Sea level rise map: official coastal hazard maps by state

There is no single official sea level rise map for Australia. Each state publishes its own coastal hazard mapping, built on its own sea level rise allowance and drawn for its own planning rules. Queensland maps storm tide and erosion areas that include 0.8 m of sea level rise by 2100. Victoria publishes coastal inundation mapping for sea levels up to 0.82 m higher, and plans for at least 0.8 m by 2100. South Australia plans for 0.3 m by 2050 and 1 m by 2100, through a Coastal Areas Overlay. Tasmania maps coastal inundation and erosion hazard bands in its planning scheme. Western Australia's State Coastal Planning Policy plans for at least 0.9 m by 2110, and the hazard maps come from each coastal council's coastal hazard risk management and adaptation plan. New South Wales has no statewide allowance, so its mapping comes from councils. To read any of them, check three things: which year and how much rise the map assumes, whether it shows everyday high tides or a storm, and the scale it was made for.

Queensland

Queensland's coastal hazard area maps, used under the State Planning Policy, show:

• Storm tide inundation areas, split into high hazard (one metre or more of water) and medium hazard (less than one metre) in the defined storm tide event, including a 0.8 m sea level rise by 2100
• Erosion prone areas, the width of coast considered vulnerable to erosion and permanent inundation over a 100-year planning period, with a sea level rise component built in

They are in the State Planning Policy interactive mapping system and the coastal hazard map application. Several councils publish their own coastal mapping as well. The Gold Coast, for example, maps storm tide inundation and sea level rise for 2010 and 2100. What the Queensland storm tide maps show in detail is in Queensland storm tide maps and sea level rise.

New South Wales

NSW dropped its statewide sea level rise planning benchmarks (40 cm by 2050 and 90 cm by 2100) in September 2012. Since then each council works out its own allowance for local conditions, through its coastal management program. So the sea level rise mapping you will find is council by council.

Two kinds of official map apply:

• Coastal management areas under the State Environmental Planning Policy (Resilience and Hazards) 2021, such as the coastal environment area and coastal use area. These are statewide and trigger extra matters in development assessment. The one meant for land exposed to coastal hazards, the coastal vulnerability area, has so far been mapped in only a handful of places.
• Coastal hazard or coastal risk maps in local environmental plans, which only some coastal councils have made. Byron Shire, for example, maps tidal inundation hazard now and at 2040, 2070 and 2120.

Coastal matters also appear on the section 10.7 planning certificate, so ask the council for that when buying.

Victoria

Victoria's planning rules require land use and development to plan for sea level rise of not less than 0.8 m by 2100, allowing for tides, storm surge and local conditions on top.

The state's Victorian Coastal Inundation Dataset, from the Future Coasts program, maps:

• land below the projected sea level today and with 0.2 m (2040), 0.47 m (2070) and 0.82 m (2100) of rise
• a 1-in-100 storm tide at each of those four sea levels

The publisher's caveat matters. It is recommended for use at about 1:75,000 or less detail, and it is stated to be not suitable for assessing risk at property level. Use it to understand a stretch of coast, not to decide whether one house floods. For a lot, the planning scheme overlays and the council's coastal or flood studies are what apply.

South Australia

South Australia was the first state to plan for sea level rise, through the Coast Protection Board. Its policy is that new development should be safe from 0.3 m of sea level rise (expected by 2050) and capable of being protected against a further 0.7 m (1 m in total, expected by 2100).

The map that applies is the Coastal Areas Overlay in the Planning and Design Code, which you can view in the SA Property and Planning Atlas (SAPPA). Development in the overlay can be referred to the Coast Protection Board, which applies those allowances.

