Low-lying areas around Tauranga’s harbour are vulnerable to inundation (flooding) by the sea, especially during storm events.
Flooding of this kind happened early January 2018, when a storm surge (low air pressure combined with high winds, resulting in higher sea levels) coincided with a high tide, to push water onto land.
Use the inundation map viewer
Inundation modelling and maps
To understand which areas near the harbour may be prone to flooding during storm events and the compounding effect that future sea level rise may have, we use inundation modelling.
Inundation modelling has previously been used to identify hazard areas, which are currently included in the Tauranga City Plan. These areas may be susceptible to harbour flooding due to their low-lying nature. Development within these areas require a resource consent under the Resource Management Act 1991 to ensure any buildings and structures are built to manage the flood hazard risk. Consideration will also be required when carrying out building works in these areas under the Building Act 2004. Generally, the requirements for building and development in these hazard areas are that:
- the land or finished floor levels are raised above the minimum level, currently 2.5m to 2.9m above Moturiki Datum – which is the local fixed reference point for all height measurements within the Bay of Plenty
- that this does not create adverse effects on existing buildings /structures and surrounding property
Inundation modelling for the Tauranga harbour was last carried out in 2009 as part of the last City Plan review.
Tauranga Harbour inundation assessment and overland inundation mapping reports 2009 (3mb pdf)
2019 harbour inundation study and maps
To refresh the 2009 modelling, we engaged the National Institute of Water and Atmospheric Research (NIWA) to carry out an updated assessment of the potential for inundation of land near the Tauranga harbour. NIWA developed a model that incorporates sea levels generated by a range of extreme storm events and the impact of potential sea level rise scenarios out to 2130. The study also used information gathered from the 5 January 2018 storm event.
NIWA’s ‘Tauranga Harbour Inundation Modelling’ full report (10mb pdf) Executive summary (81kb pdf)
The findings of the assessment are presented in maps that illustrate the inundation levels based on a set of annual exceedance probability (AEP). An AEP describes the likelihood of reaching or exceeding a flooding level in any calendar year, expressed in probabilities of 2%, 1% and 0.2%. So, for example a flood level with a 1% AEP has a 1% chance of occurring in any year.
The sea level rise projections used for the NIWA model (0.4 m, 0.6 m, 0.8 m, 1.25 m and 1.6 meters) are based on the scenarios recommended by the Ministry for the Environment and meet the requirements of the New Zealand Coastal Policy Statement and the Bay of Plenty Regional Policy Statement.
Further information on sea level rise
Further information on harbour inundation and the information produced through this assessment factsheet (120kb pdf)
Inundation mapping viewer
You can see and explore the maps produced by this study via an online viewer. This viewer allows you to select a specific property and find the current inundation area as well as see what the potential inundation hazard could look like over time, for a range of sea level rise scenarios and storm event likelihoods.
To use the inundation map viewer:
- Open the viewer using the link below
- Click on the magnifying glass symbol at the top right
- Enter the address for the property you would like to see details for
Inundation map viewer
Frequently asked questions
Information from the assessments will be used for:
- future land use planning, to help plan for and understand the effects of natural hazards and sea level rise on existing land uses, potential subdivisions and the delivery of a compact city
- Infrastructure planning - specifically to consider funding upgrades to existing infrastructure, provision of infrastructure and understanding the long term effects on the operation and performance of infrastructure
- consideration of building consent applications under the Building Act 2004
- consideration of subdivision consent applications under the Resource Management Act 1991
- Producing Land information memoranda (LIM)
The Building Act 2004 requires consideration of whether the land is likely to be subject to 1 or more natural hazards. As such, when assessing building consent applications where the proposed building or the subject property falls fully or partly within the inundation hazard area relating to 1.25m of sea level rise and 1% AEP, the consent application will be subject to an assessment under sections 71 and 72 of the Building Act 2004.
The Resource Management Act 1991 requires council to consider whether a proposed subdivision will be at significant risk from natural hazards. As a result of the information now available from this study, any application made for the subdivision of land which is located wholly or partly within a hazard area relating to a 1% AEP inundation level and subject to 0.8m, 1.25m and 1.6m of sea level rise projections will require assessment to determine this risk under paragraphs 106(1A)(b) and (c) of the Resource Management Act 1991.
A land information memorandum (LIM) is a report that provides a summary of all the information council has on file about a property. For both sellers and buyers, a LIM may answer some important questions about the land or any buildings that are on the property. Under the Local Government Official Information and Meetings Act 1987, council is required to make LIM information available to any interested party. This includes any information that Council may hold in relation to natural hazards where council is required to show all known natural hazards information, that may potentially occur.
Council gives anyone who requests a LIM:
- the range of information it holds on inundation, against varying sea level rise scenarios
- where applicants can find these reports
- where applicants can view the information using our mapping system.
We are required to make information, such as the Coastal Hazard Study, available upon request. For advice about any effect this information may have on property value or insurance, we recommend seeking professional advice from a property valuation or insurance expert.
While we have progressively researched the implications of inundation for some time, the ‘Tauranga Harbour Inundation Modelling’ is the most definitive work that complies with both the Ministry for the Environment’s Guidelines and Bay of Plenty Regional Council requirements. Next we need to consider how to manage sea level rise, along with its effect on natural hazards, as part of a long term strategy which will take time to develop. The beginning of this process is to understand where around the harbour this hazard exists and to share this information with the public.
Last Reviewed: 25/09/2019