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Coastal flooding

On this page: What causes coastal flooding, What we are doing, Useful links

Photograph of flooding, Firth of Thames

Coastal flooding is a natural hazard in the Waikato region. In the Waikato region coastal flooding is more likely to occur in:

  • the low lying areas around the Firth of Thames (including State Highway 25)
  • some eastern Coromandel Peninsula settlements
  • large, intensively farmed flood plains in the Hauraki district which are near sea-level.

High tides can also affect river flooding, increasing water levels some way up a river from where it flows into the sea.

As well as threatening people’s lives and property, coastal flooding has an economic and social effect on communities, including the:

  • damage or loss of personal belongings
  • cost of repairing houses, buildings, roads and other infrastructure
  • clean up of debris.

What causes coastal flooding

Coastal flooding can be caused by storm surges, sea level rise and tsunami:

Storm surges

Storm surges are a main cause of coastal flooding. The biggest floods occur when larger-than-normal tides (‘king tides’) and storm surges occur at the same time.

Sea level rise

Sea level rise is a relatively slow process, connected to climate change, which may increase the frequency and severity of storms, bringing unusually high tides, and changes in winds, waves and currents. Sea level rise may also increase the severity of tsunami. In some low lying areas, stop banks have been erected to protect against coastal flooding. However, many of these have not be designed to be effective against a significant change in sea level. Check out our new coastal inundation mapping tool which indicates how future sea level rise could affect low lying coastal areas. 


Tsunami are giant waves that can flood coastal areas. They can occur after earthquakes, volcanic eruptions, and deep sea landslides. To date tsunamis have not been recorded as a reason for any significant coastal flooding in our region’s coastal marine areas.

Coastal flooding can also threaten lifeline services such as water, power, telecommunication and transportation networks. The Waikato Lifeline Utilities Group website has more information about managing lifelines to deal with unexpected emergency or natural hazard events.

For more information, see our coastal indicators. Check out our publications pages to order copies of our Coastal Flooding Risk Mitigation Strategy, Coastal Hazards and Development Setback Recommendations and our coastal hazard factsheets.

Find out more about coastal development in the Waikato region.

What we are doing

Setback lines

Waikato Regional Council has produced Development Setback Lines for Coromandel beaches, which indicate the safe distance from the shore to erect buildings and other structures. These lines aim to protect the beach environment and people’s properties, taking into account coastal flooding and erosion.

Two types of setback lines have been developed:

  • Primary Development Setback (PDS) Lines identify land at risk from natural beach erosion under existing conditions.
  • Secondary Development Setback (SDS) Lines include additional land at risk from the effects of sea level rise and climate change in the next 100 years.

Find out more about our Coastal Hazards and Development Setback Recommendations, and check out setback distances for eastern Coromandel beaches.

Tide information

Waikato Regional Council measures tide information in three areas:

This information ties into our flood management and 0832 Infolines service, providing warnings of potential coastal flooding. We also keep people updated on flood levels during a flood event.

Risk mitigation plans

Waikato Regional Council develops risk mitigation plans to minimise the effect of natural hazards on the Waikato community and economy.

Response and emergency management staff

Regular training exercises for response and emergency management staff maintains expertise by:

  • using knowledge and experiences gained during previous emergencies
  • testing our response plans.

Civil Defence and Emergency Management

Waikato Regional Council's Civil Defence and Emergency Management involves:

  • assessing the risks of an emergency occurring
  • reducing those risks and minimising the impact of emergencies
  • working together with other organisations to respond to routine incidents
  • helping communities to recover as quickly as possible.

For coastal hazards policy information, see section 8 of our Regional Coastal Plan and sections 3.5 and 3.8 of our Regional Policy Statement.

Useful links