Worldwide turbidity is a huge concern for the health of aquatic ecosystems. Human activities on the land such as construction, deforestation, agriculture, and mining all have impacts on the amount of particulate solids that enter the world’s waterways. These particulate solids can pose a number of risks to aquatic life, but primary among them is the turbidity that they create in the water column. The way suspended solids interact with light creates cloudiness in the water which interferes with the vision, and visually mediated behaviours of aquatic organisms, particularly fish. The Avon-Heathcote estuary of Christchurch, New Zealand, is one such body of water that is subject to tremendous variation in turbidity, no doubt exacerbated by the destruction of Christchurch in the 2010 and 2011 earthquakes, as well as the subsequent ongoing rebuild. The yellow eyed mullet, Aldrichetta Forsteri, is one species that is common with the estuary, and uses it as a habitat for breeding. Though very common throughout New Zealand, and even a part of the catch of commercial fisheries, the yellow eyed mullet is a largely unstudied organism, with virtually no published scientific enquiry based on the species. The present work assesses how several behaviours of the yellow eyed mullet are effected by acute turbidity at 10, 50, 90, 130 and 170 NTU, finding that: 1) The optomotor response of mullet to 2.5 mm stripes drops to insignificant levels between 10 and 50 NTU, 2) The swimming activity of the yellow eyed mullet is highest at 10 NTU and drops to a significantly lower level at higher turbidities, 3) The grouping behaviour of small groups of yellow eyed mullet are unchanged by increasing turbidity levels, 4) that yellow eyed mullet do not exhibit significantly different behavioural response to a simulated predator at any of the tested turbidities, and 5) that yellow eyed mullet to do significantly alter their oxygen consumption during exposure to the turbidities in an increasing series. The results presented in these studies indicate that turbidites above 50 NTU pose a significant risk to the lifestyle of the yellow eyed mullet, potentially impacting their ability to perceive their surroundings, feed, school, and avoid predation. Future work has a lot of ground to cover to more precisely determine the relationship between yellow eyed mullet behaviour and physiology, and the turbidity of their environment. In particular, future work should focus more closely on the turbidities between 10 and 50 NTU, as well as looking to field work to see what the predominant predators of the mullet are, and specifically whether turbidity increases or decreases the risk of mullet being subject to avian predation. There is also considerable scope for studies on the effects of chronic turbidity upon mullet, which will add understand to the predicament of escalating turbidity and its effects upon this common and yet mysterious native fish.
This research attempts to understand whether community resilience and perceived livability are influenced by housing typologies in Christchurch, New Zealand. Using recent resident surveys undertaken by the Christchurch City Council, two indexes were created to reflect livability and community resilience. Indicators used to create both indexes included (1) enjoyment living in neighbourhood (2) satisfaction with local facilities (3) safety walking and (4) safety using public transport, (5) sense of community (6) neighbour interactions, (7) home ownership and (8) civic engagement. Scores were attributed to 72 neighbourhoods across Christchurch –and each neighbourhood was classified in one of the following housing typologies; (1) earthquake damaged, (2) relatively undamaged, (3) medium density and (4) greenfield developments. Spatial analysis of index scores and housing classifications suggest housing typologies do influence resident’s perceived livability and community bonds to an extent. It was found that deprivation also had a considerable influence on these indexes as well as residential stability. These additional influences help explain why neighbourhoods within the same housing classification differ in their index scores. Based on these results, several recommendations have been made to the CCC in relation to future research, urban development strategies and suburb specific renewal projects. Of chief importance, medium density neighbourhoods and deprived neighbourhoods require conscious efforts to foster community resilience. Results indicate that community resilience might be more important than livability in having a positive influence on the lived experience of residents. While thoughtful design and planning are important, this research suggests geospatial research tools could enable better community engagement outcomes and planning outcomes, and this could be interwoven into proactive and inclusive planning approaches like placemaking.
