Coastal and harbour erosion

These erosion hazard maps identify areas of our coastline that are at risk of erosion by the sea. The maps are an output of modelling by Tauranga City Council and our technical advisors.

The maps show the predicted extent of open coast erosion out to the year 2130 and includes the impact of predicted sea level rise (SLR). Present day coastal erosion hazard areas have been shown for comparison with future erosion and sea level rise scenarios.

The coastal erosion maps illustrate areas likely to be affected by erosion for the open coast based on various time and sea level rise scenarios.

Nine scenarios have been mapped which reflect the likelihood of erosion occurring within the timeframes of present day, 2080 and 2130. 

The scenarios mapped also identify coastal erosion extents as 'likely' or 'extremely unlikely' (but still possible), these scenarios are shown for each timeframe.

Broadly speaking, across the different timeframes, the areas identified as having a 66% probability are considered as ‘likely’ to be affected while areas with 5% probability are ‘extremely unlikely’ to be affected.  

A specific web viewer has been created to allow you to view any property in relation to this hazard. This website includes links to the technical study along with a series of helpful reports and links where further information can be found.

Erosion mapping viewer

The purpose of the Resource Management Act (RMA) is to promote the sustainable management of natural and physical resources. It requires that a number of nationally important matters be recognised which include the management of significant risks from natural hazards. Particular regard must also be given to the effects of climate change. 

The avoidance or mitigation of natural hazards is one of the key functions of council in giving effect to the RMA. A similar requirement also exists for councils under the Building Act, Local Government Act and Civil Defence Emergency Management Act. Consequently, we are required to have a good understanding of the areas potentially at risk from natural hazards to support appropriate land-use planning and development decisions.

The New Zealand Coastal Policy Statement also directs councils to identify areas that may potentially be affected by coastal hazards over a timeframe of at least 100 years. Mapping is the most accepted method to identify hazard-prone areas and provide the greatest level of certainty to the public.

Climate change refers to the changes to the present-day climate associated with the effects of global warming. Climate change is projected to have a significant impact on the land near the coast. This impact will come about especially through sea-level rise and intensification of storm events.

National and regional analysis of climate change impacts have also been carried out by the National Institute of Water and Atmospheric Research (NIWA).

Different sea level rise scenarios reflect different assumptions about ocean warming and the melting of land-based ice.

The four sea level rise scenarios that have been selected for use in this study are based on technical guidance from the Ministry for the Environment on projected sea level rise. 

Historic sea level rise in New Zealand has averaged 1.7 ± 0.1 mm/year with the Bay of Plenty exhibiting a slightly higher rate of 2.1 ± 0.1 mm/year. Climate change is predicted to accelerate this rate of sea level rise in the future.  

NIWA have developed a range of SLR projections for Tauranga based upon recommendations from the Ministry for the Environment (2017) for use in planning processes.

This guidance recommends the use of a range of sea level rise scenarios with a need to take a long-term view towards sea level rise scenarios up to 1.6m. 

It is expected that sea level rise will exacerbate current coastal erosion in terms of scale and frequency of erosion events. It is also likely to increase the frequency of damaging storm/weather events. For example, a modest sea level rise of 0.3m (possibly reached by 2050), is likely to change a present-day rare storm event into an annual event.

We have an obligation to make hazard information we hold available to the public under the Local Government Official Information and Meetings Act 1987. It will be made clear on any Land Information Memorandum (LIM) requested for a property within a hazard area, that council holds information in respect of coastal erosion and for the property which has been derived from a coastal hazard study.

We are required to make information, such as the Coastal Hazard Study, available upon request. We cannot advise you about any effect this information may have on property value or insurance.

It is recommended that professional advice is sought from a property valuation or insurance expert about any questions you may have regarding these matters. Refer to the letter below from Insurance Council New Zealand for more information about insurance.

Information for Property Owners (125kb pdf)

The receipt of this information allows us to continue to plan for subdivision and built development along the open coast and also understand how erosion may occur out to 2130, based upon a range of sea level rise scenarios. This will include consideration of regulatory provisions to manage future development (including intensification) within these risk zones and how to best adapt to changes in hazard information in the future.