NCCOE EA Coastal Adaptation Guidelines. Section I Emerging Technology Novel Alternative Approaches to Coastal Erosion

Transcription

1 NCCOE EA Coastal Adaptation Guidelines Section I Emerging Technology Novel Alternative Approaches to Coastal Erosion Alessio Mariani, Doug Lord, Tony Webb James Carley, Matt Blacka, Brett Miller Ian Turner, Ron Cox

2 Purpose of the Guidelines Guidance to coastal practitioners in responding to the challenges of our changing climate Specifically aimed at coastal managers and planners working in Local and State Government A simplified and structured framework to assist the coastal manager considering physical intervention options and adaptation strategies

3 Purpose of Section I General overview on the alternative methods for the mitigation of coastal hazards To assist the coastal manager when evaluating intervention options presented as innovative Asking the correct questions More questions than answers!!!

4 Challenges: Beach Erosion and Recession Mitigation Reduction Management Photo Ian Coghlan WRL

5 Challenges: Beach Erosion and Recession SLR Wave Climatology Photo James Carley WRL

6 Traditional versus Innovative Traditional approaches Well established engineering design criteria Long history of application Seawalls, groynes, breakwaters etc Innovative approaches Minimal environmental impacts? Lower costs? Easier execution?

7 Source Google Earth Traditional versus Innovative

8 Traditional versus Innovative Photo Daylan Cameron Warringah Council

9 Traditional versus Innovative Many of these structures are accepted as part of our built environment Photo WRL UNSW

10 Novel Alternative Approaches Source Sonia Beato Artificial or Reinforced Dune Natural Defences Wave Energy Converter Groundwater Defence Coastal Stabilisation Devices confer to the beach more resilience to sediment transport by wave action located in sub-aerial beach within the intertidal zone and the dunes Artificial Reef Wave Attenuation Devices induce wave energy dissipation less energy reaches the shore erosive potential of wave action is diminished located in the nearshore, in the surf zone and in the intertidal zone

11 Venice, Italy

12 Venice, Italy

13 Gold Coast, QLD

14 Gold Coast, QLD Source Gold Coast City Council Source Gold Coast City Council Source Gold Coast City Council Source Gold Coast City Council

15 Plage de Gere, France Source ecoplage Source ecoplage

16 Artificial Reefs Introduction Source Sonia Beato Artificial reef Vs Natural reef Located in shallow nearshore zone Crest levels are at Mean Low Water (MLW) or below Induce wave breaking Reduce wave energy reaching the beach Artificial Reef

17 Artificial Reefs Introduction Source Google Earth

18 Artificial Reefs Introduction Source Google Earth

19 Artificial Reefs Introduction Coastal protection Enhancement of surf amenity Enhancement of ecology Multipurpose reefs Source ASR ltd

20 Artificial Reefs Field Experience Common in Europe (~10-20%) Less common in Japan and US (<1%) Numerical and Physical modelling Analogue: natural reefs and salient formation (Black, 2001) Performance still subject of debate Ranasinghe and Turner, 2006: shoreline erosion Too close to shore

21 Artificial Reefs Field Experience List of major projects Long term, independent monitoring available

22 Artificial Reefs Conclusions ADVANTAGES Aesthetics Coastal protection? Surfing enhancement? Marine habitat enhancement Recreational amenity In some cases simplicity of constructability In some cases removability

23 Artificial Reefs Conclusions DISADVANTAGES Only suitable for small tidal range Sensitivity to sea level rise Limited design criteria Limited protection during storm conditions Scouring at base, roundheads and gaps Settlement Generation of strong currents? Construction costs?

24 Beach Groundwater Manipulation Introduction Source Sonia Beato Groundwater Defence Dewatering well-established on construction sites Artificial lowering of groundwater table Enhancement of infiltration losses Promotion of sediment deposition

25 Beach Groundwater Manipulation Introduction First established (and commercialised) in Denmark, 1980s Field experiments in Durras Beach and Dee Why, NSW Accomplished through buried pipes, collector sump and pumping station or gravity drains Source ecoplage Source ecoplage

26 Beach Groundwater Manipulation Field Experience Several beach drainage installations around the world Experimental and commercial Few established with an independent scientific review Fewer incorporating monitoring period >5 years Source ecoplage

27 Beach Groundwater Manipulation Field Experience Perhaps the exception is France Pilot installations in: Mediterranean Coast Atlantic Coast Channel Independent monitoring and review by 3 universities Published thesis

28 Beach Groundwater Manipulation Field Experience Watertable can successfully be lowered Morphological effects from negligible to possibly effective No protection from storm erosion Limited use in open coast Susceptible to storm damage

29 Beach Groundwater Manipulation Conclusions ADVANTAGES Beach stabilisation Minimal visual impact Removability Constructability Relative low costs Dry effect on beach for increase recreational use

30 Beach Groundwater Manipulation Conclusions DISADVANTAGES Not suitable for open coast environments Only suitable for low wave energy areas No protection during storms Susceptible to damage during storm conditions Durability? Maintenance costs for pumps Lack of design criteria

31 Conclusions No solution addressing coastal erosion/recession is ever final and complete Need for re-evaluation, maintenance, management and possibly modification (Pope, 1997) Non-traditional approaches can be successful Careful consideration of hydrodynamic, geographic/geologic, socio-economic and environmental factors Asking the right questions

32 Asking the right questions Check List Has the proposed technology been applied in the field? If yes: Where and what were the design wave and water level conditions? If yes: Did it perform as expected? If yes: Was the intervention independently monitored? For how many years? What is the cost compared to a traditional intervention? How would it perform during a storm event? Scouring at the base? Settlement?

33 Asking the right questions Check List What is the design life? What is the design event? What is the durability of the material? Are there any adverse impacts on adjacent foreshores? How adaptive it is to sea level rise and climate change? What is the cost of removal in case of failure? Hazard to public? Hazard to environment? If it seems too good to be true then it probably is!

34 Churchill Fellowship Investigation of international innovative coastal engineering solutions to manage beach erosion Innovative solutions still undergoing development Lack of definitive publication Visit the institutions, interview majors experts, witness the practical outcomes

35 Churchill Fellowship Travels

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