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Eastern Seaboard Climate Change Initiative: East Coast Lows Research Program: Synthesis for NRM Stakeholders

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The Eastern Seaboard Climate Change Initiative –East Coast Low (ESCCI-ECL) project is an innovative research program aimed at improving the knowledge of past, current and future projected ECL events along the eastern seaboard of Australia. Importantly it was designed to use these different time scales to provide better information on how ECLs influence coastal zone dynamics and water security. As ECLs are major drivers of ecosystem processes in this region it is imperative that we gain an understanding of them, including their impacts and their variability, and how they will change in the future. This is a necessary step in determining the impacts of climate change on natural and human systems and the implementation of effective adaptation strategies. The ESCCI-ECL project was jointly developed by the NSW Government, the Bureau of Meteorology, and three universities: University of New South Wales, Macquarie University and the University of Newcastle. The vision for the project included four principal themes: - an understanding of the historical and prehistorical (palaeo) climate variability of ECLs - an understanding of how their long-term multidecadal variability influences coastal processes and streamflows - high resolution modelling of projected ECL frequency and intensity in response to climate change - Integration of findings from the above themes into an understanding of the impacts of ECLs on coastal and water resources, and guidance on potential changes to these impacts in response to climate change.
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Eastern Seaboard
Climate Change Initiative
East Coast Lows Research Program
Synthesis for NRM Stakeholders
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This is a synthesis of the current findings and outputs of the ongoing
Eastern Seaboard Climate Change Initiative – East Coast Lows
(ESCCI-ECL) research program. The report was prepared by Peter
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program: Ian Goodwin, Acacia Pepler, Anthony Kiem and Jason Evans
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2
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3
List of figures 4
List of tables 4
1. Introduction 5
1.1 What is an east coast low? 5
1.2 An overview of the ESCCI-ECL research program 6
1.3 How the ESCCI-ECL project area aligns with the East Coast cluster group 7
2. The distinctive climate of the eastern seaboard 9
2.1 Geographical and seasonal differences in ECLs 10
2.2 Classification of ECL types 10
3. Significance of ECLs for the eastern seaboard 12
3.1 Assessing the risk of significant impacts from ECLs 12
3.2 Using climate proxies to reconstruct past climates 13
3.3 The current level of ‘storminess’ compared with the past 14
4. The impacts of ECL types on natural resources 16
4.1 ECLs and coastal systems 16
4.2 ECLs and estuary dynamics 18
4.3 ECLs and water resources 20
5. East coast lows and future projections of climate 22
6. East coast lows and natural resource management 24
6.1 ECLs and natural processes 25
6.2 Using the past climate analysis for NRM 25
6.3 Using the future climate projections for NRM 26
6.4 Future work needed to help guide NRM and emergency services 26
7. Further reading 27
Contents
4
List of figures
Figure 1: Air movement in a low presssure system versus a high pressure system 6
Figure 2: Eastern seaboard 8
Figure 3: East Coast cluster group 8
Figure 4: The warmer waters of the East Australia Current flow southwards along the coast 9
Figure 5: Schematic of the orographic effect of the Great Dividing Range 9
Figure 6: East Coast Lows in cooler and warmer months 10
Figure 7: Mean storm tracks for each classified storm type 11
Figure 8 A comparison of Australian climate variability on a global scale, using annual rainfall
as an example 12
Figure 9: Time series of Normalised extreme storm days per season 14
Figure 10: Storm risk during 1640 to 1650 based on the ECL storm frequency probability analysis 14
Figure 11: Persistent ETL storm wave events cause shoreline to rotate anticlockwise 17
Figure 12: Map for the lower Myall Coast showing the pre 1820s and the 1974 storm scarp 18
Figure 13: Influence of ECL frequency on estuarine structure and conditions 19
Figure 14: Changes in intensity of ECLs for summer and winter from the present to 2030 23
List of tables
Table 1: Seasonal dominance and geographical area of influence of ECL types 11
Table 2: Data on selected decades demonstrating dominant storm type and likely
risk of storm frequency in comparison to the late 20th century 15
Table 3: A summary of the regional variation in ECL types and their impact on coasts and
water resources 21
5
1Introduction
This report is a synthesis of the findings
of the Eastern Seaboard Climate Change
Initiative – East Coast Lows (ESCCI-ECL)
research program. It provides an overview
for natural resource managers and
emergency services on the effects of east
coast lows (ECLs) and how they may alter
under a changing climate.
The eastern seaboard, which is the area of land
between the Great Dividing Range and the coast of
NSW and southern Queensland, is home to almost
nine million Australians and billions of dollars of public
and private infrastructure. A variety of high-impact
weather events occur in this region and generate
damaging winds, flooding, heavy seas and swells
that have significant impacts on the region’s natural
resources, infrastructure and communities. These
high-impact weather events also play a critical role
in water resource management, with many of the
region’s water catchments dependent on being
replenished by the high flows generated by extreme
rainfall events.
The eastern seaboard is susceptible to east coast
lows (ECLs). ECLs are storms which can occur at any
time during the year but are most frequent during late
autumn and early winter and contribute significantly
to annual rainfall totals along the coast and adjacent
ranges. ECLs also cause a significant amount of
damage along the east coast each year through very
high winds, large waves and at times intense flooding,
yet they are also a major source of water for the
reservoirs serving coastal communities. Thus ECLs
have a paradoxical role of being both vital to, and
dangerous for, human activities in the area.
Although these storms are not generally as intense
as tropical cyclones, ECLs tend to impact the more
densely populated and developed latitudes of
Australia’s eastern seaboard, and in any one year
insured losses from ECLs can exceed those of severe
tropical cyclone events. Disaster statistics from the
Insurance Council of Australia show that Tropical
Cyclone Marcia, which was a category five cyclone,
resulted in $522 million of insured losses, while the
ECL that impacted on the Sydney and Hunter regions
in April 2015 led to $922 million of insured losses1.
The major message of this synthesis is that east coast
lows are a very common, prominent and pervasive
feature of the east coast climate, possibly even more
so than are cyclones for our tropical coastal regions.
Research into modern, historical and pre European
climates show us that ECLs are highly variable from
year to year and decade to decade, and that there
is the potential for more intense and frequent storms
than we have experienced in the recent past. It is
therefore vital that management and planning for NRM
and emergency services takes this into account.
1.1 What is an east coast low?
East coast lows (ECLs) or east coast cyclones are
low pressure systems that develop off the east coast
of Australia, from about Fraser Island in the north
down to East Gippsland in the south. East coast lows
often intensify rapidly overnight, making them one of
the more dangerous weather systems to affect the
eastern coast of Australia. At the same time, ECLs are
a very important and significant source of rainfall for
most of the coastal water supply catchments along
the eastern seaboard.
Air pressure is arguably the single most important
element driving local and regional weather. The main
reason for this is that differences in air pressure (the
gradient) drive the strength and direction of winds.
The greater the gradient in pressure the higher the
intensity of the wind. Where the wind originates and
its intensity and direction can have a major influence
on local temperature and weather conditions.
For example, during the summer period hot dry
north-westerly winds from the interior of Australia
can significantly raise local temperatures and lower
humidity.
1. Insurance Council of Australia Ltd 2015, Disaster statistics, viewed November 2015, www.insurancecouncil.com.au/industry-statistics-data/GI-
statistics
6
The air pressure on Earth is not the same everywhere
and at any one time there are areas of high and
low pressure. In simple terms, wind moves (‘blows’)
from areas of higher pressure to lower pressure, in
an attempt to make the pressure in the two areas
equal. In a high pressure system the air tends to move
outwards slightly from the centre and begins to rotate.
