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KNOWLEDGE

WHY - Disaster Reveals Vulnerability

Property Damage in extreme natural events is not a natural disaster. In most cases damage is actually due to historical building decisions made by humans...

Disasters and Ageing Housing Stock


As a case-study, the Christchurch, New Zealand earthquakes of 2010-2011 presented world-record ground-accelerations causing some of the most costly per-capita urban damage in history. This event revealed many failed assumptions and strategies within the existing built environment. However these discoveries are not unusual, and are typical of most other recent events throughout the world involving earthquake, floods, wildfires, storms and extreme wind events. 


The damage and destruction of buildings, land and infrastructure that occur in major events such as the Christchurch earthquakes are commonly described as ‘natural disasters’. However, they are in reality not that at all. Much of the damage can be attributed to human decisions and actions made in the processes of legislating, designing and constructing the built environment. These decisions directly contribute to how the built environment performs during and following disaster, and the characteristic damage and loss when nature simply does its thing. It is often said, ‘an earthquake will not kill you, but a building can’.


Housing is the most prolific and personal of all buildings. It is the building type that forms communities and characterises the human aspect of the built environment. In its sheer numbers, housing represents the largest number of individual buildings damaged in disasters, and often the greatest challenge for reconstruction and resourcing following a natural event. 


The actual physical condition of the residential built environment is seldom discussed. For example, contrary to common assumptions, houses and buildings have limited life-spans. Using New Zealand housing as an example, new modern lightweight housing is optimistically required to last 50 years, however more than 60% of the nationwide housing stock well exceeds that age. The quality of older housing stock is described in numerous research studies and reports as generally very low, and is questioned as to whether it is actually suitable for healthy human habitation. Rectifying this problem is extremely difficult and expensive to achieve, and is often more costly that building new.


Concern about the fragility, vulnerability and ‘brittleness’ of much of the existing built environment and its increasing susceptibility to damage from disaster events is also expressed by the insurance sector on an international basis. Post-disaster insurance and re-insurance arrangements often reveal the apparent risk considered by the insurance sector, with insurability factors having potentially significant implications for the finance sector. 


New Zealand’s aged housing stock is typical of many developed countries, with insufficient durability, structural resilience, energy efficiency and liveability consistently proving difficult to effectively overcome. New housing is predominantly built at the cheapest possible cost with minimal ability to guarantee long-term performance, and often constructed to standards that only meet the minimum required by law. 100% Building Code compliance has typically become a target standard although that level of compliance is only the absolute minimum legal standard for human habitation.


As illustrated above, disaster events reveal vulnerabilities in how we have conceived and constructed housing historically. The brittleness and vulnerability of traditional lightweight housing and the inherent fragility of the materials typically used are repeatedly shown to struggle in meeting reasonable resilient construction objectives. 


Resilience Thinking suggests that the future built environment needs to respond to not only the realities of nature and the historical evidence that plays out time after time, but also the need to work alongside and in anticipation of natural forces. Actively building-in resilience in an engineering sense is essential, however so is thinking about the environmental implications of demolition and rebuilding ans such things as raw material resources and waste flows, urban planning, energy use, infrastructure and communities within a dynamic natural ecological system. These are all factors of a resilient environment, and deficiencies in some or all of these factors increases vulnerability, lowers living standards and ultimately lowers overall safety for people and the natural environment.


Disaster events leave an indelible mark in time and unavoidably impose a re-evaluation of design and construction processes, materials use, building methods and even the purpose of building things. These are brief but extremely valuable moments in time, so how these re-evaluations are carried out and responded to has the power to define the built environment for future generations, and future generations are supposed to be what sustainability is all about. 


The quality of the future places we all live is precisely determined by what we design and build from now, in our current time, not by repeating what we had in the past.