case study: landslides in Hong Kong Flashcards

1
Q

Landslides in Hong Kong

A
  • between 1947 and 1997 more than 470 people died as a result of landslides
  • due to combination of high rainfall (may-sept), steep slopes and dense human development on islands
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2
Q

1996 June

A
  • rainstorms
  • avg:300 mm fell compared to 130 mm of a normal year
  • June 11 and 12 over 400 mm fell, a third in an hour
    impacts:
    • killed 64 people
    • over 2500 people made homeless
    • 800 were evacuated
    • washout, debris avalanches, rockslide
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3
Q

Hong Kong

A
  • one of most densely populated areas
  • population is 7 million
  • more than 230 islands with naturally steep terrain
  • upper slopes steeper than 30 degrees
  • urban development triggers landslides by excavation building works
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4
Q

geology

A
  • mainly 3 types: sedimentary rocks, granites and volcanic
  • sedimentary rocks generally form the lowlands
  • granites and volcanic rocks are situated on higher ground
  • both are seriously weathered, granite tends to be more deeply than volcanic: are more resistant and less prone to slope failure
  • 368 rockfall events in the 13 years
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5
Q

managing landslides in Hong Kong

A
  • The Slope Safety System: 700 activities, research and investigation, continuously updating info
  • private owners take responsibility: 50 000 HK dollars, 1 years imprisonment
  • success: risk of landslides reduced 50% since 1977
  • increasing population: building further up slopes increases potential damage
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6
Q

maintenance of slopes

A
  • surface drainage system
  • protective impermeable hard covers
  • man made slopes
    greening techniques:
  • mulching system: adhesive resistance, water retaining,
  • long-rooting grass:environment friendly, cost effective, fast and easy, low maintenance,
  • fibre reinforced soils system: low maintenance, visual improvement , restored natural habitats
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