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Coastal inundation tool

>>> Click here to launch the new and improved Coastal Inundation Tool

Important: Please note that this tool is not supported by Internet Explorer. The recommended browsers are Google Chrome or Microsoft Edge.

The new version of the Coastal Inundation Tool was developed in collaboration with Bay of Plenty Regional Council and Environment Canterbury, with the aim of creating a tool that can easily be rolled out by any regional council in New Zealand at a low cost.

What is the Coastal Inundation Tool?

The Waikato region's low-lying coastal areas are susceptible to inundation from tides, coastal storms and projected sea level rise.

The purpose of this tool is to see what areas may be subject to inundation, and to identify those areas where we need to better understand the effects of inundation.

The tool uses a 'bathtub model' to show  ‘static’ water levels. It does not include the effects of currents, friction, waves or other hydraulic processes that affect water movement or inundation.

The tool shows:

  • Connected inundation (blue shaded areas), which represent areas where water could flow directly (or via waterways) to the sea for the chosen water level.
  • Disconnected inundation (green areas), which represent areas that are at or below the chosen water level, but may have no direct flow path to the sea (e.g. due to beach ridges or flood protection structures).  These areas may still be affected by coastal inundation in some way, e.g. via groundwater.

The tool uses the best currently available water level and ground elevation information. All information will be regularly updated as required. All water levels and land elevations are provided relative to Moturiki Vertical Datum 1953.

Please note: The very first mapped water level for all locations shows the area that is likely to be inundated with a high tide (generally 0.2 m below the MHWS water level). All higher mapped water levels only show areas that would not normally be inundated by a high tide.

The tool is not intended to provide specific information that could be used to define actual coastal inundation hazards or minimum floor levels for specific properties.

Tool instructions diagramHow do I use it?

Please read the disclaimer first.

Step 1: Find your area of interest

Zoom to your area.


Click on the "Sea Level Scenario" tab, then search for your coastal area.


Use the search bar to search for your property address.

Step 2: Choose and enter a relevant sea level scenario

Sea levels vary around the Waikato region's coastline, and it's important that your sea level values best represent the specific location.

You can either:

Step 3: Map the extent of the scenario

You then adjust the slider on the map to a sea level that best matches your sea level scenario. Note the water levels are at 0.2m intervals. 

The tool will show the sea level extent on the aerial map. You can then explore the coastal inundation susceptibility of the area by adjusting the slider up and down.

As a tip, press the Play button to cycle through and 'load' all the mapped sea levels first to speed up the performance of the tool.

More information

For further help and information, you may like to check out:

Contact us

Get in touch with us! Just send an email to if you've got any comments, feedback or you need further help.


Inundation: Coastal inundation is the flooding of normally dry, low-lying coastal land. This is primarily caused by severe weather events along the coasts, estuaries, and adjoining rivers.

Mean high water springs (MHWS): The place on the shore where spring high tides reach on average over a period of time (often recognised by the upper line of debris on the beach).

Bathtub model: A bathtub model simply means treating the ocean like a bathtub, that fills up the same way that a tub does when you add water. The lower parts fill up first, and the water rises at the same level everywhere.

Datum: A fixed vertical elevation or level used as a reference point.

Sea Level Anomaly: The sea level 'anomaly' describes the variation of the non-tidal sea level on time scales ranging from month to month, through an annual sea-level cycle, up to decades due to climate variability. The variations in sea level along the coast are primarily due to changes in water temperature and wind patterns.