In the southern hemisphere, due to the rotation of the
Earth, this air rotates in an anticlockwise direction. For
low pressure systems air moves towards the centre of
the low and rotates in a clockwise direction.
The distribution of high and low pressure does not
only influence the winds. In high pressure systems
air tends to descend, and as it descends it dries
out, leading to clear skies and warmer daytime
temperatures (Figure 1). In low pressure systems air
rises. As it rises, it cools and water vapour condenses
to form clouds, which can lead to rain. Consequently,
the weather affected by a low is often cloudy, wet and
windy.
The more intense the ‘low’, that is, the greater the
pressure gradient from the centre to the outside of
the low, the stronger the winds and the higher the
chance of large rainfall events. The best known and
most extreme low pressure systems in Australia are
tropical cyclones, which are well known for producing
high winds, extreme rainfall and significant impacts.
However, tropical cyclones are not the only significant
low pressure systems to affect Australia, and east
coast lows are weather systems of potentially equal
importance for people living along the eastern
seaboard.
1.2 An overview of the ESCCI-ECL
research program
The Eastern Seaboard Climate Change Initiative –
East Coast Low (ESCCI-ECL) project is an innovative
research program aimed at improving the knowledge
of past, current and future projected ECL events along
the eastern seaboard of Australia. Importantly it was
designed to use these different time scales to provide
better information on how ECLs influence coastal
zone dynamics and water security.
As ECLs are major drivers of ecosystem processes
in this region it is imperative that we gain an
understanding of them, including their impacts and
their variability, and how they will change in the future.
This is a necessary step in determining the impacts
of climate change on natural and human systems and
the implementation of effective adaptation strategies.
The ESCCI-ECL project was jointly developed by the
NSW Government, the Bureau of Meteorology, and
three universities: University of New South Wales,
Macquarie University and the University of Newcastle.
The vision for the project included four principal
themes:
an understanding of the historical and pre-
historical (palaeo) climate variability of ECLs
an understanding of how their long-term multi-
decadal variability influences coastal processes
and streamflows
high resolution modelling of projected ECL
frequency and intensity in response to climate
change
integration of findings from the above themes
into an understanding of the impacts of ECLs
on coastal and water resources, and guidance
on potential changes to these impacts in
response to climate change.
Figure 1: Air movement in a low presssure system versus
a high pres sure system (Pears on Prentice Hall Inc 2005)
7
The NSW Office of Environment and Heritage in
conjunction with the research partners, and with seed
funding from the NSW Environmental Trust, developed
a research program that consists of a suite of inter-
related projects. A description of each of the projects
can be found at www.climatechange.environment.
nsw.gov.au/Impacts-of-climate-change/East-Coast-
Lows/Eastern-Seaboard-Climate-Change-Initiative.
Project 1: Eastern Seaboard Climate
Hazard Tool development
Project lead: Bureau of Meteorology
Project 2: Projections of future ECL
frequency and intensity along the NSW
coast
Project lead: Associate Prof. Jason Evans,
Climate Change Research Centre of the
University of NSW
Project 3: Understanding the long-term
natural variability of ECLs by using palaeo
climate information
Project lead: Associate Prof. Ian Goodwin,
Climate Futures at Macquarie University
Project 4: Regional coastal and estuarine
impacts of extreme ECLs
Project lead: Associate Prof. Ian Goodwin,
Climate Futures at Macquarie University
Project 5: Regional water security impacts
of extreme ECLs on south-eastern
seaboard reservoirs
Project lead: Prof. Garry Willgoose and Assoc.
Prof. Anthony Kiem, University of Newcastle
Project 6: Generic framework to determine
the economic impacts of natural and
human-made disaster events
Project lead: Dr Kevin Roche, Risk Frontiers,
Macquarie University
In addition to seed funding from the NSW
Environmental Trust, the project received funding from
the NSW Department of Finance and Services and
Hunter Water Corporation and was supported under
the Australian Research Council’s Linkage Project
LP120200494 and Discovery Project DP0772665.
Research partners also contributed significant
resources including staff, intellectual property and
research infrastructure.
1.3 How the ESCCI-ECL project area
aligns with the East Coast cluster
group
The ESCCI-ECL concerns itself with the eastern
seaboard of Australia (see Figure 3), with the eastern
seaboard defined as the area that is currently
impacted by ECLs, ranging from the Fraser Coast
in Queensland, south to East Gippsland in Victoria.
Figure 2 shows the study region that was the basis
of the ESCCI-ECL program. Figure 3 shows the East
Coast NRM cluster.
Collaroy-Narrabeen Beach storm e rosion, June 2016 (WRL 2016)
8
Roughly half the East Coast NRM region is affected
by ECLs. This report will focus on a discussion of the
ESCCI-ECL for the whole of the eastern seaboard
area. The reason for discussing the whole ESCCI-ECL
region is that much of the southern part of the East
Coast cluster group, that is, from the Hunter through
to Sydney, is similar to the southern regions of the
eastern seaboard, but distinct from the northern
part of the East Coast NRM cluster in terms of the
frequency and impacts of ECLs.
The Commonwealth funded national NRM climate
change adaptation program has divided the Australian
continent into groups or clusters consisting of locally
led NRM groups (or Local Land Services in NSW). The
aim of this process is to provide these groups with
information that assists them in developing climate
change adaptation programs for their sector. The
East Coast cluster group (see Figure 3) ranges from
the Fitzroy Basin in Central Queensland, south to the
Hawkesbury River Basin near Sydney.
Figure 3 (right): East Coast cluster group. Climate change in
Australia
http://www.climatechangeinaustralia.gov.au/en/impacts-and-
adaptation/east-coast/
Figure 2 (above): South-Eastern se aboard (Coutts-Smith et al 2 011 ).
The distinctive climate of the
eastern seaboard
2
9
The eastern seaboard is a special case in terms
of impacts and climate change because it is
climatologically different from the rest of south-eastern
Australia. An obvious reason for this variation is the
influence of the Tasman Sea and the proximity of the
Great Dividing Range. The Tasman Sea and the warm
East Australian Current (Figure 4) provide sources of
moisture,. The mountains of the Great Dividing Range
provide orographic enhancement. As warm moist
air rises up the mountains it cools and increases the
chance of precipitation (see Figure 5). The mountains
reduce the influence of easterly winds from the
Tasman Sea on the inland, as well as reducing the
influence of westerly winds on the coastal zone.
Another significant reason for the different climatology
of the eastern seaboard is the existence of east coast
lows. ECLs can occur throughout the year but tend
to be more common from autumn through to spring.
Climate drivers such as the El Niño/La Nina cycle,
which are known to have a major influence for most
of eastern Australia, appear to have a very poor
correlation with the frequency and intensity of ECLs.
During particularly dry El Niño periods, when most
of eastern Australia is in drought, it is still possible
for an ECL event to occur that reduces the impact
of the drought on parts of the eastern seaboard. For
example, the ‘Big Dry’ that affected south-eastern
Australia from 1990 to 2005, which was related to a
strong clustering of El Niño events, was much less
severe along the eastern seaboard. In fact, rainfall at
the time was above average for many parts of this
region. The southern part of the eastern seaboard had
high rainfall in 1990 and 1998 while the rest of eastern
Australia was in drought.
