Coastal Processes, Hazards & Adaptation

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1 Coastal Processes, Hazards & Adaptation Dr Darrell Strauss - Griffith Centre for Coastal Management

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

3 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

4 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

5 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)

6 Outline Coasts & Coastal Processes Hazards Climate Related Drivers (IPCC WGII AR5) Impacts Adaptation Knowledge Gaps Questions?

7 Coasts Land- sea interface Sediments Fine mud, sand Energy Coarse shell, gravel Wind Variability Waves Currents (incl. 7des)! Storms, seasons Climate Change Ocean Acidifica7on

8 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)

9 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, & 2013

10 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

11 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

12 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

13 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 North Harbour Beach (D. Todd) Coral fringed or rocky coasts, intertidal rock platforms and rock flats

14 Mackay - Tide modified beaches Significant Wave Height, Hs ~ 0.5 m Peak wave Period, Tp = 4 6 sec Direction, 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)

15 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)

16 Coastal System Sensitivity to Climate Change (II) Global Mean Sea Level (GMSL) rise is projected to be m by 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 ºC per decade since 1950 (NE & SE Australia; IPCC, 2014)

17 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

18 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 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) Includes: Important consideration for coastal impacts, vulnerability & adaptation 1) Climate-induced GMSL 2) Climate-induced regional variations in sea level 3) Local non-climate related sea level changes

19 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.

20 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

21 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)

22 Forecasting SLR induced retreat Observations & Numerical Modelling Alongshore processes shoreline evolution, structures Storm cut reasonably well understood and applied on wavedominated coasts Overwash Hurricane Katrina generated new research efforts SLR retreat - Bruun Rule commonly applied (1 st approximation with limitations due to profile)

23 Forecasting SLR induced retreat Tide modified beaches are poorly represented by current erosion models. Recovery processes and revegetation rates are rarely documented.

24 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

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

26 Historical Tropical Cyclones Bathurst Bay - Cyclone Mahina - 5 Mar killed Mackay Jan killed Innisfail March killed Cairns 1920 flooding Noosa Feb 1931 severe erosion Gold Coast killed 1967

27 Extreme Events Jan May 1967 TC Dinah, Barbara, Dulcie, Elaine and Glenda 1967 Erosion Scarp June East Coast Lows 8 million m 3 of sand eroded from beaches Beach Protection Authority (BPA, 1968) Delft Hydraulics report (DHL, 1970)

28 Historical Tropical Cyclones (cont.) Bathurst Bay - Cyclone Mahina - 5 Mar killed Mackay Jan killed Innisfail March killed Cairns 1920 flooding Noosa Feb 1931 severe erosion Gold Coast killed 1967 Ada - Jan 1970 Whitsunday Islands Althea - Dec 1971 Townsville Tracy - Dec 1974 Darwin - 71 killed, 650 injured, 35,362 evacuated Pam Feb Gold Coast David - Jan 1976 Yeppoon Aivu - Apr 1989 Ayr Larry - Mar 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)

29 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 people, or 20 per cent of Mackay s population requiring evacuation. Queensland Coastal Processes and Climate Change (2011)

30 Annual Average TC Occurrence Mackay Coastal Study, EPA Qld (2004)

31 Direction of Extreme Waves Mackay Coastal Study, EPA Qld (2004)

32 Storm Tide (B. Harper, 2014)

33 Storm Tide TC Yasi, February 2011 Cat 5 offshore Cat 3 - crossed coast, falling tide 3 rd highest storm tide in Qld history (after Bathurst Bay, 1899) (Harper, 2014)

34 ENSO related variability Wave Climate El Nino La Nina Mackay Coastal Study, EPA Qld (2004)

35 Projected changes in wave climate Palm Beach short groynes % ~10º Anticlockwise rotation in wave direction for SE Qld 60 N Latitude 30 N 0 30 S Anticlockwise Clockwise 60 N 60 S 60 E 120 E W 60 W 0 Longitude Latitude 30 N 0 30 S ~5% increase in wave height in Coral Sea 60 S 60 E 120 E W 60 W 0 Longitude Hemer, M. et al, (2013) NATURE CLIMATE CHANGE DOI: /NCLIMATE1791

36 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

37 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

38 Coastal Adaptation Alongshore Changes in wave climate (direction) can alter transport rates

39 Coastal Adaptation

40 Coastal Adaptation M. Sano (2014)

41 Structural Solutions Future proof? Maintenance Safety / liability Visual amenity Recreation Cost / Value

42 Innovation Submerged Control Structures

43 Coastal and Ocean Processes Summary Observed impacts of climate change: Average rate of relative SLR ( ) 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)

44 Coastal and Ocean Processes Summary Projected impacts of climate change: Regional SLR exceeding historical rate, continuing for several centuries Sea-surface temp expected to increase between 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

45 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 Mackay Coastal Study, EPA Qld (2004)

46 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

47 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

48 Nobbys Beach, Gold Coast - May 2013