During disasters, exposed and vulnerable communities bear the brunt of impacts and are first to respond. People of these communities obtain local and/or indigenous knowledge and understanding of locally-specific challenges and opportunities, which no external expert could derive alone. Participatory, community-based disaster risk reduction involves participation of people who may be directly impacted by disasters, to encourage sharing of valuable local knowledge and to empower both communities and local authorities to reduce vulnerabilities and strengthen capacities. This participatory process is carried out for, with, and by the community to form DRR initiatives that are well-informed and invested in by all involved, and thus are more effective.

Tsunami are powerful, natural phenomena which can cause considerable impacts on exposed and vulnerable communities. Wharekauri-Rekohu-Chatham Islands is an archipelago in the Pacific Ocean approximately 800 km east of Aotearoa-New Zealand (A-NZ) and is exposed on all sides to tsunami generated from local, regional and distant sources. Past tsunami events on Chatham Islands have been destructive, causing loss of property, infrastructure and, in one case, fatality. Previous tsunami research on the Chatham Islands has focused on hazard assessment. While this provides a major contribution towards understanding tsunami hazard for the Chatham Islands, the assessments are incomplete or limited by uncertainties in model input parameters. More research is required to better understand tsunami hazard for the Chatham Islands to inform effective reduction, readiness, response and recovery initiatives. Current disaster risk reduction (DRR) initiatives on the Chatham Islands are also limited by lack of understanding of societal assets exposed, their vulnerability (as well as capacity), and potential impacts.

Although A-NZ has access to pre-written records of past, high-impact, tsunami impacts within Tangata Whenua knowledge systems, Tangata Whenua knowledge of past events on the Chatham Islands has not been explored previously. High-impact tsunami events can cause considerable damage to infrastructure networks, resulting in significant disruption of essential services (water, communications, electricity, transportation corridors), which are critical during disasters to enable effective response and recovery activities. During a high-impact tsunami event which affects locations across A-NZ, the Chatham Islands may be isolated from external assistance for an extended period of time. In this situation, the performance of essential services and on-island capacity to restore services may have considerable influence on response and recovery.

The overall aim of the thesis is to inform and to engender community-led and community-based actions to reduce future tsunami impact, through participation of the Chatham Islands community throughout the research, to produce useful and usable outcomes. This involves addressing the following objectives: a) Improve the current understanding of tsunami hazard for the Chatham Islands by investigating past event impacts and inundation extents in documented accounts and Tangata Whenua knowledge/oral history. b) Assess potential impacts on societal assets, in particular infrastructure components, to evaluate resultant levels of essential services based on expert judgment from local infrastructure personnel to form a credible high-impact tsunami scenario. c) To share this information with the Chatham Islands community to co-develop actions to reduce future tsunami impact through the use of participatory tools facilitated during workshops.

To achieve these objectives, an impact assessment was conducted, following the Risk Management Framework (AS/NZS ISO 31000:2009) to identify risk (improving understanding of tsunami hazard and identify exposed societal assets), analyse risk (through combining hazard and exposure metrics to evaluate vulnerability and subsequent impacts) and evaluate risk (through the community identifying underlying vulnerabilities and capacities) to inform co-developed risk treatment options (derived in the workshops).

The combination of documented accounts and Tangata Whenua knowledge brought to light a wealth of information on past tsunami impacts and inundation extents which is not included in detailed national tsunami databases. The credible, high-impact scenario suggests that a significant amount of infrastructure is exposed and vulnerable to tsunami inundation, and that problematic impacts occur in the scenario which exceeds the capacity on-island resources to restore functionality of some assets and services. The scenario results are presented, and as discussed, are uncertain but provided a useful tool for the participatory workshops. The participatory workshops revealed that Chatham Islanders have great capacity to survive on their own if disconnected from services from A-NZ during and following a high-impact tsunami event. This is partly due to a tightly-connected community, as well as a community of people who are highly adaptive and resourceful (due to experience of living in isolation). However, workshop participants also identified key vulnerabilities in dependence on lifeline infrastructure and essential services during warnings, response and recovery. Although there was a high degree of confidence that the community could cope, the workshops highlighted some issues that had not yet been considered but would be crucial during a time of high stress. With local planning and action these issues could be addressed and help to reduce tsunami impacts on the Chatham Island community.

In summary, this thesis: • Presents the first contribution to understanding tsunami risk to Chatham Island society. This information will better inform future impact reduction, readiness, response and recovery initiatives. • Provides a demonstrable application of how community participation can be successfully incorporated into the disaster risk assessment process, especially in the New Zealand context. This work can be used to guide similar future studies to develop useful and usable outcomes for, with and by communities. • Provides a credible, high-impact tsunami scenario that includes resultant levels of essential services, which could be used to run future exercises with Civil Defence and Emergency Management (CDEM), infrastructure providers and the community, • Provides a list of community-derived recommendations for action to reduce future tsunami impact. These actions could be taken by individuals, households, businesses and agencies responsible for emergency management in the Chatham Islands.