Natural hazards encompass events with the potential to cause harm or loss due to natural phenomena.
In Otago, we collaborate with territorial authorities to manage these hazards, employing strategies like the Queenstown Lakes Flood Management Strategy and the Milton 2060 Strategy.
Reports from the Otago Regional Council extensively cover a wide range of hazards such as active faults, climate change impacts, liquefaction, debris flows, floods, seismic activity, erosion, coastal events, landslides, fire risks, and alluvial fan projects.
These publications offer detailed insights and strategies for understanding and managing natural hazards, emphasizing vulnerabilities in areas like South Dunedin and addressing coastal risks and active fault distributions throughout the region. They serve as vital resources for comprehensive hazard management in Otago and its districts.
March 2019
PDF | 4 MB
April 2021
PDF | 9 MB
October 2019
PDF | 26 MB
Otago’s climate is changing, and these changes will continue for the foreseeable future. It is internationally accepted that human greenhouse gas emissions are the dominant cause of recent global climate change, and that further changes will result from increasing amounts of greenhouse gases in the atmosphere. The rate of future climate change depends on how fast greenhouse gas concentrations increase.
July 2019
PDF | 13 MB
October 2015
PDF | 2 MB
A low-pressure system to the southeast of the South Island brought heavy rainfall to coastal Otago on 3 June 2015. This report summarises that rainfall event, the observed river flows and water levels that resulted from the rainfall, and describes the Otago Regional Council’s (ORC) response to the situation.
March 2005
PDF | 28 MB
In 2005, Opus International Consultants assessed the risk to the Otago region from seismic (earthquake) hazards. This report maps historical events, the location of faultlines, and estimated return periods for each.
May 2011
PDF | 25 MB
An alluvial fan is an accumulation of river or stream (alluvial) sediments that form a sloping landform, shaped like an open fan or a segment of a cone. Alluvial fans typically occur near the boundary between hill slopes and valleys. They owe their origins to changes in the slope of natural-drainage systems; for example, where a steep gully merges onto a flatter valley floor. The gradient decrease and widening of the flood path where a gully meets the valley floor encourages the deposition of sediment, which accumulates over time to form a fan-shaped landform. More than 2000 alluvial-fan areas, equating to 6% of the total land area, have been mapped in Otago. The principal hazards on alluvial fans are inundation by flood water, debris-flow and debris-flood deposits, channel migration, deposition and erosion. The unpredictable and variable nature of alluvial- fan hazards means that they are potentially very hazardous. Despite that, their elevated profile, with good drainage, makes them attractive places for people to live.
May 2018
PDF | 3 MB
Thunderstorms with lightning strikes, and short duration high-intensity rainfall occurred over and around Roxburgh, in Central Otago during the afternoon of 26th November 2017. A thunderstorm cell centred over Roxburgh delivered between 40 and 100 mm of rainfall between 4.00 pm and 5.00 pm. This high intensity, short duration rainfall caused debris flows in four stream catchments along the range front to the west of Roxburgh. In the last 20 years in New Zealand many homes and businesses have been impacted by debris flows and floods (Paekakariki, 2003; Matata, 2005; Port Ligar, 2011, Tasman District, 2018; Kaikoura District, 2018). During these 20 years no-one has been killed in their home by a debris flow. Three people have been killed by debris flows on walking tracks and roads.
September 2014
PDF | 1 MB
This report assesses changes in shoreline position between Nugget Point and Chrystalls Beach between 1946 and 2012. A survey of the offshore bathymetry and onshore surface profiles was completed in February and April 2013 respectively to set a baseline for future coastal monitoring. An analysis of recent and historic changes in the onshore and offshore coastal environment between Nugget Point and Chrystalls Beach is provided. The analysis contained in this report is based on terrestrial cross-section and bathymetric data collected in early 2013, LiDAR data collected in 2004 and 2009, and aerial photographs collected in 1946, 1972, 1997 and 2006. This report compares these data sources, where available, to allow comparisons of changes in the coastal zone to be quantified.
July 2012
PDF | 2 MB
This report explains the methods used to define the extent of flood risk management areas, which are included in the Milton 2060 flood risk management strategy for Milton and the Tokomairiro plain (ORC/CDC, 2012a). These areas have been shown to be susceptible to flooding. Areas with similar flood hazard characteristics have been grouped together. These characteristics include the depth of inundation, the velocity of water at the peak of the flood, and the length of time flooding may persist.
