Coastal & tsunami risks

Harbour-side, beach-front, and low-lying coastal properties face different risks from storms, elevated sea levels, cliff erosion, and tsunami events. Each council publishes different coastal layers. Your iQHOME report checks what is available for Auckland, Wellington, Christchurch, Tauranga, Dunedin, and other supported cities. See What iQHOME checks for you for the layers in your report.

Coastal inundation (AEP)

Auckland Council maps coastal inundation for a 1% Annual Exceedance Probability (1% AEP) storm tide event, with sea-level rise scenarios (+0.5 m to +2 m) layered on the interactive map. This is separate from river flood plains and tsunami evacuation zones. Relevant for properties near the Waitematā, Manukau, Kaipara, and east coast beaches.

Coastal erosion & instability (ASCIE)

Separate from storm-tide inundation, Auckland Council publishes Areas Susceptible to Coastal Instability and Erosion (ASCIE) mapping. This shows regional lines where coastal cliffs, dunes, or soft coast may be more vulnerable to erosion or instability over time, especially as sea levels rise.

On an iQHOME report, ASCIE appears as a line on the map rather than a shaded flood zone. If your pin intersects a line, or one lies within about 150 metres, council mapping flags the property as near a susceptibility area. The interactive map includes climate scenarios for 2050, 2080, and 2130 (RCP8.5), so you can compare how the mapped extent may change over time.

This layer is most relevant for clifftop homes, coastal sections, and properties backing onto soft coast or dunes, for example parts of the west coast, North Shore cliffs, and eastern bays. It is regional desktop mapping at roughly 0.5–5 km scale, not a site-specific coastal engineering assessment. A clear result does not guarantee a site will never erode; a hit means the published council layer applies and further coastal or geotechnical advice may be worth considering before you buy or build.

Storm surge

Greater Wellington models coastal flooding during a 1-in-100-year storm tide event, including sea-level rise scenarios. This shows where surge may reach during severe coastal storms around Wellington Harbour and the south coast.

Coastal inundation and tsunami inundation

Coastal inundation: Sea-level rise and coastal inundation mapping by climate scenario, showing where higher seas may affect low-lying coastal land over time.

Tsunami inundation: Modelled extent of tsunami water reaching inland, distinct from evacuation zones. This shows where water may travel in modelled tsunami scenarios, not where you must evacuate during a warning.

Harbour inundation and tsunami evacuation

Harbour inundation: Tauranga City Council models harbour-side flooding at several relative level bands (RL 2.3 m–2.7 m NZVD16), relevant for low-lying Mount Maunganui, Papamoa, and harbour margins.

Tsunami evacuation zone: Civil Defence evacuation mapping for the Tauranga urban area. Safety and planning data, not a prediction that every property in the zone will flood in every scenario.

Coastal hazard, storm surge, and tsunami

Coastal hazard (2GP): District plan coastal hazard mapping for planning and buyer due diligence.

Storm surge (1:100 year): Modelled coastal flooding during a significant storm-tide event.

Tsunami affected area: Mapping of areas that may be affected in modelled tsunami scenarios, distinct from evacuation routing.

Tsunami evacuation zones

Civil Defence evacuation zones show areas that may need evacuation during a tsunami warning. Auckland uses red and yellow zones. Wellington uses red, orange, and yellow zones. Christchurch uses red, orange, and yellow zones. Tauranga publishes a local evacuation zone layer. These are safety and planning maps, not predictions that a specific property will flood in every scenario.

• Insurance availability and premiums can differ on coastal land
• Long-term sea-level rise may affect planning and resilience rules
• Evacuation zones matter for safety and civil defence planning

If coastal layers appear on your report, review council coastal guidance for your city, ask your insurer early, and understand evacuation routes. iQHOME summarises mapping at your pin; it does not model future climate scenarios for your specific building.