Transcript Document

Coastal development and climate
change in SA
www.environment.sa.gov.au
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
2.9
2.7
Water level (m AHD)
Present risk curve + 0.3m
2.5
Present risk curve
2.3
2.1
1.9
1.7
1.5
0
10
20
30
40
50
60
70
Average return interval (years)
80
90
100
110
Effect of sea level rise on storm
return intervals
2.9
2.7
Water level (m AHD)
Present risk curve + 0.3m
2.5
Present risk curve
2.3
2.1
1.9
1.7
1.5
0
10
20
30
40
50
60
70
Average return interval (years)
80
90
100
110
Effect of sea level rise on storm
return intervals
2.9
2.7
Water level (m AHD)
Present risk curve + 0.3m
2.5
Present risk curve
2.3
2.1
1.9
1.7
1.5
0
10
20
30
40
50
60
70
Average return interval (years)
80
90
100
110
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
Shoreline
and dune
instability
near Tilley
Swamp, SE
Svy Map 37/ 19248 - 15/3/1945
Svy Map 4943/367 - 28/4/1995
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
Forum/Questions