Coastal development and climate change in SA

Coast Protection Board Coast Protection Board was established by the Coast Protection Act 1972 Administrative and technical support provided by DEH Key Duties of the Board include : Protecting and restoring the coast (working with councils) Developing the coast for aesthetic and other purposes Providing advice to the Minister Undertaking research Providing responses to development application referrals

Coastal Planning Information Package Coast Protection Board Coastal Management Branch Coastal Development Applications Planning Policy Where to find it: ‘Coast and Marine’ section of the Department for Environment and Heritage website (under Coastal Management) http://www.environment.sa.gov.au/coasts/index.html

Development assessment Development on ‘coastal land’ is referred (with some exceptions) The Coast Protection Board may direct refusal or conditions if the proposed development involves: Excavating or filling of land of more than 9 cubic metres within 100 metres landward or three nautical miles seaward of the mean high water mark, or: Construction of coastal protection works within 100 metres landward or one kilometre seaward of the mean high water mark. Otherwise, planning authorities need only have regard to the Board’s advice

Coastal hazards The Board concerns itself with ‘sensitive coastal features’: these include coastal hazards: Coastal Acid Sulfate Soils (CASS) Flooding Erosion Sand drift Climate change impacts (which exacerbate the latter three)

Climate change Impacts from climate change will be the single biggest threat to coastal development and infrastructure Board policies have been in place since 1991 to ensure that new development is not located so that it will be threatened by current and future coastal hazards The Coast Protection Board has currently established a Sea Level Rise Advisory Committee to review its sea level rise and climate change adaptation policy in 2008-09.

Impacts of climate change Sea Level Rise: global sea level currently rising at 3-5 mm per year, but accelerating Storm frequency and intensity possible decreased frequency but increased intensity Consequences: coastal flooding and erosion migration of tide dependent habitats Levees, road construction etc may constrain retreat of saltmarsh and mangroves

Sea level rise IPCC 2007 gives lower projections that previously (up to 0.59m), because it neglects aspects of land-based ice melt (tentative allowance of 0.1-0.2m), as the uncertainties are considered too large The IPCC states that ‘The projections do not include uncertainties in climate-carbon cycle feedbacks nor the full effects of changes in ice sheet flow, therefore the upper values of the ranges [tabulated by the IPCC] are not to be considered upper bounds for sea level rise.’ For all scenarios, sea level is projected to continue rising beyond 2100

IPCC sea level rise projections, 2001

Emissions Sea level rise

Coast Protection Board’s sea level rise policy A 0.3m rise in sea level to 2050 A further 0.7m in the following 50 years Include an allowance for local and/or regional land subsidence

Effect of sea level rise on storm return intervals

Effect of sea level rise on storm return intervals

Effect of sea level rise on storm return intervals

Coastal Flooding The Pines, Yorke Peninsula 1981

Flooding: storm surge Storm surge is an increased water level over predicted tide height during storms Storm surge is included in the determination of the ARI water levels Mean sea level

Wave effects on flooding Wave runup: rush of water up the beach Wave setup: locally raised water level from wave breaking

Lack of setback and elevation Lucky Bay, Eyre Peninsula The seawall is obscured by seagrass wrack, which has been cast by storm waves

The consequences of protection failure Levee breach at Gillman 1994

Coastal erosion Semaphore Park after 1981 storm

Erosion and sea level rise The “Bruun rule” predicts recession of sandy coasts with changed water levels

Insufficient setback for erosion Lucky Bay, Eyre Peninsula The unprotected coast has eroded beyond the alignment of the shacks, protected by an ad-hoc seawall

Erosion example: North Shields North Shields, Eyre Peninsula Eroding cliffs supply sediment to the adjacent coast, maintaining the foreshore

Coastal erosion and storms Storms erode sediment from the upper beach/dunes and deposit it offshore Calmer weather often pushes this material back onto the beach Erosion buffer should allow for this dynamic process

Storm erosion The Pines, Yorke Peninsula The sand eroded from the dunes can be seen as raised levels at the top of the beach

What’s wrong with this picture?

Impacts of climate change Increased aridity: Southern coastal regions around Eyre Peninsula and far SE have experienced drying trends since 1950 Rainfall for SA within 200 km of coast projected to change by between –10 and 0% by 2030 and between –30 and –3% by 2070 Annual average temperatures for SA within 200 km of coast projected to increase from 0.2 to 1.6C by 2030 and 0.5 to 4.7C by 2070 Consequences include: Increased sand drift

Increased sand drift Svy Map 37/ 19248 - 15/3/1945 Svy Map 4943/367 - 28/4/1995 Shoreline and dune instability near Tilley Swamp, SE

Increased sand drift Lake George, South-east

Increased sand drift Brighton – turn of century

Implications for coastal development A one-size-fits-all approach is not suitable for assessing coastal hazards New development (other than infill) should only be located where protection will not be required Site and floor levels are included in Development Plans where practicable Erosion, dune drift and CASS investigations are more complex, requiring expertise Protection strategies should be prepared by qualified engineers Major developments (such as new communities) should allow for 200 years of sea level rise and erosion

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