structure Networking for the future addressing climate change effects on slope instability Tom Dijkstra and Neil Dixon Loughborough University, UK

Transcription

1 Networking for the future addressing climate change effects on slope instability Tom Dijkstra and Neil Dixon Loughborough University, UK structure 1. CLIFFS an introduction 2. UK climate change forecasts 3. climate signals and slope instability 4. networking and the future key research needs 1

2 what is CLIFFS? Climate Impact Forecasting For Slopes EPSRC-funded dating service for academics, R&D agencies, stakeholders, consultants and climate specialists Aim - to stimulate an integrated research response to address the intricately linked problem of forecasting, monitoring, design, management and remediation of climate change induced variations in slope instability members Core British Geological Survey British Geotechnical Association British Waterways CF Skanska Ltd Geotechnical Consulting Group Halcrow Group Ltd Highways Agency Imperial College London Isle of Wight Council Loughborough University Mott MacDonald Nottingham Trent University Queen's University Belfast UKCIP University of Bristol University of Birmingham University of Newcastle Kingston University + more than 140 members 2

3 what does CLIFFS do? multi-disciplinary themed workshops risk and uncertainty responses of constructed slopes to changes in climate responses of natural slopes to changes in climate mitigation, remediation and dissemination (3 rd July 2007) international symposium (2008) web-based information details of the network at cliffs.lboro.ac.uk key questions Will the climate change predicted for the UK influence the mechanism and frequency of slope failures? Do stakeholders need to take any action? If they do, what is required and when? 3

4 structure 1. CLIFFS an introduction 2. UK climate change forecasts 3. climate signals and slope instability 4. networking and the future key research needs climate change forecasts UKCIP02 - UK slopes will experience higher temperatures changing precipitation patterns changes in sea level other changes such as extreme events relative likelihoods unknown UKCIP08 ensemble of different models and derived probability distributions It s getting warmer! 4

5 structure 1. CLIFFS an introduction 2. UK climate change forecasts 3. climate signals and slope instability 4. networking and the future key research needs an unstable slope contributing factors hydrological triggering pore pressures on slip surface control stability shallow deep slip surfaces climate variables rainfall, temperature, evapotranspiration other factors including geometry, stress history, vegetation, land use, engineering works, etc. 5

6 BGS National Geohazard Assessment identified some 90,000 properties (c. 20B asset) on sites with a significant potential for slope failure. A significant proportion of the risk is from the reactivation of shallow relict landslides (British Geological Survey 2006) natural slopes Max 4-month AER (mm) Blackgang The Landslip Mirables Luccombe Binnel Bay Steephill Cove Wheeler's Bay Lower Gills Cliff Bath Rd Whitwell Rd Newport Rd Castlehaven Upper Ventnor Upper Bonchurch Monk's Bay The Orchard, Niton St Lawrence Railway Station Events UKCIP Lower Bonchurch St Lawrence Old Park Luccombe Coombe R-square = # pts = 164 y = (lnx) Return Period (years) Present and forecasted (UKCIP , medium high) return periods of Isle of Wight s landslides. (Moore et al. 2006) 6

7 natural slopes Mam Tor Return Period (years) s 2050s 2080s Time Period Significant winter movement thresholds - 1-month intensity trigger (210mm) - 6-month antecedent rainfall (750mm) head scar 450 sandstone shale 350 A 250 metres hillside prior to failure solifluction lobe colluvium upper zone main mass of landslide blocks upper road transition zone metres lower road 1 debris slide buried ground surface movement direction of ground surface below arrow head 2 borehole and number B 300 remains of Blacketlay Barn landslide toe constructed slopes Ageing (>100 years old) poorly constructed fill slopes (e.g. London Underground) Recently constructed (>50 years old) highway cut and fill slopes with design based on historical climate and performance, (plus some arbitrary factors) Flood embankments with a range of ages Several studies are in progress to investigate the possible impact of climate change BIONICS 7

8 Rail embankments Flood defences (O Brien and Loveridge 2007) Highways (Utili and Dyer 2007) BIONICS (Kidd 2007) (Glendinning 2007) structure 1. CLIFFS an introduction 2. UK climate change forecasts 3. climate signals and slope instability 4. the need for networking and the future 8

9 networking At present, planning and design use relatively static information based on past behaviour (e.g. geological maps showing historical landslides). However, we operate in a dynamic system. What are the outcomes of this, how do we need to respond? Networking: stakeholders and research communities can interact ask questions find solutions networking - workshop outcomes climate change pore pressure rates of movement some fundamental questions how will climate change (in particular effective rainfall) affect slope stability? how well do we understand pore pressures in complex geological environments what happens when slides move? how do pore pressure variations lead to changes in landslide movement? how do changes in basic assumptions lead to changes in outcomes? e.g. effect of fissure flow? 9

10 what do we need to do? determine magnitude, frequency, impact of thresholds, in particular related to pore pressure changes on slip surfaces carefully (re-)consider assumptions about mechanisms and trigger events consider significance of changes in environmental conditions and uncertainty move from site specific assessments to broader understanding of slope responses what do we need to do? formulate plausible narratives of alternative futures (scenarios) for assessment of unstable slopes that relate to forecasted changes in climate. develop simple models that have flexibility to use different slope failure scenarios and integrate UKCIP08 probabilistic climate change information. analyse constructed and natural slopes (inland and coastal) develop engineering solutions and construction guidelines for the economic design and optimum management of slopes. 10

11 e: w: cliffs.lboro.ac.uk 11