What are we adapting to? David Provis Senior Principal, Oceanography, Cardno Member, Victorian Coastal Council

Transcription

1 What are we adapting to? David Provis Senior Principal, Oceanography, Cardno Member, Victorian Coastal Council

2 Sea-level -NOAA

3 Sea-level - NOAA 90% probability ranges

4 Sea-level - NOAA

5 Sea-level Port Phillip Bay Williamstown sea-level rising at 2.3 mm/yr since 1966

6 Storm surge

7 Wave height in Bass Strait

8 Point Nepean Hs (m) Point Nepean Hs (m) Joint occurrence, sea level and wave height Hovell Pile Sea-level (m CD) Hovell Pile Sea-level (m CD)

9 Variable Location /Source Scenario: RCP 2.6 (Mitigation) Scenario: RCP 8.5 (Business-as-Usual ) *Changes relative to Sea Surface Temperature (K) Ocean ph Aragonite Saturation Sea-level Rise (m) Stony Point/ NRM Marine Explorer Stony Point/ NRM Marine Explorer Stony Point/ NRM Marine Explorer Warnambool/ CoastAdapt Westernport/ CoastAdapt East Gippsland/ CoastAdapt 0.5 (0.3 to 0.8) 0.5 (0.3 to 0.9) 0.6 (0.3 to 0.9) 2.3 (1.9 to 3.8) (-0.07 to -0.06) (-0.07 to -0.06) (-0.09 to -0.08) -0.3 (-0.3 to -0.3) (-0.29 to -0.25) (-0.29 to -0.21) (-0.36 to -0.26) -1.1 (-1.2 to -1.0) [ ] 0.42 [ ] 0.13 [ ] 0.70 [ ] 0.11 [ ] 0.41 [ ] 0.12 [ ] 0.69 [ ] 0.12 [ ] 0.41 [ ] 0.13 [ ] 0.73 [ ] Other Projections Notes 2090 Waves Coastal Climate Projections Summary Storm Surge Storm surge + waves Southern Ocean/ Hemer et al 2013 South Coast/ Colberg and McInnes 2012 Gippsland O Grady et al 2015 Wave climate model run with wind forcing from several climate models. New simulations with latest climate models yield similar results Hydrodynamic model run with wind and pressure forcing from several climate models. New simulations with latest climate models yield similar results Analysis of consistent wave and hydrodynamic model projections on nearshore wave-induced and windinduced nearshore transport Future increases in southern ocean wave height and wave period Small decline in extreme sea levels (~cm) owing to southward movement of weather patterns. Increased transport to the west along Ninety Mile beach in summer due to southward movement of the subtropical ridge creating more frequent easterlies Insert Climate footer Scenarios here if required. for Victoria s Go View Coast / Slide Master Kathy to McInnes adjust or remove Page 9

10 From CSIRO projections Future increases in southern ocean wave height and wave period Increased transport to the west along the Ninety Mile Beach in summer due to southward movement of the subtropical ridge creating more frequent easterlies.

11 Lonsdale Bight, towards Point Lonsdale beach1890

12 1934 after major storm

13 1936 After rebuilding

14 1950 after construction of a sea wall

15 1982 groynes refurbished, but ineffective, dune gone

16 1977 sea wall to the north east

17 Junction of sea walls, Golightly park

18 Situation in 2010 Revetment extended 1977 Rock revetment 1966 Revetment refurbished 1996 Masonry and rock extended 1935 to 1943 First masonry wall 1900

19 Eastern end of the revetment

20 Shelley Beach, Portsea 2003 From Coastal Engineering Solutions, (2003) 2010

21 Shelley Beach, Portsea 2003 From Coastal Engineering Solutions, (2003) 2010

22 Summary Coasts are dynamic, we need to learn to live with them. Need to learn to work with the natural processes (means we need to understand them). There are variations with the seasons. There are extreme events and multi-year cycles. Any human intervention will have consequences.

23 Where to in the immediate future? Climate change???? Before we get too excited about predicting the future we need to understand what is happening at present. What are the natural processes, major driving forces? What is the natural variability in both the forcing and the outcome? Can we live with the natural processes and their variability? Are we prepared for the ongoing costs of intervention (maintenance, loss of amenity) if not, we need to retreat, hopefully in an orderly fashion, and let nature take its course.

24 Things we need to understand Wave climate wave height and period (energy) and direction at the breaker line Provides energy for sediment transport Allows computation of wave set up and run up (overtopping) Can be perturbed if climate change predictions are available Analysis of sea level and wave climate joint occurrence How often do high wave conditions coincide with high sea levels? (Realistic 1%, 2%, 10% AEP events) Geomorphology of the nearshore zone Analysis of the Future Coasts LADS bathymetry data Extraction of beach profiles Comparison with surveyed profiles Aim to repeat every 5 (?) years

25 Think about what we want to achieve. Protect the coast, or protect the assets? Thank you