coastal climate change impacts in south australia

www.environment.sa.gov.au

Coastal Climate Change impacts in South Australia

Murray TownsendManager, Public Land and Coastal Conservation

Department of Environment, Water and Natural Resources

Global SLR Summary• Increasing evidence that the SLR projections in

the IPCC assessments are underestimates.• Greatest uncertainty comes from Greenland

and West Antarctic ice sheet contributions.• Emissions and SLR observations are tracking

at, or above, the ‘worst case’ IPCC scenario. • SLR will continue to rise for several centuries

after global temperatures have been stabilised

2100 sea level rise projections (USACE 2011)

The South Australian Perspective

Sea level rise:• Estimates from tidal records indicate global rate of

SLR in the 20th century was 1.7mm per year.(South Australia 1.5mm/yr)

• National Tidal Centre’s SEAFRAME project has been using a network of satellite calibrated tidal stations to accurately measure SLR since early 1990s.

Net relative sea level trend at SEAFRAME sites in Australia (mm/yr) July 1992 to June 2011

North Glenelg

Current average sea level (2009)

Projected average sea level (2100)

North Glenelg

Implications for the Coast

Higher sea levels can mean:• Increased severity and frequency of sea flood

events.• Increased coastal erosion.• More difficult to maintain sandy beaches

Port Adelaide Seawater – Stormwater flood

mapping

100 year ARI storm, 50cm SLR,

21cm subsidence

Marion Bay

100 year ARI storm, current sea level

Yorke Peninsula Sea Flood Risk Mapping

Marion Bay

100 year ARI storm, 1.0m sea level rise

Storm Damage - erosion

North Glenelg, 1964

Implications for the Coast

Higher sea levels mean:• Landward migration of intertidal ecosystems

eg. Mangroves, saltmarsh• Higher groundwater levels.• Increased wave overtopping of protection

structures.

Port Wakefield

Rising groundwater

Wave Overtopping

The Broadway, Glenelg South

Coast Protection BoardThe Board’s strategic direction:1. Ensure that new development is not placed at

risk from coastal hazards (including climate change impacts)

2. Develop and act on strategies to protect existing at-risk development

3. Allow coastal ecosystems to adapt to the impacts of climate change (retreat, migration)

Coastal Development Policy

• The Board’s “Policy on Coast Protection and New Coastal Development” requires new development to allow for SLR.

• The Policy was endorsed by the SA Govt in 1991.• Relevant provisions were included in Development

Plans state-wide in 1994 by Ministerial DPA.

New Coastal Development

• Must allow for 0.3m of SLR, and able to be protected “by reasonable means” from a further 0.7m.

• Must allow for erosion, including effects of SLR.• Should not compromise ability of ecosystems to

adapt to climate change (eg mangrove migration)• Major developments must consider “full range of

possible climate change and sea level rise effects”.

The Board/DENR aims to minimise exposure of development and communities to coastal hazards

The Board is a referral body for developments in coastal zones - has power of direction under certain conditions, advice in others.

In 2010, of the 199 development applications referred to the Board, 83.5% of decisions were made in accord with Board advice.

New Coastal Development

ConsequencesIn the 1991 SA Government Policy on coast protection and

new coastal development:• “(The Board) does not consider that State Government

funds should be available for protection of new development approved unwisely and against the Board’s or Department’s advice.”

• “The Board considers it beneficial to retain the nexus between authority for approving coastal development and responsibility for the consequences of decisions made.”

Existing Coastal Development

• Board’s role is to coordinate the identification of areas at risk and the preparation of response strategies.

• Provides grant funding for investigation of adaptation strategies and implementation of protection works.

• Keen to leverage C’wealth funds, e.g. NDRGS.

Hazard assessment

Previous and current work informs coastal zoning to identify areas subject to current and future hazards

In these zones, the Board’s policies should apply

Need high resolution flood mapping (digital elevation models and bathymetry) to better define hazards and guide responses.

The future?

Development of human societies occurred during a 6,000-year period of stable sea level – this is not a luxury we will enjoy for some centuries.

Demand to protect existing communities might exceed capacity to do so.

Seek common strategic ground to minimise occurrences of emergencies – prevention rather than response.

Questions