ORC has undertaken its first region-wide natural hazards exposure analysis, marking a significant step in improving our understanding of how natural hazards may affect people, property, and critical facilities across Otago.
In the context of natural hazards, exposure refers to the people, buildings, infrastructure, and economic assets that are located in areas potentially affected by a natural hazard.
Understanding natural hazard exposure is an essential step for assessing risk, planning for emergencies, and supporting resilient communities.
This analysis draws on ORC’s existing regional-scale hazard mapping to estimate exposure to nine different types of natural hazards:
| Natural Hazard Type | Hazard Group |
|---|---|
| River and lake flooding | Flooding |
| Landslides | Slope stability |
| Rockfall | Slope stability |
| Alluvial fans | Slope stability |
| Active faults | Earthquakes |
| Liquefaction | Earthquakes |
| Storm surge | Coastal hazards |
| Coastal erosion | Coastal hazards |
| Tsunami | Coastal hazards |
It considers the exposure of three key elements to natural hazard processes:
- Population (also referenced as usually resident population)
- Buildings
- Critical community facilities (such as hospitals and emergency services, sometimes abbreviated as CCF)
The analysis has led to completion of a data-driven report designed to help communities, planners, and emergency services understand where exposure exists — not when an event might occur, or the level of risk from that hazard.
The report covers the entire Otago region and provides a baseline snapshot of communities’ exposure to natural hazards and allows comparisons between hazard types and across different locations.
The exposure analysis helps to:
- Identify areas with relatively high natural hazard exposure
- Support prioritisation of future hazard investigations and risk mitigation
- Inform emergency planning and land use decisions
- Contribute to ORC’s regional natural hazards prioritisation programme (starting in July 2025)
It also supports ORC’s responsibilities under national legislation like the Resource Management Act and the Civil Defence Emergency Management Act, which require regional councils to assess and manage natural hazard risks.
This is a broad-scale, regional assessment designed to inform strategic planning. It is not intended for detailed property-level assessments or project-specific decision-making. While it provides valuable insights, the analysis has limitations:
- It uses generalised hazard mapping data with varying levels of detail and accuracy
- Localised, more detailed studies are often available but were not included to ensure consistency across the region
- Some hazards incorporate climate change considerations, while others do not
As such, this exposure data is best used as a starting point—an overview to highlight areas for further investigation or to prompt checks for more detailed information where available.
Read the full Otago Region Natural Hazards Exposure Analysis Report, the presentation shared with the Science and Resilience Committee on 4 June 2025 or the media release sharing its findings
May 2025
PDF | 4 MB
This report presents findings of Otago Regional Council’s (ORC’s) first systematic analysis of natural hazard exposure for Otago. The report provides a ‘stocktake’ and baseline of the current understanding of natural hazard exposure for the region, and is a first iteration of analysis to quantify and map natural hazards exposure in Otago at a regional scale.
June 2025
PDF | 1 MB
Report to inform the Safety and Resilience Committee of the work on a region-wide natural hazards assessment programme, including presenting a report analysing natural hazards exposure within the Otago region.
To avoid confusion or alarm, here are simple definitions of some key terms used in the report.
These terms may sound technical or worrying but it is important to remember this analysis is about where we focus effort to reduce exposure — not about predicting events or sounding alarms.
- Exposure:
- Means a person or building is located in an area where a hazard process might occur — not that they are guaranteed to be affected.
- Natural hazard:
- A natural process or event (like a flood or earthquake) that could cause harm to people or property.
- Liquefaction:
- A process where ground made of loose, wet soil can behave like a liquid during strong earthquake shaking.
- Alluvial fan:
- A fan-shaped landscape feature where debris and/or floodwaters from a hillside can wash out and spread during heavy rain events.
- Critical community facility (CCF):
- Buildings that are key to post-disaster response, such as fire stations, police stations, hospitals, or emergency operation centres.
- High exposure:
- A community area has a higher number or proportion of people or buildings located within a mapped hazard area — not that an event is imminent.
If you have any questions on the report or natural hazards in Otago, you can contact ORC’s natural hazards team at NaturalHazards.Enquiries@orc.govt.nz
Alluvial fans
An alluvial fan is an accumulation of river or stream (alluvial) sediments that form where streams emerge from hill country onto a valley floor. Alluvial fans can be formed by several geomorphic processes, which become hazards when they intersect people, property or infrastructure.
Coastal erosion
Coastal erosion is the wearing away of land and beach sediments by waves, tidal currents, drainage or high winds.
Earthquakes
Earthquakes occurring both within Otago and beyond its boundary can affect people and property within the region.
Flooding
We identify areas at risk of flooding from rivers and lakes around Otago.
Landslides
The term landslide describes a wide range of ground movements, such as rockfalls, deep failure of slopes, shallow debris-slides, and flows. We hold information on known landslides in the region.
Storm surge
A storm surge is a higher than normal sea level, due to changes in barometric pressures and wind, which can result in inundation of roads and coastal property over an extended period.
Tsunami
A tsunami is a series of waves caused when a large mass of earth on the bottom of the ocean suddenly drops or rises, rapidly displacing the water above it.
Weather hazards
Weather hazards in Otago can include drought, wildfire, snow, wind, and heavy rain. These events may worsen with climate change, so understanding them helps with preparedness and resilience.
Otago Natural Hazards Database
Our hazards database is intended to improve public access to hazard information and to help the public, local authorities, and others make informed decisions about their exposure to natural hazards.
