HK Mass Movement ‘72

Question 1

Causes

Answer 1

• 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

Question 2

impacts of landslides and deaths

Answer 2

more than 156 deaths

Question 3

management response (tlews)

Answer 3

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

Question 4

geotech engineering office (6)

Answer 4

• 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

Question 5

maintenance of slopes

Answer 5

• 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

Question 6

challenges

Answer 6

• 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.

Question 7

soft engineering

Answer 7

• 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

Question 8

hard engineering

Answer 8

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