Sea-level rise | AdaptNSW

Key points

Sea levels are rising primarily due to climate change, which causes the thermal expansion of seawater and melting of land-based ice. This rise is projected to accelerate over the coming decades and to continue for centuries.
The impacts of sea-level rise may include inundation of low-lying areas and more frequent, deeper and extensive estuarine inundation. Rising sea levels may also lead to shoreline retreat, where sandy beaches migrate landward, and increase coastal erosion.
These physical changes pose risks to infrastructure, industries, coastal communities and ecosystems – including damage to homes, roads, tourism and natural habitats.
Considerable development along the NSW coast is increasingly at risk from inundation and erosion as sea levels rise. Around 80% of the NSW population live within 50 km of the coast, with the highest exposure occurring near estuaries, where low-lying development is concentrated.
Even if global greenhouse gas emissions are reduced, sea-level rise is expected to continue. As such, adaptation planning to manage ongoing coastal change is essential. This is being carried out through the NSW Coastal Management Framework, research, and raising community awareness initiatives focused on sea-level rise impacts.

The impact of sea-level rise in NSW

Sea-level rise is projected to result in higher, more extensive and more frequent inundation, with low-lying areas being more vulnerable to chronic problems associated with prolonged inundation and waterlogging.

Sea-level rise will also exacerbate the impacts of extreme weather events, by raising the baseline water level. This leads to higher storm surges, more intense coastal erosion and inundation, and greater damage to infrastructure, beaches, and ecosystems.

Impacts on people

State-wide exposure assessments indicate that while both erosion and inundation are significant concerns, long-term risks are greatest around estuaries due to increasing inundation.

Exposure to sea-level rise is projected to intensify over time, with higher levels of exposure linked to higher greenhouse gas emission scenarios. Regional differences in exposure reflect variations in coastal geomorphology, elevation, and development patterns.

In some estuarine areas, the number of days with some inundation of low-lying streets has more than doubled over recent decades.

Both erosion and inundation pose risks to infrastructure, including homes, roads, and essential services such as sewerage systems. Sea-level rise also threatens coastal areas that hold cultural significance and support social activities.

Impacts on industry and the economy

Sea-level rise poses a growing threat to agriculture, commercial precincts and light industrial areas located in low-lying coastal zones. Sea-level rise will also have major impacts on existing and future coastal developments. In addition, loss of beach amenity due to shoreline recession and erosion is expected to impact the tourism and recreation sectors, particularly in coastal regions where local economies depend on beach-based visitation.

Impacts on the environment

Sea-level rise will reshape coastlines, tidal rivers, and lagoons, driving ecological changes – including in areas protected under international agreements. Sea-level rise will also likely increase erosion and inundation of foreshore habitats and degrade water quality as saltwater intrudes further upstream into freshwater environments.

Intermittently closed and open lake and lagoons, widespread across NSW and beyond, are especially sensitive to sea-level rise due to their shallow depths, strong stratification, long residence times when closed and highly variable entrance states. Even small changes in wave energy or tidal influence can trigger morphological changes at the estuary mouth, altering estuarine hydrodynamics and driving cascading impacts on water quality and overall ecosystem health.

Some foreshore habitats, such as mangroves and saltmarsh, may adapt to low rates of sea-level rise. However, under higher rates, space may need to be set aside to allow these systems to migrate and persist.

Many coastal areas support species that are critical to food webs, including the juvenile stages of marine and terrestrial fauna. Degradation of these habitats under sea-level rise could have far-reaching ecological consequences and adversely affect associated industries.

Projected sea-level rise along the NSW coast

There is a direct relationship between climate change and sea-level rise. As the climate warms, sea levels rise primarily due to thermal expansion (as water warms, it expands) and the melting of land-based ice, including glaciers and ice sheets, which adds volume to the ocean.

Sea-level rise is also affected by local oceanographic processes, such as changes in ocean currents, and by vertical land movements (e.g., subsidence or uplift), which influence relative sea level at specific locations.

Sea-level rise is projected to accelerate over the 21st century. The most recent sea-level rise projections are from the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, and are available from NASA Sea Level Projection Tool.

For example, by 2100, sea level at Port Kembla is projected to rise by:

0.23–0.56 m under low-emissions scenario (SSP1-2.6)
0.37–0.73 m under a medium-emissions scenario (SSP2-4.5)
0.50–0.91 m under a high-emissions scenario (SSP3-7.0)
0.59–1.04 m under a very high-emissions scenario (SSP5-8.5).

These projections are relative to the 1995-2014 baseline, a reference period against which future changes are measured.

Projections depend on the level of future greenhouse gas emissions and level of socio-economic development. IPCC modelling suggests slightly higher sea-level rise to the north of the state and slightly lower to the south.

In the longer term, the IPCC data show global mean sea level is committed to rise for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and will remain elevated for thousands of years.

Adapting to sea-level rise in NSW

Adapting to sea-level rise requires coordinated action from governments, communities and individuals.

In NSW, the framework for managing sea-level rise and coastal hazards includes:

Considering sea-level rise when planning future developments is essential. For example, areas that are projected to be affected by sea-level rise can be mapped as vulnerable areas where coastal hazards need to be considered before development being allowed and zoned appropriately in Local Environment Plans. NSW government resources include a toolkit with information and guidance for councils.

Adaptation of existing settlements will also be necessary. Some of the options include raising houses and roads, installing tidal gates to restrict ingress of tidal water into stormwater systems, building levees and sea walls and undertaking beach nourishment.

Maintaining healthy coastal ecosystems can reduce the impact that sea-level rise has on surrounding areas. We can support coastal and estuarine ecosystems to help maintain natural defences. We can do this by:

maintaining or expanding coastal buffer zones
replanting and protecting coastal dunes
fencing creeks and rivers to keep livestock out
controlling invasive species
protecting and restoring mangroves and salt marsh areas.

Raising awareness of sea-level rise impacts in coastal communities is an important part of adapting. Community education programs help people understand how sea-level rise could impact them and what is being done to manage it. People who are informed are more likely to support policies or projects which aim to manage the impacts of sea-level rise.