HK Mass Movement ‘72 Flashcards

1
Q

Causes

A
  • 60% of land in HK is mountainous
  • most landslides occur during or after rainstorms
  • tropical climate increases rate of chemical weathering which decreases shear strength of slopes
  • granite and volcanic rocks on higher ground are prone to failure and are seriously weathered
  • prev v.dense population w/ lack of management = shanty towns build on slopes, increased chance of mass movements
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2
Q

impacts of landslides and deaths

A

more than 156 deaths

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3
Q

management response (tlews)

A
  • 1977 introduced territorial landslide early warning system
  • needs to be constantly improved as prospect of increasingly intense rainfall grows due to climate change
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4
Q

geotech engineering office (6)

A
  • updating + maintaining slopes
  • landslide potential index indicates areas that are most at risk (only 10 ppl had heard of it)
  • if the slope doesnt comply with rules, 50k fine and 1yr imprisonment
  • gps sensors on slopes to detect movement
  • monitored 60000 slopes
  • new warning system which gives foreast 6 hrs ahead compared to 3 hrs
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5
Q

maintenance of slopes

A
  • mulching system: high water retaining capacity, resistance to rain erosion, ability to hold position in steep slopes.
  • long rooted grass, natural, cheap, fast and easy, can be applied on steep slopes
  • fibre reinforced soil system: low maintenance fibre strengthens soil, visual improvement, restoration of habitats
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6
Q

challenges

A
  • Hk is compact
  • money available to invest in the tech needed
  • however, sierra Leone don’t, in 2017 landslide killed 1000+ & authorities have little data to provide to citizens about the likelihood of another disaster.
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7
Q

soft engineering

A
  • afforestation plan
  • used natural vegetation near roads and motorways near slopes
  • 50% risk reduction of landslides since 1977
    BUT takes time, and some plants struggle to grow on steep slopes
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8
Q

hard engineering

A

Drainage pipes:
- drainage systems in over 87 locations in Hong Kong
- prevented 2200mm of precip that HK receives from oversaturating slopes
BUT very expensive, so only richest can afford

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