Research in the governance of urban tourist spaces is characterized by a lack of argumentative inquiry and scant use of critical theory. This is evident, particularly, in the study of tourism and post-disaster urban recovery, with very few contributions assessing the phenomenon from a social theory perspective. This thesis examines the complex phenomenon of planning and governance for urban tourism spaces in contexts facing physical recovery from natural disasters. It does so by looking at the governance dynamics and the mechanism of decision- making put in place before and after triggering events like earthquakes and tsunamis. This thesis provides evidence from Christchurch, New Zealand, by focusing on the policies and strategies for the regeneration of the city centre put in place before and after the disruptive earthquakes of 2010 and 2011. The thesis looks at power relations, structures and ideologies through a Lukesian appraisal of pre-and-post disaster governance from two relevant urban tourist spaces located in the Christchurch central city area: the Arts Centre of Christchurch and the Town Hall and Performing Arts Precinct. The research strategy adopted for the study combined archival research, interviews with key stakeholders and fieldwork notes over a period of two years. The research deployed a comparative case study methodology that focuses on projects taking place within a spatially defined area of the city centre where special legislation was enacted as result of the earthquakes. The findings from the interviews and their triangulation with documents retrieved from national and local authorities suggest that the earthquakes affected the engagement among stakeholders and the mechanisms of decision-making. Also, the findings show patterns of disaster capitalism in post-earthquake governance for urban tourist spaces in the Christchurch CBD, with episodes of exclusion, lobbying and amendment of rules and legislation that directly benefited the interests of a narrow group of privileged stakeholders. Overall, the study shows that the earthquakes of 2010 and 2011 accelerated neoliberal practices of site development in Christchurch, with the seismic events used as a pretext to implement market-oriented site projects in the CBD area.
Recently developed performance-based earthquake engineering framework, such as one provided by PEER (Deierlein et al. 2003), assist in the quantification in terms of performance such as casualty, monetary losses and downtime. This opens up the opportunity to identify cost-effective retrofit/rehabilitation strategies by comparing upfront costs associated with retrofit with the repair costs that can be expected over time. This loss assessment can be strengthened by learning from recent earthquakes, such as the 2010 Canterbury and 2016 Kaikoura earthquakes. In order to investigate which types of retrofit/rehabilitation strategies may be most cost-effective, a case study building was chosen for this research. The Pacific Tower, a 22-storey EBF apartment located within the Christchurch central business district (CBD), was damaged and repaired during the 2010 Canterbury earthquake series. As such, by taking hazard levels accordingly (i.e. to correspond to the Christchurch CBD), modelling and analysing the structure, and considering the vulnerability and repair costs of its different components, it is possible to predict the expected losses of the aforementioned building. Using this information, cost-effective retrofit/rehabilitation strategy can be determined. This research found that more often than not, it would be beneficial to improve the performance of valuable non-structural components, such as partitions. Although it is true that improving such elements will increase the initial costs, over time, the benefits gained from reduced losses should be expected to overcome the initial costs. Aftershocks do increase the predicted losses of a building even in lower intensities due to the fact that non-structural components can get damaged at such low intensities. By comparing losses computed with and without consideration of aftershocks for a range of historical earthquakes, it was found that the ratio between losses due to main shock with aftershocks to the losses due to the main shock only tended to increase with increasing main shock magnitude. This may be due to the fact that larger magnitude earthquakes tend to generate larger magnitude aftershocks and as those aftershocks happen within a region around the main shock, they are more likely to cause intense shaking and additional damage. In addition to this observation, it was observed that the most significant component of loss of the case study building was the non-structural partition walls.
Christchurch City Council (Council) is undertaking the Land Drainage Recovery Programme in order to assess the effects of the earthquakes on flood risk to Christchurch. In the course of these investigations it has become better understood that floodplain management should be considered in a multi natural hazards context. Council have therefore engaged the Jacobs, Beca, University of Canterbury, and HR Wallingford project team to investigate the multihazards in eastern areas of Christchurch and develop flood management options which also consider other natural hazards in that context (i.e. how other hazards contribute to flooding both through temporal and spatial coincidence). The study has three stages: Stage 1 Gap Analysis – assessment of information known, identification of gaps and studies required to fill the gaps. Stage 2 Hazard Studies – a gap filling stage with the studies identified in Stage 1. Stage 3 Collating, Optioneering and Reporting – development of options to manage flood risk. This present report is to document findings of Stage 1 and recommends the studies that should be completed for Stage 2. It has also been important to consider how Stage 3 would be delivered and the gaps are prioritised to provide for this. The level of information available and hazards to consider is extensive; requiring this report to be made up of five parts each identifying individual gaps. A process of identifying information for individual hazards in Christchurch has been undertaken and documented (Part 1) followed by assessing the spatial co-location (Part 2) and probabilistic presence of multi hazards using available information. Part 3 considers multi hazard presence both as a temporal coincidence (e.g. an earthquake and flood occurring at one time) and as a cascade sequence (e.g. earthquake followed by a flood at some point in the future). Council have already undertaken a number of options studies for managing flood risk and these are documented in Part 4. Finally Part 5 provides the Gap Analysis Summary and