July 2021
PDF | 8 MB
July 2017
PDF | 4 MB
The Otago Regional Council (ORC) operates a natural hazards database. Landslides are a significant hazard in the Otago Region and an inventory of landslide information is an important dataset in the natural hazard database. The ORC landslide dataset documents the interpreted locations of past landslide movements based on landform characteristics, but does not provide forecasts of future landslides. Information in the ORC landslide dataset has been compiled from a variety of sources and at a variety of scales. As a result, there is considerable variation in the precision and quality of information on individual landslides. Of particular significance to communities is the exact geographic location of landslides, especially in regard to where the positions of landslide boundaries have been mapped. This is because there are potential implications for hazards associated with future landslide movement.
July 2016
PDF | 8 MB
This report describes the environmental and community setting of the South Dunedin plain. The physical characteristics of the plain include its low-lying topography, underlain by poorlyconsolidated sediment (mainly sand and silt), its proximity to the ocean and harbour, a shallow water table with strong connectivity between sea and groundwater, and an exposure to heavy rainfall events. The plain is vulnerable to natural processes which occur reasonably frequently (such as coastal storms), and also events which occur rarely but have significant consequences (such as major earthquakes on nearby faults). The South Dunedin plain is densely populated, with approximately 10,000 permanent residents, and contains infrastructure and other assets which are important at a local, district and regional level.
February 2016
PDF | 4 MB
A severe weather event that affected the Dunedin City district between the 3rd of June 2015 and midday on the 4th of June 2015 (the June 2015 rainstorm) caused flooding and numerous rain-induced landslides. This report catalogues the landslides associated with the June 2015 rainstorm and discusses the factors that may have influenced where, when and why they occurred. A digital database and GIS package accompanies this report.
October 2015
PDF | 2 MB
In this report, existing information relating to the most recently active group of known landslides in Dunedin City has been collated to help inform the review of the Dunedin City District Plan.
August 2015
PDF | 3 MB
Review of Dunedin City District Plan: Natural Hazards. As part of its current review of its District Plan, the Dunedin City Council (DCC) is reviewing the way it manages the use of land, so that the effects of natural hazards (including the effects of climate change) can be avoided, or adequately mitigated. The Otago Regional Council (ORC) is supporting the DCC by collating and presenting information on natural hazards to help inform this review.
June 2014
PDF | 7 MB
This report identifies areas where natural hazards may affect public safety, buildings and the infrastructure which supports coastal communities.
May 2014
PDF | 4 MB
Drawing upon methodologies developed for liquefaction hazard evaluation in Canterbury following the 2010–2011 earthquakes, the liquefaction assessment reported here comprised an office-based assessment utilising existing available information. The information sources include geological maps, landform and soil maps, topographic information from maps and lidar surveys, geological information from bore hole records, and measurements of depths to groundwater.
June 2014
PDF | 3 MB
Review of Dunedin City District Plan: Natural Hazards. This report defines the characteristics of flood events in Kaikorai Stream, the Water of Leith and Lindsay Creek (Dunedin’s ‘urban’ streams, as shown in Figure 1), and defines the floodplain area that may be affected if floodwater is able to overtop the main channel. The purpose of the report is to provide information and knowledge related to flood hazard, which can be incorporated into planning provisions through the DCC District Plan. This report will also assist with other activities such as the development of local emergency management response plans, building consents, and infrastructure planning, renewal and maintenance.
June 2014
PDF | 3 MB
As part of its current review of its District Plan, the Dunedin City Council (DCC) is reviewing the way it manages the use of land, so that the effects of natural hazards (including the effects of climate change) can be avoided or adequately mitigated. The Otago Regional Council (ORC) is supporting the DCC by providing natural hazards information, knowledge and opinion through a collaborative approach, to help inform this review.
June 2014
PDF | 3 MB
Review of Dunedin City District Plan: Natural Hazard. This report describes the characteristics of flood hazard on the Taieri Plain and the Strath Taieri. As well as helping to inform the management of land use through the review of the District Plan, the report will assist with other activities such as the development of local emergency management response plans, building consents and infrastructure planning, renewal and maintenance.
