Coastal Processes, Hazards & Adaptationreefcatchments.com.au/files/2013/12/coastal-processes_Strauss.pdf · Coastal Processes, Hazards & Adaptation Climate Risk in the Coastal Zone

Coastal Processes, Hazards & Adaptation

Climate Risk in the Coastal Zone Forum CQ University, Mackay 9th May, 2014

Climate Risk in the Coastal Zone Forum, Mackay. 9th May 2014

Dr Darrell Strauss - Griffith Centre for Coastal Management

Griffith Centre for Coastal Management

Prof Rodger Tomlinson, Director Coastal Settlements Node Convener - Australian Climate Change Adaptation Research Network for Settlements and Infrastructure (ACCARNSI)



•  Coastal management, research and education •  Sustainable management of urban environments in coastal areas •  Community involvement in the management of our coasts •  Understanding of natural coastal processes and management strategies

Research Interests • Coastal infrastructure and natural asset management

• Catchments and waterways • Water future • Climate Change and adapta=on

• Extreme events and disaster management

• Community engagement and educa=on – CoastED and BeachCare

• Beach and estuarine ecology • Economic values



Recent Research Activity • Gold Coast Shoreline Management Plan (GCSMP)

• Gold Coast Desalina=on Plant • GC Seaway Smart Release • Smart Coast • Q-‐Surge Storm surge modelling for Emergency response and Management

• Coastal Hazard Adapta=on Strategy

• SEQCARI (Climate Adapta=on) • ABFlags (NCCARF) • GCCRP



Water Quality Management §  Nutrients!§  Turbidity!§  Heavy metals!§  Ocean Acidifica7on / Climate

Change

§  ‘SmartRelease’ (nutrients)!§  Lake Currimundi (nutrients / E. coli) §  Tugun Desalina=on (turbidity) §  Gold Coast Dive Site (turbidity) §  Currumbin Creek dredging (nutrients, turbidity, E.coli) §  Griffith Climate Change Response Program §  ISS / NGU (Norway)



Outline



Coasts & Coastal Processes • Hazards

Climate Related Drivers (IPCC WGII AR5)

•  Impacts • Adaptation

Knowledge Gaps Questions?

Coasts •  Land-‐sea interface •  Sediments

Fine – mud, sand Coarse – shell, gravel

•  Energy Wind Waves Currents (incl. 7des)!

•  Variability Storms, seasons Climate Change Ocean Acidifica7on



Coastal Tourism and Recreation



•  Coastal tourism - largest component of the global tourism industry •  Over 100 countries benefit from recreational value of coral reefs

- US$11.5 billion globally (IPCC, 2014; Burke et al., 2011)

•  Observed extreme events impacts on coastal tourism infrastructure (e.g. beach resorts, roads, accessibility, amenity),

•  Indirect impacts of extreme events (e.g. coastal erosion, coral bleaching) - short-term tourist-adverse perception following extreme events (e.g. lack of beach, flooding, tropical storms, storm surges)

Australian Beaches – Issues -‐ Impacts

•  Early development in erosion prone areas (dune removal)

•  Coastal Infrastructure – ports, estuaries, training walls, groynes

•  Tourist destinations, accessibility

•  Storm periods

e.g. 1860s-1890s, 1930s, 1950s-1970s

•  Major Cyclones, East Coast Lows (QLD)

1954, 1967, 1972, 1974 –2009 & 2013



Australian Beaches •  10,685 beaches (Short, 2006)

•  15 beach types

•  47% Wave dominated - High wave energy, low tide range (<2m)

e.g. exposed coasts of WA, SA, Tas, Vic, NSW and SE Qld.

•  11% Tide modified – lower wave energy, medium tide range (~2-6m)

e.g. SA gulfs and bays, NW Tasmania, Central Qld

•  34% Tide dominated – high tide range (2-11m), low wave energy

e.g. Northern Australia



Wave Dominated Beaches e.g. Typical surf beaches of Gold Coast, NSW Beach states further categorised into dissipative, intermediate, reflective (Wright & Short, 1984; Short 1999) Intermediate states include:

LBT - Longshore bar & Trough RBB - Rhythmic Bar & Beach TBR - Transverse Bar & Rip LTT – Low tide Terrace

Swimmer hazards, rip currents, local erosional hotspots

Beach states change with wave conditions and affect resilience



Tide Dominated Beaches Higher tide ranges (meso- to mega-tidal), very low waves (Short, 2006). e.g. 83% in Northern Australia, elsewhere in sheltered bays, SA, Tasmania & Victoria. Morphological behaviour is not well studied.

