Impact assessment of a far-field tsunami scenario for building damage and habitability in Christchurch, New Zealand

Tsunami are powerful natural events which become hazardous if coastal communities are exposed to the effects. The potential impacts include damage to buildings, infrastructure, human casualties, and displacement of residents. The Canterbury coastline is exposed to far-field tsunamis originating from locations distant to New Zealand. Understanding the potential impacts of a major tsunami to a coastal region enables better planning and preparedness initiatives to take place. Although inundation modelling of a major far-field tsunami affecting Christchurch was available, a detailed impact assessment had not been undertaken previously. The objectives of this thesis are to assess the post-arrival impacts of specific far-field tsunami scenarios on Christchurch communities, focusing on damage to buildings, habitability of residential dwellings and the displacement of residents within the first week following the tsunami arrival. The research contributes to the RiskScape programme, and provides resources for emergency management planning and scenario exercising. The risk assessment framework is used in this thesis as a conceptual basis for tsunami impact assessment. A literature review of the tsunami hazard to Christchurch, tsunami impacts, impact assessment methodologies, and factors contributing to residential habitability and human displacement was conducted. The impact assessment process for estimating building damage related the inundation modelling with an asset database of exposed buildings, and used fragility functions to assess the probability of reaching certain damage states. The building asset database was created using GIS and field surveying data of building attributes. The residential habitability and human displacement was assessed spatially and temporally for the first week following the tsunami wave arrival. The literature review and interviews were used to inform the relative influence of factors contributing to habitability and displacement. Modelling using GIS was performed to assess the habitability and displacement within the inundation zone by considering the factors of building damage, access, and functionality of utilities (electricity, water, and wastewater). For the primary scenario modelled, approximately 950 buildings are collapsed or washed away, 2,150 suffer moderate to complete damage, and 1,600 experience minor or no damage. On the first day of the tsunami wave arrival, approximately 5,000 residential dwellings are uninhabitable 11,000 residents displaced, representing all housing and population within the inundation zone. At one week after the event, there are approximately 2,850 uninhabitable residences and 6,250 people still displaced. The results of this project may be used for enhanced emergency management planning and scenario exercising. The methodologies developed may be applied to other scenarios, locations, and different natural hazards