Stability of Slopes

Question 1

How can slope stability dec?

Answer 1

• human activities: lead to mass movement events

Question 2

How can slope stability inc?

Answer 2

• humans can reinforce slope stability by dec. hazard to envi. + human life

Question 3

What is slope stability generally caused by?

Answer 3

• an inc. in external stress on slope
• a dec. in internal strength of a slope

Question 4

What are examples of human activities that cause a dec. in slope stability?

Answer 4

• mining + quarrying
• construction
• tourism
• agriculture
• forestry

Question 5

How does mining + quarrying dec. slope stability?

Answer 5

• removes lateral support from slope (undercutting)
  
  • causes instability in slope: leads to mass movements - land/mud/rock slides or rockfalls
• brings large amounts of waste (often left on slope)
  
  • inc. stress on slopes from weight: leads to mass movement

Question 6

How does construction dec. slope stability?

Answer 6

• stress is added (e.g. weight of housing or dams)
• may be undercut so can build: causes instability
• groundwater affected due to sewage + drainage systems + water demand: creates instability
• water erosion affects slopes internal strength. Hydraulic engineering (e.g. dams) causes saturation of surrounding slope if not properly managed: triggers mass movement, esp. mudslides

Question 7

How does tourism dec. slope stability?

Answer 7

• common on alpine slopes: skiing
• creates stress on slopes
  
  • erosion of slopes inc. due to trampling of veg., skis, heavy machinery, walking: damages + compacts soil
  • alpine areas: seasonal melting is common, dramatically inc. water + triggers mass movement when slope is degraded

Question 8

How does agri. dec. slope stability?

Answer 8

• soil compacted by heavy machinery + animals
  
  • leaves slopes vulnerable to soil erosion, changing water flows + dec. veg. cover
• dec. veg. cover from overgrazing + trampling causes soil degradation
  
  • veg. vital to soil’s structure, w/o veg. rates of soil erosion + weathering inc.: inc. risk of large scale mass movements (landslides)

Question 9

How does forestry dec. slope stability?

Answer 9

• deforestation:
  
  • dec. soil strength which is enhanced by tree roots: majorly instable if not managed
  • dec. interception of pptn: more overland flow + infiltration + less water uptake by roots - inc. soil saturation: erosion + triggers mass movements
• clearcutting leaves slopes vulnerable, esp. to winds
• forest roads constructed to transport timber: interrupts natural flow of water + creates channels for run-off: can be highly erosive