Figure 4: The warmer waters of the East Australia Current
flow southwards along the coast. (BOM
http://www.bom.gov.au/oceanography/forecasts/idyoc14.
shtml?region=14&forecast=1)
Figure 5: Schematic of the orographic effect of the
Great Dividing Range (Dr Peter Smith 2016).
Fallen tree damages car (Carlos Amarillo).
10
2.1 Geographical and seasonal
differences in ECLs
There is also a geographical and seasonal variation
in the influence and intensity of ECLs. At its simplest,
there are two zones within the eastern seaboard: a
northern zone starting roughly in the Newcastle area
and ranging north to the Fraser Coast; and the other
from Newcastle south to Gippsland. In the northern
part of the eastern seaboard, ECLs can occur in any
month, while in the southern half ECLs occur more
commonly in the cooler months (Figure 6).
There are also various types of ECL (see Section
2.2) and these develop in different parts of the
region and have different atmospheric conditions
as their precursor. Depending on their origin they
have differing seasonal and geographical impacts
on the eastern seaboard. In simple terms those
storms with a tropical or subtropical origin are more
common and have a greater influence on the northern
part of the eastern seaboard, while those with an
extratropical origin have a greater influence in the
south. Importantly, the impact on our water supply
and our coasts of the different types of ECL is also
not consistent across the entire eastern seaboard.
2.2 Classification of ECL types
As part of the ESCCI-ECL project ECLs have been
classified into five different subtypes.
ECL storm types vary from year to year, and decade
to decade. This makes ECLs and their impacts
difficult to understand and predict.
Easterly trough lows are storms that form
close to the coast in the Pacific Ocean and
track mostly east of the Great Dividing Range
and in a southerly direction. These make up
about 23% of the storm types in the historical
re c ord (18712012).
Southern secondary lows are storms that
form in the southern Tasman Sea or Southern
Ocean and track mostly over the southern
Tasman Sea and in a northerly direction.
These are the most common storm type in the
historical record and account for about 34% of
historical storms.
Inland troughs are storms that evolve mostly
inland west of the Great Dividing Range and
north of 30° south. These comprise about 10%
of the storms in the historical record.
Continental lows are storms that evolve
mostly over the inland west of the Great
Dividing Range and south of 30° south. These
make up 19% of the historical records of ECL
storm types.
Extra tropical cyclones are tropical storms
that form to the north-east of Australia that
sometimes track into the northern part of the
eastern seaboard study region. These make up
about 14% of the historical record.
Table 1 shows the seasonal dominance and
geographical area of influence for each of these ECL
types, while Figure 7 shows the general origin and
average storm track of the various types of ECL.
Figure 6: East coast lows are more frequent in the north during
the warmer months and more frequent in the south during the
cooler months.
11
Figure 7: Mean storm tracks for each classified stor m type:
easterly trough lows (ETL), southern seconda ry lows (S SL), inland
trough (IT ), continental lows (CL), and extratropical cyclones (X TC)
(Browning & Goodwin, 2013).
Table 1: Seasonal dominance and geographical area of influence of ECL types
ECL type Seasonal dominance Regional location of storm activity
Easterly trough low (ETL) All year, autumn to winter peak Fraser coast to mid north coast
of NSW
Southern secondary low (SSL) All year but mid winter peak Central coast of NSW to Gippsland
Inland trough low (ITL) All year but more common in
summer, spring and early autumn
Mid north coast of NSW to Gippsland
Continental low (CL) All year but May to September
dominance
Central coast of NSW to Gippsland
Extratropical cyclone (XTC) Late summer to autumn Fraser coast to far NSW north coast
Significance of ECLs for the
eastern seaboard
3
12
East coast lows play a paradoxical role on the eastern
seaboard. On the one hand ECLs are responsible
for significant damage from high winds, large and
powerful surf, and flooding. On the other hand, they
are responsible for a significant component of the flow
into our water storage catchments. Until a decade ago
we could only give a one day warning of a likely ECL;
with improvements in forecast models, the Bureau of
Meteorology can now predict possible ECLs at least
four days ahead. However, prior to the ESCCI-ECL
project, we did not have the knowledge necessary
to start developing our capacity to give long-term or
seasonal forecasts of ECL’s.
In June 2007, an ECL caused significant damage to
the coast near Newcastle, led to nine deaths and
insurance claims of $1.6 billion, and the grounding
of the Pasha Bulka bulk carrier. In 2008, a series of
storms in south-east Queensland caused significant
flooding and storm damage in Brisbane and the Gold
Coast. In 2015 an ECL centred on the NSW central
coast caused significant flooding and damage from
high winds, with insurance losses of over $900 million.
These weather events also generate conditions
favourable to increased bushfire risk, lightning strike
and strong winds. A study showed that more than six
out of 10 high inflow events into water catchments for
the Sydney region were attributed to ECLs.
3.1 Assessing the risk of significant
impacts from ECLs
To understand the current and future risk we face
from weather events such as ECLs, we need to
consider how large, how often and where storms
are likely to occur. To do this we need information
on the probability of large storms and the clustering
(e.g. the likelihood of storms impacting areas in quick
succession) of large storms. We need to understand
how the climate, and ECLs in particular, have behaved
over long periods of time. One way of doing this is to
use historical data on the occurrence of past storms.
Prior to the ESCCI-ECL project the collation of
information on the historical extent and impacts
of ECLs was either patchy or in formats not easily
interrogated by users. ESCCI-ECL Project 1, led by
the Bureau of Meteorology, was designed to bridge
this gap. It combined a new database of ECLs
with weather impacts across the eastern seaboard.
This database was then made available via the
development of a new online product: Maps and
Tables of Climate Hazards on the Eastern Seaboard
(M ATCHES) (reg.bom.gov.au/climate - login required).
MATCHES linked historical ECL events (1950–2008)
with information on their impacts, and specifically the
location and intensity of heavy rainfall, severe winds,
extreme waves and storm surges. This new tool
provides an easy way to link historical ECLs with their
weather impacts through use of user-defined impact
Figure 8: A comparison of Australian climate variabilit y on a globa l scale, using annual rainfall as an example (Dr Phil Reid, Bureau of
Meteorology, based on the Hulme dat aset https://crudata.uea.ac.uk/cru/data/hrg/).
13
thresholds and an intuitive front-end interface.
Historical weather records in Australia are very limited
and we have a poor understanding of pre-settlement
climate. Added to this, our climate, particularly in
relation to rainfall, is highly variable. In fact, it is more
variable than most other places on the planet (Figure
8). Longer periods of data are required to cover this
variability. This is even more critical for understanding
the risk posed from large and rare events, as their
rarity means we have fewer examples to analyse
impacts.
One technique used by climatologists and water
resource planners to overcome this lack of historical
data is the use of statistical tools and simulations.
By using a process called frequency analysis they
can estimate the probability of occurrence of a given
event, often referred to as the return period. These
are commonly known as the 1 in 10 or 1 in 100 year
events. Events such as the storm that lashed Sydney,
the central coast and Newcastle in April 2015 was
considered a 1 in 10 year event. For these large
events we have very few records to use to make
judgements about their likely impacts.
3.2 Using climate proxies to reconstruct
past climates
Another way to look at the risk posed by large
events and the clustering of large events is to use
palaeoclimatology techniques to reconstruct long-
term data sets on past climates and how these may
have impacted the environment. Project 3 of the
ESCCI-ECL research program, led by Assoc. Prof. Ian
Goodwin at Macquarie University, used palaeoclimate
techniques to examine whether ECLs have been
a long-term climatic phenomenon on the eastern
seaboard. This project also wanted to investigate
what we can understand in terms of the variability
in clustering and intensity of ECLs over a 1200-year
timespan.