•  Reflective with sand ridges or flats, low gradient wide beaches

•  Steep, coarse-grained, straight, high tide beach.

•  Lower energy beaches tend towards a high tide sand beach with intertidal mud flats



Tide Modified Beaches Higher tide ranges (~2-6m), persistent low waves or wind-waves (Short, 2006). •  44% of Queensland’s 1600 beaches (Short, 2011) •  Steep coarse grain high tide beach •  Low gradient finer low tide terrace •  Low tide surf zone, may have bars and rips



Other coasts

•  Coral fringed or rocky coasts, intertidal rock platforms and rock flats

North Harbour Beach (D. Todd)

Mackay - Tide modified beaches

Significant Wave Height, Hs ~ 0.5 m Peak wave Period, Tp = 4‐6 sec Direction, 115 ‐ 125 Spring tide range = 4.56 m, highest tide = 6.41 m (EPA, 2004; Short, 2011) •  Mostly Tide‐modified, some tide-dominated beaches on sheltered coasts,

no wave dominated beaches

•  Exposed beaches aligned to waves arriving from the ESE‐SE.

•  Dune, upper beach and low-tide terrace sediments are distinctly different

•  Cross-shore transport processes between upper beach and low-tide terrace are separate and disconnected (Dalla Pozza et al, 2013)



Coastal System Sensitivity to Climate Change (I)



Long Term Coastal systems are particularly sensitive to three key drivers related to climate change:

1)  Sea Level -  Continued coastal inundation and erosion due to sea level rise -  Storm related impacts and storm surge worsened by SLR -  Continue long term SLR due to delayed response to warming

2)  Ocean Temperature - Detrimental to health of coastal ecosystems, particularly coral

reefs 3)  Ocean Acidification

-  Detrimental to health of coastal ecosystems, particularly coral reefs (Very high Confidence, IPCC 2014)

Coastal System Sensitivity to Climate Change (II)



•  Global Mean Sea Level (GMSL) rise is projected to be 0.28 – 0.98 m by 2100 -  Regional sea level rise may be higher (10% offshore Aust, IPCC 2014)

•  Ocean Acidification and Sea Surface Temperature (SST) warming -  leads to coral bleaching and loss of structural integrity -  negative impacts on reef communities and shore protection -  Reefs most vulnerable marine ecosystem, little scope for adaptation

Uncertainties regarding projections of potential impacts on coastal systems due to Climate Change remain generally high SST increased by 0.1-0.2ºC per decade since 1950 (NE & SE Australia; IPCC, 2014)

Coastal System Sensitivity to Climate Change (III)



Regional Influences of Climate Change and Global Sea Level Rise Developed Countries

Effects of erosion and storm damage to coastal areas in developed countries will influence the demand for housing, recreational activities and construction of renewable energy infrastructure on the coast

Developing Countries

Weather, sea level rise and climate extremes impact on a wide range of economic activities supporting coastal communities

Global vs Relative Sea Level Rise



Global Mean Sea Level (GMSL) Thermal expansion and melting of glaciers account for over 80% of the GMSL rise between 1993 – 2010. 1.7 mm/yr from 1900 to 2010 (very likely) 3.2 mm/yr from 1993 to 2010 (IPCC, WG1) Upper bounds estimated at up to 2.4m by 2100 (low agreement, no consensus)

Relative Sea Level Rise (RSL) Important consideration for coastal impacts, vulnerability & adaptation

Includes: 1)  Climate-induced GMSL 2)  Climate-induced regional variations in sea level 3)  Local non-climate related sea level changes

Global vs Relative Sea Level Rise



Relative Sea Level Rise (RSL) (cont.) Thermal expansion, meltwater from icecaps and ice sheets contribute to relative sea level rise globally. Regional variability of SLR is introduced by: •  Glacial isostatic rebound, relative sea level fall, gravitational effects •  Subsidence, compaction of sediment associated with development/extraction •  Dredging, harbours, dams, entrance works lead to changes in sediment

supply, erosion and accretion •  Obscured by natural climate variability, e.g. El Nino, decadal scale variability,

earthquakes •  RSL can exceed GMSL, as much as 10cm/yr (Deltas) Even a small sea level rise is projected to increase the risk of coastal inundation and erosion in NE QLD.

