Mclean r 20150708_1730_upmc_jussieu_-_amphi_herpin
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Transcript of Mclean r 20150708_1730_upmc_jussieu_-_amphi_herpin
Roger McLean School of Physical, Environmental and Mathematical Sciences
University of New South Wales at the Australian Defence Force Academy
Canberra, ACT 2610, Australia
Towards a coastal vulnerability
typology for small islands:
assessing island diversity (and
similarity) via a common framework
Wed 8 July Landscapes of Our Common Future:
Session 2210:Coastal Impacts of Climate Change
Our Common Future under Climate Change
1. Need to acknowledge the heterogeneity and
complexity of small island states and territories
2. Need to better understand within
country/territory differences in vulnerability
3. Need to include a range of climate-change
related projections and not just temperature and
sea level
IPCC AR5 WGII – Chapter 29 Small islands
One of the key messages Small islands do not have uniform climate
change risk profiles.
Research and needs challenges:
Australian Government
responded through the
Pacific-Australia Climate
Change Science and
Adaptation Programme
(PACCSAP) funded by AusAID
administered by Department
of the Environment).
Commissioned regional study
of coastal susceptibility
based on geomorphic
characteristics of Pacific
Islands and climate–ocean
drivers.
Aims of project:
1. Identify typical island types for 15 partner
countries in Pacific – data base of 1532 islands
2. Develop a regional-scale ‘indicative susceptibiity’
of island coasts using simple criteria
3. Identify key climate-ocean processes now and in
the future that can result in coastal change
4. Develop a regional-scale ‘coastal sensitivity’
based on geomorphic characteristics and
relevant climate-ocean processes
5. And ultimately develop a regional coastal
vulnerabiiity assessment
1. Island Types
Based on two criteria:
Lithology (rock type)- 5 types • volcanic
• limestone
• composite
• unconsolidated sediment (reef)
• continental
Elevation • high > 30 m above sea level
• low < 30 m above sea level
8 Island types
1/2. Volcanic High and Low Islands: Islands composed of at least 80% igneous rock with 30m above MSL to separate high and low islands
3/4. Limestone High and Low Islands: Islands composed of at least 80% calcareous rock with 30m above MSL to separate high and low islands.
Bellona, Solomon
Islands
Luon. Solomon
Islands
Tomowas, Federated
States of Micronesia
Lifuka, Tonga
Aniwa, Vanuatu
5/6. Composite High and Low Islands: Islands composed of both volcanic and limestone rock types with each type being <80%, with 30m above MSL to separate high and low islands
7. Reef Islands: Islands composed of at least 80% unconsolidated sediments and < 10m high.
Aitutaki, Cook
Islands
Onotoa, Kiribati
Vaitupu, Tuvalu
8. Continental Islands: Islands composed of at least 80% continental rocks e.g granite (Grande Terre, New Caledonia)
Island Types
Island types
by area
Island types
by number
Island types
in 15 Pacific
Island
Countries
by number
Island types in
15 Pacifc
Island
Countries by
area
2. ‘Indicative Susceptibility’ of Island Types
Certain island types are inherently more susceptible (less
resistant) to physical change than others.
Four variables:
• lithology/rock-type (for erodability-hard rock to soft
sediment; drainage-surface/subsurface)
• maximum elevation (higher less susceptible)
• island area (larger less susceptible)
• island shape (circularity) (angular more susceptible has
longer shoreline)
were used to develop a measure of indicative susceptibility.
A five-point scale susceptibility rating was derived for all
1,532 islands and for the island types within each country.
‘Indicative’ Susceptibility
Luon V 2 0.9 1 49 m 2 5 km2 4 Total 9 Low
Bellona L 4 0.7 2 79 m 2 23 km2 3 Total 11 Mod
Onotoa R 5 0.2 4 2 m 5 4 km2 4 Total 18 V
High
Island ‘Indicative Susceptibility’
Downscaling Indicative Susceptibility: 6 criteria
Adding more
criteria (11) Backshore: height
,sediment
Intertidal: platform
mangrove
Reef: fringing, barrier
Subtidal: slope
Coastal Sectors
Luon Island
• volcanic
• sheltered
• fringing reefs
• rocky bluffs
• 3 coast types
• 6 sectors
• all moderate
susceptibiity
Aitutaki
• composite
• 2 contrasting
island types
• 11 coastal
sectors
Susceptibility
1.1 High
1.2 & 3 Mod
2.1-2.5 Low
3. Climate-ocean processes that result
in coastal coastal change:
present and future
• Tidal type and range
• Ocean waves and swell
• Tropical cyclones
• Sea level and ENSO
Diurnal: Lonbrum PNG
Tidal type
Semi-diurnal Betio Kiribati
Tidal Range (m)
Pacific Wave Climate
1.Trade wind waves
2.Westerly storm waves
3.Distant- source swell
4. Tropical storm waves
Sea Level
Change
1993-2009
Average sea
level with
ENSO phase
El Nino
La Nina
Sea Level • Global sea level will continue to rise and likely accelerate.
• Projections for 2081-2100 (relative to 1986-2005) range from
0.26-0.55 m (RCP 2.6) to 0.45-0.82 m (RCP 8.5).
• Strong regional deviations from global projections of 10-20
% can be expected in tropical Pacific.
• ENSO will remain dominant driver inter-annual variability
Tides • Tide character unlikely to change except in enclosed seas
• Effect of sea-level rise felt most in areas of low tidal range –
base of mean tidal envelope could be raised
above present MSL or even high water.
Projected changes to climate-ocean
processes to 2100
Waves • Decrease in Hs of c.7% (0.1m) along the equator .
• Pole-ward shift in extra-tropical cyclone belts-reduce
damaging distant-source swells.
• Increase in trade winds in SH subtropics.
• Decrease in Hs over most oceans but increase in
Southern Ocean affects south coasts of islands.
Tropical cyclones and storms • Global frequency expected to decrease or remain
unchanged.
• Global increase in TC intensity/maximum wind speed.
• Equator-ward movement of TC tracks in NH;
pole-ward in SH.
Incorporates 2 main factors into measure:
1.Indicative susceptibility of islands/coasts
2.Key projected coastal processes in Pacific
Water level: Tide range + ENSO range
Waves: Wave height (Hs) + TC
Sea-level: Sea-level change + max tide
4. Coastal (Geomorphic) Sensitivity
to Change
Composite Water Level
Tide range + ENSO range
TC frequency + Wave height
Projected sea level
2055 with high tide (m)
Coastal (geomorphic) sensitivity
Summary: Developed a consistent and
defensible framework towards a regional
vulnerability assessment. But it falls short.
Need:
1.To develop a coastal typology
(like the island types) that is
appropriate
across the region (25 to 30 coast types)
2. To add human factors- settlement,
land use, population, infrastructure
etc
3. Upscale from coastal segment to whole
island to all islands
Thank You
Thanks to colleagues Patrick Nunn, Laiit Kumar, Ian Eliot.
And to Neil Lazarow, Kiri Yapp, Sam Hussey-Smith, Dominic
Ransan-Cooper, Lalarge Cherry of the Australian Govt
Department of Climate Change and Dept of the Environment