The Mean High Water Spring Tide Sea Levels layer provides the elevation of the high tide level equalled or exceeded by only the highest 10% of all high tides. These high tide levels include the astronomically driven tide only (due to rotational and gravitational effects) and do not include waves or storm surges (which are the rise in sea level caused by wind action and low barometric pressure related to storm events). Storm-tide levels are provided in a separate storm-tide levels dataset.

The Mean High Water Spring Tide Sea Levels have been provided for points around Auckland’s coast as part of a project to map the coastal inundation that will occur into the future with sea level rise on top of mean high water spring tides.

The mean high water spring tide sea levels have been updated based on the mean sea level averaged over the period 2001–2019. This accounts for sea level rise that has occurred up until the effective base date of 2010, but does not include sea level rise that has occurred since that period, or sea level rise that is expected to occur into the future. This is set out in the report Coastal inundation from sea-level rise in the Auckland Region (NIWA, 2023).

For guidance related to future sea level rise and vertical land movement, refer to the Ministry for Environment’s Interim guidance on the use of new sea-level rise projections | Ministry for the Environmentand NZ Sea Rise.

Mean high water spring tides are used to define the Coastal Marine Area boundary within Auckland’s Unitary Plan.

Note: The studies informing this mapping of coastal inundation generally used Auckland Vertical Datum 1946. Auckland Council is now transitioning to using New Zealand Vertical Datum 2016 so the live data on geomaps has also been converted to NZVD2016.