Research undertaken and literature reviewed show that major natural disasters present considerable risk to Governors Bay. Earthquakes, and resulting secondary hazards from natural disasters, could lead to the isolation of the Governors Bay community for an extended period. In particular, the rupture of the Alpine Fault and the resulting mega-quake could leave Governors Bay isolated for well over three weeks. Weaknesses in existing infrastructure in Governors Bay further places residents at risk. Therefore, it is essential that residents are prepared for a period of extended isolation, with little to no access to clean water, power, internet and cellular coverage. Ultimately, community preparedness will be the key to maintaining social cohesion and saving lives during an emergency event. The community hub in Governors Bay establishes a pre-determined locale for community co-ordination, collection, and distribution of supplies as well as a functional place to go when all else fails.
Surface-rupturing earthquakes can trigger the sudden avulsion of river channels, causing rapid and persistent coseismic flooding of previously unaffected areas. This phenomenon, known as fault-rupture-induced river avulsion (FIRA), occurs when fault displacement significantly alters river channel topography. The importance of understanding FIRA as a secondary seismic hazard was highlighted by events during the 2010 Darfield and 2016 Kaikoura earthquakes in New Zealand. This thesis develops a national model to identify and quantify FIRA susceptibility across New Zealand by integrating hydrological datasets (NIWA RiverMaps and Flood Statistics) with active fault information (NZ Active Faults Database and RSQSim earthquake simulations). The methodology applies the F-index framework proposed by McEwan et al. (2023), which quantifies FIRA potential based on the ratio of fault throw plus discharge-dependent depth to bank full depth at each fault-river intersection. The model successfully identified 3,796 potential FIRA-susceptible fault-river intersections nationwide, with 451 involving waterways equal to or larger than the Hororata River. Regional analysis revealed higher concentrations of FIRA-susceptible sites in the Bay of Plenty, Canterbury, and Marlborough regions. Validation against historical events showed the model effectively located known FIRA occurrences from the Kaikoura and Darfield earthquakes, though with some limitations in accurately predicting F-index values due to complex fault displacement patterns and challenges in modelling bank full depths of large, braided rivers. This research establishes New Zealand's first nationwide assessment of fault-induced river avulsion susceptibility. The approach creates a structured methodology for identifying high-risk fault-river intersections and determining which sites require thorough localised examination. The methodology developed offers a template for similar assessments in other tectonically active regions and contributes to improving earthquake hazard assessment and disaster preparedness planning.
