Coastal inundation tool

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What is the Coastal Inundation Tool?

The Waikato region's low-lying coastal areas are susceptible to inundation (flooding). Inundation is primarily caused by severe weather events along the coasts, estuaries and adjoining rivers. Projected sea level rise also needs to be considered.

The Coastal Inundation Tool allows us to see what areas may be subject to inundation, and to identify those areas where we need to better understand the effects of inundation.

Use the Coastal Inundation Tool

We recommend you launch the tool in Google Chrome or Microsoft Edge. Please read the disclaimer first before you start using the tool.

For more help and tips, read the steps and user guide, below.

launch the Coastal Inundation Tool

How to use the tool

Image - Diagram showing steps for Coastal Inundation ToolStep 1: Find your area of interest

Zoom to your area.

OR

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

OR

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:

  • select a pre-defined sea level scenario, provided in the "Sea Level Scenario" tab in the tool, or
  • create your own sea level scenario. Refer to section 2.2 in the user guide for help.

Step 3: Map the extent of the scenario

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.

User guide and sea-level records analysis

Read the user guide and sea-level records analysis for further help and scenarios.

 

How the tool works

The tool uses a 'bathtub model' to show  ‘static’ water levels. 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. The tool 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 water levels and land elevations are provided relative to Moturiki Vertical Datum 1953.

Points to note

The very first mapped water level for all locations shows the area that is likely to be inundated with a high tide. This is generally 0.2 m below the mean high water springs level (MHWS) which is 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). 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.

Some areas on the west coast are not included in the tool. However, due to their steep topography, these areas are generally not expected to be susceptible to coastal inundation.