Past climates leave an imprint in both the biological
and physical environment and these can help us
glean information about past climates. These imprints
are referred to as climate proxies; one example is
the extraction of climate information from tree rings
using a technique called dendroclimatology. This can
be used to infer rainfall and temperature from the
growth rings of very old living and fossilised trees.
In a similar way, by examining core samples taken
from corals, scientists can find evidence of past
sea surface temperature and variability. Corals also
provide information on a range of other environmental
conditions including sea surface salinity, light
penetration, water depth, and sedimentation. Ice
cores from Antarctica can provide a direct measure
of past rainfall variability and temperature. This is
important because the atmospheric circulation
patterns around coastal Antarctica are linked to
the major circulation patterns around southern
Australia. Therefore data from appropriate locations
in Antarctica provides insights into the climate at the
southern end of continents such as South Africa,
South America, and most importantly for us, Australia.
This project used multi-climate proxies from a range
of sources and locations, such as oxygen isotopes
and tree rings from both sides of the Tasman Sea,
coral cores from the eastern pacific, ice cores from
Antarctica and speleothems from caves in NSW. This
was used to infer the domination of synoptic patterns
for major modes of climate variability, such as the
Southern Annular Mode or the El Niño Southern
Oscillation.
In the context of the past thousand years the project
found that there have been three multi-decadal
periods of high storm activity in the Tasman Sea:
the mid 12th to the 13th century
the middle of the 15th century, and
a group of high storm activity periods between
the 17th century and the beginning of the 20th
ce n tur y.
14
3.3 The current level of ‘storminess
compared with the past
Project 3 found that the recent frequency of ECL
storm activity has been relatively low in comparison
with the most severe storm periods in the past
1200 years (see Figure 9 below). The 17th, 18th
and 19th centuries all had a higher occurrence of
severe storm decades than did the 20th century. The
study found that the early 1970s are a reasonable
example of some of the more extreme storm periods.
Nevertheless the record does indicate that periods of
storm activity more intense than the storm period of
the early 1970s do exist and that it would be unwise
to consider the 1970 storms as examples of the most
extreme storm risk event.
Scientists estimated and compared the number of
storm days per season during each decade. Figure
9 shows the frequency of storm events on a multi-
decadal basis over the last 1200 years. Colour
shading indicates periods of below average storm
activity (green) and above average storm activity
(orange) exceeding the 95% confidence level. The
level of storm activity is not the only indicator of
impact, different types and frequencies of ECLs
occurred with differences in where these storms
impacted the eastern seaboard during the past
periods. As such, the impact of each of these periods
is not consistent for the northern and southern coasts.
Figure 10 shows an example decade (1640-1650)
where the storm risk is different for the northern and
southern parts of the eastern seaboard.
Figure 9: Time series of Normalise d extreme storm days p er season calculated from The PaleoR-Mq Paleoclimate Reconstruction
(Browning and Goodwin, 2015, Goodwin and Browning, in preparation 2016)
Figure 10: Storm risk during 1640 -1650 based on the ECL storm
frequency probability analysis.
15
Table 2 shows selected decadal periods from the
Project 3 dataset against their risk of high frequency
storm occurrence for the northern and the southern
eastern seaboard regions. The coastal storm activity
risk categories use the 1955–2012 median as a
baseline for comparison. From Figure 9 we can see
there was a period of high storm frequency in the
1680 to 1690 period, and this was consistent for
both the northern and southern areas of the eastern
seaboard. Conversely, 1860 to 1870 was another
period of high storm frequency but it appears that
in this period the high storm frequency was for
the northern areas only and the southern regions
had a low probability of frequent storms. Using the
preliminary analysis from the Project 5 team at The
University of Newcastle, led by Assoc. Prof. Anthony
Kiem, we can also assign a tentative ‘risk factor’
to these same periods in terms of the reliability of
streamflow and how that would have affected water
security, i.e. the reliability of adequate water supply for
consumption purposes (Table 2, right-hand columns).
Table 2: Data on selected decades demonstrating dominant storm type and likely risk of storm frequency in comparison to the late 20th century.
Coastal storm activity risk is an assessment of the likelihood of the combination of frequency and magnitude of ECLs causing coastal erosion
in comparison to the risk, with the late 20th century as a baseline. Water security risk is an assessment of the risk that water supply would be
inadequate, at that nominated period, if current level of water demand and storage capacity remaine d the same.
Time period Coastal storm activity risk Water security risk
Northern eastern
seaboard
Southern eastern
seaboard
Northern eastern
seaboard
Southern eastern
seaboard
1955–2012 median
value as baseline
Moderate Low 2005–present – low
1980–2005 – high
1970–1980 Extreme High Low Low
1860–1870 Extreme Low Low Moderate
1680–1690 Extreme Extreme Low Low
1260–1280 Low Moderate Extreme Extreme
A flooded road following heavy rains (Johan Larson).
The impacts of ECL types on
natural resources
4
16
Over the next few decades sea level rise and severe
maritime weather present the largest combined
threats to the natural coastal systems and the
intensely populated areas of the east coast of
Australia. Likewise, the influence of climate variability
on annual and seasonal rainfall and how that might
alter with climate change is of major concern in
planning for water security over the medium term.
In the tropics, NRM and emergency services
managers are well aware of the impact of tropical
cyclones as a major risk factor and as an important
driver of disturbance regimes in natural systems.
As such, cyclones are deeply embedded in our
thinking in those regions. In the same way ECLs
are a prominent feature of the east coast climate,
potentially even more significant for natural resource
management than cyclones are in our tropical coastal
regions, and our management and planning needs to
reflect this.
East coast lows, though often not as large or
dramatic as cyclones, occur more frequently and are
a more consistent and pervasive feature of eastern
seaboard climate. As a minimum, the ESCCI studies
discussed show that ECLs, their origins and their
distribution have significant impacts on water resource
security and coastal dynamics. It is also important to
acknowledge that the impacts of the various types of
ECLs are not consistent across the region, and we
need to tailor our management approaches to reflect
this.
Using the reconstructed climate from Project 3,
both Projects 4 and 5 have used this data to help
understand how the variability in intensity and
clustering of storms have affected coastal processes
and potentially streamflow and water security. Project
4 at Macquarie University, led by Assoc. Prof. Ian
Goodwin, provides information on the influence of
ECLs on wave climate and coastal geomorphological
processes. An understanding of the characteristic
of storm waves associated with the different types
of ECLs has been developed. This includes the
propagation patterns and coastal impacts of such
storm waves. Project 5 is led by Prof. Gary Willgoose
and Assoc. Prof. Anthony Kiem at The University of
Newcastle. This project investigated the influence of
ECLs on precipitation and streamflow in catchments
and how changes to the frequency, timing, intensity,
location, and duration of ECLs can influence water
security.
4.1 ECLs and coastal systems
Coastal systems are dynamic areas and the shape
and location of features such as estuary inlets
and beaches are dependent on a range of factors
including the prevailing wave climate, mean sea level,
ocean currents and sediment supply. Any change to
any one of these conditions will result in a change in
the coastal landform. The result is that changes in
sand based coastal landforms occur on a continual
basis.
Old Bar Beach storm erosion, 7 July 2008 (Coastal Risk
Management Guide, DECCW, Dec 2010).
17
Wave climate, i.e. the size, direction and frequency
of waves as they hit the coast, is a significant
component of what shapes the coastal landform.
