment

commonly used in the Asian region following a disaster, a concep-

tual framework of key considerations in building damage assessment

can be developed.

While disasters widely impact various aspects of human lives,

their impact on buildings is especially catastrophic since vulnerable

populations are rendered homeless or compelled to live in unin-

habitable and unsafe homes, with livelihoods impaired due to the

destruction of workplaces. Disasters such as earthquakes, cyclones

and tsunamis, and sometimes long-duration flooding, severely

impact the housing sector in the Asian region, where a large propor-

tion of housing is semi-engineered at best.

Some of the recent disasters in the region have impacted the

housing sector quite significantly. On average, 1 per cent of India’s

housing stock is lost annually due to disasters.

In the recent 2005

Kashmir earthquake, more than 200,000 housing units in the

districts of Azad Kashmir and the Northwestern Frontier Province

(NWFP) in Pakistan were damaged or destroyed. This damage has

a huge direct impact on the community and settlement as a whole

in terms of the safety of inhabitants, security of the population, and

indirect effects on the economy of the settlement. Hence it is an

absolute must to carry out damage assessment of buildings with a

scientific approach, immediately after a disaster.

Purpose of building damage assessment

Building damage assessment is conducted in the post-disaster

context, typically by qualified, trained and authorized personnel. It

serves several important purposes.

The most immediate function is that of determining the struc-

ture’s safety for continued habitation or use by communities. This

is an essential function particularly to quell apprehension among

the affected population about the safety of their houses, especially

in the context of geological hazards such as earthquakes which

can have large-scale structural impacts followed by recurrent after-

shocks.

Building damage assessment is also essential in providing an

overall assessment of the quantum of damage and for estimating

the expected cost of disaster impacts in terms of value of replace-

ment. This kind of assessment serves as a decision support tool for

rehabilitation and reconstruction policies.

In the longer term, a database of comprehensive building damage

assessment can also be analyzed to identify typical hazard- and

location-specific building failures, which can be used to identify

future risk reduction measures. This assessment would help in learn-

ing lessons from gaps in:

• Building construction practices

• Limitations of building materials used

• Compliance with construction standards and zoning

regulations

• Guidance for the framing of long-term policies and practices

for hazard-resilient building construction.

Types of building damage assessment

Depending on the purpose of the building damage assessment, iden-

tified by the user, the assessment methodology differs slightly in

process, scope and in the human resources requirement, which may

be broadly categorized as follows:

• Rapid safety assessment

• Detailed building damage assessment and categorization

• Engineering evaluation.

Rapid safety assessment is undertaken to identify and label build-

ings that cannot be occupied (labelled “unsafe”), those that can be

reoccupied safely (“safe”), those that may be entered very briefly

after taking certain precautions (“restricted use”) and those whose

perimeters might be unsafe due to falling hazards or chemical or

other contamination (“area unsafe”). Rapid assessment also provides

insights, based on rapid reconnaissance, into the extent of impact,

to estimate the expected number of households needing refuge

centres for displaced people and temporary housing requirements.

Rapid safety assessment, as its title suggests, is undertaken in a very

short time frame and therefore does not yield adequate information

to guide decisions on the strengthening, retrofitting or demolition

of a building. It is not intended to estimate the loss of private prop-

erty, or to estimate the cost needed for strengthening, retrofitting

or demolition. The Applied Technology Council’s

ATC-20: Post-

earthquake Safety Evaluation of Buildings

is an internationally

recognized tool for this process.

Detailed building damage assessment and categorization involves

an assessment of individual structural and non-structural members

within a building to provide a composite category of damage, which

represents the severity of impact. This category may be represented

by a numerical degree between 0 and 5, or a qualitative category

(such as ‘minor’, ‘moderate’ and ‘extensive’ or others) may be

provided. This categorization has been used in past instances for

determining the extent of financial or material assistance that house-

holds may be entitled to in the post-disaster reconstruction phase.

Based on this detailed assessment, a more accurate cost estimate

Post-disaster assessment

of building damage

Arghya Sinha Roy, Supriya Prabhu Mehta, K Iftekhar Ahmed, NMSI Arambepola,

Asian Disaster Preparedness Center