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  Services » Regional Services » Regional hazards and emergency management » Coastal hazards including tsunami » Coastal flooding » Coastal inundation tool

Coastal inundation tool


What is the Coastal Inundation Tool?

The Waikato region's low-lying coastal areas are susceptible to inundation from tides, 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 extent of the effects of inundation.

The tool only shows  â€˜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 directly flow to the sea for a chosen water level.
  • Disconnected inundation (green areas), which represent areas that are at or below a chosen water level, but may have no direct flow path to the sea.  Disconnected 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.

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.

Flow chart for using the toolHow do I use it?

Please read the disclaimer first.

Step 1: Find your location

Zoom to your area of interest.

Step 2: Choose and enter a relevant water level scenario

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

You can either:

Step 3: Map the extent of the scenario

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

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

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.

As a tip, press the Play button to 'load' all the mapped water levels first to speed up exploring the susceptibility.

More information

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

Layers to be added soon

  • Mapped inundation water levels for the Hauraki Plains and Miranda/Kaiaua areas.
  • Relevant flood protection assets (for example, stopbanks).
  • Tsunami Maximum Credible Event layers for Whangamata, Whiritoa, Onemana, Opito Bay, Kuaotunu, Matarangi, Whangapoua and Kennedy Bay.

Watch our video, below, where Rick can tell you a bit more about the tool.

Contact us

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

Glossary of definitions

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).

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