Project 4 has reconstructed the storm wave climate
over a period of 500 years and has also analysed
how this has affected the coastal landform along the
eastern seaboard.
ECLs are a significant generator of coastal storms and
waves along the east coast, but the impact of those
storms on the coastline is very much a product of
their type and origin. ECL types with a more northerly
origin, i.e. easterly trough lows (ETLs) and ex-tropical
cyclones, tend to produce wave conditions with a
‘shore normal’ or easterly direction, while those from
the extratropics or of southerly origin produce waves
that are oblique or more from a southerly or SSE
direction. This directional pattern is very significant
in terms of coastal processes and coastal erosion
in the eastern seaboard. In general, periods of low
storm activity such as the 1300–1600 period result in
prograding coastlines (shorelines moving eastwards
into the sea) and a similar sequence was observed
for the 1980–2010 period. Periods of high storm
intensity can lead to either shoreline regression or
progradation, depending on the origin of the storm
and which region of the eastern seaboard is being
considered.
In general, waves from a more easterly direction have
a greater erosive impact on the beaches. Persistent
easterly waves can cause the beach profile to rotate in
an anticlockwise direction as a result of more erosion
of the northern ends of the beach. The Macquarie
University team found that this was the case during
the period from 1600 to the early 1800s, when
there was a pattern of higher frequency and higher
intensity ETLs and inland trough lows (ITLs) than we
have experienced in recent times. The Macquarie
University team have described this as the Coastal
erosion embaymentisation and stationary foredune
aggradation/transgression phase.
Waves that are more oblique, i.e. those that hit the
coast at an angle from the south have less of an
erosive impact on our beaches and can be important
sources of onshore sand transport. Periods of
high southern secondary low (SSL) type ECLs with
southerly direction waves produce conditions suitable
for alongshore sand transport. This can result in
sand deposition in the northern sectors of beaches,
resulting in a clockwise rotation of the beach planform
(Figure 11). The period 1820 to 1900 was subject
to persistent SSL storm types which led to sand
deposition and a clockwise rotation of the beaches.
The Macquarie University team have described this
period as the Coastal recovery, rotation, strandplain
and foredune progradation phase.
The coastal geology and geomorphology studies
carried out in Project 4 indicate that the NSW north
and central coasts were most impacted by storm
events between 1600 and 1820, and from 1820–1900
the south coast was most impacted, as the storm
centres shifted towards the south.
Project 4 also allows us to look at what we might
potentially term the ‘ultimate probable storm’ and the
coastal erosion along the eastern seaboard that would
happen if this were to occur. Up until now, in NSW
the 1974 storms have been typically used to estimate
the maximum measured storm erosion. Using past
climate reconstructions Assoc. Prof. Goodwin’s team
has shown that for large areas of the coastline the
1974 storm did not represent the maximum storm and
in many cases the erosion scarp was further inland
than after the 1974 storm (Figures 11 & 12). At some
sites the 'ultimate' storm cut was more than double
the observed erosion volumes seen in association
with the 1974 storms.
Figure 11: Persistent E TL storm wave events cause the shoreline
to rotate anticlockwise (red line), whilst persistent SSL storm wave
events cause the shoreline to rotate clockwise, and are often
associated with subseque nt storm recovery periods (Goodwin et
al 2015) .
18
Figure 12: Map for the lower Myall Coast, Dark Point to Yacaaba Head showing the pre 1820’s storm scarp (red) and 1974 storm scarp in
blue. This shows the pre 1820’s storm scarp is rotated anticlock wise. Source: Goodwin and Browning 2016.
From this they have recommended that future storm
erosion hazard and risk analysis for the south-east
Australian coast should consider the 1600–1900
period, using clustered statistics for extreme years of
1956, 1967, 1974, 2007 and potentially 2011 and 2014.
Again, there is a difference between the northern
eastern seaboard and the southern. Based on this
work the storm erosion hazard is underestimated for
the northern half of beach compartments on the NSW
central and north coasts and south-east Queensland
coasts, and the centre third of beach compartments
on the NSW south coast.
4.2 ECLs and estuary dynamics
As major drivers of coastal dynamics ECLs will
have a major impact on the ecological functioning
of estuarine environment. Storms and droughts
substantially influence the relationship between the
concentration of fresh versus saline water in estuaries
and can even influence tidal flow via substantial
changes in the geomorphology of coastal estuaries
and wetlands.
These type of changes have been demonstrated
for the eastern seaboard. As part of Project 4, Prof.
Goodwin’s team identified a number of periods
during the last thousand years when modelled data
sugggested ECLs were more frequent and possibly
more intense, resulting in periods where most of the
rivers and coastal lagoons were open to the sea. At
other times, with a lower frequency of storms, many of
these inlets had silted up and were closed off.
Changes in geomorphology have significant impacts
on the biota of these inlets as they alter from saline
and tidal conditions to brackish or even freshwater
environments. During the 1600–1820 period the
estuarine inlets were wide mouthed and persistently
open from frequent fluvial flood discharge. Post the
early 1800s the inlets were frequently closed and
choked by high rates of sand transport.
19
Figure 13: Influence of ECL frequency on estuarine structure and conditions.
Understanding and predicting how individual
estuaries along the eastern seaboard will respond
to the frequency and intensity of ECLs is complex.
It requires a detailed understanding of the direction,
power and frequency of waves and the nearshore and
offshore coastal geomorphology, as well as how the
ECL affects rainfall and therefore streamflow in the
catchment.
Summarised below are the potential impacts of
diferent types of ECLs on the north and south coast.
Persistent southern secondary lows and the south
coast:
High rain in catchments results in regular
flooding opening river mouths and inlets.
Shore oblique waves lead to high levels of sand
deposition in estuary mouths.
Estuaries potentially oscillate between fresh
and estuarine conditions. The more frequent
and intense the storms are in the catchment
the more likely that the estuaries will be open
mouthed.
20
Persistent southern secondary lows and the north
coast:
Shore oblique waves lead to sand deposition in
estuary mouths.
As SSLs tend to produce very little rain, on
the northern eastern seaboard river mouths
and inlets rarely open and estuaries become
freshwater dominated and non tidal.
Persistent easterly trough lows and the north coast:
High storm activity leads to high flows in
estuaries and erosion of sand along beaches.
The resulting conditions lead to more marine or
saline conditions in estuaries and they become
tidal dominated.
Persistent easterly trough lows and the south coast:
The probability of high rain events from ETLs
is lower in the southern eastern seaboard, but
the easterly wave conditions tend to erode
beaches. If these conditions persist they can
lead to intermittent opening of estuary mouths.
High wave power and high catchment flows
are more likely to result in open mouthed
estuaries. The more easterly the direction of
the wave power the greater the likelihood of
beach erosion and salt water intrusion into the
es tuar y.
4.3 ECLs and water resources
Project 5 is ongoing with results expected in late 2016.
However, the preliminary work using the MATCHES
database from Project 1 has indicated that ECLs play
a major role in catchment dynamics along the eastern
seaboard.
In terms of rainfall the eastern seaboard is not
homogenous in space or time – and can be divided
into two regions for summer, autumn and spring:
(i) Moreton (QLD) to Sydney, and (ii) Illawarra to
east-central Victoria; and three regions for winter:
(i) Moreton (QLD) to the Manning region of NSW,
(ii) Hunter to Sydney, and (iii) Illawarra to east-central
Victoria. By separating ECL-related rainfall from the
overall record and comparing the rainfall associated
with different ECL types, it appears that the timing
and location of ECL impacts are the reason for the
non-homogeneous nature of eastern seaboard rainfall.
