Assessment of potential suitability of land for town growth - Franz Josef.
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In the face of expanding urban and rural areas and land intensification, hazard events are likely to continue to become more severe and devastating. This situation is no more relevant than in Franz Josef's township, where the systems responsible for the beautiful natural environment also pose a threat. As a result of the rapid growth and increase in tourism over the last decade, and due to the hazardous location of the current town, a new residential subdivision has been proposed and is currently being developed west of the Tatare River. As a risk management measure, all infrastructures may be relocated if there is a low perceived risk of seismic hazard and sedimentation of a landslide, flood, or debris flow. However, there have been no detailed study or hazard assessment undertaken for the new townsites to ascertain suitability of land for town growth in relation to the natural hazards that surround the township. As such, it remains unknown if relocation to the new towns drastically reduces risk and acts as a good risk reduction measure. In 2020, the Westland District Council commissioned a study to carry out a relative risk analysis comparing the risks associated with moving to a potential relocation site and those associated with Franz Josef township's current location.
The purpose of this study was to directly compare the exposure of the existing and proposed townsites by carrying out a hazard analysis through a comparison between the natural hazard risk profiles for the various hazards and to estimate individual and societal risk to life. These results will help inform decision making around the future of Franz Josef. This was undertaken through a literature review of the various identified hazards that threaten both the current and new townsites, GIS and RAMMS modelling of the extents of hazard outflows and empirical methods from data identified in literature.
With the same degree of development assumed for both town sites, the results show that the average annual impact on the current town sites is approximately six more than the impact on the proposed new town sites. Moreover, both individual and societal risk to life estimates are 17 times higher in the current town sites. Currently, the most significant risk to the new townsite is debris flow from the Stoney Creek catchment. In spite of this, the maximum runout extent of the largest recurrence interval event is still minimal and can be mitigated by proper measures. The results provide a robust assessment of the hazards and risks that can be faced by the two townsites as well as conclusive evidence that risk can be mitigated or transferred from the current townsites via relocation to the new townsites.
The results of this thesis can be used to initiate fundamental dialogue on the relocation of the current township. Nonetheless, a more comprehensive risk assessment is required, where all aspects (such as societal, economic, cultural) must be examined in greater detail. It is also fundamental that other potential sites within the area are also considered as an alternative, with more investigative work.