Short term impacts



Impacts & Risks •  Inundation and erosion from storm surge events

•  Ground water intrusion, agriculture (e.g. Nicholls, 2010)

•  Increased intensity of severe storms, high winds, flooding

•  Disruptions to services, transport

•  Industry, Tourism etc

Processes/Hazards

•  Severe storms

•  Storm surge

•  Flooding

•  Erosion

Inundation and erosion



Barriers, beaches and dunes

•  Globally, natural beaches and dunes in general have undergone net erosion over the past century and beyond.

•  Distinguishing between anthropogenic induced shoreline change and natural and cyclical shoreline change is difficult (e.g. Tweed River training wall extensions)

•  Statistically linking sea level rise to observed beach erosion has had some success - coastal sea level change signal is often small compared to other processes

•  Sea level rise plus increased storm surge, increased severity of storms all have the potential to increase erosion of the coastal system IPCC (2014); Bird (2000)

Forecasting SLR induced retreat



Observations & Numerical Modelling

•  Alongshore processes – shoreline evolution, structures

•  Storm cut – reasonably well understood and applied on wave-

dominated coasts

•  Overwash – Hurricane Katrina generated new research efforts

•  SLR retreat - Bruun Rule commonly applied (1st approximation

with limitations due to profile)

Forecasting SLR induced retreat



•  Tide modified beaches are poorly represented by current erosion models.

•  Recovery processes and revegetation rates are rarely documented.

Severe Storms and Climate Change



•  Storm surge increases coastal erosion and impact of waves on upper beach

•  Projected increase in storm severity

•  Increased wind speed, rainfall

•  Widening of the topical cyclone belt

•  Poleward shift of storm tracks and jet streams

Severe Tropical Storms



Tropical Cyclone Hazards: Past, Present and Future Dr Bruce Harper Director/Principal Systems Engineering Australia Pty Ltd

Historical Tropical Cyclones



•  Bathurst Bay - Cyclone “Mahina” - 5 Mar 1899 – 400 killed

•  Mackay Jan 1918 – 30 killed

•  Innisfail March 1918 – 100 killed

•  Cairns – 1920 – flooding

•  Noosa – Feb 1931 – severe erosion

•  Gold Coast – 1954 – 30 killed

•  1967

Extreme Events - 1967 Jan – May 1967 TC Dinah, Barbara, Dulcie, Elaine and Glenda June 1967 3 East Coast Lows

8 million m3 of sand eroded from beaches Beach Protection Authority (BPA, 1968) Delft Hydraulics report (DHL, 1970)

• 2002

• 1967 Erosion Scarp

• 1967



Historical Tropical Cyclones (cont.)



Bathurst Bay - Cyclone “Mahina” - 5 Mar 1899 – 400 killed Mackay Jan 1918 – 30 killed Innisfail March 1918 – 100 killed Cairns – 1920 – flooding Noosa – Feb 1931 – severe erosion Gold Coast – 1954 – 30 killed 1967 Ada - Jan 1970 – Whitsunday Islands Althea - Dec 1971 – Townsville Tracy - Dec 1974 – Darwin - 71 killed, 650 injured, 35,362 evacuated Pam – Feb 1974 - Gold Coast David - Jan 1976 – Yeppoon

Aivu - Apr 1989 – Ayr Larry - Mar 2006 - Innisfail Hamish - Mar 2009 – Qld East Coast Yasi - Feb 2011 – Kurrimine to Tully Heads Ita – 11 Apr 2014 – Cape Flattery to Cooktown Ref: B. Harper (SEA) & J. Callaghan (BoM)

Tropical cyclone impacts - Mackay region



“Mackay is low-lying, with an average elevation of less than 10 metres above the mean sea level. A risk assessment has been made of present-day Mackay using the same storm tide inundation level experienced in the 1918 cyclone. It indicated that over 5860 buildings and other structures would be inundated with approximately 11 000 people, or 20 per cent of Mackay’s population requiring evacuation.” Queensland Coastal Processes and Climate Change (2011)

Annual Average TC Occurrence



Mackay Coastal Study, EPA Qld (2004)