Further work is now underway using the
palaeoclimate reconstructions from Project 3 to look
at long-term historical variability and how that can
guide water resource planning. As is the case with
coastal processes, it appears that the type of ECL
has a major bearing on which part of the eastern
seaboard is likely to be impacted. Table 3 summarises
the types of ECL, the time of year they are most
common, and how they influence coastal processes
and water security for the northern and southern
sectors of the eastern seaboard.
ECLs are common events and studies of ECL
frequency and their influence on rainfall from 1970 to
2006 by Acacia Pepler and others at the Bureau of
Meteorology (2010) have shown an average of 22 ECL
events each year, of which seven had rainfall of more
than 25 mm. In addition, at least one storm per year
with heavy rainfall over 100 mm occurs somewhere
in the eastern seaboard. ECLs are responsible for
23% of the rainfall in the eastern seaboard and more
importantly 40% of the widespread heavy rain events.
ECLs also feature prominently in terms of high rainfall
events. More than 78% of extreme rain events on the
central coast of NSW were attributed to ECLs and
more than six out of 10 of the high inflows into water
catchments for the Sydney region were attributed to
ECLs.
Hail (sw a182 ).
21
Table 3: A summary of the regional variation in ECL types and their impact on coasts and water resources, based on ECLs bet ween 1950
– 2012 (Kiem et al 2016; Browning a nd Goodwin 2016).
ECL TYPE Seasonal
dominance
Regional
bias for
storm
activity
Proportion
of all ECLs
(197 9 -2 0 11
only)
Summary coastal
impacts
Summary water resource
impacts (heavy rain day =
100 mm or more)
Easterly
trough lows
All year, peak
May/June
Fraser coast
to mid NSW
coast
24% (124
events)
Large and powerful
easterly waves,
anticlockwise rotation
of beaches. Minor
influence in southern
eastern seaboard;
significant influence in
middle and northern
eastern seaboard
44% of ECL heavy rain
days (15% of all heavy
rain days)
Southern
secondary
lows
All year
but peak
in Autumn/
Winter
(April to
September)
From
Sydney to
Gippsland
32% (169
events)
Large powerful waves
from the south,
clockwise rotation
of beaches. Larger
impact on central
and southern eastern
seaboard
9% of ECL heavy rain
days (3% of all heavy rain
days)
Inland trough
lows
All year
but more
common
Spring/
Summer
Nth NSW
coast to
Gippsland
14% (75
events)
SSE direction of waves,
clockwise rotation of
beaches. Influence
more significant from
central to southern
eastern seaboard
21% of ECL heavy rain
days (7% of all heavy rain
days)
Continental
lows
All year
but more
prevalent July
to December
NSW central
coast to
Gippsland
23% (122
events)
SSE direction of
waves, clockwise
rotation of beaches
17% of ECL heavy rain
days (6% of all heavy
rain days) 12% of days
associated with an CL
have heavy rain
Extratropical
cyclones
Summer and
early Autumn
(December to
April)
Fraser coast
to mid NSW
coast
7% (37
events)
Eastern direction of
waves. Can have
large effects on the
far northern eastern
seaoard (Fraser coast
down to Nambucca),
anticlockwise rotation of
beaches
9% of ECL heavy rain days
(3% of all heavy rain days)
17% of days associated
with an XTC have heavy
rain
22
East coast lows are known to be high impact events
leading to significant damages from high wind,
flooding and coastal erosion. The pervasive nature
of ECLs in the eastern seaboard climate mean they
have a significant role to play in ecosystem functioning
across the region. Therefore it is imperative to
understand if the existing pattern and frequency of
ECLs is likely to continue in the future in response to
anthropogenic (human-caused) climate change.
If ECL frequency and intensity decrease there will
be impacts on water security along the eastern
seaboard. A reduction in the frequency of ECLs,
however, leads to less impact on coastal systems
from large wave events.
An increase in the frequency and/or intensity of
ECLs could exacerbate the effects of sea level rise
on coastal erosion, but increase the probability of
maintaining water security into the future.
A significant component of the ESCCI-ECL project
was to look at how the frequency and intensity of
ECLs may change in the future. Project 2, led by Dr
Jason Evans at the University of NSW was done in
collaboration with the Bureau of Meteorology and
the NSW Office of Environment and Heritage. There
are challenges in modelling the impacts of future
changes in the frequency and intensity of ECLs that
relate to their small geographical size (compared to
global models), relatively short-lived nature, and their
multiple origins.
The first stage of the project determined how well
global climate models simulate observed ECLs. To
do that the project had to find methods for identifying
an ECL in the model datasets and then methods for
tracking its progress over space and time. Secondly,
the project also looked at which physical mechanisms
are the most important for the development of ECLs.
Finally, the project used the high-resolution NARCliM
model to perform high-resolution simulations of future
climate, see www.climatechange.environment.nsw.
gov.au/Climate-projections-for-NSW/About-NARCliM
5.1 Representing ECLs in models
The fine scale regional climate model (RCM)
data from NARCliM has provided us with the
information necessary for the identification and
tracking of ECL activity.
There is a wide range in the frequency of ECLs
in the reanalyses, with strong agreement for
the large, intense ECLs and divergence for the
smaller systems.
Satellite sea surface wind observations indicate
that there are many small systems agreeing
with the high end of the modelled frequency
range. The RCMs agree with this high
frequency.
A number of ECL tracking methods have
been developed. Each is based on different
attributes or indicators of ECLs such as
mean sea surface pressure. These various
identification and tracking methods agree and
have a high reliability for tracking large, intense
storms but are less consistent and more
variable in their ability to track small, weak
storms.
As such, Project 2 indicates that for future
modelling work it will be better to use an
ensemble or several tracking methods to
account for variability.
East coast lows and future
projections of climate
5
23
5.2 Future changes in ECLs
Project 2 modelled changes in the frequency and
intensity of ECLs without distinguishing between
different types of ECLs. As we have shown from
Projects 4 and 5, the type and location of ECLs has
a major bearing on natural resources, and therefore
further modelling of ECLs by type is being progressed
by the University of NSW.
Across all ECL types the Project 2 modelling indicates
that there will be a decrease in the frequency of winter
storms, and a small increase (or no change) in the
frequency of summer storms.
However, if we classify the storms according to
intensity we get a slightly different picture (see Figure
14 below). For low and middle level intensity ECLs,
i.e. those with a wind speed above 8 m/s, there is
a significant decline in the number of winter storms
(–19%) and a very small increase in summer storms
(+9%). If we look at the high intensity storms (>20 m/s
wind speed) we find that there is a significant increase
in the frequency of high wind summer storms (+28%)
and a slight decrease in the frequency of high wind
storms in the winter (-6%).
Without details on which types of ECL these
changes relate to it is difficult to draw specific
regional conclusions on the likely impact on coastal
systems and water security. However, there is an
indication that the winter ECLs, which are a significant
component of the dam filling events in the southern
and central eastern seaboard, are likely to be less
frequent overall, but this may be offset by the increase
in intense summer ECLs. The ongoing research in this
field will be pivotal in addressing these uncertainties.
Figure 14: Changes in intensity of ECLs for summer and winter from the present to 2030 (low and high wind speeds) (Walsh et al 2016).
