NZ Coastal Flooding Exposure and Sea Level Rise Examined

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As sea level continues to rise, coastal flooding remains a threat to New Zealand’s low-lying coastal land exposing its residents and assets.

This was the subject of the study that the National Institute of Water and Atmospheric Research (NIWA) conducted for the Deep South Challenge.

The report presents the following:

  • The report presents New Zealand’s exposure to 1% annual exceedance probability (AEP) from extreme sea level elevation (ESL1) at present-day mean sea-level (MSL) around the country’s coastline, resulting from a combination of tide, storm-surge, mean sea-level anomaly and wave setup.
  • AEP refers to the probability of a flooding event occurring in any year and the probability is expressed as a percentage. In this report, 1% AEP refers to a coastal flooding event having a 1 per cent chance of occurring in any one year.
  • On land that has available high-resolution airborne light detection and ranging (LIDAR) digital elevation models (DEM), coastal flooding is shown at many increments of up to +3m above present-day mean sea-level rise. On land with without a high-resolution DEM, but with lower resolution satellite-derived (DEM) coastal flooding is mapped for +3m above present-day mean sea-level rise.

They assessed New Zealand’s exposure to coastal flooding from extreme sea-level elevation and incremental sea-level rise using a two-step process:

  • First, it maps the land exposed to coastal inundation from 1% AEP extreme sea-levels and those of gradual sea-level rise increments.
  • Second, it identifies and enumerates populations, built assets and land cover exposed to coastal flooding at present-day mean sea-level (MSL) and future higher sea-levels, and national, regional and territory levels using coastal maps, graphs, and tables.

NIWA’s report provides comprehensive data on the exposure of New Zealand to coastal flooding from extreme sea-level elevations and various increments of sea-level rise.

They used available satellite and airborne digital elevation models to create coastal maps, identifying areas, population, and assets such as buildings, transport networks, electricity grids, and three-water infrastructure that are exposed and at risk to coastal inundation.

This report will help researchers and practitioners locate high-risk areas that need continued focus and investigation due to climate change.

The study also recommends that coastal inundation maps and information in the study should be updated as new LIDAR data is made available.

Read the entire report by clicking on the link below:


Paulik, R., Stephens, S., Wadhwa, S. et al. (2019, March). Coastal Flooding Exposure Under Future Sea-level Rise for New Zealand. National Institute of Water and Atmospheric Research. The Deep South Challenge. Retrieved from


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