Rising sea level, coastal and ocean changes

A warmer climate is melting land-based ice, increasing the amount of water flowing into our oceans and directly heating the oceans themselves, causing them to expand. This is already impacting coastal and low-lying areas.

Expected impacts  

• The sea level around our district is expected to rise over time by:  
  • 14 to 23 cm by 2050
  • 28 to 63 cm by 2080
  • 38 to 100 cm by 2100.
• Waves and storm surges could have a bigger impact on coastal areas as the sea level rises.  
• Groundwater can be closer to the surface of the ground, which can impact drainage and building foundations.
• Saltwater could move further upstream, and groundwater may become saltier.
• Seawater will be warmer, and more marine heatwaves could happen, affecting marine ecosystems and weather.  
• Oceans are becoming more acidic because more carbon dioxide is being absorbed by the ocean, producing carbonic acid.
• Land in our district is moving up in some places and down in others – a process called vertical land movement. This can occur quickly following an earthquake, but also gradually over time. This varies across our district and means that, where our coastline is sinking, sea-level rise can happen faster. When considering the impact sea level can have, it’s important to understand vertical land movement and other coastal processes. Learn more about vertical land movement in Christchurch [PDF, 818 KB].

What this means

• More frequent and severe coastal flooding can affect people’s wellbeing, homes, infrastructure, businesses and coastal ecosystems.
• Salty groundwater close to the surface could damage buried pipes and the foundations of buildings and roads. Rising damp can result in cold, damp homes which are harder to heat.  
• Higher sea levels increase risks associated with flooding, tsunami and storm surges.
• More areas of long-term standing surface water may increase flooding risks and attract insects such as mosquitoes.
• Coastal flooding and erosion may lead to loss of road access to communities in Banks Peninsula.  
• Coastal and low-lying communities would need to adapt to sea-level rise or may need to relocate.  
• Our population may grow due to climate refugees arriving from other countries.  
• Saltwater entering rivers can change freshwater ecosystems.
• The diversity, abundance and location of fish and seabirds around New Zealand could change, affecting ecosystems and food supplies.
• Marine species that form shells, including plankton and crustations which support ocean food chains, may gradually decline due to increased water acidity, significantly affecting life in the ocean and global food supplies.
• Warmer and more acidic water can impact aquaculture and fishing industries.
• Wāhi tapu, wāhi taonga (places sacred to Māori for traditional, spiritual, religious, ritual or mythological reasons) and cultural landscapes may be adversely affected or lost.  
• Some species, taonga (treasures) and mahinga kai (food gathering) could be lost.

What you can do

• Avoid living, building or investing in areas that are highly vulnerable to coastal hazards. Understand how rising sea levels could impact Christchurch at our Coastal Hazards online portal(external link).
• When building a new home in a flood management area, you must raise the height of your home. Learn more about floor-level requirements(external link).
• If you live close to the sea and you experience a strong or long earthquake, or if an official tsunami warning is issued, urgently and safely move to higher ground. Have a plan to evacuate from tsunami. Learn more about tsunami evacuation zones and routes(external link).  
• Get involved in decision-making about the long-term responses to sea-level rise and coastal hazards. Learn more about sea-level rise and the coastal hazards facing our district(external link).  
• Help care for our natural coastal buffers and ecosystems such as sand dunes and coastal landscapes. We host regular planting days and support community care of our coastal areas. Learn more about Coast Care(external link) and the Whaka-Ora Healthy Harbour Partnership(external link).

What we’re doing

• Coastal Hazards Adaptation Planning Programme – We’re working with communities to better understand and prepare for the ongoing impacts of climate change in coastal areas. This includes education activities for the community and the development of adaptation plans for public assets, like walking tracks, jetties and pipes, in at-risk locations. Learn more about how we’re adapting to coastal hazards(external link).
• Managing development in vulnerable locations– We have some existing planning rules and regulations for development in areas vulnerable to coastal hazards, such as requiring raised floors, but we don’t currently manage all of the locations or activities at risk. We’ve recently added some controls limiting housing density in high-risk areas and we’ll be looking at further changes in the coming years. Learn more about the Christchurch District Plan(external link).  
• Sand dune and coastal restoration– We’re working with the community to boost our natural defences against sea-level rise, storms and tsunami – for example, by restoring sand dunes and coastal planting. Learn more about coastal restoration(external link).