6
24
East coast lows and natural
resource management
Section 4 above outlined the significant potential
impacts of ECL events on coastal systems, estuary
dynamics and water resources; however, the impacts
of ECLs on natural resources are likely to be more
pervasive than this. Although not studied as part of
the ESCCI-ECL project, ECLs, via their influence on
major physical processes such as rainfall, storms and
coastal wave action, will have impacts on a number of
ecosystem processes.
In terms of terrestrial environments ECLs have a
significant influence on average and inter-annual
variability of rainfall. In turn, rainfall has a significant
impacts on vegetation dynamics. For example, a
reduction in the frequency and intensity of winter
ECL storm events is likely to result in drier winters.
This is particularly relevant for the southern half of
the eastern seaboard, where Bureau of Meteorology
studies have indicated that ECLs are responsible for a
third to almost half of the winter rainfall. Depending on
the following warm season rainfall and temperature,
the drier winters can result in lower soil moisture
and drier fuels leading into the warmer seasons,
thus increasing fire risk. Likewise, studies by the
Department of Primary Industries have demonstrated
that much of the forests and woodlands of NSW are
dependent on groundwater to balance out the highly
variable climate. Groundwater recharge depends on
the distribution, amount and timing of precipitation,
evapotranspiration losses, and land use or land
cover. It also depends on soil permeability and the
hydraulic properties of the regolith. Storms are a
significant component of the recharge mechanism for
groundwater and a long-term decline in storm activity
could adversely affect groundwater, even without a
significant reduction in average rainfall. In many areas
of central and western NSW, streambed recharge can
be significant. We can get significant recharge events
from flood events that happened in Queensland as
they slowly flow down the river system through NSW.
Due to the highly variable nature of rainfall in Australia
many of our streams and rivers are ephemeral in
nature. Storms or the lack of them play a major role in
river ecology. In terms of freshwater aquatic systems
ECLs are a significant component of the high flow
events that are particularly important in the hydrology
and ecology of our coastal streams.
The flooding from storms such as ECLs increases
hydrological connectivity (connection of isolated
wetlands to the river channel) and triggers booms
in productivity. Storms may also physically alter
the channel and morphology of rivers and streams
resulting in bank erosion or even creation of new
Fallen tree due to storm damage in backyard of suburban home (Margoe Edwards).
25
channels. Large events can also mitigate salinity,
such as in the Hunter catchment where saline water
is released from mines during high flows to maintain
stream water quality. A reduction in ECLs could result
in drought like conditions, which in turn alters water
quality and reduces habitat availability. An increase in
these storms could lead to significant stream and river
bank erosion but higher freshwater flows
6.1 ECLs and natural processes
ECLs are a pervasive part of the climate system; we
need to stop thinking of them just in terms of being
a natural disaster and more in terms of their role in
driving many of the ecosystem processes that natural
resources depend upon in the eastern seaboard. For
example, all NRM managers are aware that although a
single bushfire is a dramatic event, it is the sequence
of fires or the bushfire regime that drives vegetation
dynamics and the subsequent impacts on property
and ecological functioning. The same applies to
coastal tropical vegetation, with cyclones being a
major driver of rainforest dynamics. This thinking
needs to be applied to coastal ecosystems and
ECLs. Just like fire, where the regime is important,
the clustering of events drives a range of coastal
processes like shoreline position, estuary entry
conditions and water quality dynamics. ECL rain
events influence sediment and nutrient flows into the
coastal zone.
The impact of ECLs is not consistent along the
eastern seaboard and depends in large part on the
frequency and clustering of the various types of ECL.
For example, a clustering of easterly trough lows and
inland trough lows could have a greater effect on the
north coast than in the south.
6.2 Using the past climate analysis
for NRM
The analysis of past climates demonstrates that
the frequency of clustering and intensity of ECLs is
more variable than even our historical records show.
Therefore in terms of designing for extreme storm
events we need to consider the high probability of
extreme storms occurring with a frequency and
intensity outside of our historical knowledge.
The extreme erosion lines or ultimate storm scarp
developed as part of Project 4 can be used as a guide
for coastal planning. For example, when historical
climate data is combined with the information from
the palaeogeomorphological studies of beach
dunes, it gives us a very good basis from which to
understand or define how the ultimate storm will
manifest itself on the coast, giving us a better baseline
for determining risk.
The preliminary projections are that medium level
storms are likely to decline but high level storms will
potentially remain the same. This is coupled with a
slight increase in extreme rainfall events. We can look
at past climate modes to this and see what the impact
on coastlines and streamflow would look like.
For the south coast this could mean that flooding risk
from extreme storms could increase even though the
region could expect longer and harsher dry periods.
An improved version of MATCHES could allow
NRM and emergency services managers to look at
particular storms or clusters of storms and how they
impacted on precipitation, wind and waves for their
particular region.
Before and after the June 2016 East Coast Low, Narrabeen Collaroy Beach
(W RL 2016)
26
6.3 Using the future climate projections
for NRM
The existing projections were based on the modelling
of ECLs as a single storm type. This has indicated
that rainfall within the northern part of the region is
likely to increase in summer and potentially decrease
in the south, with a possibility of extended dry periods
in the southern region. This could have a major
impact on water security, forest management and
land degradation. However, as the type of ECL and
where it occurs has a significant bearing on how it
will impact on coastal and water resources, there
is a need for modelling of the future frequency and
intensity of each of the five types of ECL.
Project 5 is currently testing the projections of future
rainfall that are being delivered by Project 2 and the
NARCliM ensemble. This work will provide us with a
projection of possible impacts, but also outline the
limitations of using this specific dataset for water
resource planning.
In the meantime we can use the historical variability
outlined in Project 3 as a guide to the range of ECL
variability that we need to plan for.
6.4 Future work needed to help guide
NRM and emergency services
A key component in understanding the likely future
risks to coastal processes and water resources is the
ability to look at the frequency, intensity and timing of
each of the types of ECL. As we have demonstrated
through the work on Projects 4 and 5, it is important
to understand the type of ECL and its seasonal
frequency and intensity if we are to make definitive
projections of likely impacts due to climate change.
The University of UNSW is progressing fine scale
regional climate modelling of the five types of ECLs
identified by the ESCCI-ECL Project.
There is a high level need to improve seasonal
forecasting of ECL clustering and intensity.
In terms of future requirements, to make this
work particularly relevant to natural resource
management and emergency services managers,
there is a need for region wide improvement in
seasonal forecasting related to the probability
of ECL storms both in terms of frequency and
intensity.
As the impacts are not consistent across the
region this must be based on the types of east
coast lows. This will allow resource managers
and emergency services personnel to have
a better understanding of the likely risks they
face each season in terms of preparedness for
disaster and planning for water resource security.
The seasonal forecasting could be produced
in a format similar to the regional impact profile
proposed earlier in the report. In this way natural
resource and emergency services managers
could be provided with probabilities or visual
clues as to the likelihood of erosion events or
clustering of storms and how these may affect
streamflow and flood risk.
This will be particularly important for emergency
services personnel looking at financial and
human resources when preparing for the likely
risk in the upcoming season. To do this will
require significant investment in using information
from Project 2 to produce more reliable seasonal
outlooks. These could be similar to the cyclone
warning outlooks for the upcoming season that
the Bureau of Meteorology currently issues.
An improved version of MATCHES, which
captures information on ECL events and their
rainfall, wind and wave impacts on an ongoing
basis, would provide emergency services
managers with readily accessible and up to
date information of the risk posed by ECLs.
A new research theme looking at the effect
of ECLs on other natural processes such
as groundwater recharge, and the influence
of ECLs on fire risk would provide valuable
information in the management of the native
vegetation of the region in a changing climate.
