Environmental Geophysics for Coastal Management

Transcription

1 Environmental for Coastal Management Paul Donaldson 1, Dr Douglas Bergersen 2, Dr Matthew Barnes 3, Conor Jones 3 Coast To Coast, Hobart April BMT Newcastle, Australia, 2 Acoustic Imaging, Cooroy, Australia, 3 BMT Brisbane, Australia Image: Google Earth

2 Outline Overview What is environmental geophysics? Geophysical methods for coastal management Coastal management applications Case study examples Aim Provide a practical intro to the uses, advantages and limitations of environmental geophysics [image to go here]

3 What is Environmental? Image: NOAA

4 Geophysical Methods for Coastal Management Ground Penetrating Radar (GPR) Electro-Magnetics (EM) Seismic (various onshore methods) Image: BMT Image: USGS Image: GBG MAPS Image: GBG MAPS Resistivity Magnetometry Image: BMT Marine Acoustics Methods Image: Edge Tech

5 Geophysical Outputs for Coastal Management Ground Penetrating Radar (GPR) Image: Donaldson (2010) Electro-Magnetics (EM) Seismic (various onshore methods) Image: GBG MAPS Image: Image: GBG MAPS GSC Image: USGS Image: Acoustic Imaging Resistivity Image: USGS Magnetometry Image: USGS Marine Acoustics Methods

6 Applications Coastal Management Applications Geomorphology Geotechnical Environmental Asset Management

7 Workflow Physical Method #1?? Problem / Knowledge Gap Method #2? Scope Survey? Method #3? Field Outcome? Do Management! Method #4?

8 Scenario #1a Physical Ground Penetrating Radar 1 Problem / Knowledge Gap Coastal Erosion Risk Geological / geotechnical unknowns Method #2 Scope Survey Method #3 Method #4 Field Outcome Do Management! (Hazards, Risk, Options, Action)

9 Scenario #1b Physical Ground Penetrating Radar 1 Problem / Knowledge Gap Coastal Erosion Risk Geological / geotechnical unknowns Seismic (MASW) 2 Scope Survey Method #3 Method #4 Field Outcome Do Management! (Hazards, Risk, Options, Action)

10 Scenario #2 Marine Sediment Coring Method #1 2 Problem / Knowledge Gap Beach Nourishment Feasibility Sand source opportunities? Sand source constraints? Method #2 Scope Survey Acoustic Sub Bottom Profiling Multibeam Bathymetry Backscatter 1 1 Field Outcome Do Management! (EIA, Approvals, Action)

11 GPR Study of Coastal Geology and Erosion Hazards Blueys and Boomerang Beaches Original hazard study: applied simple engineering methods; did not consider varying geological conditions Community did not accept report / maps BMT Study GPR survey presence & depth of bedrock GPR correlated with existing boreholes Coastal geomorphology interpretation Map sand/rock interface (bedrock control) Geotechnical adjustment of hazard lines

12 GPR Coastal Geology Results

13 Bedrock Control Map Original Hazard Lines Bedrock Revised Lines

14 Sub-Bottom Profile Survey of Offshore Sediments Sunshine Coast Sand Sourcing Study SEMP: Beach nourishment preferred option Limited options: environmental and legislative constraints BMT Study Offshore sand source one of four options Bathymetry and sub-bottom profiling Basement reflection used to infer sand layer thickness (>9m in areas) Results mapped significant deposits in S

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17 GPR Survey of Buried Historic Seawalls Gold Coast Beaches 1960/70 s seawalls (A-line) buried below the ground location & condition unknown Council seeking engineering certification BMT Study Many GPR profiles collected - detailed processing and interpretation Engineering parameters imaged (crest location & height, slope, width) Results enabled certification of some walls and guided maintenance elsewhere Historic Seawall Design (1967)

18 GPR Seawall Profiles

19 GPR Analysis and Results

20 Key Messages Environmental for Coastal Management Variety of non-destructive methods, each with a suite of possibilities, advantages and limitations Can help resolve critical knowledge gaps regarding: subsurface conditions buried infrastructure Can provide alternative to (or complement) intrusive investigation (e.g. boreholes, excavation) Can provide considerable cost saving Many coastal management applications!

21 Thank you Paul Donaldson Senior Coastal Scientist Tel: (02) Brisbane, Sydney, Newcastle, Melbourne, Perth