January 2014
PDF | 2 MB
An update of the ORC landslide database for the Dunedin City district was completed in 2012, utilising data from a variety of sources. It was realised that the landslide database contains little, if any, information on the significance of the hazard posed by landslides. ORC subsequently contracted GNS Science to provide more information on the hazard significance of the landslides within six areas in and around Dunedin City, and that is the subject of this report.
March 2013
PDF | 1 MB
Hoopers Inlet is a wave-dominated inlet susceptible to closure, most probably during periods of low wave activity during which sand is deposited by wave action in the inlet mouth. It has closed at least five times over the last five decades. It last closed in August 2012 and remains closed.
July 2012
PDF | 2 MB
The report draws on tsunami and storm surge modelling undertaken by National Institute of Water and Atmosphere (NIWA) for the Otago Regional Council (ORC) in 2007/08, coastal topography data and local knowledge of each community. This information has been used to assess how people and the communities in which they live would be affected during credible, high magnitude tsunami and elevated sea level events.
November 2012
PDF | 3 MB
The Otago Regional Council (ORC) is developing a natural hazards website depicting known hazard information. Landslides are a significant hazard in the Otago Region and one of the key data sets to be made available to the public via this website. Knowledge of the location and extent of historic and prehistoric slope instability (landslide movements) is a primary means of identifying and minimising hazards to development and infrastructure posed by landsliding.
March 2013
PDF | 15 MB
The Taieri Plains is a low-lying alluvium-filled basin, approximately 210km2 in size. Bound to the north and south by an extensive fault system, it is characterised by gentle sloping topography, which grades from an elevation of about 40m in the east, to below mean sea level in the west. At its lowest point (excluding drains and ditches), it lies about 1.5m below mean sea level, and has three significant watercourses crossing it: the Taieri River, Silver Stream and the Waipori River. Lakes Waipori and Waihola mark the plain’s western boundary and have a regulating effect on drainage for the western part of the plains.
August 2005
PDF | 1 MB
The Otago Regional Council (ORC) commissioned the National Institute of Water and Atmospheric Research Ltd (NIWA) to determine extreme sea levels with return periods of 2, 5, 10, 20, 50 and 100 years for eight locations along the Otago coastline. The focus is on extreme sea levels to be used as ocean boundary conditions for river flood modelling.
March 2005
PDF | 28 MB
In 2005, Opus International Consultants assessed the risk to the Otago region from seismic (earthquake) hazards. This report maps historical events, the location of faultlines, and estimated return periods for each.
May 2019
PDF | 23 MB
This report outlines a flood hazard study undertaken by Beca Ltd for the Owhiro Stream catchment, including Mosgiel and the surrounding rural area near Dunedin, Otago. It aims to define flood hazard levels for the Owhiro Stream and determine how the rural floodplain area south of Mosgiel, including the Lower Taieri Flood Protection Scheme Lower Pond, is impacted in flood events.
October 2020
PDF | 1 MB
March 2015
PDF | 14 MB
May 2018
PDF | 3 MB
Assessment undertaken by Landcare Research of post-fire debris flow hazard, Hillend Station, Wanaka, 2018
October 2006
PDF | 3 MB
The Otago Regional Council and Queenstown Lakes District Council adopted the Flood Risk Management Strategy at a joint meeting on 3 October 2006. The joint strategy formalises the responsibilities and accountabilities of the two councils and the lakes communities in regards to flooding in the district. Flooding has been an issue in the Queenstown Lakes District since European settlement in the 1850s. In the last 150 years significant floods have occurred in 1878, 1924, 1994, 1995 and most recently and dramatically in 1999 when severe flooding in Wanaka and the Wakatipu communities of Queenstown, Glenorchy, and Kingston caused extensive damage. This impacted not only the local, but regional and national economies.
June 2007
PDF | 30 KB
Alluvial fans comprise of sediment accumulations deposited at the base of valley slopes, shaped like an open fan or segment of a flattish cone. Formed by streams losing sediment transport potential at the exit of confined valleys, alluvial fans exhibit gentle slopes when dominated by flood processes and steeper slopes when debris-dominated. Primarily formed by intense, heavy rainfall, the overall development of these features spans time scales of decades to centuries. In Otago, the streams are often ephemeral, creating an impression within the community that flood and debris flow hazard does not exist, or is insignificant. Further, the steep, incised upper parts of the catchment lead to “flashy” flood flows, often associated with concentrated, high intensity convective rainfall (“thunderplumps”) which exacerbate the hazard. The form and setting of alluvial fans often makes them an attractive location for residential development in Otago. Notable examples of this are Stoney Creek (Wanaka) and Pipson Creek (Makarora). Identifying major fans and understanding the significance of the hazards associated with each major fan is a necessary part of managing the risks associated with human occupation of alluvial fans and avoiding inappropriate development.