OEH will continue to engage in collaborative research
to address remaining knowledge needs as part of its
ongoing climate impact and adaptation research.
Further reading
7
Read an editorial on the ESCCI-ECL project and
associated papers in a special edition of the Journal
of Southern Hemisphere Earth Systems Science
2016 66(2) 95-96
Project 1 Hazard tool development
Coutts-Smith A, Gamble F, Rakich C & Schweitzer
M 2011, Eastern Seaboard Climate Hazard Tool –
MATCHES. Conference paper for the NSW coastal
Conference, 2011
Pepler AS & Coutts-Smith A 2013, A new
objective database of East Coast Lows. Australian
Meteorological and Oceanographic Journal 63, 461-47
Pepler AS, Imielska A, Coutts-Smith A, Gamble F &
Schweitzer M 2016, Identifying East Coast Lows with
climate hazards on the Eastern Seaboard. Journal of
Southern Hemisphere Earth Systems Science 66(2),
97-107
Project 2 Future ECLs
Di Luca A, Evans JP, Pepler AS, Alexander L & Argüeso
D 2015, Resolution Sensitivity of Cyclone Climatology
over Eastern Australia Using Six Reanalysis Products.
Journal of Climate 28(24), 9530 - 9549
Di Luca A, Evans JP, Pepler AS, Alexander L & Argüeso
D 2016, Evaluating the representation of Australian East
Coast Lows in a Regional Climate Model ensemble.
Journal of Southern Hemisphere Earth Systems
Science 66(2), 108-124
Evans J, Ekström M & Ji F 2012, Evaluating the
performance of a WRF physics ensemble over South
East Australia. Climate Dynamics 39, 1241–1258
Gilmore JB, Evans JP, Sherwood SC, Ekström M &
Ji F 2015, Extreme precipitation in WRF during the
Newcastle East Coast Low of 2007. Theoretical and
Applied Climatology 2015, 1-19
Ji F, Evans JP, Argueso D, Fita L & Di Luca A 2015,
Using large-scale diagnostic quantities to investigate
change in East Coast Lows. Climate Dynamics 45(9-
10), 2443-2453
Pepler AS, Di Luca A, Alexander LV, Evans JP, Ji F &
Sherwood SC 2014, Impact of identification method on
the inferred characteristics and variability of Australian
East Coast Lows. Monthly Weather Review 43(3), 864-
877
Pepler A, Alexander L, Evans J & Sherwood S 2016,
Zonal winds and southeast Australian rainfall in global
and regional climate models. Climate Dynamics 46,123-
133
Pepler AS, Di Luca A, Ji F, Alexander LV, Evans JP
& Sherwood SC 2016, Projected changes in east
Australian midlatitude cyclones during the 21st century.
Geophysical Research Letters 43(1), 2015GL067267
Walsh K, White CJ, McInnes K, Holmes J, Schuster
S, Richter H, Evans JP, Di Luca A & Warren RA 2016,
Natural hazards in Australia: storms, wind and hail.
Climatic Change 1–13
Project 3 Natural variability
Browning SA & Goodwin ID 2013, Large-scale
influences on the evolution of winter subtropical
maritime cyclones affecting Australia’s east coast.
Monthly Weather Review 141(7), 2416-2431
Browning SA & Goodwin ID 2015, Technical Summary
of Eastern Seaboard Climate Change Initiative on East
Coast Lows (ESCCI-ECLs) Project 3: Long term natural
variability and probability assessment of ECLs. Climate
Futures, Macquarie University
Browning SA & Goodwin ID 2016a, The Paleoclimate
reanalysis project. Climate of the Past Discussions 11,
4159-42 0 4
Browning SA & Goodwin ID 2016b, Large scale drivers
of Australian East Coast Cyclones since 1851. Journal
of Southern Hemisphere Earth Systems Science 66,
146 171
27
28
Project 4 Coast and estuary
impacts
Goodwin ID, Burke A, Mortlock T, Freeman R &
Browning SA 2015, Technical Report of the Eastern
Seaboard Climate Change Initiative on East Coast
Lows (ESCCI-ECLs) Project 4: Coastal System
Response to Extreme East Coast Low Clusters in the
Geohistorical Archive. Climate Futures, Macquarie
University
Goodwin ID & Browning SA 2016, Eastern Australian
coastal fingerprint of ultimate subtropical storm activity
from 1600 to 1900 AD. Nature Geoscience. In Prep
Goodwin ID, Mortlock TR & Browning S 2016,
Tropical-Extratropical origin storm wave types and
their influence on the East Australian Longshore Sand
Transport System under a changing climate. Journal of
Geophysical Research: Oceans 2016
Mortlock TR & Goodwin ID 2015, Directional wave
climate and power variability in the Tasman Sea.
Continental Shelf Research 98, 36–53
Project 5 Water security
Kiem AS, Twomey C, Lockart N, Willgoose GR,
Kuczera G, Chowdhury AF, Parana Manage N & Zhang
L 2016, Links between East Coast Lows and the spatial
and temporal variability of rainfall along the eastern
seaboard of Australia. Journal of Southern Hemisphere
Earth System Science 66(2), 162-176
Lockart N, Willgoose GR, Kuczera G, Kiem AS,
Chowdhury A.F, Parana Manage N, Zhang L and
Twomey C 2016, Case study on the use of dynamically
downscaled climate model data for assessing water
security in the Lower Hunter region of the eastern
seaboard of Australia. Journal of Southern Hemisphere
Earth System Science 66(2), 177-202
Parana Manage N, Lockart N, Willgoose GR, Kuczera
G, Kiem AS, Chowdhury AF, Zhang L & Twomey C
2016, Statistical testing of dynamically downscaled
rainfall data for the Upper Hunter region, New South
Wales, Australia. Journal of Southern Hemisphere
Earth System Science 66(2), 203-227
Verdon-Kidd DC, Kiem AS & Willgoose GR 2016, East
Coast Lows and the Pasha Bulker storm– lessons
learned nine years on. Journal of Southern Hemisphere
Earth System Science 66(2), 152-161
Kiem AS & Twomey CR 2014, Investigating the
relationship between East Coast Lows (ECLs) and east
Australian rainfall. Proc. 35th Hydrology and Water
Resources Symposium, Perth, Australia, February 2014
Twomey CR & Kiem AS 2016a, East Coast Lows
and rainfall along the eastern seaboard of Australia
- comparison of datasets used to record ECL
occurrence and impacts on rainfall. Journal of Southern
Hemisphere Earth System Science, in prep
Twomey CR & Kiem AS 2016b, Spatial and temporal
variability of Australian rainfall - insights into why
the eastern seaboard of Australia is different to the
rest of Australia and also internally inhomogeneous.
International Journal of Climatology, in prep
Twomey CR & Kiem AS 2015, Spatial analysis of
Australian seasonal rainfall anomalies and their relation
to East Coast Lows on the Eastern Seaboard of
Australia. Proc. 36th Hydrology and Water Resources
Symposium, Hobart, Australia, December 2015
Project 6 Economic impacts
Roche K & Waters D 2013, Generic framework to
determine the economic impact on NSW locations from
natural disaster events. Risk Frontiers Report prepared
for the NSW Office of Environment and Heritage
Roche K & Waters D 2016, Generic framework to
determine the economic impact on NSW locations
from natural disaster events. Australian Meteorological
and Oceanographic Journal, In Prep
29
September 2016
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Article
Full-text available
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