Recommendations to Council. The key findings of Stage 1 gap analysis are: - The spatial analysis showed eastern Christchurch has a large number of hazards present with only 20% of the study area not being affected by any of the hazards mapped. Over 20% of the study area is exposed to four or more hazards at the frequencies and data available. - The majority of the Residential Red Zone is strongly exposed to multiple hazards, with 86% of the area being exposed to 4 or more hazards, and 24% being exposed to 6 or more hazards. - A wide number of gaps are present; however, prioritisation needs to consider the level of benefit and risks associated with not undertaking the studies. In light of this 10 studies ranging in scale are recommended to be done for the project team to complete the present scope of Stage 3. - Stage 3 will need to consider a number of engineering options to address hazards and compare with policy options; however, Council have not established a consistent policy on managed retreat that can be applied for equal comparison; without which substantial assumptions are required. We recommend Council undertake a study to define a managed retreat framework as an option for the city. - In undertaking Stage 1 with floodplain management as the focal point in a multi hazards context we have identified that Stage 3 requires consideration of options in the context of economics, implementation and residual risk. Presently the scope of work will provide a level of definition for floodplain options; however, this will not be at equal levels of detail for other hazard management options. Therefore, we recommend Council considers undertaking other studies with those key hazards (e.g. Coastal Hazards) as a focal point and identifies the engineering options to address such hazards. Doing so will provide equal levels of information for Council to make an informed and defendable decision on which options are progressed following Stage 3.
This dissertation addresses several fundamental and applied aspects of ground motion selection for seismic response analyses. In particular, the following topics are addressed: the theory and application of ground motion selection for scenario earthquake ruptures; the consideration of causal parameter bounds in ground motion selection; ground motion selection in the near-fault region where directivity effect is significant; and methodologies for epistemic uncertainty consideration and propagation in the context of ground motion selection and seismic performance assessment. The paragraphs below outline each contribution in more detail. A scenario-based ground motion selection method is presented which considers the joint distribution of multiple intensity measure (IM) types based on the generalised conditional intensity measure (GCIM) methodology (Bradley, 2010b, 2012c). The ground motion selection algorithm is based on generating realisations of the considered IM distributions for a specific rupture scenario and then finding the prospective ground motions which best fit the realisations using an optimal amplitude scaling factor. In addition, using different rupture scenarios and site conditions, two important aspects of the GCIM methodology are scrutinised: (i) different weight vectors for the various IMs considered; and (ii) quantifying the importance of replicate selections for ensembles with different numbers of desired ground motions. As an application of the developed scenario-based ground motion selection method, ground motion ensembles are selected to represent several major earthquake scenarios in New Zealand that pose a significant seismic hazard, namely, Alpine, Hope and Porters Pass ruptures for Christchurch city; and Wellington, Ohariu, and Wairarapa ruptures for Wellington city. A rigorous basis is developed, and sensitivity analyses performed, for the consideration of bounds on causal parameters (e.g., magnitude, source-to-site distance, and site condition) for ground motion selection. The effect of causal parameter bound selection on both the number of available prospective ground motions from an initial empirical as-recorded database, and the statistical properties of IMs of selected ground motions are examined. It is also demonstrated that using causal parameter bounds is not a reliable approach to implicitly account for ground motion duration and cumulative effects when selection is based on only spectral acceleration (SA) ordinates. Specific causal parameter bounding criteria are recommended for general use as a ‘default’ bounding criterion with possible adjustments from the analyst based on problem-specific preferences. An approach is presented to consider the forward directivity effects in seismic hazard analysis, which does not separate the hazard calculations for pulse-like and non-pulse-like ground motions. Also, the ability of ground motion selection methods to appropriately select records containing forward directivity pulse motions in the near-fault region is examined. Particular attention is given to ground motion selection which is explicitly based on ground motion IMs, including SA, duration, and cumulative measures; rather than a focus on implicit parameters (i.e., distance, and pulse or non-pulse classifications) that are conventionally used to heuristically distinguish between the near-fault and far-field records. No ad hoc criteria, in terms of the number of directivity ground motions and their pulse periods, are enforced for selecting pulse-like records. Example applications are presented with different rupture characteristics, source-to-site geometry, and site conditions. It is advocated that the selection of ground motions in the near-fault region based on IM properties alone is preferred to that in which the proportion of pulse-like motions and their pulse periods are specified a priori as strict criteria for ground motion selection. Three methods are presented to propagate the effect of seismic hazard and ground motion selection epistemic uncertainties to seismic performance metrics. These methods differ in their level of rigor considered to propagate the epistemic uncertainty in the conditional distribution of IMs utilised in ground motion selection, selected ground motion ensembles, and the number of nonlinear response history analyses performed to obtain the distribution of engineering demand parameters. These methods are compared for an example site where it is observed that, for seismic demand levels below the collapse limit, epistemic uncertainty in ground motion selection is a smaller uncertainty contributor relative to the uncertainty in the seismic hazard itself. In contrast, uncertainty in ground motion selection process increases the uncertainty in the seismic demand hazard for near-collapse demand levels.