July 2007
PDF | 51 KB
This report is a 2nd version of the original report produced in July 2007 and is a complementary document that helps put the Stage 3 Report, “Otago Alluvial Fans Project: Supplementary maps and information on fans in selected areas of Otago” into context. This report provides information on what was completed in Stage 1 of the project including background information regarding alluvial fans within Otago and their associated hazards. An alluvial fan is an accumulation of river or stream (alluvial) sediments that form a sloping landform, shaped like an open fan or a segment of a cone. Alluvial fans typically occur near the boundary between hillslopes and valleys. They owe their origin to changes in the slope of natural drainage systems, for example where a steep gully merges onto a flatter valley floor. The gradient decrease and widening of the flood path where a gully meets a valley floor encourages the deposition of sediment. Over time, sediment accumulates to form a fan-shaped landform, with its apex at the gully mouth. Alluvial fans form on all scales, from a few tens of metres across, to several kilometres across.
April 2009
PDF | 86 KB
Alluvial fans in Otago, shaped like open fans or flattish cones, accumulate sediment where streams exit valleys. They vary in slope, influenced by flood or debris flows from heavy rainfall over decades. Despite ephemeral streams suggesting minimal hazards, Otago's steep upper catchments experience intense rainfall events ("thunderplumps"). Fans like Stoney Creek (Wanaka) and Pipson Creek (Makarora) attract residential development, requiring careful identification and management of hazards to avoid risk in these areas.
September 2017
PDF | 40 KB
This report complements Otago's review of alluvial fan hazards, conducted by GNS Science and Opus International. Alluvial fans are sloping landforms formed by river sediments transitioning from hills to valleys. They pose risks such as fast-moving floods and debris flows that can change course unexpectedly, endangering people and infrastructure. The Otago Regional Council leads the 'Otago Alluvial Fans Project' to assess these hazards and mitigate risks effectively.
May 2010
PDF | 617 KB
Glenorchy, established in the mid-19th century at Lake Wakatipu's north end, is primarily residential and tourist-oriented. Its popularity has driven substantial residential growth, heightening exposure to hazards like lake inundation, debris flows, floods from nearby rivers, and geological risks. Its remote location and geological activity increase isolation risks. Future development and climate change will intensify these challenges. The 'Natural Hazards at Glenorchy' study aims to raise awareness and guide protective measures.
May 2010
PDF | 1 MB
Glenorchy and its environs have a complex hazard setting. In fact, the sediments which Glenorchy is entirely located upon have been deposited as a result of hazardous debris and flood flows originating from the Buckler Burn. The community’s exposure to the range of identified hazards, which include river and lake flooding, seismic hazards and mass movement, is defined by their nature, magnitude and frequency. This document identifies each hazard and the implications for the community based on current knowledge.
December 2010
PDF | 2 MB
The Cardrona Valley and its environs have a complex hazard setting. The residents and wider community are exposed to a range of hazards, including flood inundation, sedimentation and erosion, seismic hazards, mass movement, and alluvial fan hazards. The level of exposure is defined by the nature, magnitude, and frequency of these hazards. This document identifies and describes each hazard, while discussing the effects they may have on residents and community based on current knowledge.
November 2011
PDF | 719 KB
The Cardrona Valley, between Wanaka and Queenstown, was first settled in 1882 with two settlements for the mining industry. A major flood in 1878 devastated the lower township, highlighting the flood risk. Today, the valley features pastoral farming, tourism, and ski fields, with Cardrona Valley Rd linking Queenstown and Wanaka. Increasing development and population growth in the Queenstown-Lakes District have heightened exposure to natural hazards.
