CLIFFS launch meeting 26 October 2005, Holywell Park, Loughborough - - PowerPoint PPT Presentation

Climate change impacts on coastal cliffs: accessing and using meaningful data

Dr Paul Fish CGeol FGS Dr Roger Moore CGeol FGS FICE Halcrow Group Ltd, Engineering Geomorphology

CLIFFS launch meeting

26 October 2005, Holywell Park, Loughborough University

Blackgang 1995 Holbeck Hall Hotel, Scarborough 1993 A3055 Isle of Wight Undercliff 2001

Shanklin Cliff failure 2001 - 8 injured Nefyn, April 2001

Recession Rates m/yr Beachy Head Cliff Falls:

Lighthouse Jan 1999 (100k tons) Devil’s Chimney Apr 2001 (50k tons) 1.25 0.96 0.76 0.48 Seven Sisters Birling Gap Period 1.12 1975-2005 0.91 1926-1975 1.41 1909-1926 0.64 1874-1909

Reactivation of relict landslides, Isle of Wight

20 12 6 8 # Major Events Period 1960-2005 1921-1960 1881-1920 1839-1880

• Ventnor Undercliff, Isle of Wight

(mm)

Likely Future Scenarios:

• Increased coastal

erosion and cliff retreat ?

• Higher winter rainfall,

groundwater levels and coastal cliff instability ?

• Reactivation of relict

coastal landslide systems ?

Climate change,cliff erosion hazard & risk

Key Parameters:

• Historical recession rate
• Landslide event frequency
• Sea-level
• Winter rainfall
• Sediment budget (beach)
• Shoreline protection

There is a great need for fundamental research into the controls and future drivers of coastal cliff instability and erosion – there are very few historical case studies or analogues to inform future projections of cliff behaviour and recession under various climate change scenarios

• Four regional climate change scenarios for the

UK (50km grid) based on IPCC global model Climate change predictions to 2080:

Temperature +2°to 3.5° C Summer rainfall & soil moisture -40% Winter rainfall +30% Increased frequency of storms Sea level in SE +26cm to 86cm Extreme sea level 10 to 20 times more frequent

UKCIP02 - Climate Change Predictions

Predicted change in temperature Predicted change in rainfall Resolution: 50km grid

UKCIP02 – regional predictions

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Cliff sensitivity to climate change

There are issues applying the UKCIP02 quarterly predictions as they may not exactly match other established relationships such as this

Available data and information

Key Factual Data:

• Satellite data
• Topographical maps
• Aerial photographs
• Elevation data (DEM)
• Morphological maps
• Site-specific data
• Hydrodynamic monitoring
• Observational records

Example Derived Data:

• Geomorphology maps
• Erosion risk maps
• Sediment transport
• Climate change

predictions i.e. rainfall and sea level rise

• Anecdotal records

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OS mapping 1860 to present

• Oldest mapping from mid 19th

Century – Possible survey error – Problems of interpretation of landforms

• All map data is georectified

– Potential problems with projection of maps pre- and post introduction of the National Grid (1940s) – Problems of distortion of old paper maps

Aerial photographs – 1941 to 2002

• Aerial photographs should be

referenced to the National Grid

• Orthorectification uses x, y and z

coordinates from digital elevation data (e.g. LiDAR, IfSAR)

• Errors are concentrated at the coast
• Georectification uses x and y from

large-scale OS maps

• Coastal areas often have few mapped

permanent features (roads, buildings, field boundaries)

• In all cases error of fit (RMS) needs to

be calculated and understood

Digital orthophotograph (19cm x, y) LiDAR ground model (2m x, y; 25cm z) Synchronised aerial surveys avoid problems with historical data

Processing issues: Need to compare repeat LiDAR datasets derived from the same processing algorithms which may change

Regional assessments

Geomorphology Cliff Behaviour

• Defines nature, extent and past

behaviour of unstable ground

• Used to rationalise subsurface

investigation and monitoring

• Framework for management of

complex coastal landslides

• Requires periodic updating

Method:

• Detailed field mapping

and interpretation of aerial photographs Accuracy:

• Scale limited up to ±1m

Site-specific assessments

Investigation, survey and monitoring

§ Real-time § mm Accurate

Modelling approaches and uncertainties

• Extrapolation from historical data:

– Historical rate of change = Predicted rate of change

• Empirical modelling of shoreline retreat from sea-level rise:

– 2D approaches, Bruun rule, sediment budgets

• Behavioural process-response models

– 3D interaction between coastal process and landforms

• Deterministic modelling

– Uses historical rates of change and judgements about future uncertainties

• Probabilistic modelling

– Permits variability in predictions and handling of uncertainty

• Gather an appreciation of the various components of

the coastal system, their dynamics and influences;

• Identify behavioural characteristics and systems;

This understanding was then used to make forecasts

• f the large-scale future evolutionary trends, and from

this to predict shoreline response for specific areas.

• Determine dominant controls, influences and

resultant pressures.

Strategic scale – FutureCoast projection

Naish Farm Cliff House Hotel M arine Drive West Barton Court M arine Drive East Becton Bunny

10 20 30 40 50 60 70 80 (m) mean maximum

Cumulative recession of cliff units: 1940-2001

Profiles used for analysis

Deterministic modelling

Historical recession data can be used to Model future change. Projections can take account of error in data, sea-level rise, sediment budgets and degradation of coastal defences

Naish Farm Cliff House Hotel

Probabilistic recession modelling

New Defra/EA R&D project FD2324 Risk Assessment of Coastal Erosion Aims to provide an approach for probabilistic assessment of coastal erosion for LA to deliver Defra high level targets

Conclusions

• Cliff instability and erosion increasing
• Climate change is a key driver
• Good historical data available
• Limited site monitoring data
• Few good case studies and analogues
• Projections of cliff behaviour rely on historical data
• Modelling approaches not widely applied in UK
• Need fundamental research on climate change

impacts on cliff behaviour and erosion potential

Acknowledgements

Andrew Bradbury (NFDC) Robin McInnes (IWC) Geoff Davis (WDDC) John Riby (SBC) SCOPAC Mark Lee