Tasmania

Tasmania publishes sea level rise planning allowances for each coastal council, and the Tasmanian Planning Scheme maps the hazard in bands:

• Coastal inundation hazard bands (high, medium and low), under the Coastal Inundation Hazard Code. The high band is land reached by the highest astronomical tide now, or by the mean high tide with sea level rise by 2050. The medium band is land vulnerable to a 1% AEP storm in 2050, and the low band land vulnerable to a 1% AEP storm in 2100.
• Coastal erosion hazard bands (high, medium and low) and coastal erosion investigation areas.

These are on the LIST, along with climate change layers showing projected sea level rise and 1% AEP storm tide extents for 2010, 2050 and 2100.

How to read a sea level rise map

1. Find the year and the amount. "2100" on one map can mean 0.8 m and on another 1 m. Read the legend or the notes.
2. Mean sea level or storm? A map of land below a future mean sea level shows where the sea would sit every day. A storm tide map shows where water reaches in a rare storm. The second covers much more land.
3. Bathtub or modelled? Many maps raise water over a ground model and shade everything lower. That ignores seawalls, drains and how long water takes to spread. A modelled study accounts for some of this.
4. Check the scale. A map drawn for a region can be well out at a single lot. If the publisher says it is not for property assessment, take that literally.

The limits

A sea level rise map is a planning tool, not a prediction for your house. It uses one chosen allowance, while the science gives a range: projections for Australian tide gauges run from about 0.4 m to about 0.8 m by 2100 depending on emissions, as set out in sea level rise for an address. A lot outside the mapped line is not guaranteed dry, and a lot inside it is not certain to flood.

Common questions

Is there an official sea level rise map for Australia?

No. Each state publishes its own coastal hazard mapping using its own allowance. Queensland, Victoria and South Australia set statewide allowances, Tasmania sets them by council, and NSW leaves it to councils.

What sea level rise does my state plan for?

Queensland plans for 0.8 m by 2100 and Victoria for not less than 0.8 m by 2100. South Australia uses 0.3 m by 2050, with development capable of protection against 1 m by 2100. Tasmania publishes an allowance for each coastal council. NSW has no statewide figure, and councils set their own.

Can I use a sea level rise map to check one house?

Only if the map is drawn for that purpose. Planning scheme coastal hazard overlays are drawn to apply to lots. Regional maps such as the Victorian Coastal Inundation Dataset are stated by the publisher to be not suitable for property-level assessment.

What is the difference between a sea level rise map and a storm tide map?

A sea level rise map shows land below a future average sea level. A storm tide map shows how far water reaches in a storm, the surge plus the tide, which covers more land. Many planning maps combine the two, showing a storm tide on top of a future sea level.

The Property Report shows coastal hazard mapping where the state or council publishes it for use at lot level, such as Queensland's storm tide hazard and erosion prone areas, the NSW coastal SEPP and LEP coastal maps, and Tasmania's coastal inundation and erosion bands. Regional maps not meant for a single property, such as Victoria's coastal inundation dataset, are not reported as a finding for the lot. Pop in your address or check out a sample report.

LayeredGeo's Property Report pulls together public planning and site data for property due diligence across Queensland, New South Wales, Victoria, South Australia, the ACT and Tasmania, so you can understand a place before you commit.

Sources

• Queensland Government. About coastal hazards. qld.gov.au
• Victorian Government. Planning Practice Note 53: Managing coastal hazards and the coastal impacts of climate change. planning.vic.gov.au
• South Australian Department for Environment and Water. How sea level rise impacts development. environment.sa.gov.au
• CoastAdapt. Planning approaches in South Australia. coastadapt.com.au
• Tasmanian State Planning Office. State Planning Provisions fact sheet: Coastal hazards, August 2021. stateplanning.tas.gov.au

About this article. Published by LayeredGeo and written from the published research cited in the Sources section above. It is general information about how property and ground conditions are assessed in Australia, not engineering, planning, legal or financial advice, and it is not specific to any property. Check anything that matters against the source dataset or a suitably qualified professional before you rely on it. If you spot something wrong, tell us at hello@layeredgeo.com.au and we will fix it.

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