Direction of Extreme Waves



• 


Storm Tide



(B. Harper, 2014)

Storm Tide – TC Yasi, February 2011



•  Cat 5 offshore •  Cat 3 - crossed coast, falling tide •  3rd highest storm tide in Qld

history (after Bathurst Bay, 1899)

(Harper, 2014)

ENSO related variability – Wave Climate



El Nino

La Nina


Projected changes in wave climate

Palm Beach short groynes

Hemer, M. et al, (2013) NATURE CLIMATE CHANGE DOI: 10.1038/NCLIMATE1791

Latit

ude

¬10 ¬5 0 5 10

%

60° N

30° N

0°

30° S

60° S

60° E 120° E 180° 120° W 60° W 0°

Longitude

Latit

ude

¬10 0 10 °Anticlockwise °Clockwise

60° N

30° N

0°

30° S

60° S

60° E 120° E 180° 120° W 60° W 0°

Longitude

~5% increase in wave height in Coral Sea

~10º Anticlockwise rotation in wave direction for SE Qld



Coastal Adaptation



PLANNING / ADAPTATION / OPTIONS

•  Proactive planning reduces need for reactive response to damage by extreme events •  Construction of coastal protection structures e.g. Sea walls, groynes, bypassing •  Maintain natural coastal system to act as a buffer (e.g. mangroves, dunes)

•  Managed retreat of coastal infrastructure and communities

•  Retro-fitting buildings, revising design standards

Coastal Adaptation – Cross-shore



Coastal response influenced by: •  high sea level, strong currents, winds, waves •  high rainfall, runoff •  coastal sand transport offshore

Conceptual model: •  rise in sea level = recession / retreat

Breaching of coastal sand barriers and dunes

Coastal Adaptation – Alongshore



Changes in wave climate (direction) can alter transport rates

Coastal Adaptation



Coastal Adaptation



M. Sano (2014)

Structural Solutions



•  Future proof? •  Maintenance •  Safety / liability •  Visual amenity •  Recreation •  Cost / Value

Innovation – Submerged Control Structures



Coastal and Ocean Processes Summary



Observed impacts of climate change:

•  Average rate of relative SLR (1900-2011) 1.4±0.6 mm/yr •  Average climate zones shifted south by more than 200 km in NE Aus since 1950 •  Sea-surface temp increased by about 0.12 C per decade since 1950 •  Increased ocean storage of carbon has led and will continue to lead to an increase in ocean acidification •  No regional change in number of Tropical Cyclones (TC’s)

Coastal and Ocean Processes Summary



Projected impacts of climate change:

•  Regional SLR exceeding 1971-2000 historical rate, continuing for several centuries •  Sea-surface temp expected to increase between 1.2 – 2.5°C by 2070 •  Increased coastal erosion, landslips and flooding induced by SLR, temperature and rainfall •  Continued coral bleaching due to increased sea surface temperatures and ocean acidification •  TC’s to increase in intensity but with similar or slightly decreased numbers subject to decadal variability

• 

Coastal Management Lessons



•  Coastal development historically took place with limited understanding of

natural processes

•  Coastal hazards result from developments poorly located with respect to

prevailing coastal processes

•  Identified hazards in the Mackay region:

•  short term beach erosion associated with storm events

•  coastline recession

•  recession related to climate change and SLR

•  storm tide flooding


Management Responses to Extreme Events

•  Investigations – concerns, data, processes

•  Planning – setbacks, flood hazards, cost-benefits

•  Construction – seawalls, nourishment projects, longevity

•  Monitoring – performance, design modifications

•  Maintenance – seawalls, structures, dredging, nourishment

•  Education – awareness, community engagement



Conclusions

•  Understanding coastal processes plays a critical role in sustainable coastal management and decision making processes

• Ongoing monitoring is invaluable for process understanding, modelling and project performance evaluation

•  Regional modelling: Useful as a research tool and to support decision making

•  Collaborations improve capacity, leverage existing resources, and lead to more efficient coastal & hazard management





Nobbys Beach, Gold Coast - May 2013

Documents

Coastal Processes, Hazards & Adaptationreefcatchments.com.au/files/2013/12/coastal-processes_Strauss.pdf · Coastal Processes, Hazards & Adaptation Climate Risk in the Coastal Zone