1 ENV-3A1Y/ENVF3A1Y: Natural Hazards: Landslide Hazards N.K. Tovey Н.К.Тови Landslide on Main Highway at km 365 west of Sao Paulo: August 2002 Lecture 2 Lecture 3 Lecture 4 Lecture 1 15,699 days ago today 43 years ago next Wednesday

2 Lecture 1: Wednesday Week 4 09 – 10 Lab A –Introduction Landslides as a Hazard and their consequences background to why they occur Lecture 2: Thursday Week 4 12 – 12:50 CD Annexe 0.01 Types of Landslide Lecture 3: Wednesday Week 5 09 – 10 CD Annexe 0.01 [ but may be in Lab A depending on how things goes in Week 1] Landslide Warning systems Lecture 4: Thursday Week 5 12 – 12:50 CD Annexe 0.01 –Landslide and Slope Management –Field Excursion: Week 4 or Week 5 starting at 12:55 –from bus stop [watch for details] Bring Field Clothing and a packed lunch – meet at CD annexe Bus Stop ENV-3A1Y/ENVF3A1Y: Natural Hazards:

New Book Published October Enduring Landslides and Floods in the Caribbean Region by Angella Cropper 1 Landslides 2Modelling Landslides in Tropical Environments by Keith Tovey 15 3Planning for Hillside Terrains by Deborah Thomas and Senwan M. J. Baban 40 4Developing a GIS-based Landslide Susceptibility Map for Tropical Mountainous Environments by Serwan M. J. Baban and Kamal Sant 64 5Using Contemporary Geo-imaging Technologies for Landslide Investigations in Tropical Environments by Raid Al-Tahir and Vernon Singhroy 81 Floods 6Using GIS for Flood Management and Mitigation in Trinidad and Tobago by Bheshem Ramlal 107 7Using GIS for Flood Risk Assessment and Flood Sensitivity Maps for a Watershed in Trinidad and Tobago by Serwan M. J. Baban and Ronnie Kantasingh 124 8A New Examination of Floods in the Region: Debris Floods and Debris Flows in the Caribbean by Rafi Ahmad 141 9Mapping Flood-prone Areas: A Geoinformatics Approach by Serwan M. J. Baban and Francis Cannisus 157 Geohazards Management 10Developing a Proactive Approach to Geohazards Management in Trinidad and Tobago by Serwan M. J. Baban Issues in Flood Risk Management by Andrew Fox192 12Recognizing and Managing Unstable Slopes in Trinidad and Tobago by Serwan M. J. Baban and John B. Ritter Developing Early "Warning Systems for Managing Geohazards in the Caribbean by Serwan M. J. Baban and Kelly Aliasgar Beyond Humanitarianism: Building Resilient Communities, Revisiting the Development Dialogue by Jeremy Collymore 244

4 Aims of the course An introduction to Landslide Hazard Management Factor of Safety the causes Why they occur Can we predict them the consequences The types of landslide Landslide Warning – Development of the Hong Kong System and what was learnt Strategic Planning for the future Slope management ENV-3A1Y/ENVF3A1Y: Natural Hazards:

5 Landslides as a Hazard Grossly Under Represented as a Hazard Often treated as a secondary issue e.g Rain Storm Disasters of 18 th June 1972 in Hong Kong 2 major landslides each killing over 60 people No one was killed by drowning/flooding or as a result of the typhonn. Failure of slope above Po Shan Road in June 1972 ENV-3A1Y/ENVF3A1Y: Natural Hazards:

6 Landslides associated with Heavy Rain (Tropical Cyclones) –~ 500+ landslides affected man in Hong Kong 28 th May to 2 nd June –As a result of NKTs actions Yuen Mo village ceased to exist. Earthquakes –Cause liquefaction and rise of pore pressures Volcanic Eruptions ENV-3A1Y/ENVF3A1Y: Natural Hazards:

days ago today at 09:15 N K Tovey a second year PhD student was listening to a lecture by Andrew Schofield. Theme of lecture was Landslide Hazards At 09:15 he turned his attention to a landslide disaster which had occurred a few year earlier in Belgium. A colliery tip collapsed killing around 20 people in the village. At precisely the time he was speaking about the disaster >>>>>>>>>>>>>>>>>>>>> ENV-3A1Y/ENVF3A1Y: Natural Hazards:

8 Aberfan: 21 st October 1966 Tip 7 collapsed, engulfed Pantglas School and parts of the village killing 144 mostly children ENV-3A1Y/ENVF3A1Y: Natural Hazards:

Main Manchester – Sheffield Road (A625) Alternative route – only suitable for light vehicles – gradient of 1 in 4 Landslides: Removing the Consequence Manchester 1 km

10 Geotechnics – the discipline needed for detailed analysis "the application of the laws of mechanics and hydraulics to the mechanical problems relating to soils and rocks" Factor of Safety (F s ): Forces resisting landslide movement arising from the inherent strength of the soil. Forces trying to cause failure (i.e. the mobilizing forces). F s = F s > 1 stable But is it? F s = 1 just stable F s < 1 unstable But is it? ENV-3A1Y/ENVF3A1Y: Natural Hazards:

11 berms Heave at toe Landslide in man made Cut Slope at km 365 west of Sao Paolo - August 2002

12 berms Steep scar to rotational failure

13 Landslide Consequence Remedial Measures Remove Consequence Safe at the moment Cost Build Landslide Warning No Danger Temporarily Safe Design Landslide Preventive Measures Stability Assessment Slope Profile Geology Erosion/Deposition Glaciation Weathering Geochemistry Cut / Fill Slopes Construction Drainage Pumping Mans Influence (Agriculture /Development) Earthquakes Material Properties (Shear Strength) Ground Loading (Consolidation) Slope Management Hydrology (rainfall) Ground Water Surface Water GIS

14 N S =W N S W Relationship between mobilizing & resisting forces Force (S) required to move block is proportional to Normal Force (N) On a slope N depends on weight and N = W cos S also depends on weight and N = W sin S1S1 N1N1 S2S2 N2N2 S3S3 N3N3 N S W W Normal Force Shear Force