UGRC 144 Science and Technology in Our LivesGeohazards

UGRC 144 Science and Technology in Our Lives/Geohazards Session 10 – Mass Movement Hazards and Preventive Measures Lecturer: Dr. Patrick Asamoah Sakyi Department of Earth Science, UG Contact Information: pasakyi@ug. edu. gh College of Education School of Continuing and Distance Education 2014/2015 – 2016/2017

Session Overview • This session introduces students to the hazards that accompany mass movements and the accompanying potential disastrous effects • We shall also look at possible preventive measures that could be employed to reduce its effects on human lives and property. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 2

Session Outline The key topics to be covered in the session are as follows: • Topic One – Consequences/Hazards of Mass Movements • Topic Two – Possible Preventive Measures of Mass Movements Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 3

Reading List • Chapter 8 of Environmental Geology 4 th Edition, Wm. C. Brown Publishers – by Carla W Montgomery (1995) • Chapter 19 of Physical Geology. 3 rd Edition. Wm. C. Brown Publishers – by Carla W Montgomery. (1993). • Chapter 7 of Geology and the Environment. 3 rd Edition. Brooks/Cole Thomson Learning – by Pipkin, B. W. and Trent, D. D. (2001) • Unit 2, Sections 6 of UGRC 140 II Geohazards – Institute of Continuing and Distance Education. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 4

Topic One CONSEQUENCES/HAZARDS OF MASS MOVEMENTS Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 5

Consequences/Hazards of Mass Movements • Mass movements is accompanied by hazards that may have damaging effects on life and property. • They can cause dam formation of streams/rivers and subsequently flooding. • Most of the dams formed by these processes later fail, causing other damages in the subsequent events. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 6

Consequences of Mass Movements • Mass movements can also cause extensive damage to; – buildings, – roads – railways • The damage disrupts transport services and cause the loss of human life. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 7

Consequences/Hazards of Mass Movements • They also destroy crops when they occupy farmlands, water distribution pipes and power transmission poles. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 8

Consequences/Hazards of Mass Movements • On 27 th February, 2011, a sudden seismic activity caused a "megamudslide" in the Bolivian capital of La Paz • The mudslide destroyed at least 400 homes and left over 5000 families homeless. • It was triggered by movement along a fault. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 9

Consequences/Hazards of Mass Movements • On Saturday 22 nd March, 2014, a mudslide in Seattle, Washington, USA caused the death of 8 people with 108 missing Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 10

Topic Two POSSIBLE PREVENTIVE MEASURES OF MASS MOVEMENTS Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 11

Possible Preventive Measures of Mass Movements • A number of measures have been employed to prevent mass movements. Some of these measures are outlined in the subsequent slides. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 12

Possible Preventive Measures of Mass Movements Slope Reduction • This is done by; – decreasing the slope angle – supporting the slope by adding materials at the foot, – decreasing the weight on the slope Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 13

Possible Preventive Measures of Mass Movements Retention Structures • This is done by planting stabilizing vegetation or using ground covers • Fast-growing plants with strong root systems are usually used in the vegetation cover. • In some cases, solid retaining walls are built against the slope. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 14

Possible Preventive Measures of Mass Movements Fluid Removal • This method deals with major ways of reducing the water content or pore pressure of rocks or soils. • It may be done by covering the surface with an impermeable material and diverting surface runoff above the slope. • Drainage pipes are driven into the foot of a shallow slide to drain water from the material Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 15

Possible Preventive Measures of Mass Movements Fluid Removal Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 16

Possible Preventive Measures of Mass Movements Rock bolts • Rock bolts can also be used in tunneling and mining pits to stabilize walls. This can also be used to stabilize rockslides by anchoring them to stable rocks. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 17

Possible Preventive Measures of Mass Movements Chain-link fencing • Another strategy is to construct chain-link fencing, draped over roadcut to protect vehicles from rock falls. • Boulders encased in chain-link fencing are for slope stabilization purposes. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 18

Summary • Mass movements can result in loss of life and cause extensive damage to buildings, roads and railways, water distribution pipes and power transmission poles, thereby, disrupting the provision of essential services. • They may also destroy crops when they occupy farmlands and render some places inhabitable. • Mass movements can be reduced by such procedures as modifying slope geometry, reducing the weight acting on the slope, planting vegetation, or dewatering the rock or soil. Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 19

END Dr. Patrick A. Sakyi, Dept. of Earth Science Slide 20