In September 2010 and February 2011, the Canterbury region experienced devastating earthquakes with an estimated economic cost of over NZ$40 billion (Parker and Steenkamp, 2012; Timar et al., 2014; Potter et al., 2015). The insurance market played an important role in rebuilding the Canterbury region after the earthquakes. Homeowners, insurance and reinsurance markets and New Zealand government agencies faced a difficult task to manage the rebuild process. From an empirical and theoretic research viewpoint, the Christchurch disaster calls for an assessment of how the insurance market deals with such disasters in the future. Previous studies have investigated market responses to losses in global catastrophes by focusing on the insurance supply-side. This study investigates both demand-side and supply-side insurance market responses to the Christchurch earthquakes. Despite the fact that New Zealand is prone to seismic activities, there are scant previous studies in the area of earthquake insurance. This study does offer a unique opportunity to examine and document the New Zealand insurance market response to catastrophe risk, providing results critical for understanding market responses after major loss events in general. A review of previous studies shows higher premiums suppress demand, but how higher premiums and a higher probability of risk affect demand is still largely unknown. According to previous studies, the supply of disaster coverage is curtailed unless the market is subsidised, however, there is still unsettled discussion on why demand decreases with time from the previous disaster even when the supply of coverage is subsidised by the government. Natural disaster risks pose a set of challenges for insurance market players because of substantial ambiguity associated with the probability of such events occurring and high spatial correlation of catastrophe losses. Private insurance market inefficiencies due to high premiums and spatially concentrated risks calls for government intervention in the provision of natural disaster insurance to avert situations of noninsurance and underinsurance. Political economy considerations make it more likely for government support to be called for if many people are uninsured than if few people are uninsured. However, emergency assistance for property owners after catastrophe events can encourage most property owners to not buy insurance against natural disaster and develop adverse selection behaviour, generating larger future risks for homeowners and governments. On the demand-side, this study has developed an intertemporal model to examine how demand for insurance changes post-catastrophe, and how to model it theoretically. In this intertemporal model, insurance can be sought in two sequential periods of time, and at the second period, it is known whether or not a loss event happened in period one. The results show that period one demand for insurance increases relative to the standard single period model when the second period is taken into consideration, period two insurance demand is higher post-loss, higher than both the period one demand and the period two demand without a period one loss. To investigate policyholders experience from the demand-side perspective, a total of 1600 survey questionnaires were administered, and responses from 254 participants received representing a 16 percent response rate. Survey data was gathered from four institutions in Canterbury and is probably not representative of the entire population. The results of the survey show that the change from full replacement value policy to nominated replacement value policy is a key determinant of the direction of change in the level of insurance coverage after the earthquakes. The earthquakes also highlighted the plight of those who were underinsured, prompting policyholders to update their insurance coverage to reflect the estimated cost of re-building their property. The survey has added further evidence to the existing literature, such as those who have had a recent experience with disaster loss report increased risk perception if a similar event happens in future with females reporting a higher risk perception than males. Of the demographic variables, only gender has a relationship with changes in household cover. On the supply-side, this study has built a risk-based pricing model suitable to generate a competitive premium rate for natural disaster insurance cover. Using illustrative data from the Christchurch Red-zone suburbs, the model generates competitive premium rates for catastrophe risk. When the proposed model incorporates the new RMS high-definition New Zealand Earthquake Model, for example, insurers can find the model useful to identify losses at a granular level so as to calculate the competitive premium. This study observes that the key to the success of the New Zealand dual insurance system despite the high prevalence of catastrophe losses are; firstly the EQC’s flat-rate pricing structure keeps private insurance premiums affordable and very high nationwide homeowner take-up rates of natural disaster insurance. Secondly, private insurers and the EQC have an elaborate reinsurance arrangement in place. By efficiently transferring risk to the reinsurer, the cost of writing primary insurance is considerably reduced ultimately expanding primary insurance capacity and supply of insurance coverage.
