An integrated earthquake impact assessment on the built-environment for community resilience planning

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Uma, S.R.; Sadashiva, V.K.; Buxton, R.; Nayyerloo, M. 2017 An integrated earthquake impact assessment on the built-environment for community resilience planning. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/64. 71 p.; doi: 10.21420/G2QS3P

 

Abstract: The built environment comprises all buildings and infrastructure networks essential for community living. As recent earthquakes have demonstrated, widespread damage to many buildings and infrastructure networks which adversely impact a community’s ability to maintain functionality. Prolonged outage of buildings and services can result in an outmigration of residents and businesses thereby affecting the social and economic viability of the community. Normally, impact assessment studies are independently carried out for buildings or for each infrastructure network to model the likelihood of damage and disruption to their respective services. It is important to estimate the ‘recovery time’, i.e. the period required to restore their services and provide functionality, so that community can be prepared to being resilient in such unfavourable situations. A number of initiatives have been undertaken internationally to develop a framework for community resilience planning and they emphasize the need for an integrated performance assessment of the built environment in which the damage to buildings and the lack of utility services at those building sites are collectively looked at. Depending on the damage to buildings and the outage of utility services, the buildings can be a ‘shelter-in-place’ facility or be ‘functional’ or ‘not fit for occupancy’. Hence, to plan for community resilience, it is necessary to understand the performance of the built environment and its recovery time. In this study, a framework for community resilience planning with a focus on understanding the performance of the built environment for a given hazard scenario is proposed. The objective of the framework is to provide estimates of the availability of buildings and utility services at different times following the event. The approach is similar to that developed by the National Institute of Standards and Technology (NIST) for community resilience planning and adopts a ‘recovery period’ to regain functionality as the metric by which to measure resilience. The approach calls for the linking of the components of the built-environment with the social and economic structure of the community and identifies cluster groups that need to be prioritised in terms of recovery. To illustrate the proposed approach, we have considered the four suburbs of Wellington City, namely, Pipitea, Thorndon, Wellington Central and Te Aro, as the region of interest. We have modelled buildings and three important infrastructure networks namely electricity, potable water and road network. For a given earthquake, the damage models and recovery models are used to determine the impact of both building damage ad service provisions on building occupancy status. As the network operations and recovery are interdependent, a high level interdependency model is adopted to arrive at the final recovery period for each service. According to the contribution to community recovery, three recovery groups are identified in the study region, namely short-term, intermediate-term, and long-term. Each recovery group is assigned with a ‘target’ recovery time within which the buildings and infrastructure services need to be restored so that social and economic impact could be within acceptable limits. The ‘actual’ recovery time computed from the model is compared with the ‘target’ time to identify if the facilities are available for community recovery or not. Thus, the proposed framework enables to assist the identification of those built environment components that need to be improved in their performance so that gap between the ‘actual’ recovery time and ‘target’ recovery time will be reduced thereby supporting community resilience. (auth)