September 2013
PDF | 371 KB
The township of Glenorchy has a history of flooding. This is a natural process resulting from extended periods of heavy rain and snowmelt. North-westerly fronts moving over the southern part of the South Island can cause heavy rainfall in the headwaters of Lake Wakatipu, especially if they ‘stall’ and remain stationary over the Alps for a number of days.
September 2013
PDF | 386 KB
The township of Kingston has a history of flooding. This is a natural process resulting from extended periods of heavy rain and snowmelt. North-westerly fronts moving over the southern part of the South Island can cause heavy rainfall in the headwaters of Lake Wakatipu, especially if they ‘stall’ and remain stationary over the Alps for a number of days.
September 2013
PDF | 383 KB
Flooding of Lake Wanaka is caused by prolonged heavy rain and snowmelt. North-westerly fronts over the Southern Alps can stall and lead to heavy rainfall. Multiple fronts are usually needed to cause flooding. Several rivers flow into the lake, but only the Clutha River/Mata-Au flows out, leading to floods when inflow exceeds outflow. The Otago Regional Council (ORC) and Queenstown Lakes District Council (QLDC) provide flood warnings and information to help people prepare.
October 2014
PDF | 457 KB
Flooding of Lake Wanaka is a natural process resulting from extended periods of heavy rain and snowmelt in the catchment headwaters. North-westerly fronts moving over the southern part of the South Island can cause heavy rainfall in the lake’s headwaters, especially if they ‘stall’ and hover over the Southern Alps for days at a time. However, it generally takes a series of these fronts to raise the lake to the point where it floods. Several large rivers and streams flow into the lake, and only one (the Clutha River/Mata-Au) flows out. Flooding can occur when more water is flowing into the lake than can flow out, and when there is insufficient time for levels to drop between heavy rainfall events. The Otago Regional Council (ORC) works with the Queenstown Lakes District Council (QLDC) to provide flood warning and information services. These aim to help people prepare for, and respond to, a major flood event.
April 2015
PDF | 1 MB
The township of Arrowtown has previously been affected by flooding and riverbank erosion associated with the Arrow River, which passes the town to the north. This report assesses the current flood-hazard characteristics of the Arrow River, including the extent and depth of floodwater during a 1:100-year flood event and the potential for bank erosion. Changes in the morphology of the Arrow River are also described, using cross-section survey data obtained in December 2011. A comparison is made not only with previous bed-level surveys dating back to 1987, but also with historical information. The implications of ongoing changes in river-bed morphology on flood and erosion hazard are considered.
August 2015
PDF | 2 MB
The Otago Regional Council is assessing the seismic hazard across parts of Otago, with a focus on the more densely populated urban areas of Wanaka, Queenstown, Alexandra and Dunedin. This review focuses on the seismic hazard facing the Queenstown Lakes district, encompassing the Upper Clutha region around Wanaka, and the Wakatipu Basin area surrounding Queenstown. Previous assessments of the seismic hazard in the broader Otago region were provided by Johnston and Heenan (1995) and Murashev and Davey (2005).
April 2015
PDF | 504 KB
The Queenstown CBD area has a history of flooding. This is a natural process resulting from extended periods of heavy rain and snowmelt. North-westerly fronts moving over the southern part of the South Island can cause heavy rainfall in the headwaters of Lake Wakatipu, especially if they ‘stall’ and hover over the Southern Alps for days at a time. A series of such fronts is generally needed before lake levels rise enough to cause flooding. Several large rivers flow into the lake while only one (the Kawarau River) flows out. Flooding can occur when more water flows into the lake than can flow out, and when there is insufficient time for levels to drop between heavy rainfall events.
March 2019
PDF | 4 MB
February 2021
PDF | 6 MB
PDF | 9 MB
March 2019
PDF | 9 MB
This report looks at the erosion and flooding hazards in the Waitaki area, particularly areas like Kakanui Estuary and Oamaru Port foreshore. NIWA mapped coastal hazard zones for both erosion and inundation, looking ahead 100 years for planning purposes.
December 2016
PDF | 8 MB
This report presents a general outline of the locations and character of active geological faults and folds in the Waimate and Waitaki districts. A fault is a fracture within the rock of the Earth’s crust, along which movement has occurred. Commonly, strain builds up in the rock of the Earth’s crust, and is released suddenly by a slip event (rupture) on a fault, causing an earthquake. Folds represent bending or buckling of rock, and commonly form above an underlying fault.
